Alison Pouch

Research Associate

I am a member of the Penn Image Computing and Science Laboratory in the Department of Radiology and the Gorman Cardiovascular Research Group in the Department of Surgery. My general research interests include 3D echocardiographic (3DE) imaging, cardiovascular physiology, and quantitative medical image analysis, especially image segmentation and shape theory. Within this broad scope, my research goals focus on developing quantitative methods for 4D morphological assessment of heart valves in real-time 3DE images. The motivation for these goals is to maximize the potential of cardiac ultrasound for image-based guidance of surgical treatment for heart valve disease.

Projects

Education

University of Pennsylvania, 2007 – 2013

  • Ph.D. in Bioengineering
  • HHMI-NIBIB Interfaces Program in Biomedical Imaging and Informational Sciences

The College of William and Mary, 2003 – 2007

  • B.S. in Physics with a dual concentration in Anthropology

Links

Research Gate | PubMed | Google Scholar

Peer-reviewed journal and conference publications

  • [DOI] A. S. Jassar, M. M. Levack, R. Solorzano, A. M. Pouch, G. Ferrari, A. Cheung, V. A. Ferrari, J. H. Gorman 3rd, R. Gorman, and B. M. Jackson, “Feasibility of In Vivo Human Aortic Valve Modeling Using Real-Time Three-Dimensional Echocardiography.,” Ann Thorac Surg, 2014.
    [Bibtex] 
    @ARTICLE{Jassar2014ATS,
author = {Jassar, Arminder S. and Levack, Melissa M. and Solorzano, Ricardo
D. and Pouch, Alison M. and Ferrari, Giovanni and Cheung, Albert
T. and Ferrari, Victor A. and Gorman, 3rd, Joseph H and Gorman, Robert
C. and Jackson, Benjamin M.},
title = {{F}easibility of {I}n {V}ivo {H}uman {A}ortic {V}alve {M}odeling
{U}sing {R}eal-{T}ime {T}hree-{D}imensional {E}chocardiography.},
journal = {{A}nn {T}horac {S}urg},
year = {2014},
month = {Feb},
abstract = {Surgical techniques for aortic valve (AV) repair are directed toward
restoring normal structural relationships in the aortic root and
rely on detailed assessment of root and valve anatomy. Noninvasive
three-dimensional (3D) imaging and modeling may assist in patient
selection and operative planning.Transesophageal real-time 3D echocardiographic
images of 5 patients with normal AV were acquired. The aortic root
and the annulus were manually segmented at end diastole using a 36-point
rotational template. The AV leaflets and the coaptation zone were
manually segmented in parallel 1-mm cross sections. Quantitative
3D models of the AV and root were generated and used to measure standard
anatomic parameters and were compared to conventional two-dimensional
echocardiographic measurements. All measurements are given as mean
± SD.Annular, sinus, and sinotubular junction areas were 4.1 ± 0.6
cm(2), 7.5 ± 1.2 cm(2), and 3.9 ± 1.0 cm(2), respectively. Root diameters
(measured in three locations) by 3D model inspection and two-dimensional
echocardiography measurement correlated (R(2) = 0.75). Noncoapted
areas of the left, right, and noncoronary leaflets were 1.9 ± 0.2
cm(2), 1.6 ± 0.3 cm(2), and 1.6 ± 0.3 cm(2), respectively. Mean coaptation
areas for the left-right, left-noncoronary, and right-noncoronary
coaptation zones were 87.7 ± 36.9 mm(2), 69.9 ± 20.7 mm(2), and 114.2
± 23.0 mm(2), respectively. The mean ratio of noncoapted leaflet
area to annular area was 1.3 ± 0.2.High-resolution 3D models of the
in vivo normal human aortic root and valve were generated using 3D
echocardiography. Quantitative 3D models and analysis may assist
in characterization of pathology and decision making for AV repair.},
doi = {10.1016/j.athoracsur.2013.12.017},
institution = {{D}epartment of {S}urgery, {U}niversity of {P}ennsylvania, {P}hiladelphia,
{P}ennsylvania. {E}lectronic address: benjamin.jackson@uphs.upenn.edu.},
language = {eng},
medline-pst = {aheadofprint},
owner = {alison},
pii = {S0003-4975(13)02852-X},
pmid = {24518577},
timestamp = {2014.02.27},
url = {http://dx.doi.org/10.1016/j.athoracsur.2013.12.017}
}
  • [DOI] E. K. Shang, E. Lai, A. M. Pouch, R. Hinmon, R. C. Gorman, J. H. Gorman 3rd, C. Sehgal, G. Ferrari, J. E. Bavaria, and B. Jackson, “Validation of semiautomated and locally resolved aortic wall thickness measurements from computed tomography.,” J Vasc Surg, 2014.
    [Bibtex] 
    @ARTICLE{Shang2014JVS,
author = {Shang, Eric K. and Lai, Eric and Pouch, Alison M. and Hinmon, Robin
and Gorman, Robert C. and Gorman, 3rd, Joseph H and Sehgal, Chandra
M. and Ferrari, Giovanni and Bavaria, Joseph E. and Jackson, Benjamin
M.},
title = {{V}alidation of semiautomated and locally resolved aortic wall thickness
measurements from computed tomography.},
journal = {{J} {V}asc {S}urg},
year = {2014},
month = {Jan},
abstract = {Aortic wall thickness (AWT) is important for anatomic description
and biomechanical modeling of aneurysmal disease. However, no validated,
noninvasive method for measuring AWT exists. We hypothesized that
semiautomated image segmentation algorithms applied to computed tomography
angiography (CTA) can accurately measure AWT.Aortic samples from
10 patients undergoing open thoracoabdominal aneurysm repair were
taken from sites of the proximal or distal anastomosis, or both,
yielding 13 samples. Aortic specimens were fixed in formalin, embedded
in paraffin, and sectioned. After staining with hematoxylin and eosin
and Masson's trichrome, sections were digitally scanned and measured.
Patients' preoperative CTA Digital Imaging and Communications in
Medicine (DICOM; National Electrical Manufacturers Association, Rosslyn,
Va) images were segmented into luminal, inner arterial, and outer
arterial surfaces with custom algorithms using active contours, isoline
contour detection, and texture analysis. AWT values derived from
image data were compared with measurements of corresponding pathologic
specimens.AWT determined by CTA averaged 2.33 ± 0.66 mm (range, 1.52-3.55 mm),
and the AWT of pathologic specimens averaged 2.36 ± 0.75 mm (range,
1.51-4.16 mm). The percentage difference between pathologic specimens
and CTA-determined AWT was 9.5\% ± 4.1\% (range, 1.8\%-16.7\%). The
correlation between image-based measurements and pathologic measurements
was high (R = 0.935). The 95\% limits of agreement computed by Bland-Altman
analysis fell within the range of -0.42 and 0.42 mm.Semiautomated
analysis of CTA images can be used to accurately measure regional
and patient-specific AWT, as validated using pathologic ex vivo human
aortic specimens. Descriptions and reconstructions of aortic aneurysms
that incorporate locally resolved wall thickness are feasible and
may improve future attempts at biomechanical analyses.},
doi = {10.1016/j.jvs.2013.11.065},
institution = {{D}epartment of {S}urgery, {U}niversity of {P}ennsylvania, {P}hiladelphia,
{P}a; {D}ivision of {V}ascular {S}urgery and {E}ndovascular {T}herapy,
{U}niversity of {P}ennsylvania, {P}hiladelphia, {P}a. {E}lectronic
address: benjamin.jackson@uphs.upenn.edu.},
language = {eng},
medline-pst = {aheadofprint},
owner = {alison},
pii = {S0741-5214(13)02160-5},
pmid = {24388698},
timestamp = {2014.02.27},
url = {http://dx.doi.org/10.1016/j.jvs.2013.11.065}
}
  • [DOI] A. M. Pouch, M. Vergnat, J. R. McGarvey, G. Ferrari, B. M. Jackson, C. M. Sehgal, P. A. Yushkevich, R. C. Gorman, and J. Gorman 3rd, “Statistical assessment of normal mitral annular geometry using automated three-dimensional echocardiographic analysis.,” Ann Thorac Surg, vol. 97, iss. 1, pp. 71-77, 2014.
    [Bibtex] 
    @ARTICLE{Pouch2014ATS,
author = {Pouch, Alison M. and Vergnat, Mathieu and McGarvey, Jeremy R. and
Ferrari, Giovanni and Jackson, Benjamin M. and Sehgal, Chandra M.
and Yushkevich, Paul A. and Gorman, Robert C. and Gorman, 3rd, Joseph
H},
title = {{S}tatistical assessment of normal mitral annular geometry using
automated three-dimensional echocardiographic analysis.},
journal = {{A}nn {T}horac {S}urg},
year = {2014},
volume = {97},
pages = {71--77},
number = {1},
month = {Jan},
abstract = {The basis of mitral annuloplasty ring design has progressed from qualitative
surgical intuition to experimental and theoretical analysis of annular
geometry with quantitative imaging techniques. In this work, we present
an automated three-dimensional (3D) echocardiographic image analysis
method that can be used to statistically assess variability in normal
mitral annular geometry to support advancement in annuloplasty ring
design.Three-dimensional patient-specific models of the mitral annulus
were automatically generated from 3D echocardiographic images acquired
from subjects with normal mitral valve structure and function. Geometric annular
measurements including annular circumference, annular height, septolateral
diameter, intercommissural width, and the annular height to intercommissural
width ratio were automatically calculated. A mean 3D annular contour
was computed, and principal component analysis was used to evaluate
variability in normal annular shape.The following mean ± standard
deviations were obtained from 3D echocardiographic image analysis:
annular circumference, 107.0 ± 14.6 mm; annular height, 7.6 ± 2.8
mm; septolateral diameter, 28.5 ± 3.7 mm; intercommissural width,
33.0 ± 5.3 mm; and annular height to intercommissural width ratio,
22.7\% ± 6.9\%. Principal component analysis indicated that shape
variability was primarily related to overall annular size, with more
subtle variation in the skewness and height of the anterior annular
peak, independent of annular diameter.Patient-specific 3D echocardiographic-based
modeling of the human mitral valve enables statistical analysis of
physiologically normal mitral annular geometry. The tool can potentially
lead to the development of a new generation of annuloplasty rings
that restore the diseased mitral valve annulus back to a truly normal
geometry.},
doi = {10.1016/j.athoracsur.2013.07.096},
institution = {{G}orman {C}ardiovascular {R}esearch {G}roup, {U}niversity of {P}ennsylvania,
{P}hiladelphia, {P}ennsylvania; {D}epartment of {S}urgery, {U}niversity
of {P}ennsylvania, {P}hiladelphia, {P}ennsylvania. {E}lectronic address:
gormanj@uphs.upenn.edu.},
language = {eng},
medline-pst = {ppublish},
owner = {alison},
pii = {S0003-4975(13)01709-8},
pmid = {24090576},
timestamp = {2014.02.27},
url = {http://dx.doi.org/10.1016/j.athoracsur.2013.07.096}
}
  • [DOI] A. M. Pouch, H. Wang, M. Takabe, B. M. Jackson, J. Gorman 3rd, R. C. Gorman, P. A. Yushkevich, and C. M. Sehgal, “Fully automatic segmentation of the mitral leaflets in 3D transesophageal echocardiographic images using multi-atlas joint label fusion and deformable medial modeling.,” Med Image Anal, vol. 18, iss. 1, pp. 118-129, 2014.
    [Bibtex] 
    @ARTICLE{Pouch2014MIA,
author = {Pouch, A. M. and Wang, H. and Takabe, M. and Jackson, B. M. and Gorman,
3rd, JH and Gorman, R. C. and Yushkevich, P. A. and Sehgal, C. M.},
title = {{F}ully automatic segmentation of the mitral leaflets in 3{D} transesophageal
echocardiographic images using multi-atlas joint label fusion and
deformable medial modeling.},
journal = {{M}ed {I}mage {A}nal},
year = {2014},
volume = {18},
pages = {118--129},
number = {1},
month = {Jan},
abstract = {Comprehensive visual and quantitative analysis of in vivo human mitral
valve morphology is central to the diagnosis and surgical treatment
of mitral valve disease. Real-time 3D transesophageal echocardiography
(3D TEE) is a practical, highly informative imaging modality for
examining the mitral valve in a clinical setting. To facilitate visual
and quantitative 3D TEE image analysis, we describe a fully automated
method for segmenting the mitral leaflets in 3D TEE image data. The
algorithm integrates complementary probabilistic segmentation and
shape modeling techniques (multi-atlas joint label fusion and deformable
modeling with continuous medial representation) to automatically
generate 3D geometric models of the mitral leaflets from 3D TEE image
data. These models are unique in that they establish a shape-based
coordinate system on the valves of different subjects and represent
the leaflets volumetrically, as structures with locally varying thickness.
In this work, expert image analysis is the gold standard for evaluating
automatic segmentation. Without any user interaction, we demonstrate
that the automatic segmentation method accurately captures patient-specific
leaflet geometry at both systole and diastole in 3D TEE data acquired
from a mixed population of subjects with normal valve morphology
and mitral valve disease.},
doi = {10.1016/j.media.2013.10.001},
institution = {{D}epartment of {B}ioengineering, {U}niversity of {P}ennsylvania,
{P}hiladelphia, {PA}, {U}nited {S}tates; {G}orman {C}ardiovascular
{R}esearch {G}roup, {U}niversity of {P}ennsylvania, {P}hiladelphia,
{PA}, {U}nited {S}tates. {E}lectronic address: pouch@seas.upenn.edu.},
language = {eng},
medline-pst = {ppublish},
owner = {alison},
pii = {S1361-8415(13)00142-4},
pmid = {24184435},
timestamp = {2014.02.27},
url = {http://dx.doi.org/10.1016/j.media.2013.10.001}
}
  • A. M. Pouch, H. Wang, M. Takabe, B. M. Jackson, C. M. Sehgal, J. H. Gorman 3rd, R. C. Gorman, and P. A. Yushkevich, “Automated segmentation and geometrical modeling of the tricuspid aortic valve in 3D echocardiographic images.,” Med Image Comput Comput Assist Interv, vol. 16, iss. Pt 1, pp. 485-492, 2013.
    [Bibtex] 
    @ARTICLE{Pouch2013MICCAI,
author = {Pouch, Alison M. and Wang, Hongzhi and Takabe, Manabu and Jackson,
Benjamin M. and Sehgal, Chandra M. and Gorman, 3rd, Joseph H and
Gorman, Robert C. and Yushkevich, Paul A.},
title = {{A}utomated segmentation and geometrical modeling of the tricuspid
aortic valve in 3{D} echocardiographic images.},
journal = {{M}ed {I}mage {C}omput {C}omput {A}ssist {I}nterv},
year = {2013},
volume = {16},
pages = {485--492},
number = {Pt 1},
abstract = {The aortic valve has been described with variable anatomical definitions,
and the consistency of 2D manual measurement of valve dimensions
in medical image data has been questionable. Given the importance
of image-based morphological assessment in the diagnosis and surgical
treatment of aortic valve disease, there is considerable need to
develop a standardized framework for 3D valve segmentation and shape
representation. Towards this goal, this work integrates template-based
medial modeling and multi-atlas label fusion techniques to automatically
delineate and quantitatively describe aortic leaflet geometry in
3D echocardiographic (3DE) images, a challenging task that has been
explored only to a limited extent. The method makes use of expert
knowledge of aortic leaflet image appearance, generates segmentations
with consistent topology, and establishes a shape-based coordinate
system on the aortic leaflets that enables standardized automated
measurements. In this study, the algorithm is evaluated on 11 3DE
images of normal human aortic leaflets acquired at mid systole. The
clinical relevance of the method is its ability to capture leaflet
geometry in 3DE image data with minimal user interaction while producing
consistent measurements of 3D aortic leaflet geometry.},
institution = {{D}epartment of {R}adiology, {U}niversity of {P}ennsylvania, {P}hiladelphia,
{PA}, {USA}.},
language = {eng},
medline-pst = {ppublish},
owner = {alison},
pmid = {24505702},
timestamp = {2014.02.27}
}
  • [DOI] A. M. Pouch, C. Xu, P. A. Yushkevich, A. S. Jassar, M. Vergnat, J. H. Gorman 3rd, R. C. Gorman, C. M. Sehgal, and B. M. Jackson, “Semi-automated mitral valve morphometry and computational stress analysis using 3D ultrasound.,” J Biomech, vol. 45, iss. 5, pp. 903-907, 2012.
    [Bibtex] 
    @ARTICLE{Pouch2012JB,
author = {Pouch, Alison M. and Xu, Chun and Yushkevich, Paul A. and Jassar,
Arminder S. and Vergnat, Mathieu and Gorman, 3rd, Joseph H and Gorman,
Robert C. and Sehgal, Chandra M. and Jackson, Benjamin M.},
title = {{S}emi-automated mitral valve morphometry and computational stress
analysis using 3{D} ultrasound.},
journal = {{J} {B}iomech},
year = {2012},
volume = {45},
pages = {903--907},
number = {5},
month = {Mar},
abstract = {In vivo human mitral valves (MV) were imaged using real-time 3D transesophageal
echocardiography (rt-3DTEE), and volumetric images of the MV at mid-systole
were analyzed by user-initialized segmentation and 3D deformable
modeling with continuous medial representation, a compact representation
of shape. The resulting MV models were loaded with physiologic pressures
using finite element analysis (FEA). We present the regional leaflet
stress distributions predicted in normal and diseased (regurgitant)
MVs. Rt-3DTEE, semi-automated leaflet segmentation, 3D deformable
modeling, and FEA modeling of the in vivo human MV is tenable and
useful for evaluation of MV pathology.},
doi = {10.1016/j.jbiomech.2011.11.033},
institution = {{D}epartment of {B}ioengineering, {U}niversity of {P}ennsylvania,
{P}hiladelphia, {PA}, {USA}.},
keywords = {Echocardiography, Three-Dimensional, methods; Echocardiography, Transesophageal,
methods; Finite Element Analysis; Heart Valve Diseases, pathology/ultrasonography;
Humans; Image Interpretation, Computer-Assisted, methods; Mitral
Valve, pathology/ultrasonography; Models, Cardiovascular; Ultrasonics,
methods},
language = {eng},
medline-pst = {ppublish},
owner = {alison},
pii = {S0021-9290(11)00715-9},
pmid = {22281408},
timestamp = {2014.02.27},
url = {http://dx.doi.org/10.1016/j.jbiomech.2011.11.033}
}
  • [DOI] A. M. Pouch, P. A. Yushkevich, B. M. Jackson, A. S. Jassar, M. Vergnat, J. H. Gorman, R. C. Gorman, and C. M. Sehgal, “Development of a semi-automated method for mitral valve modeling with medial axis representation using 3D ultrasound.,” Med Phys, vol. 39, iss. 2, pp. 933-950, 2012.
    [Bibtex] 
    @ARTICLE{Pouch2012MP,
author = {Pouch, Alison M. and Yushkevich, Paul A. and Jackson, Benjamin M.
and Jassar, Arminder S. and Vergnat, Mathieu and Gorman, Joseph H.
and Gorman, Robert C. and Sehgal, Chandra M.},
title = {{D}evelopment of a semi-automated method for mitral valve modeling
with medial axis representation using 3{D} ultrasound.},
journal = {{M}ed {P}hys},
year = {2012},
volume = {39},
pages = {933--950},
number = {2},
month = {Feb},
abstract = {Precise 3D modeling of the mitral valve has the potential to improve
our understanding of valve morphology, particularly in the setting
of mitral regurgitation (MR). Toward this goal, the authors have
developed a user-initialized algorithm for reconstructing valve geometry
from transesophageal 3D ultrasound (3D US) image data.Semi-automated
image analysis was performed on transesophageal 3D US images obtained
from 14 subjects with MR ranging from trace to severe. Image analysis
of the mitral valve at midsystole had two stages: user-initialized
segmentation and 3D deformable modeling with continuous medial representation
(cm-rep). Semi-automated segmentation began with user-identification
of valve location in 2D projection images generated from 3D US data.
The mitral leaflets were then automatically segmented in 3D using
the level set method. Second, a bileaflet deformable medial model
was fitted to the binary valve segmentation by Bayesian optimization.
The resulting cm-rep provided a visual reconstruction of the mitral
valve, from which localized measurements of valve morphology were
automatically derived. The features extracted from the fitted cm-rep
included annular area, annular circumference, annular height, intercommissural
width, septolateral length, total tenting volume, and percent anterior
tenting volume. These measurements were compared to those obtained
by expert manual tracing. Regurgitant orifice area (ROA) measurements
were compared to qualitative assessments of MR severity. The accuracy
of valve shape representation with cm-rep was evaluated in terms
of the Dice overlap between the fitted cm-rep and its target segmentation.The
morphological features and anatomic ROA derived from semi-automated
image analysis were consistent with manual tracing of 3D US image
data and with qualitative assessments of MR severity made on clinical
radiology. The fitted cm-reps accurately captured valve shape and
demonstrated patient-specific differences in valve morphology among
subjects with varying degrees of MR severity. Minimal variation in
the Dice overlap and morphological measurements was observed when
different cm-rep templates were used to initialize model fitting.This
study demonstrates the use of deformable medial modeling for semi-automated
3D reconstruction of mitral valve geometry using transesophageal
3D US. The proposed algorithm provides a parametric geometrical representation
of the mitral leaflets, which can be used to evaluate valve morphology
in clinical ultrasound images.},
doi = {10.1118/1.3673773},
institution = {{D}epartment of {B}ioengineering, {U}niversity of {P}ennsylvania,
{P}hiladelphia, {PA} 19104, {USA}. pouch@seas.upenn.edu},
keywords = {Algorithms; Computer Simulation; Echocardiography, Three-Dimensional,
methods; Humans; Image Enhancement, methods; Image Interpretation,
Computer-Assisted, methods; Mitral Valve, anatomy /&/ histology/ultrasonography;
Models, Anatomic; Models, Cardiovascular; Pattern Recognition, Automated,
methods; Reproducibility of Results; Sensitivity and Specificity},
language = {eng},
medline-pst = {ppublish},
owner = {alison},
pmid = {22320803},
timestamp = {2014.02.27},
url = {http://dx.doi.org/10.1118/1.3673773}
}
  • [DOI] A. M. Pouch, H. Wang, P. A. Yushkevich, M. Takabe, B. M. Jackson, J. H. Gorman 3rd, R. C. Gorman, and C. M. Sehgal, Fully automatic segmentation of the open mitral leaflets in 3D transesophageal echocardiographic images using multi-atlas label fusion and deformable medial modeling, 2012.
    [Bibtex] 
    @PROCEEDINGS{2012,
title = {{F}ully automatic segmentation of the open mitral leaflets in {3D}
transesophageal echocardiographic images using multi-atlas label
fusion and deformable medial modeling},
year = {2012},
author = {Pouch, Alison M. and Wang, Hongzhi and Yushkevich, Paul A. and Takabe,
Manabu and Jackson, Benjamin M. and Gorman, 3rd, Joseph H. and Gorman,
Robert C. and Sehgal, Chandra M.},
booktitle = {{U}ltrasonics {S}ymposium ({IUS}), 2012 {IEEE} {I}nternational},
doi = {10.1109/ULTSYM.2012.0055},
owner = {alison},
pages = {220--223},
timestamp = {2014.02.27},
url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6562275}
}
  • [DOI] D. P. Nathan, C. Xu, A. M. Pouch, K. B. Chandran, B. Desjardins, J. H. Gorman 3rd, R. M. Fairman, R. C. Gorman, and B. M. Jackson, “Increased wall stress of saccular versus fusiform aneurysms of the descending thoracic aorta.,” Ann Vasc Surg, vol. 25, iss. 8, pp. 1129-1137, 2011.
    [Bibtex] 
    @ARTICLE{Nathan2011AVS,
author = {Nathan, Derek P. and Xu, Chun and Pouch, Alison M. and Chandran,
Krishnan B. and Desjardins, Benoit and Gorman, 3rd, Joseph H and
Fairman, Ron M. and Gorman, Robert C. and Jackson, Benjamin M.},
title = {{I}ncreased wall stress of saccular versus fusiform aneurysms of
the descending thoracic aorta.},
journal = {{A}nn {V}asc {S}urg},
year = {2011},
volume = {25},
pages = {1129--1137},
number = {8},
month = {Nov},
abstract = {Repair of fusiform descending thoracic aortic aneurysms (DTAs) is
indicated when aneurysmal diameter exceeds a certain threshold; however,
diameter-related indications for repair of saccular DTA are less
well established.Human subjects with fusiform (n = 17) and saccular
(n = 17) DTAs who underwent computed tomographic angiography were
identified. Patients with aneurysms related to connective tissue
disease were excluded. The thoracic aorta was segmented, reconstructed,
and triangulated to create a mesh. Finite element analysis was performed
using a pressure load of 120 mm Hg and a uniform aortic wall thickness
of 3.2 mm to compare the pressure-induced wall stress of fusiform
and saccular DTAs.The mean maximum diameter of the fusiform DTAs
(6.0 ± 1.5 cm) was significantly greater (p = 0.006) than that of
the saccular DTAs (4.4 ± 1.8 cm). However, mean peak wall stress
of the fusiform DTAs (0.33 ± 0.15 MPa) was equivalent to that of
the saccular DTAs (0.30 ± 0.14 MPa), as found by using an equivalence
threshold of 0.15 MPa. The mean normalized wall stress (peak wall
stress divided by maximum aneurysm radius) of the saccular DTAs was
greater than that of the fusiform DTAs (0.16 ± 0.09 MPa/cm vs. 0.11
± 0.03 MPa/cm, p = 0.035).The normalized wall stress for saccular
DTA is greater than that for fusiform DTA, indicating that geometric
factors such as aneurysm shape influence wall stress. These results
suggest that saccular aneurysms may be more prone to rupture than
fusiform aneurysms of similar diameter, provide a theoretical rationale
for the repair of saccular DTAs at a smaller diameter, and suggest
investigation of the role of biomechanical modeling in surgical decision
making is warranted.},
doi = {10.1016/j.avsg.2011.07.008},
institution = {{D}epartment of {G}eneral {S}urgery, {H}ospital of the {U}niversity
of {P}ennsylvania, {P}hiladelphia, {PA} 19104, {USA}.},
keywords = {Aged; Aged, 80 and over; Aorta, Thoracic, physiopathology/radiography;
Aortic Aneurysm, Thoracic, physiopathology/radiography; Aortography,
methods; Biomechanical Phenomena; Blood Pressure; Chi-Square Distribution;
Computer Simulation; Female; Finite Element Analysis; Hemodynamics;
Humans; Male; Middle Aged; Models, Cardiovascular; Philadelphia;
Prognosis; Retrospective Studies; Stress, Mechanical; Tomography,
X-Ray Computed},
language = {eng},
medline-pst = {ppublish},
owner = {alison},
pii = {S0890-5096(11)00359-1},
pmid = {22023944},
timestamp = {2014.02.27},
url = {http://dx.doi.org/10.1016/j.avsg.2011.07.008}
}
  • [DOI] A. S. Jassar, C. J. Brinster, M. Vergnat, D. J. Robb, T. J. Eperjesi, A. M. Pouch, A. T. Cheung, S. J. Weiss, M. A. Acker, J. H. Gorman 3rd, R. C. Gorman, and B. Jackson, “Quantitative mitral valve modeling using real-time three-dimensional echocardiography: technique and repeatability.,” Ann Thorac Surg, vol. 91, iss. 1, pp. 165-171, 2011.
    [Bibtex] 
    @ARTICLE{Jassar2011ATS,
author = {Jassar, Arminder Singh and Brinster, Clayton J. and Vergnat, Mathieu
and Robb, J Daniel and Eperjesi, Thomas J. and Pouch, Alison M. and
Cheung, Albert T. and Weiss, Stuart J. and Acker, Michael A. and
Gorman, 3rd, Joseph H and Gorman, Robert C. and Jackson, Benjamin
M.},
title = {{Q}uantitative mitral valve modeling using real-time three-dimensional
echocardiography: technique and repeatability.},
journal = {{A}nn {T}horac {S}urg},
year = {2011},
volume = {91},
pages = {165--171},
number = {1},
month = {Jan},
abstract = {Real-time three-dimensional (3D) echocardiography has the ability
to construct quantitative models of the mitral valve (MV). Imaging
and modeling algorithms rely on operator interpretation of raw images
and may be subject to observer-dependent variability. We describe
a comprehensive analysis technique to generate high-resolution 3D
MV models and examine interoperator and intraoperator repeatability
in humans.Patients with normal MVs were imaged using intraoperative
transesophageal real-time 3D echocardiography. The annulus and leaflets
were manually segmented using a TomTec Echo-View workstation. The
resultant annular and leaflet point cloud was used to generate fully
quantitative 3D MV models using custom Matlab algorithms. Eight images
were subjected to analysis by two independent observers. Two sequential
images were acquired for 6 patients and analyzed by the same observer.
Each pair of annular tracings was compared with respect to conventional
variables and by calculating the mean absolute distance between paired
renderings. To compare leaflets, MV models were aligned so as to
minimize their sum of squares difference, and their mean absolute
difference was measured.Mean absolute annular and leaflet distance
was 2.4±0.8 and 0.6±0.2 mm for the interobserver and 1.5±0.6 and
0.5±0.2 mm for the intraobserver comparisons, respectively. There
was less than 10\% variation in annular variables between comparisons.These
techniques generate high-resolution, quantitative 3D models of the
MV and can be used consistently to image the human MV with very small
interoperator and intraoperator variability. These data lay the framework
for reliable and comprehensive noninvasive modeling of the normal
and diseased MV.},
doi = {10.1016/j.athoracsur.2010.10.034},
institution = {{D}epartment of {S}urgery, {H}ospital of the {U}niversity of {P}ennsylvania,
{P}hiladelphia, {P}ennsylvania 19104, {USA}.},
keywords = {Echocardiography, Three-Dimensional; Echocardiography, Transesophageal;
Heart Valve Diseases, pathology/ultrasonography; Humans; Image Processing,
Computer-Assisted, methods; Mitral Valve; Models, Cardiovascular;
Monitoring, Intraoperative; Observer Variation; Predictive Value
of Tests; Reproducibility of Results},
language = {eng},
medline-pst = {ppublish},
owner = {alison},
pii = {S0003-4975(10)02379-9},
pmid = {21172507},
timestamp = {2014.02.27},
url = {http://dx.doi.org/10.1016/j.athoracsur.2010.10.034}
}
  • [DOI] M. Vergnat, A. S. Jassar, B. M. Jackson, L. P. Ryan, T. J. Eperjesi, A. M. Pouch, S. J. Weiss, A. T. Cheung, M. A. Acker, J. H. Gorman 3rd, and R. C. Gorman, “Ischemic mitral regurgitation: a quantitative three-dimensional echocardiographic analysis.,” Ann Thorac Surg, vol. 91, iss. 1, pp. 157-164, 2011.
    [Bibtex] 
    @ARTICLE{Vergnat2011ATS,
author = {Vergnat, Mathieu and Jassar, Arminder S. and Jackson, Benjamin M.
and Ryan, Liam P. and Eperjesi, Thomas J. and Pouch, Alison M. and
Weiss, Stuart J. and Cheung, Albert T. and Acker, Michael A. and
Gorman, 3rd, Joseph H and Gorman, Robert C.},
title = {{I}schemic mitral regurgitation: a quantitative three-dimensional
echocardiographic analysis.},
journal = {{A}nn {T}horac {S}urg},
year = {2011},
volume = {91},
pages = {157--164},
number = {1},
month = {Jan},
abstract = {A comprehensive three-dimensional echocardiography based approach
is applied to preoperative mitral valve (MV) analysis in patients
with ischemic mitral regurgitation (IMR). This method is used to
characterize the heterogeneous nature of the pathologic anatomy associated
with IMR.Intraoperative real-time three-dimensional transesophageal
echocardiograms of 18 patients with IMR (10 with anterior, 8 with
inferior infarcts) and 17 patients with normal MV were analyzed.
A customized image analysis protocol was used to assess global and
regional determinants of annular size and shape, leaflet tethering
and curvature, relative papillary muscle anatomy, and anatomic regurgitant
orifice area.Both mitral annular area and MV tenting volume were
increased in the IMR group as compared with patients with normal
MV (mitral annular area=1,065±59 mm2 versus 779±44 mm2, p=0.001;
and MV tenting volume=3,413±403 mm3 versus 1,696±200 mm3, p=0.001,
respectively). Within the IMR group, patients with anterior infarct
had larger annuli (1,168±99 mm2) and greater tenting volumes (4,260±779
mm3 versus 2,735±245 mm3, p=0.06) than the inferior infarct subgroup.
Papillary-annular distance was increased in the IMR group relative
to normal; these distances were largest in patients with anterior
infarcts. Whereas patients with normal MV had very consistent anatomic
determinants, annular shape and leaflet tenting distribution in the
IMR group were exceedingly variable. Mean anatomic regurgitant orifice
area was 25.8±3.0 mm2, and the number of discrete regurgitant orifices
varied from 1 to 4.Application of custom analysis techniques to three-dimensional
echocardiography images allows a quantitative and systematic analysis
of the MV, and demonstrates the extreme variability in pathologic
anatomy that occurs in patients with severe IMR.},
doi = {10.1016/j.athoracsur.2010.09.078},
institution = {{D}epartment of {S}urgery, {U}niversity of {P}ennsylvania, {P}hiladelphia,
{P}ennsylvania, {USA}.},
keywords = {Aged; Aged, 80 and over; Echocardiography, Three-Dimensional; Female;
Humans; Male; Middle Aged; Mitral Valve Insufficiency, etiology/surgery/ultrasonography;
Myocardial Ischemia, complications/surgery/ultrasonography; Predictive
Value of Tests; Reproducibility of Results; sisted},
language = {eng},
medline-pst = {ppublish},
owner = {alison},
pii = {S0003-4975(10)02217-4},
pmid = {21172506},
timestamp = {2014.02.27},
url = {http://dx.doi.org/10.1016/j.athoracsur.2010.09.078}
}
  • A. M. Pouch, T. W. Cary, S. M. Schultz, and C. M. Sehgal, “In vivo noninvasive temperature measurement by B-mode ultrasound imaging.,” J Ultrasound Med, vol. 29, iss. 11, pp. 1595-1606, 2010.
    [Bibtex] 
    @ARTICLE{Pouch2010JUM,
author = {Pouch, Alison M. and Cary, Theodore W. and Schultz, Susan M. and
Sehgal, Chandra M.},
title = {{I}n vivo noninvasive temperature measurement by {B}-mode ultrasound
imaging.},
journal = {{J} {U}ltrasound {M}ed},
year = {2010},
volume = {29},
pages = {1595--1606},
number = {11},
month = {Nov},
abstract = {This study investigated the use of ultrasound image analysis in quantifying
temperature changes in tissue, both ex vivo and in vivo, undergoing
local hyperthermia.Temperature estimation is based on the thermal
dependence of the acoustic speed in a heated medium. Because standard
beam-forming algorithms on clinical ultrasound scanners assume a
constant acoustic speed, temperature-induced changes in acoustic
speed produce apparent scatterer displacements in B-mode images.
A cross-correlation algorithm computes axial speckle pattern displacement
in B-mode images of heated tissue, and a theoretically derived temperature-displacement
relationship is used to generate maps of temperature changes within
the tissue. Validation experiments were performed on excised tissue
and in murine subjects, wherein low-intensity ultrasound was used
to thermally treat tissue for several minutes. Diagnostic temperature
estimation was performed using a linear array ultrasound transducer,
while a fine-wire thermocouple invasively measured the temperature
change.Pearson correlations ± SDs between the image-derived and thermocouple-measured
temperature changes were R² = 0.923 ± 0.066 for 4 thermal treatments
of excised bovine muscle tissue and R² = 0.917 ± 0.036 for 4 treatments
of in vivo murine tumor tissue. The average differences between the
two temperature measurements were 0.87°C ± 0.72°C for ex vivo studies
and 0.97°C ± 0.55°C for in vivo studies. Maps of the temperature
change distribution in tissue were generated for each experiment.This
study demonstrates that velocimetric measurement on B-mode images
has potential to assess temperature changes noninvasively in clinical
applications.},
institution = {{D}epartment of {R}adiology, {U}niversity of {P}ennsylvania, 3400
{S}pruce {S}treet, {P}hiladelphia, {PA} 19104 {USA}. pouch@seas.upenn.edu},
keywords = {Algorithms; Animals; Cattle; Female; Hyperthermia, Induced, instrumentation/methods;
Image Processing, Computer-Assisted; Lung Neoplasms, therapy/ultrasonography;
Mice; Mice, Nude; Temperature; Transducers; Ultrasonography, methods},
language = {eng},
medline-pst = {ppublish},
owner = {alison},
pii = {29/11/1595},
pmid = {20966471},
timestamp = {2014.02.27}
}
  • [DOI] J. E. Lynch, A. Pouch, R. Sanders, M. Hinders, K. Rudd, and J. Sevick, “Gaseous microemboli sizing in extracorporeal circuits using ultrasound backscatter.,” Ultrasound Med Biol, vol. 33, iss. 10, pp. 1661-1675, 2007.
    [Bibtex] 
    @ARTICLE{Lynch2007UMB,
author = {Lynch, John E. and Pouch, Alison and Sanders, Randi and Hinders,
Mark and Rudd, Kevin and Sevick, John},
title = {{G}aseous microemboli sizing in extracorporeal circuits using ultrasound
backscatter.},
journal = {{U}ltrasound {M}ed {B}iol},
year = {2007},
volume = {33},
pages = {1661--1675},
number = {10},
month = {Oct},
abstract = {This paper describes efforts to estimate the size of gaseous microemboli
(GME) in extracorporeal blood circuits based on the amplitude of
backscattered ultrasound, starting with analytic modeling of the
scattering behavior of GME in blood. After neglecting resonance effects,
this model predicts a linear relationship between the amplitude of
backscattered echoes and the diameter of GME. Computer simulations
based on the cylindrical acoustic finite integration technique were
performed to test some of the simplifying assumptions of the analytical
model, with the simulations predicting small deviations from the
linear approximation that could be treated as random scatter. Ultrasonic
and microscopic measurements of injected GME were then performed
on a test circuit to determine the linear correlation coefficient
between echo amplitude and GME diameter in conditions like those
employed in real cardiopulmonary bypass (CPB) circuits. The correlation
coefficient determined through this study was further validated in
a closed-loop CPB circuit using canine blood. This study shows that
the amplitude of ultrasonic backscattered echoes can be used to accurately
estimate the size distribution of a population of detected GME when
the spacing of emboli is great enough to minimize interference and
other multi-path scattering effects. With the high flow rates found
in CPB circuits, typically ranging from 2 to 6 L per minute (equivalent
to a flow velocity of 0.3 to 1 m/s through the circuit tubing), this
assumption will be valid even when hundreds of emboli per second
pass through the circuit. Therefore, sizing of GME using the ultrasonic
backscatter models described in this paper is a viable method for
estimating embolic load delivered to a patient during a CPB procedure.},
doi = {10.1016/j.ultrasmedbio.2007.04.008},
institution = {{L}una {I}nnovations {I}ncorporated, {H}ampton, {VA} 23185, {USA}.
lyncht@lunainnovations.com},
keywords = {Algorithms; Animals; Cardiopulmonary Bypass, adverse effects; Computer
Simulation; Dogs; Embolism, Air, ultrasonography; Extracorporeal
Circulation, adverse effects; Humans; Image Interpretation, Computer-Assisted;
Models, Animal; Scattering, Radiation; Ultrasonics},
language = {eng},
medline-pst = {ppublish},
owner = {alison},
pii = {S0301-5629(07)00204-9},
pmid = {17570578},
timestamp = {2014.02.27},
url = {http://dx.doi.org/10.1016/j.ultrasmedbio.2007.04.008}
}

Short conference papers and abstracts

  • [DOI] A. M. Pouch, H. Wang, P. A. Yushkevich, M. Takabe, B. M. Jackson, J. H. Gorman 3rd, R. C. Gorman, and C. M. Sehgal, Fully automatic segmentation of the open mitral leaflets in 3D transesophageal echocardiographic images using multi-atlas label fusion and deformable medial modeling, 2012.
    [Bibtex] 
    @PROCEEDINGS{2012,
title = {{F}ully automatic segmentation of the open mitral leaflets in {3D}
transesophageal echocardiographic images using multi-atlas label
fusion and deformable medial modeling},
year = {2012},
author = {Pouch, Alison M. and Wang, Hongzhi and Yushkevich, Paul A. and Takabe,
Manabu and Jackson, Benjamin M. and Gorman, 3rd, Joseph H. and Gorman,
Robert C. and Sehgal, Chandra M.},
booktitle = {{U}ltrasonics {S}ymposium ({IUS}), 2012 {IEEE} {I}nternational},
doi = {10.1109/ULTSYM.2012.0055},
owner = {alison},
pages = {220--223},
timestamp = {2014.02.27},
url = {http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6562275}
}