This page has been created as a followup on the June 1, 2009 ASPECT group meeting at Rockville. The primary goal of ASPECT-I is to develop clinical imaging protocols and methodologies that will yield data that is useful for engineering analysis, boundary condition definition, and clinical decision making. These protocols must be detailed and inclusive enough to provide complete and comprehensive data, while being as simple as possible to minimize complexity, cost, and non-compliance. This is a working page for defining the "wish list" of endpoint objectives, to help guide the clinical and imaging protocols. Per Brian's excellent suggestion, please add endpoint objectives (and potential imaging techniques and methodologies, if know) to the bullet-list below, and provide comments at the bottom of this page in the "comment" area.
- Plaque Composition, Cross Section, Volumetric Analysis
- Define plaque composition of target lesion as a function of spatial position prior to intervention. This requires pre-intervention IVUS, and analysis by the techniques developed by Paul Bishop et al.
- Define cross sectional area of target lesion as a function of spatial position prior to intervention. Requires pre-intervention IVUS, and standard analysis techniques.
- Define cross sectional area of target lesion as a function of spatial position immediately after intervention.
- Stent Deformation with Limb Flexion
- 3D geometry of stent with straight limb. Requires a set of two orthogonal (digital) plain X-ray views.
- 3D geometry of stent with flexed limb. Requires a set of two orthogonal (digital) plain X-ray views, with limb in two defined flexion conditions (90°/90° and 70°/ 20°). Define cross sectional area of target lesion as a function of spatial position with flexed limb (90°/90° perhaps more important than 70°/ 20°, if possible both).
Draft table of endpoint objectives (AZ, 2009-07-29)
|
|
objective |
data/ locations |
Time Points |
Leg Configuration |
imaging techniques and methodologies (preferred technique on top) |
comments (see also minutes from July, 23rd & 29th, 2009) |
|
|
|
|
|
|
|
|
1a |
|
|
Pre, Post, Follow-up |
straight, 70/20 |
|
post-processing of IVUS data (see IVUS protocol) |
|
Plaque compositon |
characterization |
|
|
IVUS |
combine IVUS & CT data for characterization |
|
|
immediate margins where stent meets vessel & record location |
|
|
CT |
pre, collect data for post/ follow-up for later evaluation? |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
1a |
|
|
Pre, Post, Follow-ups |
straight/ 90-90/70-20 |
|
Std IVUS Pullback (see IVUS protocol) |
|
Cross-section |
ovalization (a/b) |
IVUS |
two border: lumen border, internal elastic membrane and external elastic membrane (where vessel meets surrounding tissue); for post/ FU only lumen border possible; orientation difficult, use CT or with the help of landmark perhaps possible? |
|
|
immediate margins where stent meets vessel & record location, every 0.5mm |
CT |
ovalization means minor/ major axes of ellipse |
|
|
|
MR? |
90-90? |
|
|
|
|
|
|
|
|
|
1b |
Radial deflection (pulsatile) |
diameter change ("systolic diameter"-"diastolic diameter") |
|
|
|
See IVUS protocol, pick a few specific locations within the stent and the adjacent vessel (4-8 points) and collect IVUS images for ~5 sec to get diameter oscillations from blood pressure, also for averaging. See also cross-section comments. |
|
immediate margins where stent meets vessel & record location (outside, transition and inside stent) |
Pre, Post, Follow-ups |
straight/ 90-90/ 70-20 |
IVUS |
standard analysis techniques |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
1b |
|
|
Prio 1: 3 months FU Prio 2: 6 months FU Prio 3: 1 year FU at least 6 months after implantation, post procedure depending on discretion of physician, pre difficult to get |
straight/ 90-90/ 70-20 (all configurations important, if only one bent position possible 90/90 preferred) |
|
|
|
Bending |
minimum bending radius [mm], representing the inner radius of stent |
x-ray |
two orthogonal plain x-ray views, at least one is lateral..more planes are better for averaging and determination of vessel centerline; standing position with equal amount of weight on both legs preferred, record if on table or standing, equal weight or not, etc. (on a form) |
|
|
immediate margins where stent meets vessel & record location and related amount of bending |
CT |
90° knee flexion should be possible, probably less than < 90° for hip flexion, to be recorded on a form |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
1b |
|
|
see bending |
see bending |
|
|
|
|
mm change of length / mm initial length |
x-ray |
see bending |
|
Axial deformation |
immediate margins where stent meets vessel & record location |
CT |
see bending |
|
|
20 mm resolution if possible, measurement of entire length and division into segments if struts not detectable |
|
Could use IVUS for more accurate pathlength, but may be difficult for follow-up or flexed knee configurations |
|
|
|
|
|
|
|
|
|
2 |
|
|
see bending |
see bending |
|
|
|
Twist |
change of angle per initial length [°/mm] |
IVUS |
second option, need landmarks and small distances |
|
|
immediate margins where stent meets vessel & record location |
CT |
Challenging to identify same side branches, primarly modality |
|
|
|
|
Use torsion analysis in G. Choi '08 |
|
|
|
|
|
|
|
|
|
2 |
Flow Analysis |
|
Pre, Post, Follow-ups, any time when a duplex is performed |
straight/ 90-90/ 70-20 |
external Ultrasound |
standard analysis techniques, start or end of stent, landmark easy:in and out velocity measurement, diastole and systole; see Duplex protocol |
|
|
|
|
|
|
|
liter/minute & cm/sec |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
UPDATE: P. Bishop 2/22/2010
Below is a table from the R01 grant submission based on the desired data from the above table.
Table 3. Description of the subject-specific datasets that can be used for development of FE models for stent design.
|
Data Type |
Content |
Format |
Time of collection |
|
Angiography |
Straight & Bent leg curvatures,
Patency/Run-off perfusion information |
DICOM |
During- Intervention |
|
IVUS |
Radial Pulsatility
Lumen and vessel (Media-Adventitia) surface
Plaque Spatial Distribution
Calcification Classification (Nodule size/location) |
DICOM
Axial Bitmaps/contours
Text files |
Pre, Post- Intervention, Follow-up |
|
Gait |
Arterial stretch and shortening
Joint Angles |
Standard Gait data files → XLS |
Post- Intervention |
|
Duplex Ultrasound |
Arterial stretch
Velocities (Velocity vs. Time X,Y) straight leg
Velocities (Velocity vs. Time X,Y) bent leg |
Text files →XLS |
Follow-up |
|
CT/ DynaCT |
Vessel length, centerline, and curvature X,Y,Z
Lumen surface and Bony structure locations
Straight & Bent leg curvatures |
STL
DICOM |
Pre, During and Post- Intervention, Follow-up |
|
Xray |
Straight leg/Bent leg, bend angle (º)
Stent compression/geometries
Diameter of stent radial interference |
DICOM |
Post-Intervention, Follow-up |
|
I started this page with my top two endpoint wishes: plaque composition as a function of position, and stent deformation with limb flexion. Assuming the pre-stent and post-stent IVUS datasets can be co-registered with each other, it should be possible to register both IVUS datasets with X-ray derived stent geometry by matching the proximal and distal ends of the stent on IVUS and Xray. Now local flexion driven defomations of the stent derived from the Xray images can be compared with local plaque composition, which is quite novel.
I was impressed by the CT images of the proximal popliteal that Alexander showed in bent and straight configurations. I'm wondering if first 5 pts should have all imaging in straight, 70/20 and 90/90, so that we can work out kinks regarding imaging collection issues, and can also compare data from various types of imaging modalities.
I added on the "Stent Deformation with Limb Flexion" Bullet Point the cross-section determination with flexed limb.
I added a first draft of a table which summarizes the endpoint objectives and potential imaging techniques/ methodologies. Please add your comments. The next step is then to invert the table in that way, that the imaging technique, data/ location and time points are summarized in the clinical protocol and a second table. This table provides the information for which endpoint objective the data will be used. Please feel also free to comment on that.
Update of table after call July, 22nd. For further comments and discussed items see the minutes from July, 22nd. Discussed topics were bending and axial deformation.
Thanks to Mike for getting us a copy of this interesting paper. I've copied some excerpts here that provide some insight into the discussions we had last week about what might be reasonable to expect with respect to X-ray follow-up for SFA cases. I'm actually surprised at the number of time points that they have in this study: 1d, 3d, 30d, and subsequently every 3 months (out to 4 years!?). It suggests that there are 4 projections at each time point, but does not describe what projections these are, though it does state that they did NOT image bent limbs in this study. I suspect that they took two (orthagonal) images of the upper SFA, and two of the lower SFA / proximal popliteal.
Follow-up and outcomes. Clinical evaluations including
symptom changes, ankle brachial index, lesion patency
evaluated by ultrasound, and stent fracture assessed by X-ray
were performed at baseline, approximately at 24 h, 72 h, 1
month, and at every 3 months after procedure. Primary
patency was defined as peak systolic velocity ratio !2.4 by
duplex ultrasound (12). Stent fracture was defined as clear
interruption ($1 to 2 mm) of stent struts identified by
X-ray from 4 projections, with resulting kink or misalignment
along the axial length of the stent. Morphology of the
stent fracture was classified based on Appendix A: the Viva
Physicians, Inc., Research Program of Rocha-Singh et al.
(13). In brief, a single-tine fracture was defined as type 1;
multiple-tine fractures, type 2; stent fracture(s) with preserved
alignment of the components, type 3; stent fracture(
s) with mal-alignment of the components, type 4; stent
fracture(s) in a trans-axial spiral configuration, type 5. An
X-ray from 4 projections was performed at each follow-up
period to evaluate the stent fracture by 2 observers who had
the experience of more than 500 EVT cases within a year.
If different grades of stent fracture were observed within a
stent, the severest grade was adopted. Bent knee radiography
was not performed. The outcomes of this study were
overall primary patency, patency associated with and without
stent fracture, patency according to the types of nitinol
stents, and the morphology of stent fracture during the
follow-up period.
Update of table after call July, 29th. For further comments and discussed items see the minutes from July, 29th. Table is now complete. Please send your comments or write them onto this page.
Siemen's site on DynaCT:
http://www.siemens.com/DynaCT
Link to some papers on DynaCT:
http://www.medical.siemens.com/webapp/wcs/stores/servlet/PSGenericDisplay?catalogId=-11&catTree=100010,1007660,12751,14420&langId=-11&pageId=102654&productId=175891&storeId=10001