Clinical feasibility study for the use of implanted gold seeds in the prostate as reliable positioning markers during megavoltage irradiation.
OBJECTIVE
The aim of this study was to assess the feasibility of using gold seed implants in the prostate for position verification, using an a-Si flat panel imager as a detector during megavoltage irradiation of prostate carcinoma. This is a study to guarantee positioning accuracy in intensity-modulated radiotherapy.


METHODS
Ten patients with localized prostate carcinoma (T2-3) received between one and three fiducial gold markers in the prostate. All patients were treated with 3-D conformal radiotherapy with an anterior-posterior (AP) and two lateral wedge fields. The acute gastrointestinal (GI) and genitourinary (GU) toxicities were scored using common toxicity criteria scales (CTC). Using three consecutive CT scans and portal images obtained during the treatment we have studied the occurrence of any change in prostate shape (deformation), seed migration and the magnitude of translations and rotations of the prostate.


RESULTS
We observed no acute major complications for prostate irradiation regarding the seed implantation. The maximum acute GU toxicity grade 2 (dysuria and frequency) was observed in seven patients during the treatment. The maximum grade 2 (diarrhoea) was scored in two patients regarding the acute GI toxicities. No significant prostate deformation could be detected in the consecutive CT scans. It appeared that the distances between the markers only slightly changed during treatment (S.D. 0.5 mm). Random prostate translations were (1 S.D.) 2.1, 3.2 and 2.2 mm in the lateral (LR), AP and cranial-caudal (CC) directions, respectively, whereas systematic translations were 3.3, 4.8 and 3.5 mm in the LR, AP and CC directions, respectively. Random prostate rotations were (1 S.D.) 3.6, 1.7 and 1.9 degrees around the LR, AP and CC axis, respectively, whereas systematic rotations were 4.7, 2.0 and 2.7 degrees around the LR, AP and CC axis, respectively.


CONCLUSIONS
We found that the fiducial gold seeds are a safe and appropriate device to verify and correct the position of prostate during megavoltage irradiation. The amount of seed migration and prostate deformation is far below our present tumour delineation accuracy.
Dehnad
Homan
H
Department of Radiotherapy, University Medical Centre Utrecht, MS Q00.118, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands. h.dehnad@radcl.ruu.nl
Nederveen
Aart J
AJ
van der Heide
Uulke A
UA
van Moorselaar
R Jeroen A
RJ
Hofman
Pieter
P
Lagendijk
Jan J W
JJ
D000368:Aged; D001918:Brachytherapy / Q000379:methods*; D005240:Feasibility Studies; D006050:Gold Radioisotopes / Q000008:administration & dosage*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011467:Prostate / Q000502:physiology / Q000503:physiopathology / Q000528:radiation effects; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011882:Radiotherapy, High-Energy / Q000379:methods*; D012044:Regression Analysis
D006050:Gold Radioisotopes