Port placement guide based on an inflated patient torso model and normalized surgical targets

Abstract

The invention name of the present disclosure is "Port placement guide based on aerated patient torso model and normalized surgical targets." A method for determining surgical port placement for minimally invasive surgical procedures. Based on received measurements, an instance of a parameterized torso model is determined, the parameterized torso model defining an outer surface and an internal viscera surface, each having a dome shape that accounts for aerated effects. A normalized surgical target location in the parameterized torso model is determined in response to an identification of a surgical procedure, and is mapped to an unnormalized surgical target location. Based on characteristics of a surgical tool and based on the unnormalized surgical target location, an allowed port location on the instance of the parameterized torso model is computed. Other aspects are described and claimed.

Description

[0001] Cross Reference To

[0002] This application claims the benefit of the earlier filing date of U.S. Non-Provisional Application 16 / 894,625, filed June 5, 2020, which is incorporated by reference in its entirety. TECHNICAL FIELD

[0003] Various aspects of the present disclosure relate to the design of surgical tools for minimally invasive surgery (MIS) and robotically assisted MIS. BACKGROUND

[0004] Minimally invasive surgery (MIS) such as laparoscopic surgery uses techniques intended to reduce tissue damage during a surgical procedure. A laparoscopic procedure typically requires forming several small incisions in the patient (e.g., in the abdomen), and then inserting several surgical tools (such as an endoscope, a blade, graspers, and needles) into the patient through these small incisions. Gas is injected into the abdomen, which inflates the abdomen, thereby providing more space around the tips of the tools, making it easier for the surgeon to see (via the endoscope) and manipulate tissue at the surgical site. MIS can be performed more quickly and with less surgeon fatigue using a surgical robotic system in which surgical tools are operatively attached to the distal ends of robotic arms, and a control system actuates the arms and their attached tools. When a surgeon manipulates a handheld user input device (UID), the tip of the tool will mimic its position and orientation movements. The surgical robotic system can have multiple surgical arms, with one or more surgical arms having attached endoscopes, and other surgical arms having attached surgical instruments for performing certain surgical actions.

[0005] Manufacturers of surgical tools designed for MIS can be required to specify a list of anatomical structures in a reference patient torso model that can be reached by a given surgical tool design. This is a challenging problem. A subjective solution to this problem is to develop a virtual reality model of the anatomical structures (in the reference patient torso model), and then perform a virtual reality simulation that shows whether a given surgical tool can reach a given portion of the anatomical structures. However, with this solution, the manufacturer of the surgical tool cannot specify requirements for using the tool, or what situations the surgical tool is expected to work (pass) and what situations the tool is expected to not work (fail). SUMMARY

[0006] Requirements for use of MIS tools should be specified in the form of a geometric model of the human torso that takes into account the effect of inflation on the torso. One aspect of the present disclosure is here a set of criteria for making a pass / fail determination on whether a given surgical tool design for MIS can reach a reference patient's anatomy. This determination in turn provides guidance on placement of surgical ports (into which the surgical tool will be inserted on the reference patient) to perform a minimally invasive surgical procedure, such as an endoscopic procedure (e.g., where the tool is a laparoscopic hand-held surgical instrument) and a robotically-assisted endoscopic procedure (e.g., where the tool is a wristed surgical instrument or endoscope attached to a surgical robot arm with a certain number of links and motorized joints).

[0007] An elliptic-cylinder-based parametric geometric patient torso model is described. In one aspect, the model is instantiated for a number of reference patient dimensions based on two or more of the following parameters: height, waist circumference, body mass index (BMI), and gender of the reference patient, thereby producing a parametric model for patients of arbitrary dimensions. The BMI can be computed based on the height and weight of the patient.

[0008] For a given surgical procedure's specified activities, surgical target locations in the normalized coordinates of the model are determined, and these locations are then mapped to corresponding (un-normalized) locations in the instantiated reference patient dimensions.

[0009] Based on the tool reach of a given surgical tool and on the surgical target locations inside the torso model, surgical port locations in the normalized coordinates on the entry surface of the model are determined. These surgical port locations are then mapped to corresponding (un-normalized) surgical port locations in each of the instantiated reference patient dimensions. An accessibility map can be generated for each of the reference patient dimensions, showing the locations on the entry surface of the reference patient dimension where a surgical port can be placed (through which the particular surgical tool can reach the relevant surgical target location).

[0010] Another application of the parametric geometric patient torso model is a process that takes as input a given surgical target location in the torso model and provides as its output a set of allowed surgical port locations and required reach of a surgical tool (to be used in a minimally invasive surgical procedure such as an endoscopic or laparoscopic procedure and a robotically-assisted endoscopic / laparoscopic procedure).

[0011] Another application of the model is a process that outputs an objective assessment of the functionality of a surgical robot, such as the reach of a surgical tool and the available clearance around the tool or around a target surgical location.

[0012] The foregoing summary does not constitute an exhaustive list of all aspects of this disclosure. It is contemplated that this disclosure encompasses all systems and methods that can be implemented by all suitable combinations of the aspects outlined above, as well as those disclosed in the detailed description below and specifically pointed out in the claims section. Such combinations may have specific advantages not specifically described in the foregoing summary. Attached Figure Description

[0013] Several aspects of this disclosure are illustrated herein by way of example and not by way of limitation in the accompanying drawings, wherein similar reference numerals indicate similar elements. It should be noted that references to “a” or “an” aspect in this disclosure do not necessarily refer to the same aspect, and they refer to at least one. Furthermore, for the sake of brevity and to reduce the total number of drawings, a given drawing may be used to illustrate features of more than one aspect of this disclosure, and not all elements in the drawing may be necessary for a given aspect.

[0014] Figure 1 The reference anatomical axes and planes (or reference coordinate systems) used in the parametric geometric patient torso model are shown.

[0015] Figure 2 The human torso is shown as an elliptical cylinder with magnified features.

[0016] Figure 3 This is a table summarizing an example of parametric elliptic cylinders.

[0017] Figure 4 The visceral control surface and abdominal wall are shown, which can also be modeled using elliptical cylinders as part of a parametric geometric patient model.

[0018] Figure 5 The reshaping and stretching phases of the abdominal cross-section during inflation are shown.

[0019] Figure 6 A graph illustrating inflation-induced abdominal expansion is shown.

[0020] Figures 7A-7D These are four exemplary patient reference dimensions for a parametric geometric patient torso model.

[0021] Figure 8 An example of normalized coordinates on an elliptical cylinder is shown.

[0022] Figure 9 The process used to derive the surgical target location from the reference sample is visualized.

[0023] Figures 10A-10D Surgical goals including active pathways are shown in four exemplary patient sizes.

[0024] Figure 11 An exemplary reachability map related to an elliptic cylinder is shown. DETAILED DESCRIPTION

[0025] Several aspects of the disclosure are explained with reference to the drawings. Whenever the shapes, relative positions and other aspects of the parts described are not explicitly defined, the scope of the invention is not limited only to the parts shown, which are shown for illustrative purposes only. In addition, although many details are set forth, it is to be understood that some aspects of the disclosure can be practiced without these details. In other instances, well-known structures and techniques have not been shown in detail so as not to obscure the understanding of this description.

[0026] Torso Model

[0027] Parametric geometric patient torso models are described that can be scaled according to multiple dimensions or parameters, such as standard anthropometric measurements of height, waist circumference, body mass index (BMI), and two or more of gender. Several instances of models representing human torsos of different sizes (with reference to patient dimensions) are generated, aiming to cover a significant portion of a patient population. The model predicts or outputs internal and external surfaces (e.g., as wireframes), and takes into account the effect of inflation on the torso.

[0028] The model will be illustrated using the reference anatomical axes and planes shown in Figure 1 In this model, as seen in the example of Figure 2 , the cross-section of the torso is abstracted to an ellipse, and the shape of the torso is represented by the surface of a generalized elliptic cylinder (or simply, elliptic cylinder), which has several ellipses as cross-sections in transverse planes (planes perpendicular to the X axis). The surface is symmetric about the mid-sagittal plane (XZ plane). Each cross-section can have an offset with respect to the dorsal plane (XY plane).

[0029] In one aspect, the elliptic cylinder surface is controlled or defined by four ellipse cross-sections, as shown in Figure 2 , namely the cross-sections at the hip plane, waist plane, chest plane, and upper chest plane. Due to this simplification, the elliptic cylinder can be described by a relatively small number of parameters, such as the five parameters shown in Figure 3 However, for a finer granularity, the elliptic cylinder surface can be defined by more than four ellipse cross-sections and / or by more than five parameters.

[0030] Here, in one aspect of the disclosure, one or more of the elliptical cross sections that make up the torso are composed of two half-ellipses (a ventral half-ellipse joined to a dorsal half-ellipse), which can have different radii of curvature. Such cross sections are also referred to as a “duet” of two half-ellipses. In one aspect, at least one such cross-sectional duet passes through the waist plane, which better models the effect of inflation compared to a regular ellipse. The cross sections at the ends of the torso, i.e., the upper chest plane and the hip plane, can be regular ellipses. In another aspect, all four cross sections are duets. Refer to Figure 3 for a table as an example, where each cross section in this case is a duet. A duet can be characterized by the five parameters shown: radial dimension along the medio-lateral (Y) direction, two radial dimensions along the dorso-ventral (Z) direction (one ventral and one dorsal), position along the caudo-cranial (X) axis, and dorsal offset. The dorsal offset can be used to account for the curvature of the spine (when the torso is in a supine position as shown). Refer to Figure 3 for a table to note the following:

[0031] - The horizontal is defined as the caudo-cranial (X) position relative to the origin of the model (the hip level is zero);

[0032] - The upper chest width (lateral, excluding arms) is assumed to be the same as the width of the chest;

[0033] - The lateral radius is half the width, and the dorsal radius is half the depth;

[0034] - The ventral radius of the hip, chest, and upper chest is the same as the dorsal radius; and

[0035] - The ventral radius at the waist is used to account for inflation (this will be described in detail below), but in the non-inflated state, it is the same as the dorsal radius.

[0036] The elliptical cylinder can be used not only to approximate the external shape of the torso (also referred to herein as the outer surface), but also to approximate the surface of deeper anatomical structures, such as the internal viscera cavity (also referred to herein as the internal viscera surface). In other words, in addition to the outer surface, the model can also define an internal viscera surface (also referred to as an internal viscera control surface), as seen in Figure 4 . The internal viscera surface can be based on, for example, as seen in the table Figure 3The outer surface (in the non-inflated state) is summarized in the middle and the internal organ control surface is inferred based on the abdominal wall thickness. It can be conjectured that the latter is uniform across the torso (based on research reports on subcutaneous fat and muscle thickness), except near the breasts and the "love handles", which can be a function of the body mass index (BMI) expected. In other words, the abdominal wall thickness can be computed as a function of the input BMI. Such an abstraction of the internal organ control surface enables mapping of the respective organ positions between models of different sizes and obesity levels (this mapping is described below).

[0037] Inflation of the Abdomen

[0038] One element of laparoscopic surgery is the creation of an abdominal working space by pumping a gas (e.g., carbon dioxide) into the peritoneal cavity. This creation of an abdominal working space is referred to as inflation. When the abdomen is inflated, three phases can be observed: reshaping, stretching, and pressurization - see the graph in Figure 5 Reshaping occurs when the intra-abdominal pressure (IAP) is relatively small, although this changes the waist plane cross-section from a fairly wide elliptical shape to a more circular cross-sectional shape. The second phase of inflation (stretching) involves higher IAP values and an increase in the abdominal cross-section, while maintaining a close-to-unit aspect ratio (quasi-circular shape). After some stretching, the stiffness of the abdominal wall transitions to a significantly higher value, such that a small increase in the abdominal volume requires a very large increase in pressure.

[0039] The abdominal compliance is highly variable across the patient population (as shown by the two sample curves in Figure 5 ), and is particularly difficult to predict in obese patients. Having said that, it is worth noting that the inflation behavior described herein includes IAP levels that are not nominally expected during a surgical procedure. During a normal laparoscopy (inflation pressure is limited to around 15 mm Hg), the abdomen either does not enter, or hardly begins, the transition to the third phase. Therefore, based on the general behavior observed in the range of interest for IAP, it can be assumed that the typical inflation during a laparoscopic surgery is in the stretching phase (typically not entering the pressurization phase).

[0040] As seen in Figure 5 , during the reshaping phase, the lateral dimension of the abdominal cross-section decreases, but then increases (change reversal) during the stretching phase. At the same time, the dorso-ventral dimension increases during both phases. In view of this effect, an aspect of the present disclosure here is to configure the model such that it makes the additional assumption that the net change in the lateral dimension of the waist plane cross-section is close to zero, while the main effect of inflation tends to increase its dorso-ventral dimension. This captures the general behavior of abdominal inflation while minimizing the information content.

[0041] Abdominal inflation does not significantly affect the cross-section of the torso at the level of the hips or at the level of the chest. This is due in part to the bony constraints. On the caudal side, the abdomen is constrained by the pelvis, while on the cranial side it is constrained by the ribcage. On the dorsal side, the entire torso is constrained by the spine. This means that the volumetric effect of inflation is primarily manifested as a change in the cross-sectional shape in the abdominal region of the waist, which is consistent with the behavior of the model described herein. The effects outlined herein can be observed in the domed shape of the inflated abdomen.

[0042] More generally, in one aspect of the disclosure, herein, the effect of inflation on the torso ellipsoid is achieved in the model by increasing the abdominal radius of the waist plane ellipse, while the other control ellipses (hips, chest, and upper chest) remain unchanged relative to the non-inflated state. More specifically, a distention factor, fdistention, is determined, which can be used to calculate the supine abdominal height (SAH) at inflation based on the SAH at deflation using the following relationship:

[0043] SAHinsufflated = fdistention - SAHdeflated

[0044] As Figure 6 illustrated, several distention factors were evaluated and plotted against BMI (specifically, points to the right of BMI = 32). The trend of this data shows that the distention factor decreases as the BMI of the obese patient increases. A potential reason for this is that a relatively uniform inflation pressure (approximately 15 mm Hg) results in a smaller relative deformation of the abdomen when the abdominal wall mass is higher. In one aspect, the model disclosed herein uses a quadratic curve to predict the distention factor as a function of BMI, as illustrated by the red curve in Figure 6 The distention factor can thus be stored as a variable in a computer-readable medium that is a function of the body mass index (BMI).

[0045] In one aspect, the parameters of the torso ellipsoid, such as the five parameters illustrated in the example above Figure 3 , can be instantiated for a relatively small number of different sizes that are expected to cover a large population of humans adequately. Based on an analysis of anthropometric indicators of height and obesity (the latter expressed in terms of waist circumference) for a given male and female population, as illustrated in Figures 7A-7D , four "patient reference sizes" were selected. A patient reference size is a torso model that is selected to represent a statistically significant set of actual torso sizes. Note that more than four patient reference sizes can be determined for a finer granularity. More generally, the model can be composed of two or more patient reference sizes.

[0046] Normalized Cylindrical Coordinates

[0047] One aspect of the parametric geometric patient model is how it can be used to map a point of a surgical target location, such as an ellipse within a "nominal" torso model, to an equivalent point in a parametric geometric reference patient dimension (torso model of arbitrary dimension). This can be achieved through the use of normalized cylindrical coordinates defined as follows.

[0048] Given a torso model surface S with the following properties: symmetric with respect to the mid-sagittal plane (XZ plane) and cross-sections along the transverse plane (parallel to the YZ plane) are closed convex curves (such as an elliptic duality), then a point P can be located with respect to the center of the cross-section with coordinates {L, Θ, R} as follows (see also Figure 8 ) :

[0049] L: normalized (dimensionless) distance along the X-axis (longitudinal direction of the torso model) with a range of and a key value of L = 0 at the hip plane and a key value of L = 1 at the upper chest plane (suprasternal level);

[0050] R: normalized (dimensionless) distance from the center of the cross-section (transverse plane) to the point P, where the normalization is with respect to the distance along R to the control surface, with a range of R > 0 and a key value of 0 < R < 1 inside the control surface, a key value of R = 1 at the control surface, and a key value of R > 1 outside the control surface; and

[0051] Theta (Θ): angle between the +Z-axis and the R vector (in the cross-section or transverse plane), where theta (Θ) is positive if P is on the right side of the patient and negative if P is on the left side of the patient, and with a range of -180° < theta (Θ) < 180°, with a key value of theta (Θ) = 0 at the mid-sagittal plane.

[0052] Normalized Surgical Target

[0053] In one aspect of the disclosure, surgical target locations in the parametric geometric patient model (representative of specific surgical procedures, such as gastrectomy, gastric bypass, and cholecystectomy, to name a few) are given here in normalized coordinates, where these coordinates are then mapped by a processor to the coordinates of the "corresponding" target locations in a torso model of a specific dimension patient. In other words, the same surgical target location (e.g., as defined above) given by a set of normalized cylindrical coordinates can be mapped to a varying, corresponding, and un-normalized target location in a patient model of different dimensions. The normalized coordinates are with respect to a torso model reference coordinate system (e.g., Figure 1 ) and a torso model reference surface (e.g., Figure 2) to express. This mapping process (normalization to un-normalization) relies on the patient surface defined by the model and discussed above, e.g., the inflated state outer surface and the inflated state inner organ surface. With reference to Figure 1 The reference coordinate system of the torso model can be defined as follows:

[0054] Origin, intersection of the hip plane, the dorsal plane and the median sagittal plane;

[0055] X-axis, along the caudo-cranial axis, positive in the cranial direction;

[0056] Z-axis, along the dorso-ventral axis, positive in the ventral direction; and

[0057] Y-axis, along the lateral axis, positive towards the right side of the patient,

[0058] and wherein Figure 4 depicts the inner organ surface in the non-inflated state.

[0059] The surgical target locations are normalized with respect to the best-fit inner organ surface (as described above). Furthermore, the surgical target locations do not necessarily correspond to precise anatomical locations in the model, as the surgeon can apply reasonable clinical judgment to determine "generic" target locations. Figure 9 The process for deriving surgical target locations from a reference sample, which is normalized with respect to the best-fit inner organ surface from the same model, is visualized. The following table gives an exemplary data structure for a number of normalized surgical targets, wherein each row specifies a target point expressed in normalized coordinates {L, Theta, R}, which describes a location of interest in a given surgical procedure:

[0060]

[0061] Using the methods described previously, a given set of normalized surgical targets is then mapped to four reference patient sizes - see the example of four patient sizes of FIG. 10. Thus, for a particular type of minimally invasive surgical procedure and a given set of normalized target locations that need to be reached in such surgical procedure, a respective set of target locations in each of a number (in this case, four) of patient sizes is computed. The corresponding set of target locations (in a particular reference patient size) can then be used together with the location of the entry port on that particular reference patient size and a given surgical tool geometry to determine in a pass / fail manner whether the given surgical tool geometry reaches the target surgical locations.

[0062] Port Placement

[0063] Once it is known where in the torso model a surgical tool needs to reach, as computed using the normalized surgical target positions above, one or more entry ports need to be described, or more precisely, the location of the ports in terms of the normalized coordinates {L, 0, R} as defined above, which will allow the surgical tool (when inserted in the port) to reach the normalized surgical target positions. Note that here R refers to the port location and is located on an entry surface, which can be the outer surface, the inner viscera surface, or somewhere in between (within the abdominal wall). The reachable and non-reachable regions on the entry surface are referred to as the reachability map here.

[0064] It should also be noted that a given port location can apply to more than one patient reference size among the several available patient reference sizes.

[0065] The following criteria enable to determine a port location that is consistent with the geometric constraints, while taking into account the specific surgical procedure (and its associated surgical target positions), the different patient sizes, and of course the constrained tool length. The criteria are related to the reachability and collision avoidance. A reference port location (expressed in the normalized coordinates as defined above) is described, which can be used as a guide when selecting a port location for a patient of different size. The criteria rely on a torso model reference coordinate system, such as the one described above in connection with Figure 1 and Figure 2 The port surface can be defined as the surface on which the port is located and is constrained to be on the ventral half of the torso model (for procedures where the patient is placed supine). The reachability map is constructed by evaluating (in a grid fashion) whether all of the surgical target positions among the one or more applicable surgical target positions (see e.g. the table above) can be reached from a given port location. In doing so, the constraints are applied, namely the maximum and minimum tool reach distance (also referred to as tool reach range of the surgical tool here) that the tool can reach. It can be assumed that the tool implementation is that of a straight shaft sliding on the coordinate system and the coordinate system is pivoted with respect to a fixed point (the port, e.g. at the remote center of motion (RCM) maintained by the surgical robotic system controller). Tool reach range can be specified for two types of tools: surgical instruments (such as needle drivers or graspers) and endoscopes.

[0066] The limits of the tool reach range can be defined as follows: for surgical instruments, the upper limit of the reach is the maximum distance between the port (at the remote center of motion (RCM)) and the end of the tool shaft corresponding to the proximal tool wrist, and the lower limit is the distal edge of a standard cannula (trocar). For endoscopes, the upper limit of the reach is the maximum distance between the port (at the RCM) and the distal edge of the working distance. The lower limit is the distal edge of a standard cannula plus the minimum working distance.

[0067] A reachability map is then computed for the selected tool and the selected surgical procedure (with the associated surgical target locations). The reachability map contains reachable regions and unreachable regions. If a port is placed in a reachable region, the selected tool (when inserted into the port) is able to reach the associated surgical target locations. In other words, when the tool is inserted into a port placed within a reachable region, the associated surgical target locations are within the specified tool reach of that selected tool. If a port is placed in an unreachable region, the selected tool (when inserted into the port) is unable to reach the associated surgical target locations. The reachability map enables a more objective port placement method. For a port to be feasible in terms of reach, the port must be placed within a reachable region that has been computed for the selected tool. In Figure 11 A feasible port is shown within the triangle in the example reachability map.

[0068] The following example can be used to describe the process for creating a reachability map. Assume that a given surgical procedure has several activities or stages, and each activity can require a tool to reach a respective set of surgical target locations indicated in a parameterized geometric patient torso model. Candidate port locations are selected. If a candidate port location does not allow the tip of the tool to reach all sets of surgical target locations (for all activities required in the surgical procedure), then that candidate port location is classified as part of an unreachable region. In other words, for a candidate port to be classified into a reachable region, the surgical target locations of all activities associated with the given surgical procedure need to be reachable from that port. Repeat the process with different candidate port locations, classifying each port location as either in a reachable region or in an unreachable region, but not both. In some cases, there can not be a single port location that allows the tool to reach the target locations for all activities of a given surgical procedure. In this case, a change of port can be required during the surgical procedure in order for the tool to reach all target locations of all activities of the procedure (from at least two different port locations).

[0069] Another criterion for port placement (or further constraint for determining a reachability map) can be that the surgical tool tip needs to be able to travel or move along each of a set of target paths. A target path connects two or more surgical target locations. Thus, the (port placement) reach region now also needs to allow the surgical tool (with a given tool reach at its tip) to traverse all of that set of target paths required for the relevant surgical procedure.

[0070] Yet another criterion for port placement can be to require a minimum distance between ports to help avoid collisions between two or more tools that have been inserted into those ports. To allow for a reasonable spacing of hardware around the ports, a minimum distance between ports needs to be limited. To reduce the occurrence of collisions near the ports, a lower limit of 50 mm or more for the minimum distance can be chosen. Additional guidance for port placement can be added to the reachability map procedure as a simplified representation of the iliac crest, the pelvic brim, and the navel. These are sized by specific anthropometric parameters for the selected patient size (e.g., iliac crest height, tenth rib height, xiphoid height, and waist height).

[0071] As detailed above and using examples, one aspect of the present disclosure is here a computer system for providing guidance on surgical port placement, the system comprising: a processor; and a memory having stored therein the following data structures: a plurality of reference patient sizes, each reference patient size being of a different size and defining a torso model of an outer surface and an internal viscera surface, the outer surface and the internal viscera surface each having a dome shape that accounts for an inflation effect; a set of normalized surgical target locations for a given surgical procedure; and a mapping of the set of normalized surgical target locations to a plurality of corresponding or un-normalized sets of surgical target locations, wherein each corresponding set of surgical target locations is in a respective one of the plurality of reference patient sizes; and a plurality of reachability maps, each map showing reachable and unreachable regions on a respective one of the plurality of reference patient sizes, wherein i) positioning a surgical tool port in a reachable region allows a surgical tool that has been inserted through the surgical port to reach all of the corresponding set of surgical target locations, and ii) positioning a surgical tool port in an unreachable region does not allow the surgical tool to reach all of the corresponding set of surgical target locations. The normalized surgical target locations can be in normalized cylindrical coordinates L, theta, and R, where L is a distance in a longitudinal direction of the torso model, theta is an angle in a lateral plane of the torso model, and R is a distance in the lateral plane. The torso model can comprise a plurality of elliptical cross-sections, wherein one of the cross-sections consists of two half-ellipses, a ventral half-ellipse joined to a dorsal half-ellipse, the two half-ellipses having different radii of curvature. In particular, said one of the cross-sections consisting of two half-ellipses can pass through a waist plane of the torso model. Further, the torso model can be derived from a non-inflated state torso model by increasing a ventral radius of an elliptical cross-section passing through the waist plane, while leaving other elliptical cross-sections of the non-inflated state torso model unchanged. Even more particularly, the ventral radius can be increased by a bulging factor given by a quadratic curve as a function of body mass index (BMI).

[0072] In one aspect, the torso model defines an outer surface and an internal viscera surface, and the surgical tool port is to be located on an entry surface that is on the outer surface, on the internal viscera surface, or between the outer surface and the internal viscera surface.

[0073] In one aspect, each of the plurality of reachability maps has been determined for the same surgical procedure and the same tool reach.

[0074] In yet another aspect of the computer system, the memory has stored therein a further data structure comprising a plurality of sets of target paths in a plurality of reference patient sizes, respectively, wherein each target path connects two or more surgical target locations, and wherein a reach area is determined such that positioning a surgical tool port in the reach area allows a surgical tool to reach all target paths in the set of target paths.

[0075] Also as detailed above and using examples, a computer system for providing guidance regarding surgical port placement for minimally invasive surgery, the system comprising: a processor; and a memory having stored therein data structures comprising: a plurality of reference patient sizes, each reference patient size being of a different size and defining a torso model of an outer surface and an internal viscera surface; a plurality of sets of surgical target locations, wherein each set of surgical target locations is within a volume of a respective one of the plurality of reference patient sizes; and a plurality of sets of allowed port locations, wherein each set of allowed port locations is on one of the plurality of reference patient sizes, wherein each allowed port location in a set of allowed port locations has been selected such that a surgical tool having specified reach characteristics and placed at the allowed port location is able to reach all surgical target locations in the set of surgical target locations within the reference patient size. In particular, the torso model can be dome shaped due to intentional consideration of the effect of inflation.

[0076] Also as detailed above and using examples, a method for determining surgical port placement for a minimally invasive surgical procedure, the method comprising: receiving a plurality of measurements of a patient, the plurality of measurements including two or more of a group consisting of height, waist circumference, body mass index (BMI), and gender; selecting one of a plurality of reference patient sizes based on the plurality of measurements, wherein each of the reference patient sizes is of a different size and defines a torso model of an outer surface and an inner visceral surface; receiving an identification of a surgical procedure; receiving an identification or characteristics of a surgical tool; and performing a table lookup based on the selected reference patient size, the identification of the surgical procedure, and the identification or characteristics of the surgical tool, wherein the table lookup directly yields a set of allowed port positions on the selected reference patient size. The allowed port positions can have been pre-determined and stored in a lookup table. The plurality of measurements can include height and waist circumference. The set of allowed port positions can be given in normalized cylindrical coordinates, and in this case, the method can further comprise mapping the set of allowed port positions from normalized cylindrical coordinates to un-normalized coordinates on the selected reference patient size.

[0077] In one aspect, the method further comprises accessing a lookup table associated with the selected reference patient size, wherein the lookup table associates the identification of the surgical procedure with a set of surgical target locations within the selected reference patient size.

[0078] Also as detailed above and using examples, a method for determining whether a surgical tool model can reach a surgical target location of a minimally invasive surgical procedure, the method comprising: receiving characteristics of a surgical tool; performing a table lookup based on the characteristics of the surgical tool to determine whether there is a matching entry in a plurality of entries of a lookup table that contains matching surgical tool characteristics, wherein each entry of the plurality of entries of the lookup table comprises i) a reference patient size; ii) an identification of a surgical procedure; iii) a set of allowed port positions with respect to the selected reference patient size; and iv) surgical tool characteristics. The characteristics of the surgical tool can include a tool reach range. If the surgical tool is a surgical instrument, the tool reach range comprises: an upper limit that is a maximum distance between an allowed port position and an end of a tool shaft corresponding to a proximal tool wrist; and a lower limit that is a distal edge of a cannula. If the surgical tool is an endoscope, the tool reach range comprises: an upper limit that is a maximum distance between an allowed port position and a distal edge of a working distance of the endoscope; and a lower limit that is i) a distal edge of a cannula plus ii) a minimum working distance of the endoscope.

[0079] In one aspect of the method, in the set of allowed port locations, i) the allowed port locations and ii) each of a set of surgical target locations associated with a given surgical activity fall within a tool reach of the surgical tool, the given surgical activity being associated with an identification of a surgical procedure.

[0080] Another application of the above concepts is a validation process for proving that a given design of a surgical robot arm and its attached surgical tool reaches surgical target locations in a selected one of a reference patient size and avoids collisions, where collisions can be between two or more arms or between an arm and the patient skin. Collisions are avoided when the tip of the tool traverses a given path between various surgical target locations.

[0081] Another aspect of the present disclosure is a computer-implemented method (a method executed by one or more digital processors that have been configured according to instructions stored in a memory of a computer system) for determining surgical port placement for a minimally invasive surgical procedure. The method is as follows. A plurality of measurements of a patient are received, e.g., including one or more measurements obtained from a medical imaging procedure performed on the patient or manual measurements. Based on the received measurements, an instance of a parameterized torso model is determined, the parameterized torso model defining an outer surface and an internal viscera surface, each having a dome shape that accounts for an inflation effect. An identification of a surgical procedure is received, and in response, a set of normalized surgical target locations in the parameterized torso model is determined. The set of normalized surgical target locations is then mapped to a set of unnormalized surgical target locations in the instance of the parameterized torso model. Characteristics of a surgical tool are also received. Based on the characteristics of the surgical tool and based on the set of unnormalized surgical target locations, a set of allowed port locations on the instance of the parameterized torso model is computed. This set of allowed port locations can then be presented to a surgeon during a surgical procedure on the patient, based on which the surgeon can decide where to place a port on the patient’s abdomen.

[0082] As mentioned above, the parameterized torso model can include an elliptic cylinder having at least four elliptical cross sections at a hip plane, a waist plane, a chest plane, and an upper chest plane. The waist plane elliptical cross section can be composed of two half-ellipses having different radii of curvature, namely an abdominal half-ellipse joined to a dorsal half-ellipse.

[0083] When determining the instance of the parameterized torso model, the inflated state outer surface can be derived by applying an inflation factor to the non-inflated state outer surface. The inflation factor can vary according to a body mass index (BMI). In other cases, when determining the instance of the parameterized torso model, the outer surface is directly generated based on the received plurality of measurements obtained while inflating the patient.

[0084] While certain aspects of the application have been described and shown in the drawings, it will be understood that these are simply aspects of the application and are not to be considered in a limiting sense, and are not intended to show all aspects to which the application is deemed applicable. Accordingly, the description is not to be taken as limiting the scope of the application.

Claims

1. A method for determining a set of allowed surgical port locations for a given minimally invasive surgical (MIS) surgical tool, the method comprising: receiving a plurality of measurements of a patient; based on the received measurements, determining an instance of a parameterized torso model having a dome shape that accounts for an inflation effect; receiving an identification of a surgical procedure, and in response, determining a set of normalized surgical target locations in the parameterized torso model; mapping the set of normalized surgical target locations to a set of unnormalized surgical target locations in the instance of the parameterized torso model; receiving characteristics of a surgical tool, wherein the surgical tool is to be coupled to a robotic arm or is a handheld surgical instrument; based on the characteristics of the surgical tool and based on the set of unnormalized surgical target locations, computing a set of allowed port locations on the instance of the parameterized torso model; and based on the computed set of allowed port locations, generating an accessibility map, wherein the accessibility map indicates accessible and inaccessible regions on an entry surface of the instance of the parameterized torso model.

2. The method of claim 1, wherein the plurality of measurements of the patient include one or more measurements obtained from a medical imaging procedure performed on the patient.

3. The method of claim 1, wherein the parameterized torso model comprises an elliptic cylinder having at least four elliptical cross sections at a hip plane, a waist plane, a chest plane, and an upper chest plane.

4. The method of claim 3, wherein the waist plane elliptical cross section is comprised of two half-ellipses having different radii of curvature.

5. The method of claim 4, wherein the two half-ellipses are a ventral half-ellipse joined to a dorsal half-ellipse.

6. The method of claim 1, wherein determining an instance of a parameterized torso model comprises deriving an inflated state outer surface by applying an inflation factor to a non-inflated state outer surface.

7. The method of claim 6, wherein the inflation factor varies according to a body mass index (BMI).

8. The method of claim 1, wherein determining an instance of a parameterized torso model comprises directly generating an outer surface based on the received plurality of measurements that have been obtained while inflating the patient.

9. A computer system for determining surgical port placement for a minimally invasive surgical procedure, the computer system comprising: a processor; and a memory having instructions stored therein that configure the processor to: receive a plurality of measurements of a patient; based on the received measurements, determine an instance of a parameterized torso model, the parameterized torso model defining an outer surface and an internal viscera surface, each having a dome shape that accounts for an inflation effect; receive an identification of a surgical procedure, and in response, determine a set of normalized surgical target locations in the parameterized torso model; map the set of normalized surgical target locations to a set of unnormalized surgical target locations in the instance of the parameterized torso model; ​ receiving characteristics of a surgical tool, wherein the surgical tool is to be coupled to a robotic arm or is a hand-held surgical instrument; computing a set of allowed port locations on the instance of the parameterized torso model based on the characteristics of the surgical tool and based on the set of un-normalized surgical target locations; and generating an accessibility map based on the computed set of allowed port locations, wherein the accessibility map indicates reachable and unreachable regions on an entry surface of the instance of the parameterized torso model.

10. The computer system of claim 9, wherein the plurality of measurements of the patient comprise one or more measurements obtained from a medical imaging procedure performed on the patient.

11. The computer system of claim 9, wherein the parameterized torso model comprises an elliptic cylinder having at least four elliptical cross-sections at a hip plane, a waist plane, a chest plane, and an upper chest plane.

12. The computer system of claim 11, wherein the waist plane elliptical cross-section is comprised of two half-ellipses having different radii of curvature.

13. The computer system of claim 12, wherein the two half-ellipses are a ventral half-ellipse joined to a dorsal half-ellipse.

14. The computer system of claim 9, wherein the processor determines an instance of a parameterized torso model by: deriving an inflated state of the outer surface by applying an inflation factor to a non-inflated state of the outer surface.

15. The computer system of claim 14, wherein the inflation factor varies according to body mass index (BMI).

16. The computer system of claim 9, wherein the processor determines an instance of a parameterized torso model by: directly generating the outer surface based on received measurements of a plurality of measurements that have been obtained while inflating the patient.

17. An article comprising a computer-readable storage medium having stored therein instructions that, if executed by a processor, configure the processor to determine a set of allowed surgical port locations for a minimally invasive surgical procedure by: receiving a plurality of measurements of a patient; based on the received measurements, determining an instance of a parameterized torso model, the parameterized torso model defining an outer surface and an internal viscera surface, each having a dome shape that accounts for inflation effects; receiving an identification of a surgical procedure, and in response, determining a set of normalized surgical target locations in the parameterized torso model; mapping the set of normalized surgical target locations to a set of un-normalized surgical target locations in the instance of the parameterized torso model; receiving characteristics of a surgical tool, wherein the surgical tool is to be coupled to a robotic arm or is a hand-held surgical instrument; computing a set of allowed port locations on the instance of the parameterized torso model based on the characteristics of the surgical tool and based on the set of un-normalized surgical target locations; and generating an accessibility map based on the computed set of allowed port locations, wherein the accessibility map indicates reachable and unreachable regions on an entry surface of the instance of the parameterized torso model. generate a reachability map based on the computed set of allowed port locations, wherein the reachability map indicates reachable and unreachable regions on an entry surface of the instance of the parameterized torso model.

18. The article of manufacture of claim 17, wherein the plurality of measurements of the patient comprise one or more measurements obtained from a medical imaging procedure performed on the patient.

19. The article of manufacture of claim 17, wherein the processor determines an instance of a parameterized torso model by: deriving an inflated state outer surface by applying an inflation factor to a non-inflated state outer surface.

20. The article of manufacture of claim 19, wherein the computer readable storage medium has stored therein as a variable the inflation factor that is a function of body mass index (BMI).

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