Systems and methods for creation of narrow pencil beams and minibeams in a proton scanning nozzle

Abstract

A nozzle for proton beam scanning capable of producing proton minibeams includes an octupole doublet and a quadrupole. The octupole doublet is spinnable about an octupole central axis. The octupole doublet includes a first octupole defining a first central aperture and a second octupole defining a second central aperture. The first central aperture and the second central aperture are coaxially aligned to define the octupole central axis. The second octupole is rotatable about the octupole central axis and translatable along the octupole central axis with respect to the first octupole. The quadrupole defines a quadrupole aperture, the quadrupole spinnable about the quadrupole central axis.

Description

SYSTEMS AND METHODS FOR CREATION OF NARROW PENCILBEAMS AND MINIBEAMS IN A PROTON SCANNING NOZZLECross-Reference to Related Applications

[0001] This application claims priority to, and the benefit of, U.S. Provisional Patent Application Serial No. 63 / 558,616, filed February 27, 2024. The entire contents of the above application is hereby incorporated by reference.Background1. Technical Field

[0002] The present disclosure relates to proton beam therapy systems and, more specifically, to nozzles for proton beam therapy systems capable of forming narrow proton pencil beams or proton minibeams and magnetically scanning these beams.2. Discussion of Related Art

[0003] Pencil beam spot scanning has several advantages over other forms of radiation therapy, and more specifically, advantages over conventional passively scattered proton therapy. Tn passive scattering, a small diameter proton beam is spread out into a lager diameter beam to produce a spatially uniform dose distribution, both laterally and in depth. The depth may be controlled by a range modulator and may be a spinning propeller, wedge, or ridge filter, that produces a spread- out Bragg peak. The field of the beam is typically shaped laterally with a custom-designed aperture, block, or multi-leaf collimator, and may be shaped in depth to match the distal edge of the treatment volume using a patient-specific compensator. However, the dose distribution produced by this approach can only achieve distal conformity to the target (e.g., a tumor) and not proximal conformity.

[0004] Proton beams used in proton therapy are typically produced by a particle accelerator (e g., a cyclotron) and delivered to a patient treatment room by a beam transport system. The narrow diameter “pencil” beams used in spot scanning, also known as pencil beam scanning (PBS), are magnetically scanned to deliver dosed radiation to the target tissue. The size of the pencil beams is generally much smaller than those beams used in passive scattering delivery. The use of smaller pencil beams allows the beam shape to be defined using the scanning magnets rather than an aperture. However, the lateral dose intensity profiles of the treatment fields produced by pencilbeam scanning systems tends to be less sharp than those produced using an aperture or conventionally collimated broad beams. In other words, the penumbra of the lateral dose profiles produced by pencil beam scanning tends to be larger than the penumbra produced by conventional collimation (e.g., mechanical collimation). As such, more radiation may be deposited lateral to the target tissue. On the other hand, pencil beam spot scanning does not require the expensive and labor intensive, patient specific apertures of other therapies. However, in some cases, including treatment with lower energy protons, static apertures are still used in pencil beam scanning treatments to reduce the penumbra at the periphery of the treatment field. In pencil beam scanning, the energy of the pencil beams can be varied, and the depth of the Bragg peak can be thus controlled. In contrast to passive scattering, this allows not only good distal target conformity, but proximal conformity as well.

[0005] Spatially fractionated radiation therapy is a paradigm of dose delivery where the dose is intentionally delivered in a homogeneous pattern, where there are narrow high dose peaks separated from low dose valleys. It has been found experimentally that normal tissue is able to tolerate surprisingly high dose peaks when receiving such a heterogeneous pattern of dose (or, spatially fractionated dose) whereas tumor tissue lethality is the same or increased when receiving a spatially fractionated dose. The potential use of spatially fractionated dose distributions in proton therapy using beams with diameters of a few millimeters (e.g., FWHM less than or equal to 5 mm) has been termed proton minibeam therapy. The creation and delivery of the small diameter proton minibeams in a PBS nozzle is a challenging problem of keen clinical interest.Summary

[0006] Accordingly, there is a need for systems and methods for producing pencil beams for spot scanning that reduces the radiation dose delivered to healthy tissue outside the target tissue. This disclosure relates generally to a nozzle for proton pencil beam spot scanning capable of creating pencil beams with a smaller dose spot size and penumbra. More specifically, this disclosure relates to a nozzle capable of forming proton pencil beams with reduced dose spot size and penumbras including proton minibeams.

[0007] In an aspect of the present disclosure, a nozzle for proton beam scanning capable of forming proton minibeams includes an octupole doublet and a quadrupole. The octupole doublet is spinnable about an octupole central axis. The octupole doublet includes a first octupole defining a first central aperture and a second octupole defining a second central aperture. The first centralaperture and the second central aperture are coaxially aligned to define the octupole central axis. The second octupole is rotatable about the octupole central axis and translatable along the octupole central axis with respect to the first octupole. The quadrupole defines a quadrupole aperture. The quadrupole is spinnable about the quadrupole central axis.

[0008] In aspects, the second octupole is rotated with respect to the first octupole such that the magnetic poles of the second octupole are radially offset from the magnetic poles of the first octupole in a range of 1 degree to 90 degrees. The first octupole and the second octupole may be spaced apart such that an octupole gap is defined therebetween and translating the second octupole with respect to the first octupole a first direction increases the octupole gap and translating the second octupole a second direction opposite the first direction decreases the octupole gap.

[0009] In some aspects, the first octupole and the second octupole have a magnetic field gradient in a range of l.OxlO6T / m3to l.OxlO8T / m3. The first octupole and the second octupole may have different magnetic field gradients. The first octupole, the second octupole, and the quadrupole each have a length in a range of 20 mm to 150 mm.

[0010] In certain aspects, the quadrupole has a magnetic field gradient in a range of 50 T / m to 375 T / m. The octupole doublet may spin about the octupole central axis at a rate in the range of 150 RPM to 40,000 RPM. The quadrupole may spin about the quadrupole central axis at a rate that is that is equal to or up to five times faster than the rate the octupole doublet spins about the octupole central axis.

[0011] In particular aspects, the first octupole and the second octupole are permanent magnets. The quadrupole may be a permanent magnet. The first octupole, the second octupole, and the quadrupole may each include a plurality of magnetic segments arranged in an array such that a magnetic field of the first octupole, a magnetic field of the second octupole, and a magnetic field of the quadrupole is substantially contained within a respective one of the first central aperture, the second central aperture, or the quadrupole aperture. The first octupole, the second octupole, and the quadrupole may be Halbach cylinders.

[0012] In aspects, the octupole doublet is positioned at a first end of the nozzle and the quadrupole is positioned at a second end of the nozzle opposite the first end. The nozzle may have a total length, between the first end and the second end, less than or equal to 1.75 meters. Thenozzle may further include scanning magnets positioned between the octupole doublet and the quadrupole. The scanning magnets may include a X-coil and a Y-coil. The X-coil and the Y-coil may be nested within each other.

[0013] In another aspect of the present disclosure, a nozzle for proton beam scanning capable of forming proton minibeams includes an octupole doublet and a quadrupole. The octupole doublet is configured to selectively spin about a proton beam. The octupole doublet is configured to magnetically collimate the proton beam. The quadrupole is configured to selectively spin about the proton beam. The quadrupole is configured to magnetically focus the proton beam.

[0014] In some aspects, spinning the octupole doublet about the proton beam magnetically collimates the proton beam such that the proton beam has a profile of a first effective diameter when the proton beam enters the octupole doublet and a second effective diameter that is smaller than the first effective diameter when the proton beam exits the octupole doublet. Spinning the quadrupole about the proton beam may magnetically focus the proton beam such that the proton beam may have a circular profile of a third effective diameter when the proton beam exits the quadrupole that is smaller than the second effective diameter. The quadrupole may be configured to magnetically focus the proton beam into a proton minibeam. The proton minibeam may have an effective diameter with a full width at half maximum that is less than or equal to 5 millimeters.

[0015] In certain aspects, the quadrupole is configured to magnetically focus the proton beam such that the proton beam has an elongated profile when the quadrupole is stationary with respect to the proton beam. The quadrupole may be configured to magnetically focus the proton beam into a planar proton minibeam. The planar proton minibeam may have an effective half-diameter with a full width at half maximum that is less than or equal to 5 millimeters. The nozzle may include scanning magnets configured to steer the proton beam toward a portion of a target tissue by deflecting the proton beam. The nozzle may include a robotic arm configured to position the quadrupole with respect to the proton beam such that the proton beam passes through the quadrupole after the proton beam is deflected by the scanning magnets.

[0016] In particular aspects, the octupole doublet includes a first octupole and a second octupole that is rotatable and translatable with respect to the first octupole.

[0017] In aspects, a system for proton beam scanning includes a proton beam source and a nozzle operably coupled to the proton beam source.

[0018] In another aspect of the present disclosure, a method of shaping a proton beam includes selecting an operation mode for a nozzle from one of a PB mode, an OD mode, an ODS mode, an ODSQ mode, or an ODSQS mode. The nozzle is configured to shape the proton beam. The method also includes passing the proton beam through the nozzle. The method also includes deflecting the proton beam with scanning magnets of the nozzle. The scanning magnets are configured to steer the proton beam at a portion of a target tissue.

[0019] In aspects, selecting the OD mode, the ODS mode, the ODSQ mode, or the ODSQS mode includes positioning an octupole doublet of the nozzle with respect to the proton beam such that the proton beam passes therethrough as the proton beam is passed through the nozzle to magnetically collimate the proton beam. Selecting the ODS mode, the ODSQ mode, or the ODSQS mode may include positioning an octupole doublet of the nozzle with respect to the proton beam such that the proton beam passes therethrough as the proton beam passes through the nozzle and spinning the octupole doublet about the proton beam as the proton beam passes therethrough to magnetically collimate the proton beam. Spinning the octupole doublet may include spinning a first octupole of the octupole doublet and a second octupole of the octupole doublet the same speed and the in the same direction.

[0020] In some aspects, selecting the ODSQ mode or the ODSQS mode includes positioning an octupole doublet of the nozzle with respect to the proton beam such that the proton beam passes therethrough as the proton beam passes through the nozzle and spinning the octupole doublet about the proton beam as the proton beam passes therethrough to magnetically collimate the proton beam. Selecting the ODSQ mode or the ODSQS mode may also include positioning a quadrupole of the nozzle with respect to the proton beam such that the proton beam passes therethrough as the proton beam passes through the nozzle to magnetically focus the proton beam. Positioning the quadrupole may include aligning the quadrupole with the proton beam such that the proton beam passes through the quadrupole after the proton beam is deflected by the scanning magnets.

[0021] In certain aspects, selecting the ODSQS mode includes spinning the quadrupole about the proton beam as the proton beam passes therethrough. Spinning the quadrupole may includespinning the quadrupole at a speed that is equal to or up to five times faster than the octupole doublet.

[0022] In particular aspects, selecting the PB mode includes positioning an octupole doublet and a quadrupole of the nozzle with respect to the proton beam such that the proton beam does not pass through the octupole doublet or the quadrupole.

[0023] Further, to the extent consistent, any of the embodiments or aspects described herein may be used in conjunction with any or all of the other embodiments or aspects described herein.Brief Description of the Drawings

[0024] Various aspects of the present disclosure are described hereinbelow with reference to the drawings, which are not necessarily drawn to scale, which are incorporated in and constitute a part of this specification, wherein:

[0025] FIG. 1 is a schematic illustration of a nozzle in accordance with embodiments of the present disclosure;

[0026] FIG. 2 is a perspective view of an octupole in accordance with embodiments of the present disclosure;

[0027] FIG. 3 is a schematic illustration representing a magnetic field of the octupole of FIG. 2;

[0028] FIG. 4 is a perspective view of a quadrupole in accordance with embodiments of the present disclosure;

[0029] FIG. 5 is a schematic illustration representing a magnetic field of the quadrupole of FIG. 4;

[0030] FIGS. 6 - 8 are transverse phase space portraits graphically illustrating the displacement (horizontal axis) and divergence (vertical axis) with respect to the beam axis of a proton beam passed through a nozzle operating in ODS mode in accordance with embodiments of the present disclosure;

[0031] FIGS. 9 and 10 are transverse phase space portraits graphically illustrating the displacement (horizontal axis) and divergence (vertical axis) with respect to the beam axis of a proton beam passed through a nozzle operating in PB mode in accordance with embodiments of the present disclosure;

[0032] FIG. 11 is a front view of a robotic arm in accordance with embodiments of the present disclosure;

[0033] FIG. 12 is a side view of the robotic arm of FIG. 11;

[0034] FIG. 13 is a flowchart illustrating a method of forming and shaping proton pencil beams or proton minibeams in accordance with embodiments of the present disclosure;

[0035] FIG. 14 is a dose map comparing dose distributions of an example proton beam (150 MeV source beam) passed through a nozzle operating in a OD mode (top), and a proton beam passed through a nozzle operating in PB mode (bottom), in accordance with embodiments of the present disclosure, taken upon exit of the respective nozzle;

[0036] FIGS. 15 and 16 are graphical representations of the widths (FWHM, FW20M) of the proton beams of FIG. 14 at various penetration depths in a water tank;

[0037] FIG. 17 is a graphical representation of the penumbra of the proton beams in FIG. 14 at various penetration depths in a water tank;

[0038] FIG. 18 is a dose map comparing dose distributions of another example proton beam (225 MeV source beam) passed through a nozzle operating in OD mode (top), and a proton beam passed through a nozzle operating in PB mode (bottom), in accordance with embodiments of the present disclosure, taken upon exit of the respective nozzle;

[0039] FIGS. 19 and 20 are graphical representations of the widths (FWHM, FW20M) of the proton beams of FIG. 18 at various penetration depths in water tank;

[0040] FIG. 21 is a graphical representation of the penumbra of the proton beams in FIG. 18 at various penetration depths in a water tank;

[0041] FIG. 22 is a dose map in a water tank from an example proton beam composed of three planar beamlets that each passed through a nozzle operating in ODS mode in accordance with embodiments of the present disclosure;

[0042] FIGS. 23-27 are graphical representations of the dose in the horizontal and vertical transverse planes from the proton beam of FIG. 22 at discrete locations between the entrance to the water tank and the target depth;

[0043] FIG. 28 is a graphical representation of the peak and valley depth dose profiles, respectively taken along the central beamlet, and a valley adjacent to the central beamlet, from the proton beam of FIG. 22;

[0044] FIG. 29 is a dose map in a water tank from an example proton beam composed of nine symmetric beamlets that each passed through a nozzle operating in ODSQ mode in accordance with embodiments of the present disclosure;

[0045] FIGS. 30-35 are graphical representations of the dose in the horizontal and vertical transverse planes from the proton beam of FIG. 29 at discrete locations between the entrance to the water tank and the target depth; and

[0046] FIG. 36 is a graphical representation of the peak and valley depth dose profiles, respectively taken along the central beamlet, and a valley adjacent to the central beamlet, from the proton beam of FIG 29.Detailed Description

[0047] The present disclosure will now be described more fully hereinafter with reference to example embodiments thereof with reference to the drawings in which like reference numerals designate identical or corresponding elements in each of the several views. These example embodiments are described so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Features from one embodiment or aspect can be combined with features from any other embodiment or aspect in any appropriate combination. For example, any individual or collective features of method aspects or embodiments can be applied to apparatus, product, or component aspects or embodiments and vice versa. The disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure willsatisfy applicable legal requirements. As used in the specification and the appended claims, the singular forms “a,” “an,” “the,” and the like include plural referents unless the context clearly dictates otherwise. In addition, while reference may be made herein to quantitative measures, values, geometric relationships or the like, unless otherwise stated, any one or more if not all of these may be absolute or approximate to account for acceptable variations that may occur, such as those due to manufacturing or engineering tolerances or optimizations or the like.

[0048] Referring now to FIG. 1, an example nozzle 100 for proton beam scanning (PBS) is schematically shown. The nozzle 100 includes an octupole doublet 120, scanning magnets 140, and a quadrupole 160. In embodiments, the nozzle 100 includes a robotic arm 180. The nozzle 100 can be operatively coupled to a proton source 10, e.g., a particle transport system, that delivers a narrow proton source beam or a proton beam 12 from a particle accelerator to the entrance of the nozzle 100. The nozzle 100 can selectively modify the proton beam 12 and direct the proton beam 12 toward a target tissue 20, e.g., a cancerous tumor, for treatment. For example, the nozzle 100 may form the proton beam 12 into a proton minibeam and may aim the proton beam 12 toward a portion of the target tissue 20. The scanning magnets 140 deflect the proton beam 12 from the central axis of the nozzle 100 and thus deposit radiation dose across the lateral dimensions of the target tissue 20. Often the target tissue 20 has an irregular profile and, as such, different techniques are used to adequately treat the target tissue 20 while minimizing the amount of radiation delivered to healthy tissue surrounding the target tissue 20. These techniques may include reducing the spot size of the proton beam 12 which may allow for better dose conformity with the target tissue 20. Additionally or alternatively, treatment of the target tissue 20 may include delivery of spatially fractionated dose distributions that spare entrance tissue and also conform to the target tissue 20. The octupole doublet 120 and the quadrupole 160 of the nozzle 100 may modify the proton beam 12 and reduce its diameter (spot size) using “magnetic collimation” and magnetic focusing. Depending on the extent of the spot size reduction of the proton beam 12, the nozzle 100 may produce proton minibeams, e.g., a diameter of 5 mm or less. In embodiments, the nozzle 100 may produce an array of minibeams with a spatially fractionated dose distribution. The use of magnets for beam reduction has several advantages over the use of direct collimation. Spot size reduction can be accessed by measuring the full width at half maximum (FWHM) of the dose deposited by proton beam 12 or fluence of the proton beam 12 (the distance between two points on the beam profile where the value is half the maximum value). In addition, the magnetic collimation of theproton beam 12 by the octupole doublet 120 may produce proton beams 12 that deposit a dose with reduced dose penumbras, e.g., the distance between the 80% and 20% dose levels.

[0049] The nozzle 100 may have an overall length L that is shorter than conventional proton beam scanning nozzles. Conventional PBS nozzles that are typically long making the creation of small diameter beams a challenge because of beam broadening due to finite beam divergence and multiple Coulomb scattering. In embodiments, the overall length L of the nozzle 100 may be in the range of 0.75 m to 1.75 m, e.g., 1 m. The nozzle 100 has a first end or a breech 102 and a second end or a muzzle 104. The proton beam 12 may enter the nozzle 100 through the breech 102 and may exit through the muzzle 104. The breech 102 of the nozzle 100 may be configured to couple the nozzle 100 to the proton source 10, e.g., a synchrotron or cyclotron, such that the nozzle 100 is operably coupled to the proton source 10. Coupling to the proton source 10 may be achieved by a proton transport system or by other means. The octupole doublet 120 may be positioned at or adjacent to the breech 102 of the nozzle 100, the quadrupole 160 may be positioned at or adjacent to the muzzle 104 of the nozzle 100, and the scanning magnets 140 may be positioned between the octupole doublet 120 and the quadrupole 160. The octupole doublet 120, the scanning magnets 140, and the quadrupole 160 may be generally coaxially aligned with one another so that, as the proton beam 12 travels downstream and passes through the nozzle 100, the proton beam 12 passes through the octupole doublet 120, the scanning magnets 140, and the quadrupole 160. In some embodiments, the proton beam 12 may pass through the octupole doublet 120 and the scanning magnets 140, but not the quadrupole 160. For example, the quadrupole 160 may be moved outside of the beam path of the proton beam 12 such that the proton beam 12 does not pass therethrough. More specifically, as described below, the nozzle 100 has several operational modes to shape the proton beam 12 emitted by the nozzle 100. In embodiments, the robotic arm 180 may be entirely contained within the nozzle 100 or may be positioned externally of the nozzle 100. The robotic arm 180 may position the quadrupole 160 to be coaxially aligned with the proton beam 12 after the proton beam 12 exits the scanning magnets 140. In embodiments, the nozzle 100 may be fluidly sealed from a surrounding environment. For example, the nozzle 100 may be filled with a gas, e.g., helium, or evacuated such that the interior of the nozzle 100 is a vacuum. In some embodiments, the nozzle 100 is in fluid communication with the surrounding environments and may be filled with ambient air.

[0050] The muzzle 104 of the nozzle 100 may be positioned near a target body 24, e.g., a patient or a test phantom. The muzzle 104 of the nozzle 100 may be a distance D from an entrance 22 of the target body 24. The target tissue 20 may be a target depth T from the entrance 22 of the target body 24.

[0051] Continuing to refer to FIG. 1, the octupole doublet 120 “magnetically collimates” the proton beam 12 as the proton beam 12 passes therethrough. The magnetic collimation may decrease the effective diameter of the proton beam 12 and may reduce beam penumbra at delivery to the target tissue 20 compared to beams not shaped by the octupole doublet 120. The magnetic collimation of the proton beam 12 may be attributed to shaping of the proton beam 12 by phase space tail folding that mostly effects the periphery of the proton beam 12. The effective diameter of the proton beam 12 may be considered the dimension of the proton beam 12 at full width at half maximum (FWHM) or full width at 20% maximum (FW20M) measured along any desired axis of the effective diameter. For example, the effective diameter may be considered the FWHM of the minor axis of an elliptical profile where the minor axis of the profile is oriented along a horizontal axis (e.g., a hFWHM). In certain embodiments, the effective diameter may be defined by any definition of diameter deemed suitable by the art. For example, the effective diameter may be defined by the Equivalent Circular Diameter of a proton beam 12 with an elliptical profile. The effective diameter of the proton beam 12 may be measured at any desired point along the trajectory of the proton beam 12. For example, the effective diameter of the proton beam 12 may be measured when the proton beam 12 exits the nozzle 100. Further, as used herein, the term “effective diameter” refers to the dimension of the proton beam 12 at FWHM, FW20M, or other definitions deemed suitable by the art, and includes the effective diameter of circular beam profiles and noncircular beam profiles such as, but not limited to, elongate beam profiles, ovular beam profiles, elliptical beam profiles, superellipse beam profiles, or beam profiles exhibiting phase space tail folding. The effective diameter of the proton beam 12 after magnetic collimation may be dictated by several factors including, but not limited to, the energy of the proton beam 12, the magnetic field strength of the octupole doublet 120, or the length of the octupole doublet 120. In embodiments, compared to mechanical collimation, magnetic collimation with the octupole doublet 120 may reduce secondary particle production, e g., neutron production, which may result in delivery of an unwanted dose of radiation to the target tissue 20 or surrounding healthy tissue. Directly intercepting the proton beam 12 with direct mechanical collimation (e.g., passing the proton beam 12 through a relatively narrow aperture) leads to secondary particle productionbecause of physical interactions between protons and collimator materials. However, because direct interception of the proton beam 12 with the walls of the octupole doublet 120 is relatively minimal, fewer secondaries are produced.

[0052] Additionally, referring to FIGS. 2 and 3, the octupole doublet 120 includes a first octupole 122 and a second octupole 124. In some embodiments, the octupoles 122, 124 may be Halbach cylinders. The octupoles 122, 124 may include a plurality of magnetic segments 121 arranged in an array to create a magnetic field with eight poles, as shown in FIG. 3. The magnetic segments 121 may be a permanently magnetic material. The octupoles 122, 124 may each define a central aperture 126. The array of magnets may be arranged such that the magnetic field of the octupoles 122, 124 is substantially confined within the central aperture 126. The central apertures 126 of the first octupole 122 and the second octupole 124 may coaxially align to define an octupole central axis extending between the central apertures 126 of the octupoles 122, 124. The octupoles 122, 124 may have a high magnetic field gradient. For example, the octupoles 122, 124 may have a magnetic field gradient in the range of l.OxlO6T / m3to l.OxlO8T / m3, e.g., 7.5xl06T / m3. The octupoles 122, 124 may have the same magnetic field strength or may have different magnetic field strength. In some embodiments, the first octupole 122, the second octupole 124, or both octupoles 122, 124 may be replaced by swapping into or out of the nozzle 100 an alternate octupole with other properties (e.g., a stronger or weaker magnetic field) to achieve the desired level of magnetic collimation of the proton beam 12. The octupoles 122, 124 may each have a length in the range of 20 mm to 150 mm, e.g., 50 mm, 65 mm, 80 mm, or 100 mm, etc. The octupoles 122, 124 may have the same length or may have different lengths.

[0053] In particular embodiments, each octupole 122, 124 may include more than one Halbach cylinder coaxially aligned with one another. Forming the octupoles 122, 124 with more than one Halbach cylinder can increase the effective length of each octupole 122, 124 and, thus, also increase the extent of the magnetic collimation that the proton beam 12 experiences. In embodiments where the octupoles 122, 124 are formed of more than one Halbach cylinder, each Halbach cylinder may have the same magnetic field. In certain embodiments where the octupoles 122, 124 are formed of more than one Halbach cylinder, each Halbach cylinder may have a different magnetic field. As such, the octupole doublet 120 may be modular and may include a plurality of Halbach cylinders that can be combined and swapped into and out of the nozzle 100 to achieve the desired level of magnetic collimation of the proton beam 12.

[0054] The octupoles 122, 124 are moveable with respect to each other. More specifically, the octupoles 122, 124 may translate or rotate with respect to each other. Translating the first octupole 122 or the second octupole 124 may increase or decrease an octupole gap OG between the first octupole 122 and the second octupole 124. More specifically, the first octupole 122 or the second octupole 124 may translate along the octupole central axis toward or away from the other of the octupoles 122, 124. Increasing or decreasing the octupole gap OG may alter the magnetic collimation of the proton beam 12. For example, increasing or decreasing the octupole gap OG may result in a proton beam 12 having a smaller or larger spot size. Rotating the octupoles 122, 124 with respect to each other may radially offset the poles and, consequently, the orientations of the magnetic fields of the first octupole 122 and the second octupole 124. The octupoles 122, 124 may be radially offset from one another by a fixed angle in the range of 1 degree to 90 degrees, e.g., 20, 45, 80, or 90 degrees. Rotating the octupoles 122, 124 with respect to each other by a fixed angle may alter the shaping of the proton beam 12 by the octupole doublet 120.

[0055] The octupole doublet 120 spins about the central octupole axis and the proton beam 12 as the proton beam 12 passes therethrough. Spinning the octupole doublet 120 about the proton beam 12 can create a proton beam 12, and more particularly a proton beam 12 with a circularly symmetric proton fluence (protons / unit area, e.g., protons / mm2) downstream of the octupole doublet 120 (e.g., at the target tissue 20). In embodiments, spinning the octupole doublet 120 creates a statistically identical beam phase space in both transverse planes, e.g., the horizonal plane and the vertical plane, of the proton beam 12. For example, spinning the octupole doublet 120 about the proton beam 12 may result in essentially identical average displacement, average divergence, displacement-divergence correlations and emittance of the proton beam 12 in the vertical and the horizontal planes. The octupole doublet 120 may spin at a rate in the range of 150 revolutions per minute (RPM) to 20,000 RPM, depending on factors including, but not limited to, nozzle operational mode and dose rate. The octupole doublet 120 may spin clockwise or counterclockwise about the proton beam 12. The first octupole 122 and the second octupole 124 may spin together at the same rate and in the same direction. In some embodiments, the first octupole 122 and the second octupole 124 may spin independently of each other. For example, the first octupole 122 may spin at a first rate in a clockwise direction and the second octupole 124 may spin at a second rate in a counterclockwise direction. In some embodiments, the octupole doublet 120 remains stationary with respect to the proton beam 12, e.g., not spinning. In embodiments, only one octupole 122, 124 spins with the other octupole 122, 124 remainingstationary. In some embodiments, the octupole doublet 120 would only spin when pencil beams are being placed at the periphery of the target tissue 20.

[0056] Continuing to refer to FIG. 1, the scanning magnets 140 are positioned downstream from the octupole doublet 120. The scanning magnets 140 deflect the proton beam 12 to steer or aim the proton beam 12 and deliver a dose of radiation to the target tissue 20. The scanning magnets 140 may include an X-coil 142 and a Y-coil 144. In embodiments, the scanning magnets 140 may include a plurality of X-coils 142 and Y-coils 144. The X-coil 142 may be configured to deflect the proton beam 12 in the horizontal plane (into the page). The Y-coil 144 may be configured to deflect the proton beam 12 in the vertical plane. The scanning magnets 140 may be nested. For example, the X-coil 142 may be disposed within the footprint of the Y-coil 144. In some embodiments, the Y-coil 144 may be disposed within the footprint of the X-coil 142. Nesting the scanning magnets 140 reduces the total length L of the nozzle 100. In some embodiments, the scanning magnets 140 are electromagnets. In such an embodiment, the X-coil 142 and the Y-coil 144 are electrically coupled to an energy source capable of delivering electrical energy to the scanning magnets 140. The amount of electrical energy delivered to the X-coil 142 and the Y-coil 144 may be independently adjusted. Adjusting the amount of electrical energy delivered to the X- coil 142 or the Y-coil 144 increases or decreases the magnitude of the magnetic field of each coil, respectively. Accordingly, the proton beam 12 may be steered by increasing or decreasing the strength of the magnetic field of the X-coil 142 or the Y-coil 144.

[0057] The penetration depth of proton beam 12 may be controlled by increasing or decreasing the energy of the proton beam 12. More specifically, the higher the energy of the proton beam 12 the deeper the proton beam 12 may penetrate the target body 24 and the lower the energy of the proton beam 12 the more superficially the proton beam 12 may penetrate the target body 24. The energy of the proton beam 12 may be selected based on the target tissue 20. For example, treatment of prostate cancer may require a higher energy proton beam 12 than treatment of certain brain cancers. The nozzle 100 may deliver the proton beam 12 with an energy such that the Bragg peak of the protons occur within the target body 24 and the protons stop in the target tissue 20, as is typical in conventional PBS therapies. In some embodiments, the nozzle 100 may deliver the proton beam 12 with an energy for use in “pass through” treatments where energies are chosen such that the Bragg depth occurs outside of the target body 24. In embodiments, the energy of theproton beam 12 may be in the range of 20 MeV to 350 MeV, e.g., 70 MeV, 100 MeV, 150 MeV, 225 MeV, or 250 MeV.

[0058] The quadrupole 160 magnetically focuses the proton beam 12 as the proton beam 12 passes therethrough. The proton beam 12 may first be reduced by the magnetic collimation due to the spinning octupole doublet 120 and then is further reduced by the magnetic focusing of the quadrupole 160 placed at the second end of the nozzle. The magnetic focusing of the proton beam 12 may decrease the effective diameter of the proton beam 12 at delivery to the target tissue 20. The effective diameter of the proton beam 12 after magnetic focusing may be dictated by several factors including, but not limited to, the energy of the proton beam 12, the magnetic field strength of the quadrupole 160, or the length of the quadrupole 160. The quadrupole 160 may magnetically focus the proton beam 12 to form proton minibeams having a minimum effective diameter less than or equal to 5mm, e.g., 0.5, 1, 2, 3, or 4 mm. More particularly, the quadrupole 160 may focus the proton beam 12 from a proton pencil beam magnetically collimated by the octupole doublet 120 to a proton minibeam. For example, the proton beam 12 may exit the octupole doublet 120 and enter the quadrupole 160 at a first effective diameter, e.g., a pencil beam diameter, and exit the quadrupole 160 at a second effective diameter, e.g., a minibeam diameter, that is smaller than the first effective diameter. For example, at the first effective diameter the proton beam 12 may be narrow but have a diameter greater than 5 mm and at the second effective diameter the proton beam 12 may have an effective diameter less than or equal to 5 mm. In contrast to creating of minibeams by direct collimation using a physical collimator, magnetic focusing with the quadrupole 160 may reduce secondary particle production, e.g., neutron production, which may result in delivery of an unwanted dose of radiation to the target tissue 20 or healthy tissue. More particularly, because direct interception of the proton beam 12 with the walls of the quadrupole160 is relatively minimal, fewer secondaries are produced. Directly intercepting the proton beam 12 with direct mechanical collimation (e.g., passing the proton beam 12 through a relatively narrow aperture) leads to secondary particle production because of physical interactions between protons and collimator materials.

[0059] Referring to FIGS. 1, 4, and 5, in some embodiments, the quadrupole 160 may be a Halbach cylinder. The quadrupole 160 may include a plurality of magnetic segments 161 arranged in an array to create a magnetic field with four poles, as shown in FIG. 5. The magnetic segments161 may be a permanently magnetic material. The quadrupole 160 may define a quadrupoleaperture 162. The quadrupole aperture 162 may define a central quadrupole axis. The array of magnets may be arranged such that the magnetic field of the quadrupole 160 is substantially confined within the quadrupole aperture 162. The quadrupole 160 may have a high magnetic field gradient. For example, the quadrupole 160 may have a magnetic field gradient in the range of 50 T / m to 375 T / m, e.g., 250 T / m. The quadrupole 160 may have a length in the range of 20 mm to 100 mm, e.g., 50 mm, 55 mm, 60 mm, or 65 mm, etc. In particular embodiments, the quadrupole 160 may include more than one Halbach cylinder coaxially aligned with one another. Forming the quadrupole 160 with more than one Halbach cylinder can increase the effective length of the quadrupole 160 and, thus, also increase the effective lens power of the quadrupole 160. Increasing the lens power of the quadrupole 160 increases the amount that the proton beam 12 is focused. In embodiments where the quadrupole 160 is formed of more than one Halbach cylinder, each Halbach cylinder may have the same magnetic field gradient. In certain embodiments where the quadrupole 160 is formed of more than one Halbach cylinder, each Halbach cylinder may have a different magnetic field gradient. In embodiments, the amount of focusing of the proton beam 12 may be varied by swapping quadrupoles 160 of different magnetic field gradients or lengths into or out of the nozzle 100.

[0060] The quadrupole 160 may be configured to selectively spin about the central quadrupole axis and the proton beam 12 or to remain stationary when the proton beam 12 is passed through the quadrupole aperture 162. Spinning the quadrupole 160 about the proton beam 12 may create a proton minibeam with a circularly symmetric proton fluence, e.g., at the target tissue 20. In embodiments, spinning the quadrupole 160 may create a statistically identical beam phase space in both transverse planes, e.g., the horizonal plane and the vertical plane. For example, spinning the quadrupole 160 about the proton beam 12 may result in essentially identical average displacement, average divergence, displacement-divergence correlations and emittance of the proton beam 12 in the vertical and the horizontal planes. The quadrupole 160 may spin at a rate that is the same or two or more times, e.g., two, three, four, five, or more than five times faster than that of the octupole doublet 120. For example, the quadrupole 160 may spin at a rate in the range of 300 revolutions per minute (RPM) to 40,000 RPM, depending on factors including, but not limited to, nozzle operational mode and dose rate. The quadrupole 160 may spin clockwise or counterclockwise about the proton beam 12. In embodiments, the quadrupole 160 may spin the same direction as the octupole doublet 120. In other embodiments, the quadrupole 160 may spin the opposite direction as the octupole doublet 120. In certain embodiments, the quadrupole 160spins the same direction as one of the first octupole 122 or the second octupole 124, while spinning the opposite direction as the other of the first octupole 122 of the second octupole 124. In embodiments where the quadrupole 160 is held stationary and does not spin around the proton beam 12, the nozzle 100 may produce proton beams 12 having an elongated cross-sectional profile, e.g., an ovular or elliptical profile. In embodiments, nozzle 100 may produce planar proton minibeams, the planar minibeams may have an effective half-diameter at the beam waist (the location along the proton beam 12 with the minimum minor axis) less than or equal to 5 mm. The orientation of the elongated beams, including planar minibeams, may be controlled by rotating the quadrupole 160 to a different fixed position with respect to the proton beam 12. More particularly, rotating the quadrupole 160 to a different fixed position repositions the magnetic poles of the quadrupole 160 with respect to the axis of the proton beam 12. As such, the elongated profile, e.g., the effective major diameter of a planar minibeams, may be aligned with the horizontal axis, the vertical axis, or at an angle between horizontal and vertical axes, e.g., at a 45-degree angle to the horizontal or the vertical axis. For example, rotating the quadrupole 160 to a first fixed position may position the magnetic poles of the quadrupole 160 such that the proton beam 12 is focused into a vertical planar minibeam and rotating the quadrupole 160 to a second fixed position may position the magnetic poles of the quadrupole 160 such that the proton beam 12 is focused into a horizontal planar minibeam. In embodiments, the second fixed position of the quadrupole 160 may be radially offset 90 degrees from the first fixed position. In some embodiments, the rotating the quadrupole 160 to a third fixed position may position the magnetic poles of the quadrupole 160 such that the proton beam 12 is focused into a planar minibeam radially orientated at an angle between the horizonal and vertical axes. The third fixed position may be between the first fixed position and the second fixed position.

[0061] The nozzle 100 may operate in one of several modes defined by whether the octupole doublet 120 and the quadrupole 160 are positioned such that the proton beam 12 passes therethrough, as well as their rotational status (e.g., spinning or stationary). The nozzle modes allow the creation of variable sized and shaped spots from the same initial source beam, including the creation of symmetric and planar minibeams. Specifically, the nozzle 100 may have a pencil beam mode (PB mode), a reduced-diameter pencil beam mode (OD mode), a spinning reduced- diameter pencil beam mode (ODS mode), a reduced single semi-diameter mode (ODSQ mode), and a reduced diameter mode (ODSQS mode). The PB mode is comparable to a shortened conventional pencil beam nozzle. In the PB mode both the octupole doublet 120 and thequadrupole 160 may be positioned outside the path or trajectory of the proton beam 12 such that the proton beam 12 passes through only the scanning magnets 140. When the nozzle 100 is in the OD mode, the octupole doublet 120 is positioned so that the proton beam 12 passes therethrough and does not spin about the proton beam 12. In the ODS mode, the octupole doublet 120 is positioned so that the proton beam 12 passes therethrough and spins about the proton beam 12. In both the OD mode and the ODS mode the quadrupole 160 is positioned outside the path of the proton beam 12. When the nozzle 100 is operating in the OD mode or the ODS mode, the nozzle 100 may magnetically collimate the proton beam 12 to produce a pencil beam with a smaller effective diameter, and a reduced penumbra as compared to the proton beam 12 produced when the nozzle 100 is operating in the PB mode for a proton beam 12 of the same characteristics, e.g., of the same energy. When the nozzle 100 is in the ODSQ mode or the ODSQS mode the proton beam 12 passes through both the octupole doublet 120 and the quadrupole 160. In both the ODSQ mode and the ODSQS mode the octupole doublet 120 spins about the proton beam 12. In the ODSQ mode the effective diameter of the proton beam 12 is first reduced by the magnetic collimation due to the spinning octupole doublet 120 and then is further reduced by the magnetic focusing of the quadrupole 160. In the ODSQ mode the quadrupole 160 is held stationary, e.g., not spinning. In ODSQ mode, the nozzle 100 may produce proton beams 12 with an elongated transverse profile (i.e., where the effective diameter of the cross section of the beam is reduced along only one axis, e.g., an oval cross section). The elongated profile of the proton beam 12 may be oriented with the long axis aligned with the horizontal axis, the vertical axis, or at an angle to the horizontal or vertical axes, as described above. In some embodiments, the nozzle 100 may produce proton minibeams when in the ODSQ mode. Specifically, where the quadrupole 160 has a large enough magnetic lens power the elongated cross sections may become very narrow, planar profile, and thus the nozzle 100 may thus produce planar minibeams. When the nozzle 100 is in the ODSQS mode the octupole doublet 120 and the quadrupole 160 spins about the proton beam 12. In the ODSQS mode the effective diameter of the proton beam 12 is first reduced by the magnetic collimation due to the spinning octupole doublet 120 and then is further reduced by the magnetic focusing of the quadrupole 160. In embodiments where the quadrupole 160 has a large enough magnetic lens power, the nozzle 100 may produce proton minibeams in the ODSQS mode. Additionally, since the quadrupole 160 is spinning in the ODSQS mode, the proton minibeams may have a substantially circular profile, as shown in FIG. 29. In all operational modes, the pencil beams produced by the nozzle 100 may be deflected by the scanning magnets 140 to deliverenergy-dependent layers of dose to cover the target as in conventional PBS nozzle implementations.

[0062] The nozzle 100 may deliver a single spot dose distribution proton beam 12 to the target tissue 20 or may sequentially deflect many proton beams 12 using the scanning magnets and thus deliver a transverse pattern of many beam spots to the target tissue 20. Specifically, when proton minibeams are created by the nozzle 100 in the ODSQ and ODSQS modes, the proton minibeams can be deflected by the scanning magnets 140 so as to create spatially fractionated dose distributions (FIGS. 22 and 29) in the target tissue 20. For example, the nozzle 100 may deliver a spatially fractionated dose distribution using three elongate pencil beams separated by 5 millimeters to the target tissue 20 using the ODSQ mode. Where the nozzle 100 delivers proton beam 12 with a single spot dose distribution to target tissue 20, the nozzle 100 may be in any of the operational modes. For example, in embodiments, the nozzle 100 may deliver a single reduced effective diameter pencil beam to the target tissue 20 using the ODS mode. As will be appreciated from the description above, when the nozzle 100 is in the ODS mode or the ODSQS mode the nozzle 100 may produce symmetric proton fluence and symmetric transverse phase space, and when the nozzle 100 is in the ODSQ mode or the ODSQS mode the nozzle 100 may produce planar and symmetric (i.e., circular cross section) proton minibeams, respectively.

[0063] The nozzle 100 is selectively switchable between modes to deliver pencil beams with differing characteristics during the same patient treatment or radiobiological experiment. For example, the nozzle 100 may be in the PB mode, which produces proton beams 12 with the largest effective diameters, that can be used to quickly cover medial portions of a relatively large target tissue 20 with dose. When the extremities of the target tissue 20 are treated, the nozzle 100 may be switched to the ODS mode to deliver smaller effective diameter proton beams 12 to the edge of the target tissue 20 for better dose conformity or in areas near sensitive structures (e.g., optic nerve) to reduce penumbra.

[0064] The extent of beam effective diameter and penumbra reduction effected by the magnetic collimation and focusing of the proton beam 12 by the nozzle 100 may be dependent upon several factors such as, but not limited to, the magnetic field strength of the octupole doublet 120, the magnetic field gradient of the quadrupole 160, the lengths of the octupoles 122, 124 and the quadrupole 160, the length L of the nozzle 100, the distance the proton beam 12 travels from the muzzle 104 to an entrance 22 of a target body 24, the depth of the target tissue 20 within the targetbody 24, or the energy of the proton beam 12. Example embodiments illustrating possible reductions in beam effective diameter and penumbra of the nozzle 100 are described hereinbelow.

[0065] Referring to FIGS. 6 and 7, the mechanism of magnetic collimation of the proton beam 12 may be mainly attributed to tail folding in particle phase space. Tail folding reduces the spread of the proton beam 12 as it travels through the octupole doublet 120 by the non-linear bending of the low fluence margins or “tails” of the proton beam 12 in phase space. The tails are bent toward the origin of the horizontal axis in phase space (i.e., toward the center of the proton beam 12) with symmetry about the origin. The non-linear nature of the octupole magnetic field of the octupole doublet 120 means the tails of the proton beam 12 are preferentially folded compared to the center of the proton beam 12 which contains the greatest density of particles. Thus, the beam effective diameter is reduced by this process of “magnetic collimation. For example, FIG. 6 shows the proton beam 12 in the nozzle 100 operating in ODS mode represented in phase space upstream of the spinning octupole doublet 120, and FIG. 7 shows the proton beam 12 represented in phase space downstream of the spinning octupole doublet 120. Comparing FIGS. 6 and 7 shows that a sample portion of the peripheral tails 14 of the proton beam 12 may be bent or folded toward the center of the proton beam 12 after the after the proton beam 12 has passed through the spinning octupole doublet 120.

[0066] Referring to FIGS. 9 and 10, for reference, where the nozzle 100 is operating in PB mode, pencil beam scanning systems without octupole shaping may not exhibit tail folding. For example, FIG. 9 shows a phase space representation of a proton beam 12 that is equivalent to the proton beam 12 represented in FIG. 6. However, the proton beam of FIG. 9 is not shaped by the octupole doublet 120. FIG. 10 shows the proton beam 12 of FIG. 9 represented in phase space at the muzzle 104 of the nozzle 100. Comparing FIGS. 9 and 10 shows that the proton beam 12 transported through the nozzle 100 has not experienced a non-linear distortion in phase space because it has not undergone tail folding.

[0067] A comparison of FIGS. 8 and 10 shows that at the muzzle 104 of the nozzle 100 (FIG. 1), on the average, the protons are clustered around the origin of the horizontal phase space axis in FIG. 8, compared to FIG.10, indicating that the average displacement of the proton beam 12 is smaller in the magnetically collimated beam of FIGS. 6-8 versus the non-magnetically collimated beam of FIGS. 9 and 10. The magnetic collimation of the proton beam 12 in FIGS. 6-8 leads to a smaller effective diameter beam (e.g., FWHM) at the muzzle 104 compared to the proton beam 12of FIGS. 9-10, as confirmed by FIG 18. In some embodiments, the quadrupole 160 placed at the muzzle 104 of the nozzle 100, upstream from the entrance 22, may additionally reduce the beam effective diameter as the proton beam 12 passes therethrough by magnetically focusing the proton beam 12. For example, in ODSQS mode the spinning quadrupole 160 may additionally focus the proton beam 12, and the nozzle 100 may form symmetric minibeams.

[0068] Referring to FIGS. 1, 11, and 12, the robotic arm 180 positions the quadrupole 160 with respect to the proton beam 12. Specifically, the robotic arm 180 coaxially aligns the quadrupole aperture 162 of the quadrupole 160 with the proton beam 12 downstream of the scanning magnets 140 just before the muzzle 104. The quadrupole 160 is mounted on an end of the robotic arm 180. The quadrupole 160 may be moved based on the deflection of the proton beam 12 by the scanning magnets 140. The robotic arm 180 may have up to six degrees of freedom, e.g., a six-axis robot, to manipulate and position the quadrupole 160. The robotic arm 180 includes a head 182 defining a passage 184 through the head 182. The quadrupole 160 is mounted to the robotic arm 180 such that the quadrupole aperture 162 coaxially aligns with the passage 184. The robotic arm 180 may be in signal communication with the control system for the scanning magnets 140. The robotic arm 180 receives signal communications from the scanning magnets 140 control system indicating the deflection and trajectory of the proton beam 12. The robotic arm 180 may position the head 182 and, thus, the quadrupole 160, based on signals received from the scanning magnets 140 control system. In embodiments, the robotic arm 180 may position the quadrupole 160 dynamically, e.g., without a break or with a partial break in the proton beam 12. In some embodiments, the robotic arm 180 positions the quadrupole 160 iteratively or by stepped movement. For example, the quadrupole 160 may be positioned at a first position, the proton beam 12 may be delivered through the quadrupole 160 at the first position to dose a first portion of the target tissue 20, the quadrupole 160 may be repositioned at a second position, and the proton beam 12 may be delivered through the quadrupole 160 at the second position to dose a second portion of the target tissue 20.

[0069] In some embodiments, the robotic arm 180 may position the octupole doublet 120 with respect to the proton beam 12. For example, the robotic arm 180 may position the octupole doublet 120 outside the path of the proton beam 12 to switch the nozzle 100 to the PB mode. In some embodiments, the nozzle 100 includes a second robotic arm 180 to position the octupole doublet

[0070] Referring to FIG. 13, a method 1000 of forming proton beams in accordance with embodiments, of the present disclosure is described with reference to the nozzle 100 of FIGS. 1- 12.

[0071] The desired operational mode for the nozzle 100 is selected and the nozzle 100 is switched to the selected operational mode (Step 1100). The nozzle 100 may be in any of the PB mode, the OD mode, the ODS mode, the ODSQ mode, or the ODSQS mode. The nozzle 100 may switch between modes automatically, e.g., by the robotic arm 180 or another automated control systems. In some embodiments, the nozzle 100 may be manually switched between modes by a technician. The mode of the nozzle 100 may be selected based on several parameters including, but not limited to, location of the target tissue 20 within the target body 24, the size and shape of the target tissue 20, the energy of the proton beam 12, the desired extent of collimation by the octupole doublet 120, the desired extent of the focusing by the quadrupole 160, whether a spatially fractionated dose distribution is to be delivered, or whether an elongated or circular dose distribution is to be delivered. For example, as described above, the nozzle 100 may be in the PB mode with both the octupole double 120 and the quadrupole 160 outside the path of the proton beam 12. In the PB mode the nozzle 100 produces proton beams 12 with the largest effective diameters to quickly cover medial portions of a relatively large target tissue 20 with dose. When the extremities of the target tissue 20 are treated, the nozzle 100 may be switched to the ODS mode to deliver smaller effective diameter proton beams 12 to the edge of the target tissue 20 for better dose conformity or in areas near sensitive structures (e.g., optic nerve) to reduce penumbra.

[0072] The octupole doublet 120 may be positioned in the path of the proton beam 12 (Steps 1200). Positioning the octupole doublet 120 in the path of the proton beam 12 may switch the nozzle 100 to one of the OD mode, the ODS mode, the ODSQ mode, or the ODSQS mode. The octupole doublet 120 may be positioned in the path of the proton beam 12 such that the proton beam 12 passes therethrough for magnetic collimation of the proton beam 12.

[0073] The octupole double 120 may be set spinning about the proton beam 12 (Step 1300). Spinning the octupole doublet 120 may be included in switching the nozzle 100 to one of the ODS mode, the ODSQ mode, or the ODSQS mode. The octupole doublet 120 may spin at a rate in the range of 150 revolutions per minute (RPM) to 40,000 RPM. The rate the octupole doublet 120 spins may be determined by the dose rate delivered to the target tissue 20. For example, where conventional dose rates are used the octupole doublet 120 may spin at a rate in a range 150 RPMto 3,000 RPM. Where ultra-high (e.g., those dose rates used in FLASH therapy) are used the octupole doublet 120 may spin at a rate in the range of 3,000 RPM to 40,000 RPM. More particularly, in some embodiments, the octupole doublet 120 may spin at 1,500 RPM for operation in the ODS mode and with conventional dose rates, and may spin at 15,000 RPM in the ODS mode with ultra-high dose rates. The octupole doublet 120 may spin clockwise or counterclockwise about the proton beam 12. The first octupole 122 and the second octupole 124 may spin together at the same rate and in the same direction. In some embodiments, the first octupole 122 and the second octupole 124 may spin independently of each other. For example, the first octupole 122 may spin at a first rate in a clockwise direction and the second octupole 124 may spin at a second rate in a counterclockwise direction. Spinning the octupole doublet 120 may create a magnetically collimated proton beam 12 of reduced effective diameter with circularly symmetric proton fluence. In embodiments, spinning the octupole doublet 120 creates a statistically identical beam phase space in both transverse planes, e.g., the horizonal plane and the vertical plane, of the proton beam 12. Accordingly, spinning the octupole doublet 120 may create proton beams 12 with a reduced effective diameter and symmetric beam spots at the target tissue 20 in ODS mode, and upstream of the quadrupole 160 in ODSQ and ODSQS modes.

[0074] The quadrupole 160 may be positioned such that the proton beam 12 passes through the quadrupole 160 (Step 1400). Positioning the quadmpole 160 may be included in switching the nozzle 100 to the ODSQ mode or the ODSQS mode. For example, the quadrupole 160 may be positioned such that the quadrupole aperture 162 coaxially aligns with the proton beam 12. The robotic arm 180 may position the quadrupole 160 with respect to the proton beam 12. In embodiments, the robotic arm 180 may position the quadrupole 160 dynamically, e.g., without a break in the proton beam 12. In some embodiments, the robotic arm 180 positions the quadrupole 160 iteratively. For example, the quadrupole 160 may be positioned at a first position, the proton beam 12 may be delivered through the quadrupole 160 at the first position, the quadrupole 160 may be repositioned at a second position, and the proton beam 12 may be delivered through the quadrupole 160 at the second position. In the ODSQ mode the quadrupole 160 does not spin about the proton minibeam 12. As described above, in the ODSQ mode, the nozzle 100 may produce proton beams 12 having an elongated profile. For large enough quadrupole magnetic lens powers the elongated cross sections become very narrow and thus the nozzle 100 may form planar minibeams. The elongated profile of the planar minibeams may be oriented with the long axis aligned with the horizontal axis, the vertical axis, or at an angle to the horizontal or vertical axes,depending on the orientation of the magnetic poles of the quadrupole 160 with respect to the proton beam 12.

[0075] In some embodiments, positioning the quadrupole 160 includes positioning the quadrupole 160 outside the path of the proton beam 12 such that the proton beam 12 does not pass through the quadrupole 160. For example, when the nozzle 100 is switched to the PB mode, the OD mode, or the ODS mode, the quadrupole 160 may be positioned outside the path of the proton beam 12. In such an embodiment, the proton beam 12 is only magnetically collimated by the octupole doublet 120 and is not focused by the quadrupole 160.

[0076] The quadrupole 160 may be set spinning about the proton beam 12 as the proton beam 12 passes through the quadrupole 160 when the ODSQS mode is selected and the nozzle 100 switched thereto (Step 1500). In ODSQS mode, the beam effective diameter is first reduced by magnetic collimation due to the spinning octupole doublet 120 and then is further reduced by the magnetic focusing of the quadrupole 160. Spinning the quadrupole 160 may produce beams of circular cross section and circularly symmetric fluence. For large enough quadrupole magnetic lens powers, the nozzle 100 may produce minibeams. Additionally, when the nozzle 100 is in the ODSQS mode, the minibeams may have a circular profile. The quadrupole 160 may spin at a rate in the range of 300 revolutions per minute (RPM) to 40,000 RPM, e g., 1,000 RPM for conventional dose rates and 10,000 RPM for ultra-high dose rates. In some embodiments, the quadrupole 160 may spin at a rate of 3,000 RPM for operation in ODSQS mode and conventional dose rates, and may spin at 6,000 RPM in ODSQS mode with ultra-high dose rates. The quadrupole 160 may spin clockwise or counterclockwise about the proton beam 12. In embodiments, the quadrupole 160 may spin the same direction as the octupole doublet 120. In other embodiments, the quadrupole 160 may spin the opposite direction as the octupole doublet 120.

[0077] The proton beam 12 is delivered or passed through the nozzle 100 in the selected mode (Step 1600). The proton beam 12 enters the nozzle 100 at the breech 102 and exits through the muzzle 104. The proton beam 12 may pass through the octupole doublet 120, the quadrupole 160, or both the octupole doublet 120 and the quadrupole 160. As the proton beam 12 passes through the nozzle 100, the proton beam 12 is deflected by the scanning magnets 140 to steer or aim the proton beam 12 at the target tissue 20 or a portion of the target tissue 20 (Step 1700). The proton beam 12 may be deflected after passing through the spinning octupole doublet 120. As describedabove, the X-coil 142 may be configured to deflect the proton beam 12 in the horizontal plane and the Y-coil 144 may be configured to deflect proton beam 12 in the vertical plane. The extent the proton beam 12 may be deflected by the scanning magnets 140 may be dictated by the magnitude of the magnetic field produced by the X-coil 142 and the Y-coil 144. In embodiments, where the scanning magnets 140 are electromagnets, the magnitude and direction of the magnetic field may be altered by the amount of electrical energy delivered to the X-coil 142 or the Y-coil 144 to increase or decrease the magnetic field of each coil.

[0078] In embodiments, the method 1000 may be repeated as necessary to treat the target tissue 20. The nozzle 100 may remain in the same operational mode for the entire duration of a treatment. For example, in some embodiments, the nozzle 100 may remain in the PB mode, the OD mode, the ODS mode, the ODSQ mode, or the ODSQS mode for the entirety of the treatment duration. In some embodiments, the nozzle 100 may switch between any of the modes throughout the duration of a treatment. For example, the nozzle 100 may be in the OD mode for approximately half of a treatment and may be switched to the ODSQS mode for the remainder of the treatment. More particularly, the nozzle 100 may in the OD mode to treat the medial portions of the target tissue 20 and may be switched to the ODSQS mode to treat the periphery of the target tissue 20.

[0079] Although the method steps are described in a specific order, it should be understood that other steps may be performed in between described steps, described steps may be adjusted so that they occur at slightly different times, described or sub-steps may occur simultaneously or overlap in time, or the described steps may occur in any order unless otherwise specified.

[0080] Referring to FIGS. 1 and 14-36, hereinbelow several example embodiments in accordance with the present disclosure are described. The underlying data representing the example embodiments is generated by Monte Carlo simulations. The described example embodiments are not limiting and are only illustrative examples.

[0081] In an example embodiment, and with particular reference to FIGS. 1 and 14 - 17, the nozzle 100 operating in the reduced pencil beam mode (ODS mode) may reduce the effective diameter and penumbra of the proton beam 12, compared to the PB mode. More particularly, in an example embodiment where the overall length L of the nozzle 100 is 96 cm, the nominal energy of the Gaussian proton source beam 12 is 100 MeV, G = 3mm and o’ = 3 mrad, the magnetic field gradient, diameter and length of the octupoles 122, 124 of the octupole doublet 120 is 6.94xl06T / m3, 12 mm, and 50 mm, respectively; the nozzle 100 is filled with helium; the depth T of the target tissue 20 is 76 mm, and the target medium is water, e.g., a test phantom placed adjacent to the muzzle 104, the nozzle 100 may reduce beam effective diameter and penumbra. In FIG. 14 dose distributions produced by the nozzle 100 operating in the ODS mode (“ODS”, top in FIG. 14) and the PB mode (“PB”, bottom in FIG. 14) are compared as the respective beams exit the muzzle 104 of the nozzle 100. The ODS beam effective diameter and penumbra reductions are reflected in the decrease of dose FWHM by 2.9 mm or 29%, a FW20M decrease of 3.7 mm or 25%, and dose penumbra reduction of 1.1 mm or 23%, compared to the PB beam. In addition, FIGS. 15, 16 and 17 respectively compare dose FWHM, FW20M and penumbra throughout the path of the proton beam 12 in the test target body 24 from the entrance 22 to the target tissue 20, or Bragg depth, in the same example embodiment. The data shown in FIG. 15 reveals the proton beam 12 created by the nozzle 100 in the ODS mode has a FWHM as much as 2.9 mm or 29% less, and at least 2.3 mm or 20% less, than that of proton beam 12 created by the nozzle 100 in the PB mode at each water equivalent depth (WED). FIG. 16 shows FW20M for the ODS beam is as much as 3.7 mm or 25% less, and always at least 3 mm or 18% less, than that of the PB beam. FIG. 17 shows that compared to the PB beam, the penumbra for the ODS beam is as much as 1.0 mm or 23% less, and always more than 0.8 mm or 15% less at each WED.

[0082] In another example embodiment, and with particular reference to FIGS. 1 and 18-21, the nozzle 100 operating in the reduced pencil beam mode (ODS mode) may reduce the effective diameter and penumbra of the proton beam 12, compared to the PB mode. More particularly, in an example embodiment where the overall length L of the nozzle 100 is 96 cm, the nominal energy of the Gaussian proton source beam 12 is 150 MeV, G = 3mm and o’ = 2 mrad, the magnetic field gradient, diameter and length of the octupoles 122, 124 of the octupole doublet 120 is 6.94xl06T / m3, 12 mm, and 50 mm, respectively; the nozzle 100 is filled with helium; the depth T of the target tissue 20 is 156 mm, and the target medium is water, e.g., a test phantom placed adjacent to the muzzle 104, the nozzle 100 may reduce beam effective diameter and penumbra. In FIG. 18 the dose distributions produced by the nozzle 100 operating in the ODS mode (“ODS”, top in FIG. 18) and the PB mode (“PB”, bottom in FIG. 18) are compared as the respective beams exit the muzzle 104 of the nozzle 100. The ODS beam effective diameter and penumbra reductions are reflected in the decrease of dose FWHM by 2.8 mm or 34%, a FW20M decrease of 4.3 mm or 34%, and dose penumbra reduction of 1.4 mm or 34%, compared to the PB beam. In addition, FIGS. 19, 20 and 21 respectively compare dose FWHM, FW20M and penumbra throughout thepath of the proton beam 12 in the test target body 24 from the entrance 22 to the target tissue 20, or Bragg depth, in the same example embodiment. The data shown in FIG. 19 reveals the proton beam 12 created by the nozzle 100 in ODS mode has a FWHM as much as 3.0 mm or 34% less, and at least 1.6 mm or 13% less, than that of the proton beam 12 created by the nozzle 100 in the PB mode at each WED. FIG. 20 shows FW20M for the ODS beam is as much as 4.3 mm or 34% less, and always at least 2.2 mm or 12% less, than that of the PB. FIG. 21 shows that compared to the PB beam, the penumbra for the ODS beam is as much as 1.5 mm or 36% less, and always more than 0.8 mm or 13% less at each WED.

[0083] Referring to FIGS. 22-28, in another example embodiment, nozzle 100 may be operated in the ODSQ mode and may produce a treatment beam composed of several planar minibeams with a spatially fractionated dose distribution having a quasi-homogeneous dose at a target depth T. The nozzle 100 scans proton beams 12 and focuses them with the quadrupole 160, such that after they exit the muzzle 104 of the nozzle 100, they enter the target body 24 with a beamlet separation S of 8 mm. In this example, the nominal energy of the Gaussian source beam 12 is 150 MeV, o = 3mm and o’ = 2 mrad, the magnetic field gradient, diameter, length and separation of the octupoles 122, 124 of the octupole doublet 120 is 6.94xl06T / m3, 12 mm, 50 mm, and 10 mm, respectively; the gradient, diameter and length of the quadrupole 160 is 275 T / m, and 12 mm, 60 mm, respectively; the nozzle 100 is filled with helium. As shown in FIGS. 23 - 27, the composite dose distributions were determined in both the horizontal and vertical planes at discrete locations along the path of the minibeams between the entrance 22 of a target body 24 composed of water and the target tissue 20 at a depth T from the entrance 22. In this example, the deflection of the proton beams 12 by the scanning magnets 140 was not directly simulated. Instead, the spatially fractionated dose distribution was modeled by laterally shifting the dose distribution of a single proton minibeam 12 in the target body 24 to represent each beamlet, and all shifted distributions were summed to obtain the composite dose distribution. The distance D between the target body 24 and the muzzle 104 is 9 cm. As indicated by FIGS. 22 to 28, and by the horizontal FWHM (hFWHM) and the peak to valley dose ratio (PVDR) shown in Table 1 below, when the proton beam 12 is near the entrance 22 the beamlets are clearly distinct from one another as shown by the highly heterogenous composite dose distribution consisting of narrow beamlets with relatively high dose peaks separated by relatively low dose valleys. More specifically, the hFWHM is as low as 0.8 mm and the hFWHM < 2.4 mm for the first 50 mm WED of the proton path in the target body 24, and the PVDR is as high as 381 and the PVDR > 40 of the first 50 mm of WED in thetarget body 24, where the entrance 22 of the target body 24 is 1.05 m downstream from the breech 102, and a distance D of 9 cm downstream of the muzzle 104. As the beamlets travel away from the entrance 22, each beamlet diverges or spreads eventually contributing to the resulting quasi- homogeneous combined dose distribution at or near the target depth T. This behavior is indicated by the increasing hFWHM and decreasing PVDR shown in Table 1 below which lists the hFWHM of a single (isolated) beamlet and the PVDR for the composite dose distribution. More specifically, at the target depth T of 156 mm the hFWHM of each isolated beamlet is 10.2 mm, over 2 mm larger than the separation S of 8 mm, meaning that individual dose contributions of adjacent beamlets overlap. In addition, the PVDR has approached 1 indicating that protons increasingly fill and deposit dose in the valleys between the beamlets eventually depositing a substantially uniform dose at the target depth T. This can also be seen in the nearly common Bragg peaks of the peak and valley depth dose distributions of FIG. 28. The configuration of the nozzle 100 depends on several parameters, and with other parameter values and / or optimizations (e.g., smaller initial source beam 12 divergence, and / or larger quadrupole 160 lens power), lower hFWHM and higher PVDR may be achieved (e.g., it is estimated that minimum hFWHM could be < 0.5 mm and maximum PVDR > 1000).

[0084] Referring to FIGS. 29-36, in another example embodiment, nozzle 100 may be operated in the ODSQS mode and may produce a treatment beam composed of several symmetric minibeams with a spatially fractionated dose distribution having a quasi-homogeneous dose at a target depth T. The nozzle 100 scans proton beams 12 and focuses them with the quadrupole 160, such that after they exit the muzzle 104 of the nozzle 100 they enter the target body 24 with a beamlet separation S of 17.0 mm. In this example, the nominal energy of the Gaussian source beam 12 is 225 MeV, a = 3mm and o’ = 1 mrad, the magnetic field gradient, diameter, length and separation of the octupoles 122, 124 of the octupole doublet 120 is 6.94xl06T / m3, 12 mm, 50 mm,and 10 mm, respectively; the gradient, diameter and length of the quadrupole 160 is 275 T / m, and 12 mm, 55 mm, respectively; the nozzle 100 is filled with helium. As shown in FIGS. 30 - 35, the composite dose distributions were determined in both the horizontal and vertical planes at discrete locations along the path of the minibeams between the entrance 22 of a target body 24 composed of water and the target tissue 20 at a depth T from the entrance 22. In this example, the deflection of the proton beams 12 by the scanning magnets was not directly simulated. Instead, the spatially fractionated dose distribution was modeled by laterally shifting the dose distribution of a single proton minibeam 12 in the target body 24 to represent each beamlet, and all shifted distributions were summed to obtain the composite dose distribution. The distance D between the target body 24 and the muzzle 104 is 12.5 cm. As indicated by FIGS. 30 - 36, and by the FWHM and the PVDR shown in Table 2 below, when the proton beam 12 is near the entrance 22 the beamlets are clearly distinct from one another as shown by the highly heterogenous composite dose distribution consisting of narrow beamlets with relatively high dose peaks separated by relatively low dose valleys. More specifically, the FWHM is as low as 1.0 mm and the FWHM < 3.5 mm for the first 50 mm WED of the proton path in the target body 24, and the PVDR is as high as 164 and the PVDR > 30 of the first 50 mm WED of the target body 24, where the entrance 22 of the target body 24 is approximately 1.1 m downstream from the breech 102, and a distance D of 12.5 cm downstream of the muzzle 104. As the beamlets travel away from the entrance 22, each beamlet diverges or spreads eventually contributing to the resulting quasi-homogeneous combined dose distribution at or near the target depth T. This behavior is indicated by the increasing FWHM and decreasing PVDR shown in Table 2 which lists the FWHM of a single (isolated) beamlet and the PVDR for the composite dose distribution. More specifically, at the target depth T of 315 mm the FWHM of each isolated beamlet is 20.1 mm, over 3 mm larger than the separation S of 17.0 mm, meaning that individual dose contributions of adjacent beamlets overlap. In addition, the PVDR has approached 1 indicating that protons increasingly fill and deposit dose in the valleys between the beamlets eventually depositing a substantially uniform dose at the target depth T. This can also be seen in the nearly common Bragg peaks of the peak and valley depth dose distributions of FIG. 36. The configuration of the nozzle 100 depends on several parameters, and with other parameter values and / or optimizations (e.g., smaller initial source beam 12 divergence, and / or larger quadrupole 160 lens power), lower hFWHM and higher PVDR may be achieved (e.g., it is estimated that minimum hFWHM could be < 0.8 mm and maximum PVDR > 500).

[0085] While several embodiments of the disclosure have been shown in the drawings, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Any combination of the above embodiments is also envisioned and is within the scope of the appended claims. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope of the claims appended hereto.

Claims

What is Claimed:

1. A nozzle for proton beam scanning capable of forming proton minibeams, the nozzle comprising: an octupole doublet that is spinnable about an octupole central axis, the octupole doublet comprising: a first octupole defining a first central aperture; and a second octupole defining a second central aperture, the first central aperture and the second central aperture coaxially aligned to define the octupole central axis, the second octupole rotatable about the octupole central axis and translatable along the octupole central axis with respect to the first octupole; and a quadrupole defining a quadrupole aperture, the quadrupoles spinnable about a quadrupole central axis.

2. The nozzle according to claim 1, wherein the second octupole is rotated with respect to the first octupole such that the magnetic poles of the second octupole are radially offset from the magnetic poles of the first octupole in a range of 1 degree to 90 degrees.

3. The nozzle according to claim 1 , wherein the first octupole and the second octupole are spaced apart such that an octupole gap is defined therebetween and translating the second octupole with respect to the first octupole a first direction increases the octupole gap and translating the second octupole a second direction opposite the first direction decreases the octupole gap.

4. The nozzle according to claim 1, wherein the first octupole and the second octupole have a magnetic field gradient in a range of l .OxlO6T / m3to l.OxlO8T / m3.

5. The nozzle according to claim 4, wherein the first octupole and the second octupole have different magnetic field gradients.

6. The nozzle according to claim 4, wherein the first octupole, the second octupole, and the quadrupole each have a length in a range of 20 mm to 150 mm.

7. The nozzle according to claim 1, wherein the quadrupole has a magnetic field gradient in a range of 50 T / m to 375 T / m.

8. The nozzle according to claim 1, wherein the octupole doublet spins about the octupole central axis at a rate in a range of 150 RPM to 40,000 RPM.

9. The nozzle according to claim 8, wherein the quadrupole spins about the quadrupole central axis at a rate that is equal to or up to five times faster than the rate the octupole doublet spins about the octupole central axis.

10. The nozzle according to claim 1, wherein the first octupole and the second octupole are permanent magnets.

11. The nozzle according to claim 10, wherein the quadrupole is a permanent magnet.

12. The nozzle according to claim 11, wherein the first octupole, the second octupole, and the quadrupole each comprise a plurality of magnetic segments arranged in an array such that a magnetic field of the first octupole, a magnetic field of the second octupole, and a magnetic field of the quadrupole is substantially contained within a respective one of the first central aperture, the second central aperture, or the quadrupole aperture.

13. The nozzle according to claim 12, where the first octupole, the second octupole, and the quadrupole are Halbach cylinders.

14. The nozzle according to claim 1, wherein the octupole doublet is positioned at a first end of the nozzle and the quadrupole is positioned at a second end of the nozzle opposite the first end.

15. The nozzle according to claim 14, wherein the nozzle has a total length, between the first end and the second end, less than or equal to 1.75 meters.

16. The nozzle according to claim 14, further comprising scanning magnets that are positioned between the octupole doublet and the quadrupole.

17. The nozzle according to claim 16, wherein the scanning magnets includes an X-coil and a Y- coil, the X-coil and the Y-coil nested within each other.

18. A nozzle for proton beam scanning capable of forming proton minibeams, the nozzle comprising: an octupole doublet configured to selectively spin about a proton beam, the octupole configured to magnetically collimate the proton beam; and a quadrupole configured to selectively spin about the proton beam, the quadrupole configured to magnetically focus the proton beam.

19. The nozzle according to claim 18, wherein spinning the octupole doublet about the proton beam magnetically collimates the proton beam such that the proton beam has a profile of a first effective diameter when the proton beam enters the octupole doublet and a second effective diameter that is less than the first effective diameter when the proton beam exits the octupole doublet.

20. The nozzle according to claim 19, wherein spinning the quadrupole about the proton beam magnetically focuses the proton beam such that the proton beam has a circular profile of a third effective diameter of the proton beam when the proton beam exits the quadrupole that is smaller than the second effective diameter.

21. The nozzle according to claim 20, wherein the quadrupole is configured to magnetically focus the proton beam into a proton minibeam, the proton minibeam having an effective diameter with a full width at half maximum that is less than or equal to 5 millimeters.

22. The nozzle according to claim 18, wherein the quadrupole is configured to magnetically focus the proton beam such that the proton beam has an elongated profile when the quadrupole is stationary with respect to the proton beam.

23. The nozzle according to claim 22, wherein the quadrupole is configured to magnetically focus the proton beam into a planar proton minibeam, the planar proton minibeam having an effective half-diameter with a full width at half maximum that is less than or equal to 5 millimeters.

24. The nozzle according to claim 18, further comprising scanning magnets configured to steer the proton beam toward a portion of a target tissue by deflecting the proton beam.

25. The nozzle according to claim 24, further comprising a robotic arm configured to position the quadrupole with respect to the proton beam such that the proton beam passes through the quadrupole after the proton beam is deflected by the scanning magnets.

26. The nozzle according to claim 18, wherein the octupole doublet comprises: a first octupole; and a second octupole rotatable and translatable with respect to the first octupole.

27. A system for proton beam scanning, the system comprising: a proton beam source; and a nozzle according to claim 18 operably coupled to the proton beam source.

28. A method of shaping a proton beam, the method comprising: selecting an operational mode for a nozzle from one of a PB mode, an OD mode, an ODS mode, an ODSQ mode, or an ODSQS mode, the nozzle configured to shape the proton beam; passing the proton beam through the nozzle; and deflecting the proton beam with scanning magnets of the nozzle, the scanning magnets configured to steer the proton beam at a portion of a target tissue.

29. The method according to claim 28, wherein selecting the OD mode, the ODS mode, the ODSQ mode, or the ODSQS mode includes positioning an octupole doublet of the nozzle with respect to the proton beam such that the proton beam passes therethrough as the proton beam passes through the nozzle to magnetically collimate the proton beam.

30. The method according to claim 28, wherein the selecting the ODS mode, the ODSQ mode, or the ODSQS mode includes positioning an octupole doublet of the nozzle with respect to the proton beam such that the proton beam passes therethrough as the proton beam passes through the nozzle and spinning the octupole doublet about the proton beam as the proton beam passes therethrough to magnetically collimate the proton beam.

31. The method according to claim 30, wherein spinning the octupole doublet includes spinning a first octupole of the octupole doublet and a second octupole of the octupole doublet the same speed and in the same direction.

32. The method according to claim 28, wherein selecting the ODSQ mode or the ODSQS mode includes: positioning an octupole doublet of the nozzle with respect to the proton beam such that the proton beam passes therethrough as the proton beam passes through the nozzle and spinning the octupole doublet about the proton beam as the proton beam passes therethrough to magnetically collimate the proton beam; and positioning a quadrupole of the nozzle with respect to the proton beam such that the proton beam passes therethrough as the proton beam passes through the nozzle to magnetically focus the proton beam.

33. The method according to claim 32, wherein positioning the quadrupole includes aligning the quadrupole with the proton beam such that the proton beam passes through the quadrupole after the proton beam is deflected by the scanning magnets.

34. The method according to claim 32, wherein selecting the ODSQS mode includes spinning the quadrupole about the proton beam as the proton beam passes therethrough.

35. The method according to claim 34, wherein spinning the quadrupole includes spinning the quadrupole at a speed that is equal to or up to five times faster than the octupole doublet.

6. The method according to claim 28, wherein selecting the PB mode includes positioning an octupole doublet and a quadrupole of the nozzle with respect to the proton beam such that the proton beam does not pass through the octupole doublet or the quadrupole.

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