SHAPE Society

1. Intravascular Characterization of
Atheroscleotic Lesions with 18
F-FDG &
A Novel Intravascular Beta Probe
A. Tawakol*, D. Elmaleh*, H. Gewirtz*, J. Muller*,
A. J. Fischman*, & F. Daghighian†
*Harvard Medical School and
*Massachusetts General Hospital, Boston, MA
† IntraMedical Imaging Inc., Los Angeles, CA.

2. • An intravascular method is needed to
detect vulnerable plaques (VP).
• VP contain abundant inflammatory
cells, which in turn accumulate 18
F-
Fluorodeoxyglucose (FDG).
Introduction:

3. Objective:
To test the hypothesis that a catheter-
mounted scintillation detector can
detect experimental atherosclerotic
lesions after injection of FDG.

4. Methods:
• Atherosclerotic Animal Model:
– New Zealand rabbits
– Balloon injury of the infradiaphragmatic aorta
– High cholesterol diet for 10 weeks.
• At 10 weeks, 1 mCi/kg FDG was administered to
atherosclerotic and control rabbits.
• 3-4 hours after FDG, rabbits were sacrificed, and
aortas removed as a single segment.

5. Intra-Vascular Beta Probe
• More sensitive to positron emissions than γ rays
• A 1 mm diameter, 2 mm-long plastic scintillator was
optically coupled to a PMT via a 40 cm long fiber.
• Over-all diameter of probe is 1.6 mm.
IntraMedical Imaging Inc. LA, CA

6. Measurement in Animals:
• The flexible beta probe was inserted into the
abdomino-thoracic aortae.
• Measurements made :
– At sites of grossly visible plaque,
– At non-injured sites in the cholesterol fed rabbits,
– In corresponding areas in control aorta,
– Each, in triplicate, (at 2 sec/measurement),
• The queried aortic segments were then excised and
examined using standard well counting.

7. Results:
• Sensitivity of the probe was 850±11 cps/microCi
• Catheter-determined activity correlated with well
counting measurements:

8. Results: Beta Probe Counts
Plaque Non-plaque
5
10
BetaProbeCounts(cps)
n=9
n=15
(P<0.001)
15

9. Conclusions:
• Atherosclerotic plaques can be readily
distinguished from non-injured regions by
the beta probe.
• This newly developed intravascular
detector, together with FDG, has promise
for the in vivo detection of vulnerable
plaques

10. Discussion
• Thinner, more sensitive beta probes are
being developed at IntraMedical.
• Combination of detection and therapy may
enhance the clinical applicability of this
technique.

11. Contacts
Ahmed Tawakol, M.D.
Mass. General Hospital, Boston, MA
atawakol@partners.org
Farhad Daghighian, PhD
IntraMedical Imaging Inc. LA, CA
fd@intra-medical.com