WO2015087191A1

WO2015087191A1 - Personalized scan sequencing for real-time volumetric ultrasound imaging

Info

Publication number: WO2015087191A1
Application number: PCT/IB2014/066462
Authority: WO
Inventors: Sanghamithra Korukonda; Emil George Radulescu; Jean-Luc Robert; Maxim Fradkin; John Edward Dean; Gerardus Henricus Maria Gijsbers; Wilhelmus Johannes Antonius PASMAN; Karl Erhard Thiele; Douglas Robert MAXWELL; Steven Russell Freeman
Original assignee: Koninklijke Philips N.V.
Priority date: 2013-12-09
Filing date: 2014-12-01
Publication date: 2015-06-18

Abstract

An imaging apparatus (100) includes at least one imaging probe and an occlusion avoidance processor and is configured for:using the at least one probe to form different imaging apertures;via multiple apertures, detecting imaging blockage; and deciding by the processor, based on a result of the detecting, upon one or more apertures to utilize for image acquisition. In a scouting mode, ultrasound patches (204) may be arranged in a checkerboard pattern to form odd apertures and even apertures that are interspersed for coherence estimation used in assessing blockage. A volumetric occlusion layer may be made by beam-wise projecting coherence values into a 2D map so that openings in the layer correspond to non-blockage in the map, or a connected segment thereof. An independent group (152, 156-158) of acquistion apertures can be pre-tested against the layer to find an optimal one or more acquisition apertures,and a scanning sequence,personalized to the anatomy (120) scouted. The layer can be incrementally updated over the course of a natural cycle of the body, for cyclical acquisition in accordance.

Description

Personalized Scan Sequencing for Real-Time Volumetric Ultrasound Imaging

FIELD OF THE INVENTION

The present invention relates to imaging-aperture selection and, more particularly, to selection based on detected imaging blockage.

BACKGROUND OF THE INVENTION

Real-time volumetric ultrasound imaging has been successfully introduced for diagnostic imaging in various clinical fields ranging from obstetrics to cardiovascular diseases. In addition, its use as an image guidance tool for percutaneous interventions is being explored, primarily for device placement in structural heart disease (SHD) treatment or cardiac electrophysiology (EP) ablation procedures. The reason for this is the promise of X- ray-less direct visualization of the interventional ablation catheter or device placement catheter on the target anatomical position. In EP there is the additional potential to continuously visualize soft tissue and the interventional devices during the ablation process itself. SUMMARY OF THE INVENTION

The imaging modalities currently used in interventional therapy are fluoroscopy and transesophageal echo ultrasound (TEE). Fluoroscopy provides excellent images of the interventional devices, but provides poor soft tissue contrast. Additionally it is a projection based imaging method and hence is not capable of providing direct 3D information of the device location within the heart. And finally, fluoroscopy is a form of ionizing radiation, thereby exposing both the patient and the interventionists to unwanted radiation.

The TEE probe introduced into the patient's esophagus provides very high quality images of the heart owing to its proximity of the heart and a field of view that is unimpeded by skin, ribs, fat and lung tissue as is the case in transthoracic echocardiography (TTE). However, TEE requires a team of skilled medical personal and takes continued manipulation to maintain proper imaging positioning. Also the prolonged interventional procedures require that the patient be maintained under general anesthesia.

In current practice, ultrasound based interventional guidance is restricted to the use of two-dimensional (2D) or matrix transesophageal echography (TEE) probes. Transthoracic echography (TTE) is not used for interventional guidance because of current limitations of field of view and handheld use.

Thus, there is the need for a device that can be deployed transthoracically and that can provide, in real time and with minimal user intervention, high quality volumetric images of heart valves, the entire heart and interventional devices within the heart.

What is proposed herein below is directed to addressing one or more of these concerns.

In an aspect of the present invention, an imaging apparatus includes at least one imaging probe and an occlusion avoidance processor. The apparatus is configured for: using the at least one probe to form a plurality of different imaging apertures; via multiple ones of the plural apertures, detecting imaging blockage; and deciding by the processor, based on a result of the detecting, upon a set of one or more apertures to utilize for image acquisition.

For such an apparatus, a computer readable medium or alternatively a transitory, propagating signal is part of what is proposed herein. A computer program embodied within a computer readable medium as described below, or, alternatively, embodied within a transitory, propagating signal, has instructions executable for performing the corresponding method steps listed above.

Details of the novel, occlusion-avoidance, live, TTE imaging are set forth further below, with the aid of the following drawing, which is not drawn to scale.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic view serving as an exemplary overview of a novel, occlusion-avoidance, live, transthoracic echocardiography (TTE) imaging system and of a particular acquisition scenario, according to the present invention;

Fig. 2 is a schematic and conceptual illustration of a version of the system of Fig. 1, according to the present invention;

Fig. 3 is a flow chart showing one example of a scouting mode of a novel, occlusion-avoidance, live, TTE imaging process, according to the present invention;

Fig. 4 is a flow chart showing one possible realization of personalized scan sequence (PSS) parameter generation and PSS-based image acquisition, according to the present invention; and

Fig. 5 is a flow chart representative of a time gated procedure whereby image acquisition is dynamically optimized, according to the present invention. DETAILED DESCRIPTION OF EMBODIMENTS

Fig. 1 shows, by illustrative and non-limitative example, a novel, occlusion- avoidance, live, TTE imaging apparatus 100. It includes an occlusion avoidance processor 104, a beamformer 108, a scan sequence generator 112, and an ultrasound imaging probe 116 having a face 118. Other well-known components of an ultrasound imaging system, such as a user interface are included although not shown in Fig. 1. The constituents such as the processor 104, beamformer 108 and generator 112 are implementable by any known and suitable combination of software, hardware and firmware.

The probe 116 is applied to the anatomy 120 of a human being or animal, here the chest. Between a first rib 122 (e.g., the third rib from the bottom of the rib cage) and a second rib 124, a 3D sector scan 128 is performed. Between the second rib 124 and a third rib 132, another 3D sector scan 136 is performed.

The two imaging acquisition scans 128, 136 are simultaneous (in that the acquisition is interleaved). They can be time-gated for respiration or heartbeat. In this case, the scans 128, 136 may change, e.g., as to aperture choice, dynamically to adapt to the movement of obstructions within the body due to respiration and heartbeat. The imaging acquisition scans 128, 136 are to be distinguished from the scans in a scouting mode, discussed further below, that precedes the acquisition. The time gating need not be tied to respiration or heartbeat; instead, the scouting mode can, as an initialization, be iteratively executed over the course of a heart cycle. The results of each iteration are used in successively adapting the acquisition aperture configuration. As an alternative, in a short procedure in which the patient is conscious, the patient can be told to hold his or her breath. Alternatively, too, time gating can be omitted, for example when acquisition is from a single probe which is often adequate for imaging of a small structure such as a heart valve. A time gating implementation is described in more detail further below in connection with the procedures exemplified in Figs. 3 and 4.

A region of interest (ROI) 140, is partially within the fields of view (FOV) 144, 148 of the respective imaging acquisition scans 128, 136. The ROI 140 in this example of full-volume imaging is a heart, although modes for small-volume imaging and imaging of X-planes are available. The scans 128, 136 are made from two respective imaging apertures 152, 156 of the probe 116 which here are non-overlapping, or spatially disjoint, although the two apertures may partially overlap. The probe 116 may instead consist of two or more separate probes rigidly interconnected, each having one or more of the apertures. In any event, many more additional apertures 157, 158 are formable from the probe(s), a set 159 of the best one or more apertures 152, 156 being chosen for image acquisition. Illustratively, for the first aperture 152, some of the transmit beams 160, or "transmits", that are part of the imaging acquisition scan 128 are shown. A C-plane 164 of the ROI 140 is taken along the broken line 168, and is therefore portrayed in Fig. 1 in an orientation 90° apart from that of the ROI, as it would be viewed onscreen. The C-plane 164 affords a wider FOV 172, and is formed by fusing respective partial C-planes within each of the constituent FOVs 144, 148, the two FOVs having been acquired from respectively differently angled views. Here, the acquiring apertures 152, 156 are spatially disjoint, although they could partially overlap. Three or more differently angled views can also be fused.

The two imaging acquisition scans 128, 136 are performed according to an imaging-acquisition scan sequence provided by the scan sequence generator 112. Here, too, the imaging-acquisition scan sequence is to be distinguished from a preceding scouting scan sequence to be described further below. The imaging acquisition scan sequence specifies, among other parameters, the aperture(s), and, for the aperture(s), the transmits 160 and the receive beams, or "receives", that make up the imaging acquisition scan 128, 136. For example, the directions of each transmit 160, in the scanned series of transmits, are specified. The same are specified for the receive beam, or "receive", that immediately follows each transmit 160. The receive beam can also be referred to as a scan line. The transmit 160 and responsive receive need not be spatially aligned, although they do for the example discussed herein below. The maximum imaging depth for which imaging is acquired on receive, or "signal length", is also part of the imaging acquisition scan sequence. Other parts include apex placement and beam density which are discussed further below.

The probe 116 may be a large area transthoracic echocardiography

("LATTE") probe for concurrently spanning a few or several ribs 122, 124, 132. It can be held in place to search for the best aperture(s) in the scouting mode of operation. Although the ribs 122, 124, 132 here are represented as the cause of imaging blockage, lungs and fatty tissue for example may also potentially occlude anatomy 120. The apparatus 100 uses the scouting mode to plan on how to navigate around these barriers and to minimize obstruction of a complete, high-image-quality view of the ROI 140. Then, with the probe 116 still in place, above-mentioned parameters for an imaging-acquisition scan sequence are generated. These parameters are personalized to the anatomy 120, based on the results of the scouting mode. Finally, in an acquisition mode, the selected at least one aperture is utilized to provide live imaging. The transition from scouting mode to acquisition mode, or the whole procedure following launch of the scouting mode, can appear seamless, performed automatically in real time without the need for user intervention. As discussed further below, the scouting mode can provide imaging acquisition parameters that are optimized dynamically over the course of a natural cycle (e.g., respiratory, cardiac) of the body. Once derived, the time-sequenced set of parameters can be reapplied cyclically in real time for live, continuous imaging acquisition throughout a medical procedure, imaging that is optimized moment by moment.

Fig. 2 depicts machine settings and concepts that underly the functioning of the apparatus 100. The face 118 of each of the one or more probes 116 is dividable into an array of ultrasound transducer elements 202. The elements 202 are apportionable to patches 204. The patches 204 which as shown in Fig. 2 are mutually interspersed, or enmeshed, in a checkerboard pattern but make up two different apertures 206a, 206b, with the even-aperture patches shown as blank and the odd-aperture patches marked with an "x." The number of active patches 204 of an active aperture 206a, 206b may grow with imaging depth during receive. Hereinafter, any reference to the size of an aperture 206a will assumes its full dimensions. An aperture 206a is electronically translatable across the face 118 of the probe 116, and each subsequent location will be referred to herein after as a separate aperture. The odd and even complementary apodizations described above will also be referred to as two separate apertures. Scouting mode apertures 202a, 202b, 202c on the face 118 of the probe 116 can, and as shown in the example of Fig. 2, do overlap, although another exemplary scouting mode aperture 202d is non-overlapping with any other aperture used in the scouting mode. The aperture(s) used in the acquisition mode are unlimited by the configuration, dimensions, or number of apertures used in the scouting mode.

Although what is proposed herein is not limited to sector scans, a sector scan will be assumed in the description that follows. A scouting mode aperture 202a-202d issues a transmit 208 and dynamically receives up until a receive beam endpoint 210, i.e., up until the signal length is reached. The transmit 208 is shown in Fig. 2 to be the third azimuthal beam in a scan plane or "slice" 214a. The responsive receive line, or "scan line", 212 is aligned, and is portrayed here in Fig. 1 as coincident despite its transmit 208 having a beam width. Successive scan lines 212 continue azimuthally for perhaps about a dozen more beams. Scanning follows successively for scan plane 214b and then scan plan 214c, and so on. This all constitutes a single 3D scouting scan from the aperture 202d. Other scanning patterns are possible. The total number of scan lines 212, or transmit events, available might be limited by the number of scouting mode apertures 202a-202d, the imaging depth, the sound transmission speed through the particular body tissue, and acceptable delay between applying the results of the scouting mode to personalized scan sequence (PSS) parameter generation and subsequent acquisition.

Two exemplary transmits 216a, 216b are each followed by respective receives 218a, 218b. The scan lines 212 share their respective common origin or apex 222. However, here, the origin 222 is offset from a physical center 224 of the face 118 by a "positive" distance. The benefits of positive and negative offsetting, in terms of increased field of view, increased image quality and imaging through obstructions, are described in connection with Figs. 5 and 8 of commonly-owned U.S. Patent No. 6,709,395 to Poland, the entire disclosure of which is incorporated herein by reference.

The dashed lines 224a, 224b, which are actually planar surfaces, outwardly define an occlusion layer 226. It faces the probe face 118 and is an end product of the scouting mode. A frustum 228 of the transmit 216b is seen in Fig. 2 as a dotted region within the occlusion layer. The analogous region of the other transmit 216a, or both regions collectively, are also a frustum. If the transmit 216b is, judging from its receive, assessed not to be blocked, an "opening" 229 is made in the occlusion layer 226 for the frustum 228. If, on the other hand, based on the receive line as a whole, the transmit 216a is assessed to be blocked 230, as represented by the "x", an opening is not made.

Multiple ones of the apertures 202a-202d over the face 118 of the probe 116 are selected for the scouting mode. The probe 116 can be dimensioned and configured such that the selected apertures 202a-202d collectively span at least 7 centimeters (cm). Thus, the search for optimal apertures benefits from the large search area. If, for example, the ROI 140 is the heart which has respective spatial width, the span can be adjusted accordingly. Lateral dimensions of the span other than 7 cm are also within the intended scope of what is proposed herein.

The multiple, or "scouting", apertures 202a-202d are divisible into pairs as mentioned herein above, one aperture of the pair having an odd apodization and the other an even apodization. Apodization thus chosen generates beamformed signals that are similar except for a small change in phase. Coherent signals, such as those reflected by tissue, are unaffected by this change of phase. However, signals from body locations occluded by ribs or lung, or plain noise, decorrelate greatly due to this change of phase. This property can thus be used to distinguish between valid and invalid echoes.

Once the beamformed data is acquired from the scouting apertures, signal processing and analysis is performed to determine the imaging parameters for subsequent modes. The degree of coherence or correlation between the two beamformed signals is computed by comparing select kernels (of length K) from corresponding, i.e., complementary, beams in s_x and s₂. The coherence value p for a given beam at a depth r is given by:

These computations are performed for all acquired beams to generate a volumetric coherence map, or "multi-dimensional occlusion map", 231. The values of a respective intensity, e.g., as red in a colored presentation, correspond to regions of high coherence, indicative of the presence of tissue. A moving average filter of width T (corresponding for example to a few or several millimeters, the average thickness of the heart wall) is applied to the coherence values along the depth direction, to emphasize the presence of heart tissue. The maximum of each filtered coherence signal computed as:

where j=l : length of signal-Τ} is stored to generate a projected coherence map, part of which is denoted in Fig. 2 by the reference number 232. Twelve filtered coherence values 234a-2341 of four respective receive lines 236a-236d at a common spatial depth, and azimuthal angle, from the probe face 238 are seen in Fig. 2. In actuality there would be many more values than twelve and four, respectively. The circled values 240a-240d in the part 232 of the projected coherence map are the line-wise maximum values p_max(e_x> θ_γ). The direction of projection is shown, line by line, by the arrows. Here, the filtered coherence values and receive lines are shown in the elevation direction 244, but both continue azimuthally and axially as a 3D map. The coherence map, on the other hand, is 2D. Thus, line-specific blockage assessments in the form of the filtered coherence values have, via their maximums p_max {p_x> #_y), been consolidated into a map of less spatial dimensionality. The values in the 2D projected coherence map are compared to an acoustic-window quality threshold TAW_Q 246. Those that meet the threshold, here values 240a, 240b and 240d, are entries in a segmented projected coherence map 248. This is seen in a column 250 of the map 248, where, from the blank entry 252, the value 240c is missing, having been filtered out by the threshold TAW_Q 246. The segmented image is subjected to morphologically image processing to retain the largest connected segmented region 254. Alternatively, the requirement of strict horizontal and/or vertical connectedness can be loosened by using an algorithm based on, for example, Mahalanobis distance. This region 254, i.e., the finalized segmented projected coherence map, represents the valid acoustic window for the current scouting aperture pair 206a, 206b. The analysis is done for all scouting apertures pairs 206a, 206b of the one or more probes 116. As an alternative to coherence factor as a metric, any other image quality metric may be used, such as brightness or energy; in which case, the even-odd apodization would not be needed and scouting apertures would not be paired. Thus, for instance, the assessment of blockage diminishes with pixel brightness. For the ensuing discussion, it will be assumed that even-odd apodization is implemented.

Next, the occlusion layer 226 is formed by introducing, into a volumetric block outwardly defined by the surfaces 224a, 224b, openings, or "passageways", 229 for the region 254 of each respective scouting aperture pair 206a, 206b. In other words, the block is populated with the valid acoustic windows of the aperture pairs 206a, 206b, thereby yielding the occlusion layer 226. The openings 229 correspond to imaging-blockage assessments and the occlusion avoidance processor 104 has decided where the openings are to exist. In the alternative embodiment that uses an image metric other than the coherence factor, the population with valid acoustic windows occurs aperture by aperture, rather than by aperture pairs.

The occlusion layer 226 serves as a template against which candidate acquisition-apertures are tested. Two frustums 256a, 256b, of respective acquisition apertures 157, 158, are depicted cross-sectionally in a cut by a layer-wise slice of the occlusion layer 226. The checks 258a-258c represent areas that have been assessed as non- blocked like, for example, an area aligned with the receive line 236d which appears in the finalized segmented projected coherence map 254. The entry 260, marked by an "x", in the map 254 for receive line 236c, by contrast, corresponds to blockage. Illustratively, a portion 262 of the left-sided frustum 256a overlaps with the occlusion layer 226, the whole overlap being representative of blockage. An acquisition scanning sequence is thus formed by picking apertures 152, 156, scan lines 212 for each aperture, and other parameters such those mentioned further above.

Fig. 3 demonstrates one example of a scouting mode of the novel, occlusion- avoidance, live, TTE imaging process, and Fig. 4 provides one possible realization of personalized scan sequence (PSS) parameter generation and PSS-based image acquisition. Processing points to a first scouting aperture (step S304). A transmit portion of the beamformer 108 creates a transmit 160, and a receive portion creates the receive 212.

Scanning is performed according to a pattern that is shared among all scouting apertures 202a-202d (step S308). The pattern is set by the scan-sequence generator 112, and may consist of a set of scan lines 212 whose endpoints 210 form, for example, a 16 by 8 array. The apodization is then alternated odd-even-wise (step S312), and the scan is repeated with the complementary apodization (step S316). If there exists a next aperture 202a-202d (step S320), processing points to that next aperture as the current aperture (step S324), and return is made to step S308. Otherwise, if there does not exist a next aperture 202a-202d (step

S320), processing points to the first scouting aperture pair 206a, 206b (step S328). Blockage 260 is assessed point-wise in 3D (step S332). The assessments 234a-2321 are, according to their maximums, consolidated direction by direction into a 2D coherence map (step S336). Acoustic passageways 229 are assessed from the map and selectively retained according to the largest connected segment 254 formable from the map (step S340). If a next aperture pair 206a, 206b exists (step S344), processing points to that next pair (step S348) and returns to step S332. Otherwise, if a next aperture pair 206a, 206b does not exist (step S344), processing again points to the first aperture pair (step S352). Processing also points to the first imaging direction, i.e., scan line 212 (step S356). If the current imaging direction 212 is blocked (step S360), an opening 229 is created in the occlusion layer 226 (step S364). In either case, if another direction 212 remains (step S368), processing points to that next direction as the current direction (step S372) and processing returns to step S360. Otherwise, if no other direction 212 remains (step S368), the direction pointer is reset (step S376), and query is made as to whether another aperture pair 206a, 206b remains (step S380). If another aperture pair 206a, 206b remains (step S380), processing points to that next pair 206a, 206b (step S384) and return is made to step S360. Otherwise, if there is no other aperture pair 206a, 206b (step S380), processing points to a first candidate image-acquisition aperture 152, 156-158 (step S404). Query is now made as to whether increased FOV and/or increased image quality is to be achieved by offsetting the apex 222. If the apex 222 is to be offset (step S405), a "virtual apex" is set (step S406). Scan lines 212 whose endpoints 210 are occluded by the occlusion layer 226 are to be excluded from the acquisition scan sequence in the event the current candidate acquisition aperture is selected for utilization. In particular, if a ray 264 from the endpoint 210 to the physical center 224 of the face 118 is blocked by the occlusion layer 226, the scan line 212 is excluded (step S407). If, on the other hand, the apex 222 is not to be offset (step S405), processing branches ahead to step S408. In either event, blockage in the frustum 256a, 256b of the aperture 152, 156-158 is quantified (step S408). For example, the number of scan lines 212 that are blocked can be counted. Many of those blockages 260 were determined by the largest connected segmented region 254. If a next aperture 152, 156-158 exists (step S412), processing points to that next aperture (step S416) and return is made to the previous step S408. Otherwise, if a next aperture 152, 156-158 does not exist (step S412), an optimal group of candidate apertures 152, 156-158 is determined based on lack of blockage 260 (step S420). Query is made as to whether the ROI 140 is small, i.e., whether the focus of attention is on a small feature such as a heart valve, or region of pulmonary veins with their immediate anatomical contexts. The ROI mode is typically initially set by the user as large volume, e.g., the entire heart; small volume or X- planes. In particular, the span of the scouting apertures 202a-202d would typically be designed in accordance with, i.e., somewhat wider than, the width of the ROI 140. If the ROI mode is small volume (step S424), the optimal aperture is selected from the group 152, 156- 158 (step S428). Otherwise, if the ROI mode is large volume or X-planes (step S424), a center, such as the center of mass 266, is found of the frustums 256a, 256b of the optimal group 152, 156-158 (step S432). The aperture 152, 156-158 whose frustum 256a, 256b is closest to the center is selected (step S436). For a short period, acquisition is made from the selected acquisition aperture (step S440). Query is made as to whether the ROI 140 is fully covered by the view. A generalized Hough transform (GHT) may be used to detect a feature, e.g., an organ such as the heart. A method for performing a GHT is discussed in commonly- assigned U.S. Patent Publication No. 2008/0260254 to Schramm et al. Alternatively or additionally, a coarse segmentation of the image can be performed for greater reliability, with a segmentation time period of up to about two seconds, in identifying the desired ROI 140. An example of model-based segmentation that uses coarse and fine meshes is found in commonly-assigned U.S. Patent Publication Number 2009/0202150 to Fradkin et al.

("Fradkin"). Both publications are incorporated herein by reference. As another alternative, the view, such as the apical view of the heart, can be displayed and the user can verify whether coverage of the ROI 140 is complete. If the ROI 140 is full covered (step S444), the current, optimal aperture is deemed sufficient (step S448). Otherwise, if the ROI 140 is not fully covered (step S444), an additional aperture is selected from the optimal candidates for a differently-angled view (step S452). In either case, if the ROI mode is set for full-volume imaging (step S456), the PSS is set for low beam-density (step S460) with a low frame rate (step S464). If, on the other hand, the ROI mode is for small-volume or X-plane imaging (step S456), the PSS is set for high beam-density (step S468) with a high frame rate (step S472).

In a time gated embodiment shown in Fig. 5, the imaging acquisition scan sequence just computed in Figs. 3 and 4 is stored (step S510). In the case of

electrocardiograph (ECG) gating, the stored sequence is paired with the ECG phase (step S520). The procedures of Figs. 3 and 4 are repeated continually, each time storing the sequence and its phase. If a full cardiac cycle is sufficiently populated in the recording (step S530), image acquisition mode is launched (step S540), and image acquisition continues until halted by the operator (step S550). Thus, any sequence changes from moment to moment are dynamically realized. The analogous protocol can be followed for respiration, using a respiratory belt instead of an ECG. Use of these devices, and alternative means, are disclosed in commonly-owned U.S. Patent Publication No. 2011/0201915 to Gogin et al. Monitoring by the device is continued during acquisition so that the apparatus 110 can continuously match the appropriate sequence to the current phase detected by the device. Thus, acquisition is dynamically reconfigurable in synchrony with the recorded updates of the occlusion layer, the updating having occurred in synchrony with a natural cycle of the body such as a cardiac or respiratory cycle. In effect, the apparatus 100 is configured for, over the course of a natural cycle of the body, dynamically deciding upon which one or more apertures, and upon which beams, to utilize for image acquisition. It is further configured for, in a subsequent mode of operation, dynamically reconfiguring the acquisition in synchrony with the decisions that were made. The acquisition is personalized to the anatomy, and natural cycle, of the patient.

While what has been proposed above is framed in the context of cardiac ultrasound, it can easily be translated to general imaging scenarios such as imaging the liver through intercostal spaces, or generating higher resolution images of kidneys by

compounding views across multiple apertures.

An imaging apparatus includes at least one imaging probe and an occlusion avoidance processor and is configured for: using the at least one probe to form different imaging apertures; via multiple apertures, detecting imaging blockage; and deciding by the processor, based on a result of the detecting, upon one or more apertures to utilize for image acquisition. In a scouting mode, ultrasound patches may be arranged in a checkerboard pattern to form odd apertures and even apertures that are interspersed for coherence estimation used in assessing blockage. A volumetric occlusion layer may be made by beam- wise projecting coherence values into a 2D map so that openings in the layer correspond to non-blockage in the map, or a connected segment thereof. An independent group of acquistion apertures can be pre-tested against the layer to find an optimal one or more acquisition apertures, and a scanning sequence, personalized to the anatomy scouted. The layer can be incrementally updated over the course of a natural cycle of the body, for cyclical acquisition in accordance. While the invention has been illustrated and described in detail in the drawing and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

For example, all processors are implementable in one or more integrated circuits.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. Any reference signs in the claims should not be construed as limiting the scope.

A computer program can be stored momentarily, temporarily or for a longer period of time on a suitable computer-readable medium, such as an optical storage medium or a solid-state medium. Such a medium is non-transitory only in the sense of not being a transitory, propagating signal, but includes other forms of computer-readable media such as register memory, processor cache, RAM and other volatile memory.

A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

CLAIMS: What is claimed

1. An imaging apparatus comprising:

at least one imaging probe; and

an occlusion avoidance processor (104),

said apparatus configured for:

using said at least one probe to form a plurality of different imaging apertures (152, 156-158);

via multiple ones of the plural apertures, detecting imaging blockage; and deciding by said processor, based on a result of said detecting, upon a set of one or more apertures to utilize for image acquisition.

2. The apparatus of claim 1, said at least one probe amounting to a single probe (116).

3. The apparatus of claim 2, configured for performing said deciding dynamically over a natural cycle of a body (S510-S530) and for dynamically reconfiguring said acquisition in synchrony with the decisions made in said deciding (S540-S550).

4. The apparatus of claim 1, further configured for acquiring data via said at least one probe, said at least one probe respectively comprising multiple ultrasound transducer elements (202), said multiple ones of the plural apertures being formed from associated ones of said elements such that for a pair of said multiple ones the elements of one of the pair are, for assessing coherence of said data, interspersed with the elements of the other of the pair.

5. The apparatus of claim 1, said detecting comprising forming a volumetric coherence map (231).

6. The apparatus of claim 1, said detecting comprising spatially projecting, from a multidimensional map, imaging-blockage assessments in forming a map (232) of less spatial- dimensionality.

7. The apparatus of claim 6, further comprising an ultrasound beamformer (108) for forming a receive line, said detecting comprising the spatial projecting, of an assessment from among said assessments, along said line.

8. The apparatus of claim 1, said processor being configured for forming a multi-dimensional occlusion map (231), said result, upon which said deciding is based, comprising said map.

9. The apparatus of claim 8, further configured for acquiring data (212) via said at least one probe, said processor being configured for, in said forming, introducing, into a volumetric block (224a, 22b), openings that correspond to imaging-blockage assessments that are based on said data and for using said block with said openings in delimiting said acquisition.

10. The apparatus of claim 9, said block being shared aperture-wise in that said apparatus is further configured for, with respect to the plural apertures, deciding aperture pair-by-aperture pair (206a, 206b), or aperture by aperture, where said openings exist and for populating said block with the existing openings.

11. The apparatus of claim 1, further configured for acquiring data via said at least one probe, for making imaging-blockage assessments (234a-2341) based on said data, and for forming a map from said assessments, said processor being configured for distinguishing, from among said assessments in said map, a largest connected segment of said assessments that meet an acoustic-window quality threshold.

12. The apparatus of claim 1, said acquisition being performed according to an ultrasound scan sequence, said processor being configured for forming an occlusion map, said result, upon which said deciding is based, comprising said map, said apparatus further comprising a scan-sequence generator (112) configured for, based on said occlusion map, generating said sequence.

13. The apparatus of claim 1, further configured for, responsive to said deciding, based on a decision made in said deciding, generating an ultrasound scan sequence for performing said acquisition.

14. The apparatus of claim 1, further configured for, based on a decision made in said deciding, generating an ultrasound scan sequence for performing said acquisition, and for performing said generating so as to cause transmits (160), issued in the sequence, to avoid the detected blockage.

15. The apparatus of claim 1, said detecting comprising:

assessing blockage (260) point-wise aperture pair by aperture pair, or aperture by aperture;

consolidating the assessments direction-by-direction; and

selectively retaining, based on acoustic window quality, passageways, for said acquisition, in corresponding ones of the directions.

16. The apparatus of claim 1, said set comprising at least two apertures such that said apparatus is configured for imaging, from correspondingly differently angled views, a same region (140), said apparatus being further configured for fusing the at least two differently- angled components of said acquisition to enlarge a field of view with respect to said region.

17. The apparatus of claim 16, two (152, 156) or more of said at least two apertures being spatially disjoint from each other.

18. The apparatus of claim 1, configured for:

utilizing, for said detecting, a same ultrasound scanning pattern for said multiple ones of the plural apertures (S308); and

forming, as said result, a shared occlusion map based on the scanning via said multiple ones.

19. The apparatus of claim 1, an aperture of said set not being among said plural apertures.

20. The apparatus of claim 1, configured for using, in said deciding, spatial overlap (262) between:

a) an occlusion layer, having outer surfaces and openings, said layer facing a given one from among said at least one probe and being representative of said blockage; and

b) a frustum of ultrasound transmits of a candidate aperture of said given probe, said frustum being defined by said outer surfaces.

21. The apparatus of claim 20, said candidate being one from among multiple candidate apertures for which respective spatial overlap is used in said deciding, said apparatus being further configured for selecting, based on lack of said blockage, an optimal group of said candidate apertures, finding a center (266) of the aperture frustums of said group, and using proximity to said center in said deciding.

22. The apparatus of claim 1, said acquisition comprising ultrasound acquisition via a sector scan (128, 136) from a probe from among said at least one probe that has a face having a physical center, said sector scan comprising receive beams from a common apex offset from said face, said apparatus being further configured for generating, based on a decision made in said deciding, a sequence for said scan, said generating comprising selectively excluding, from said sequence, a beam from among said beams based on an endpoint of said beam being, from a viewpoint at said center, occluded by the detected blockage.

23. The apparatus of claim 1, said imaging blockage existing within anatomy (120) of a human being, or of an animal, to be examined via said apparatus, said apparatus further comprising a scan-sequence generator configured for generating an ultrasound scan sequence personalized to said anatomy.

24. A computer readable medium embodying a program for imaging-blockage avoidance, said program having instructions executable by a processor for performing a plurality of acts, from among said plurality there being the acts of:

using at least one imaging probe to form a plurality of different imaging apertures; via said at least one probe, detecting imaging blockage; and deciding, based on a result of said detecting, upon a set (159) of one or more apertures to utilize for image acquisition.