Postprostatectomy target-normal structure overlap volume differences using computed tomography and radioimmunoscintigraphy images for radiotherapy treatment planning.
OBJECTIVE
The purpose of this study was to analyze regions of uptake in normal structures on postprostatectomy radioimmunoscintigraphy (RIS) images by evaluating differences in the overlap volumes of prostate fossa clinical target volume (CTV) and planning target volume (PTV) using correlative computed tomography (CT) images.


METHODS
The electronic records of 13 patients who received external beam radiotherapy postprostatectomy and who underwent a vessel-based RIS/CT registration were reviewed. For each patient, the RIS-defined CTV (CTV(RIS)) was compared (in terms of the overlap volume with the surrounding bladder, rectum, pubic symphysis, and penile bulb) with the CT-defined CTV(pre) before this registration and also with CTV(post) (the final target volume used for treatment). Similar analyses were done for PTV(RIS), PTV(pre), and PTV(post) defined in each case to be the corresponding CTV + 1-cm margin.


RESULTS
CTV(RIS) overlapped significantly more with the bladder, rectum, and symphysis, but not with the penile bulb, than did either the CTV(pre) or CTV(post). However, the corresponding PTV analyses revealed no significant differences between any of the overlap volumes of any of the PTVs with the bladder, rectum, and penile bulb, but did reveal a significant difference between the PTV(RIS) and PTV(post) overlap volumes with the symphysis compared with PTV(pre) overlap volumes with the symphysis.


CONCLUSIONS
On RIS images, there appear to be areas of uptake in the bladder, rectum, and pubic symphysis but not the penile bulb; however, the dosimetric consequences of this uptake for radiation treatment planning are minimal on the bladder, rectum, and penile bulb, but require segmentation for dose reduction to the pubic symphysis.
Department of Radiation and Cellular Oncology, University of Illinois at Chicago, Chicago, IL 60637, USA.
Andy
A
Su
Michael J
MJ
Blend
Danny
D
Spelbring
Russell J
RJ
Hamilton
Ashesh B
AB
Jani
D006801:Humans; D008297:Male; D011182:Postoperative Care / Q000379:methods; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000175:diagnosis* / Q000628:therapy*; D011829:Radiation Dosage; D016719:Radioimmunodetection / Q000379:methods*; D011874:Radiometry / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012189:Retrospective Studies; D013382:Subtraction Technique; D014057:Tomography, X-Ray Computed / Q000379:methods*