Impact of transrectal ultrasound- and computed tomography-based seed localization on postimplant dosimetry in prostate brachytherapy.
OBJECTIVE
To study the impact of seed localization, as performed by different observers using linked (125)I seeds, on postimplant dosimetry in prostate brachytherapy and, to compare transrectal ultrasound (TRUS)-based with CT-based approach for the dosimetric outcomes.


METHODS
Nineteen permanent prostate implants were conducted using linked (125)I seeds. Postimplant TRUS and CT images were acquired and prostate glands were, after implantation, delineated on all images by a single oncologist, who had performed all 19 seeding procedures. Six observers independently localized the seeds on both TRUS and CT images, from which the principle dosimetric parameters V(100) (volume of prostate that received the prescribed dose), V(150) (volume of prostate that received 150% of the prescribed dose), and D(90) (minimal dose delivered to 90% of the prostate) were directly calculated for each patient. A single-factor analysis of variance was first applied to determine interobserver variability in seed localization. A nonparametric comparison of the approach using TRUS and CT was then carried out by the Wilcoxon paired-sample test.


RESULTS
Analysis from the analysis of variance for TRUS showed that the null hypothesis for equal means, could not be rejected for all six observers based on a significance level alpha=0.05. TRUS-based and CT-based approaches were then cross compared by the Wilcoxon paired-sample test, which suggested that the null hypothesis was insignificant for V(100) and D(90), but was significant for V(150).


CONCLUSIONS
Both TRUS- and CT-imaging modalities provided indistinguishable postimplant dosimetry results as far as V(100) and D(90) were concerned. There was comparable observer independence between TRUS- and CT-based seed localization for linked-seed implant procedures. With other advantages that TRUS-imaging modality had over CT in the evaluation of postimplant dosimetry, TRUS would be a preferred choice in conjunction with linked seeds for intraoperative procedures in prostate brachytherapy.
Chew
Meng-Sang
MS
Department of Radiation Oncology, Cooper University Hospital, Camden, NJ; Department of Mechanical Engineering, Lehigh University, Bethlehem, PA.
Xue
Jinyu
J
Department of Radiation Oncology, Cooper University Hospital, Camden, NJ. Electronic address: Xue-jinyu@cooperhealth.edu.
Houser
Chris
C
Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA.
Misic
Vladimir
V
Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA.
Cao
Junsheng
J
Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA.
Cornwell
Thomas
T
Department of Radiation Oncology, Frankford Hospital, Philadelphia, PA.
Handler
Jay
J
Department of Urology, Frankford Hospital, Philadelphia, PA.
Yu
Yan
Y
Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA.
Gressen
Eric
E
Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA.
D001918:Brachytherapy / Q000379:methods*; D004307:Dose-Response Relationship, Radiation; D019160:Endosonography / Q000379:methods*; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D015588:Observer Variation; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012007:Rectum / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome