Effectiveness of using fewer implanted fiducial markers for prostate target alignment.
OBJECTIVE
To evaluate the impact of the number and location of intraprostatic fiducial markers on the accuracy and reproducibility of daily prostate target alignment and to evaluate the migration of such markers.


METHODS
Three gold fiducial markers were implanted transrectally under ultrasound guidance near the apex, middle, and base of the prostate in 10 prostate cancer patients. The patients had pretreatment in-room computed tomography (CT) scans three times a week, for approximately 25 CT scans per patient during the 8-week treatment course. A total of 1280 alignments were performed using different alignment scenarios: whole-prostate soft tissue alignment (the gold standard), bone alignment, and seven permutations of alignments using one, two, or three fiducial markers. The results of bone alignment and fiducial alignment were compared with the results of whole-prostate alignment. Fiducial migration was also evaluated.


RESULTS
Single-fiducial-marker alignment was more accurate and reproducible than bone alignment. However, due to organ deformation, single fiducial markers did not always reliably represent the position of the entire prostate. The use of two-fiducial combinations was more accurate and reproducible than single-fiducial alignment, and use of all three fiducials was the best. Use of an apex fiducial together with a base fiducial rivaled the use of all three fiducials markers together. Fiducial migration was minimal.


CONCLUSIONS
The number and the location of implanted fiducial markers affect the accuracy and reliability of daily prostate target alignment. The use of two or more fiducial markers is recommended.
Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA. rkudchad@mdanderson.org
Rajat J
RJ
Kudchadker
Andrew K
AK
Lee
Zhiqian H
ZH
Yu
Jennifer L
JL
Johnson
Lifei
L
Zhang
Yongbin
Y
Zhang
Richard A
RA
Amos
Hiroyuki
H
Nakanishi
Atsushi
A
Ochiai
Lei
L
Dong
D001842:Bone and Bones / Q000000981:diagnostic imaging; D005548:Foreign-Body Migration / Q000000981:diagnostic imaging*; D006046:Gold; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D011467:Prostate / Q000000981:diagnostic imaging*; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D019736:Prostheses and Implants / Q000706:statistics & numerical data*; D061766:Proton Therapy; D015203:Reproducibility of Results; D012984:Software; D014057:Tomography, X-Ray Computed
D006046:Gold