Combined magnetic resonance imaging and positron emission tomography apparatus

Abstract

The invention concerns a combined magnetic resonance imaging and positron emission tomography apparatus (1) comprising: a magnetic resonance imaging machine (2), adapted to provide a total-body anatomical image of a patient undergoing diagnostic testing; a positron emission tomography machine (3), adapted to provide a total-body metabolic image of said patient undergoing diagnostic testing; at least one sliding table (4), adapted to accommodate the patient undergoing diagnostic testing by means of said machines (2, 3); a control console (5), operatively associated with said machines (2, 3) and with said sliding table (4), wherein the machines (2, 3) are configured to cooperate reciprocally to generate total-body diagnostic images obtained with the acquisition, reconstruction and analysis of PET metabolic images integrated with MRI attenuation maps, thus allowing total-body MRI-PET diagnostic images to be obtained deriving from the superimposition of metabolic and anatomical images of the patient under examination.

Description

[0001] COMBINED MAGNETIC RESONANCE IMAGING AND POSITRON EMISSION TOMOGRAPHY APPARATUS

[0002] Technical field of application

[0003] The invention concerns the technical sector of medical diagnostic imaging apparatus.

[0004] More specifically the invention is relative to a combined magnetic imaging and positron emission tomography apparatus.

[0005] In the description below, the term total-body will refer to radiological investigations designed to highlight the condition of internal organs and / or tissues of the torso, neck, head or limbs of a patient under examination, machines for performing said radiological investigations, and anatomical and functional images generated by said machines.

[0006] Prior art

[0007] As known, PET (Positron Emission Tomography) is a nuclear medicine methodology that uses beta-emitting radiopharmaceuticals to generate metabolic images of internal organs and / or tissues of the patient under examination for diagnostic purposes; CAT (Computerized Axial Tomography) is a nuclear medicine methodology that uses ionizing radiations to generate anatomical images of internal organs and / or skeletal structures of the patient under examination for diagnostic purposes; MRI (Magnetic Resonance Imaging), or also more simply MR, is a diagnostic methodology that uses non-harmful magnetic fields to generate anatomical images of internal organs and / or skeletal structures of specific anatomical regions of the patient under examination.

[0008] As known, in the current forms, said methodologies cannot be used effectively in total-body screening of patients who are ostensibly healthy, young or generally fragile.

[0009] This is due to the ionizing radiations used in CAT and the radiopharmaceuticals used in PET, the dosages of which far exceed the directive proposed by the ICRP (International Commission on Radiological Protection, 1990 60 and subsequent revisions), and also due to the execution times and radiological reporting procedures required by MR, which are incompatible with screening activities.

[0010] Furthermore, MR is currently used to perform mainly regional examinations and to provide consequent diagnostic images acquired with a plurality of contrast media. The difficulty of interpreting said diagnostic images, combined with the need to cover the entire body of the patient under examination, results in an important criticality: totalbody MR can be performed only at specialist radiological centres and in general with high costs for each single MR performed.

[0011] Lastly, even if acquisition of the diagnostic images provided by MR were limited only to DWI (Diffusion Weighted Imaging), which is the most effective for the detection of tumours, it would nevertheless be necessary to modify the operating configurations of the current MR scanners to reduce image acquisition times and therefore make the scanners functional to performance of the above-mentioned screening activities.

[0012] In short, the ionizing radiations necessary for the current CAT scans, the doses of radiopharmaceuticals necessary in the current PET scans and the current lengthy performance times of MR scans make these investigation procedures unsuitable for total-body diagnostic use aimed at early diagnosis of tumoral and / or degenerative pathologies in patients who are ostensibly healthy, young or generally fragile.

[0013] The commonest form of PET scanner has a longitudinal FoV (Field of View) of 16-26 cm, depending on the specific model, and is usually combined with CAT machine for the generation of attenuation maps used for correcting the PET images and processing anatomy reference images used to interpret the PET images.

[0014] A clinical study carried out in 2016 (Quinn: 2016) showed that the radiation dose actually absorbed by a patient undergoing a TAC-PET scan, with approximately 90 cm coverage, is due both to the activity of the CAT (mean effective dose 5.0 ± 1.0 mSv for the generation of attenuation maps, and 15.4 ±5.0 mSv for the processing of anatomy reference images) and to the activity of the radiopharmaceutical of the PET (9.0 ± 1 .6 mSv with administration of 450 ± 32 MBq of 18FDG).

[0015] The ultra-sensitive PET scanners with long longitudinal FoV (50 cm, 150 cm, 200 cm), which are still not widespread, for example the Explorer scanner (Moses: 2016; Badawi: 2019; Nadig: 2022), have shown efficiency between 30 and 100 times superior to the traditional PET scanners.

[0016] The results of the Explorer scanner, published by numerous scientific journals, show that it is possible to produce total-body PET scanners and consequently obtain diagnostic images with extremely low ionizing radiation doses and detect for a longer time the radiopharmaceuticals administered to the patients under examination.

[0017] The high efficiency of the Explorer scanner also shows the ability of the ultra-sensitive PET with long longitudinal FoV to generate totalbody diagnostic images with extremely rapid acquisition times, of 1 -2 minutes, compared to the traditional PET scanners with short FoV, which have acquisition times of at least 20 minutes, split into consecutive acquisition blocks.

[0018] The Explorer scanner is also normally combined with a CAT machine, used in the generation of attenuation maps, useful for reconstruction of the PET images, and anatomy reference images, useful for interpretation of the PET images.

[0019] The drawbacks of the Explorer scanner are its high production costs, at least 10 times higher than the costs of traditional PET scanners, and the persistence of high ionizing radiation doses generated by the CAT machine normally combined with it.

[0020] Recent clinical studies (Freitag: 2017; Keereman: 2010; Han: 2020; Gong: 2018; Chen: 2021 ; Marshall: 2013) have shown that the acquisition of MR images by means of the DIXON® technique, with ultra-short echo times and other variations, allows the processing of attenuation maps similar to those provided by the traditional CAT machines.

[0021] The acquisition of MR images via the DIXON® technique has shown a good anatomical resolution and a reduced acquisition time, and allows the position of the bones to be estimated, thus permitting correction by attenuation of the PET images during their reconstruction.

[0022] The combination of MR scanners and PET scanners is currently limited since the traditional PET scanners with longitudinal FoV of 20 cm require total-body PET images to be acquired by means of a series of successive stations with a reduced sensitivity to radiopharmaceuticals compared to the ultra-sensitive PET scanners with long FoV.

[0023] Presentation of the invention

[0024] The invention aims to overcome the above-mentioned criticalities by proposing a combined magnetic imaging and positron emission tomography apparatus able to perform total-body MR-PET examinations with reduced times and low radiopharmaceutical doses.

[0025] A further object of the invention is to invert the current diagnostic imaging model, in which CAT / MR anatomical images are a support for PET metabolic images, by proposing an apparatus able to generate PET metabolic images, with long Fov, supported by MR anatomical images, with rapid acquisition, thus optimizing the quality of the diagnostic images obtained without altering the modes of interpretation thereof by the specialists in the sector.

[0026] This and other objects of the invention are achieved by a combined magnetic imaging and positron emission tomography apparatus according to the independent claim 1 .

[0027] Further characteristics of the apparatus subject of the invention are described in the dependent claims.

[0028] A combined magnetic imaging and positron emission tomography apparatus, according to the invention, offers the following important advantages:

[0029] - it allows total-body, specific and sensitive, non-invasive MR- PET diagnostic imaging, with reduced times and reduced radiopharmaceutical dosages;

[0030] - by reducing the relative execution times and relative radiopharmaceutical dosages, the above-mentioned MR-PET total-body diagnostic imaging examinations can be performed on young or fragile asymptomatic patients, normally excluded from said examinations.

[0031] Further advantages of a combined magnetic imaging and positron emission tomography apparatus according to the invention are:

[0032] - early diagnosis of asymptomatic tumoral or degenerative pathologies, originating in any part of the body, in the context of screening of ostensibly healthy patients;

[0033] - early diagnosis both of the most frequent tumours (lung, breast, colorectal, prostate, etc.) and the rarer ones (pancreas, pleura, etc.), which can generally be diagnosed only much later;

[0034] - early diagnosis of neurodegenerative pathologies (Alzheimer, etc.), identifying abnormal levels of inflammatory processes in ostensibly healthy patients;

[0035] - evaluation of the distribution of radiopharmaceuticals with reduced affinity or with more limited target density than those currently in use;

[0036] - use of theranostics via the radiopharmaceuticals, namely integrating specific diagnostic systems with specific therapeutic interventions;

[0037] - use of PET to perform diagnostic examinations that are repeatable within a time interval, a practice that is currently impossible, so as to evaluate at an early stage the effectiveness of therapies implemented and consequently the need for possible adjustments;

[0038] - follow-up diagnostic examinations are performed more rapidly by re-using previous MR anatomical images, when possible and if unchanged over time, so that only the PET metabolic images have to be acquired new, since they tend to evolve earlier than previous MR anatomical images.

[0039] Brief description of the drawings

[0040] Further characteristics and advantages of the invention will be more evident from the more detailed description provided below, with the help of the drawings, which show preferred embodiments thereof, illustrated by way of non-limiting example, in which:

[0041] - fig. 1 shows, in longitudinal plane section and in functional layout, a possible operating configuration and relative operating logic of a combined magnetic imaging and positron emission tomography apparatus, according to the invention, in which the sliding table of one of the machines, lying on a plane at a greater distance from the point of view of the observer, is hidden by the sliding table of the other machine, lying on a plane at a lesser distance from the point of view of the above- mentioned observer;

[0042] - fig. 2-3 show, in longitudinal plane section, further possible operating configurations of said apparatus.

[0043] Detailed disclosure of the invention

[0044] With reference to the details of the figures, a combined magnetic imaging and positron emission tomography apparatus 1 , according to the invention, essentially comprises:

[0045] - a magnetic resonance machine 2, adapted to provide a totalbody anatomical image of a patient undergoing diagnostic examination;

[0046] - a positron emission tomography machine 3, adapted to provide a total-body metabolic image of said patient undergoing diagnostic examination;

[0047] - at least one sliding table 4, adapted to accommodate the patient undergoing diagnostic examination by means of the machines 2, 3;

[0048] - a control console 5, operatively associated with said machines 2, 3 and with said sliding table 4.

[0049] In particular, the machines 2, 3 reciprocally cooperate to generate total-body diagnostic images obtained with the acquisition, reconstruction and analysis of PET metabolic images integrated with MR attenuation maps, thus allowing total-body MR-PET diagnostic images to be obtained deriving from superimposition of the metabolic image and the anatomical image of the patient under examination.

[0050] Said apparatus 1 comprises operating configurations in which:

[0051] - the magnetic resonance machine 2 and the positron emission tomography machine 3 are arranged beside each other, parallel, and are each associated with a respective sliding table 4, as shown in fig. 1 , or with one single sliding table 4, shared by both;

[0052] - the magnetic resonance machine 2 and the positron emission tomography machine 3 are arranged one after the other, linearly, and are associated with one single sliding table 4, shared by both, as shown in fig. 2;

[0053] - the magnetic resonance machine 2 and the positron emission tomography machine 3 are integrated in each other and are associated with one single sliding table 4, shared by both, as shown in fig. 3.

[0054] The magnetic resonance machine 2 essentially comprises:

[0055] - a subsystem 6 adapted to generate magnetic fields;

[0056] - a subsystem 7 adapted to generate gradients able to induce variations in said magnetic fields;

[0057] - a subsystem 8 adapted to receive and transmit radiofrequency signals generated by the variations induced in said magnetic fields by said gradients. The magnetic resonance machine 2 further comprises:

[0058] - DIXON® software S1 , for the acquisition of total-body images, with ultra-short echo time, for the generation of attenuation maps used to correct the metabolic images acquired by the positron emission tomography machine 3.

[0059] Said software S1 can be designed to acquire, alternatively to said DIXON® images, images from DWI (Diffusion Weighted Imaging), images from transverse weighted imaging (T2), ultra-short echo time images or images from other contrast methods.

[0060] The positron emission tomography machine 3 essentially comprises:

[0061] - a longitudinal FoV 9, with length equal to at least 100 cm, for capturing a large part of the photons generated by the decay process of the radiopharmaceutical administered to the patient undergoing diagnostic examination.

[0062] The positron emission tomography machine 3 further comprises:

[0063] - software S2, for the acquisition and reconstruction of PET metabolic images optimized with the integration of attenuation maps provided by the software S1 of the magnetic resonance machine 2;

[0064] - software S3 for the quantitative analysis of said PET metabolic images according to the SUV (Standardized Uptake Value) technique.

[0065] The software S2, S3 can be chosen for example from the following: - Q. Clear®, software developed by GE Healthcare®, which offers advanced algorithms for reconstruction of the PET images, including the possibility of displaying the distribution of the radioactive tracers according to density;

[0066] - Syngo.via®, software developed by Piattaforma Siemens Healthineers® to allow the processing and display of multimodal images, including PET. It offers instruments for quantifying and displaying the density of the radioactive tracers;

[0067] - OsiriX MD®, open-source software widely used for display and analysis of medical images, including PET. It supports plugins and instruments for displaying the density;

[0068] - PMOD®, software for quantitative analysis of PET images, which allows the density of the radioactive tracers to be measured in regions of specific interest;

[0069] - MIM®, software for quantitative analysis of PET images developed by the University of Brussels, which offers instruments for measuring the density and evaluating the therapeutic response.

[0070] Obviously, said software S2, S3 can be chosen from among other software functionally similar to the ones cited, and can also be developed ex-novo, in order to cooperate synergically with the large number of PET sensors present in the positron emission tomography machines 3, of the type with long longitudinal FoV 9.

[0071] Said software S1 and S2, S3 can include advanced processing functions, also comprising artificial intelligence, which facilitate the speed of reconstruction of the anatomical images acquired by the magnetic resonance machine 2 and of the metabolic images acquired by the positron emission tomography machine 3 and at the same time ensure the maximum possible quality.

[0072] Furthermore, said software S1 and S2, S3 can reside in and be run locally by the magnetic resonance machine 2 and by the positron emission tomography machine 3 or reside, and be run, in dedicated clouds accessible in remote mode from said machines 2, 3.

[0073] The sliding table 4 comprises:

[0074] - movement means 10, adapted to determine bidirectional sliding thereof inside the magnetic resonance machine 2 and the positron emission tomography machine 3, as a function of the different operating configurations of the machines;

[0075] - calibration means 11 , adapted to determine correlation of the position of the patient undergoing diagnostic examination in the anatomical and metabolic images respectively acquired by said machines 2, 3.

[0076] The control console 5 comprises:

[0077] - interface means 12, of wired or wireless type, adapted to allow interconnection with the magnetic resonance machine 2, with the positron emission tomography machine 3 and with the sliding table 4 associated therewith;

[0078] - means 13, 14 for display and filing of the MR-PET images processed by said machines 2, 3 by means of the respective software S1 and S2, S3. Detailed operation of the invention is described below.

[0079] The patient undergoing diagnostic examination is administered a radiopharmaceutical functional to the performance of PET scans such as, for example, fluorodeoxyglucose (FDG).

[0080] Advantageously, thanks to the sensitivity of the long FoV 9 of the positron emission tomography machine 3, the dosage of said radiopharmaceutical can be reduced down to 10 MBq, for patients with average weight, therefore reaching an effective dosage of approximately 0.2 mSv, similar to that of a mammography.

[0081] The patient undergoing diagnostic examination lies on a sliding table 4, also included in the apparatus 1 .

[0082] The sliding table 4 comprises movement means 10, adapted to determine the bidirectional sliding thereof inside the magnetic resonance machine 2 and the positron emission tomography machine 3, according to the different operating configurations of the apparatus 1.

[0083] In fact, in the case of arrangement of the magnetic resonance machine 2 and the positron emission tomography machine 3 beside each other, one patient at a time can undergo diagnostic testing, by means of a single sliding table 4 shared between said machines.

[0084] The same occurs in the case of reciprocal integration of the magnetic resonance machine 2 and the positron emission tomography machine 3.

[0085] However, in the case of parallel arrangement of the magnetic resonance machine 2 and the positron emission tomography machine 3, two patients can be examined at the same time, by means of respective sliding tables 4 associated with said machines.

[0086] The sliding table 4 further comprises calibration means 11 , adapted to determine correlation of the position of the patient undergoing diagnostic examination in the anatomical and metabolic images acquired by the magnetic resonance machine 2 and by the positron emission tomography machine 3 respectively.

[0087] The apparatus 1 is started and controlled by the control console 5 for the entire duration of the diagnostic examination.

[0088] By means of the software S1 , the magnetic resonance machine 2 generates a total-body anatomical image of the patient under examination in an overall time of approximately 3 minutes.

[0089] In particular, said software S1 generates a sequence of DIXON® images, optimized for repeated coverage and spatial resolution of successive stations, adapted to determine coverage of the entire torso of the patient under examination. The DIXON® images, as reported in the scientific literature, are particularly suitable for estimating the position of the bones and consequently they facilitate the generation of attenuation maps useful for reconstruction of the PET images (Freitag: 2017). The DIXON® images also offer good anatomical representation and can be used as a support in the display of said PET images. Other methods of acquisition and generation of attenuation maps (Keereman, Han: 2020; Gong: 2018; Chen: 2021 ; Marshall: 2013) can be adopted as an alternative to said DIXON® images. By means of the long FoV 9 and the software S2, S3, the positron emission tomography machine 3 generates a total-body metabolic image of the patient undergoing examination in a total time of approximately 2 minutes.

[0090] In particular, said software S2 generates a PET image obtained from recording of the radioactive decay of the radiopharmaceutical administered to the patient undergoing examination and integrated with the attenuation map provided by the magnetic resonance machine 2 for the same patient, while said software S3 performs a quantitative analysis of said PET image according to the SUV (Standardized Uptake Value) technique, thus allowing an MR-PET image to be obtained deriving from superimposition of the metabolic image and anatomical image of the patient undergoing diagnostic examination, which can be reported by radiology technicians according to the usual methods of interpretation.

[0091] The MR-PET image obtained can therefore be reported immediately, via the display means 14 included in the control console 5 of the apparatus 1 , of display or projector type or similar, or kept for subsequent reporting, via the filing means 15 which can be a hard disk, NAS (Network Attached Storage), PACS (Picture Archiving and Communication System) or similar, also comprised in said control console 5.

[0092] The description refers to a combined magnetic resonance and positron emission tomography apparatus 1 , the operation of which entails firstly the intervention of the magnetic resonance machine 2 and subsequently the positron emission tomography machine 3; however, the same result, namely obtaining of the desired MR-PET diagnostic images, can be obtained by inverting the intervention order of said machines 2, 3.

[0093] The combined magnetic resonance and positron emission tomography apparatus 1 , subject of the invention, makes it possible to perform total-body diagnostic imaging examinations by using known and widely tested machines 2, 3, in synergy via operating configurations and methods that are currently non-existent.

[0094] Said apparatus 1 advantageously allows the generation of totalbody magnetic resonance images, associated with positron emission tomography images, also of total-body type, in an overall time of approximately 5 minutes, limiting the use of ionizing radiations for generation of the attenuation maps and reducing the dosages of radiopharmaceuticals administered to the patients undergoing examination.

[0095] The reduced exposure to ionizing radiations advantageously allows diagnostic imaging examinations to be performed on patients at risk but ostensibly healthy, or on fragile patients, for whom the current radiological risks are not justified.

[0096] Furthermore, the high execution speed also advantageously allows diagnostic imaging examinations to be carried out on children or the elderly, who are known to manifest discomfort when undergoing lengthy treatments.

[0097] Said apparatus 1 furthermore allows, with undoubted advantage, tumour masses and / or extremely slight metabolic alterations to be detected, thus allowing very early diagnosis of pathologies which are currently impossible to detect at the initial stage, and to perform diagnostic imaging examinations aimed at monitoring the effectiveness of treatments in progress.

[0098] Lastly, said apparatus 1 allows, with further undoubted advantage, diagnostic imaging examinations to be performed with a much lower cost per single examination than the current average cost.

Claims

CLAIMS1. A combined magnetic resonance imaging and positron emission tomography apparatus (1 ) characterized in that it comprises:- a magnetic resonance imaging machine (2), adapted to provide a total-body anatomic image of a patient undergoing diagnostic testing;- a positron emission tomography machine (3), adapted to provide a total-body metabolic image of said patient undergoing diagnostic testing;- at least one sliding table (4), adapted to accommodate the patient undergoing diagnostic testing by means of said machines (2, 3);- a control console (5), operatively associated with said machines (2, 3) and with said sliding table (4), wherein the machines (2, 3) cooperate reciprocally to generate total-body diagnostic images obtained with the acquisition, reconstruction and analysis of PET metabolic images integrated with MRI attenuation maps, thus allowing total-body MRI-PET diagnostic images to be obtained deriving from the superimposition of metabolic and anatomic images of the patient under examination.

2. The apparatus (1 ) according to claim 1 , characterized in that the magnetic resonance imaging machine (2) comprises at least:- a subsystem (6) adapted to generate magnetic fields;- a subsystem (7) adapted to generate gradients able to inducevariations in said magnetic fields;- a subsystem (8) adapted to receive and transmit radiofrequency signals generated by the variations induced in said magnetic fields by said gradients.

3. The apparatus (1 ) according to claim 1 , characterized in that the magnetic resonance imaging machine (2) comprises DIXON software (S1) for the acquisition of total-body images, with ultrashort echo time, for the generation of attenuation maps used to correct the metabolic images acquired by the positron emission tomography machine (3).

4. The apparatus (1 ) according to claim 1 , characterized in that the positron emission tomography machine (3) comprises a longitudinal FoV (9), having length equal to at least 100 cm, for capturing a large part of the photons generated by the decay process of a radiopharmaceutical administered to the patient undergoing diagnostic testing.

5. The apparatus (1 ) according to claims 1 and 3, characterized in that the positron emission tomography machine (3) comprises:- a software (S2), for the acquisition and reconstruction of PET metabolic images integrated with attenuation maps provided by the software (S1) of the magnetic resonance imaging machine (2);- software (S3) for the quantitative analysis of said PET metabolic images according to the SUV (Standardized Uptake Value) technique.

6. The apparatus (1 ) according to claim 5, characterized in that the software (S2, S3) is chosen from known commercial or open- source software, or is chosen from software functionally similar, or is chosen from software developed ex-novo in order to be suitable for use with positron emission tomography machines (3).

7. The apparatus (1 ) according to claim 1 , characterized in that the magnetic resonance imaging machine (2) and the positron emission tomography machine (3) are arranged beside each other, parallel, and are each associated with a respective sliding table (4), or with a single sliding table (4) shared by both.

8. The apparatus (1 ) according to claim 1 , characterized in that the magnetic resonance imaging machine (2) and the positron emission tomography machine (3) are arranged one after the other, linearly, and are associated with a single sliding table (4), shared by both.

9. The apparatus (1 ) according to claim 1 , characterized in that the magnetic resonance imaging machine (2) and the positron emission tomography machine (3) are integrated in each other and are associated with a single sliding table (4), shared by both.

10. The apparatus (1 ) according to claim 1 , characterized in that the sliding table (4) comprises:- movement means (10), adapted to determine bidirectional sliding inside the magnetic resonance imaging machine (2) and / or the positron emission tomography machine (3),according to the different operating configurations of said machines;- calibration means (11 ), adapted to determine correlation of the position of the patient undergoing diagnostic testing in the anatomic and metabolic images acquired respectively by said machines (2, 3).

11. The apparatus (1 ) according to claim 1 , characterized in that the control console (5) comprises:- interface means (12), of wired or wireless type, adapted to allow interconnection with the magnetic resonance imaging machine (2), with the positron emission tomography machine (3) and with at least one sliding table (4) associated therewith;- display and filing means (13, 14) for displaying and filing the MRI-PET images processed by the machines (2, 3) by means of the respective software (S1 , and S2, S3).

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