Comparison of combined x-ray radiography and magnetic resonance (XMR) imaging-versus computed tomography-based dosimetry for the evaluation of permanent prostate brachytherapy implants.

PURPOSE To present a method for the dosimetric analysis of permanent prostate brachytherapy implants using a combination of stereoscopic X-ray radiography and magnetic resonance (MR) imaging (XMR) in an XMR facility, and to compare the clinical results between XMR- and computed tomography (CT)-based dosimetry. METHODS AND MATERIALS Patients who had received nonstranded iodine-125 permanent prostate brachytherapy implants underwent XMR and CT imaging 4 weeks later. Four observers outlined the prostate gland on both sets of images. Dose-volume histograms (DVHs) were derived, and agreement was compared among the observers and between the modalities. RESULTS A total of 30 patients were evaluated. Inherent XMR registration based on prior calibration and optical tracking required a further automatic seed registration step that revealed a median root mean square registration error of 4.2 mm (range, 1.6-11.4). The observers agreed significantly more closely on prostate base and apex positions as well as outlining contours on the MR images than on those from CT. Coefficients of variation were significantly higher for observed prostate volumes, D90, and V100 parameters on CT-based dosimetry as opposed to XMR. The XMR-based dosimetry showed little agreement with that from CT for all observers, with D90 95% limits of agreement ranges of 65, 118, 79, and 73 Gy for Observers 1, 2, 3, and 4, respectively. CONCLUSIONS The study results showed that XMR-based dosimetry offers an alternative to other imaging modalities and registration methods with the advantages of MR-based prostate delineation and confident three-dimensional reconstruction of the implant. The XMR-derived dose-volume histograms differ from the CT-derived values and demonstrate less interobserver variability.

[1]  J. Williamson,et al.  Update of AAPM Task Group No. 43 Report: A revised AAPM protocol for brachytherapy dose calculations. , 2003, Medical physics.

[2]  Tom Pickles,et al.  125I reimplantation in patients with poor initial dosimetry after prostate brachytherapy. , 2004, International journal of radiation oncology, biology, physics.

[3]  S L Schoeppel,et al.  Treatment planning issues related to prostate movement in response to differential filling of the rectum and bladder. , 1991, International journal of radiation oncology, biology, physics.

[4]  H. Hricak,et al.  Brachytherapy for prostate cancer: endorectal MR imaging of local treatment-related changes. , 2001, Radiology.

[5]  J J Prete,et al.  Intraobserver and interobserver variability of MR imaging- and CT-derived prostate volumes after transperineal interstitial permanent prostate brachytherapy. , 1998, Radiology.

[6]  Paul J. Besl,et al.  A Method for Registration of 3-D Shapes , 1992, IEEE Trans. Pattern Anal. Mach. Intell..

[7]  Roberto Orecchia,et al.  MR and CT image fusion for postimplant analysis in permanent prostate seed implants. , 2004, International journal of radiation oncology, biology, physics.

[8]  Ivan Yeung,et al.  MRI-CT fusion to assess postbrachytherapy prostate volume and the effects of prolonged edema on dosimetry following transperineal interstitial permanent prostate brachytherapy. , 2004, Brachytherapy.

[9]  M van Herk,et al.  Definition of the prostate in CT and MRI: a multi-observer study. , 1999, International journal of radiation oncology, biology, physics.

[10]  Kawal S. Rhode,et al.  Registration and tracking to integrate X-ray and MR images in an XMR Facility , 2003, IEEE Transactions on Medical Imaging.

[11]  Dan Ash,et al.  Impact of prostate volume evaluation by different observers on CT-based post-implant dosimetry. , 2002, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[12]  M A Moerland,et al.  Evaluation of permanent I-125 prostate implants using radiography and magnetic resonance imaging. , 1997, International journal of radiation oncology, biology, physics.

[13]  Ivan Yeung,et al.  Interobserver variation in postimplant computed tomography contouring affects quality assessment of prostate brachytherapy. , 2002, Brachytherapy.

[14]  Charles A Kunos,et al.  Migration of implanted free radioactive seeds for adenocarcinoma of the prostate using a Mick applicator. , 2004, Brachytherapy.

[15]  David Beyer,et al.  Interobserver variability leads to significant differences in quantifiers of prostate implant adequacy. , 2002, International journal of radiation oncology, biology, physics.

[16]  J J Prete,et al.  Source localization following permanent transperineal prostate interstitial brachytherapy using magnetic resonance imaging. , 1997, International journal of radiation oncology, biology, physics.

[17]  H. Hricak,et al.  Prostate volumes defined by magnetic resonance imaging and computerized tomographic scans for three-dimensional conformal radiotherapy. , 1996, International journal of radiation oncology, biology, physics.

[18]  S Nag,et al.  The American Brachytherapy Society recommendations for permanent prostate brachytherapy postimplant dosimetric analysis. , 2000, International journal of radiation oncology, biology, physics.

[19]  A. Beckett,et al.  AKUFO AND IBARAPA. , 1965, Lancet.

[20]  Masayuki Matsuo,et al.  Comparison of MRI-based and CT/MRI fusion-based postimplant dosimetric analysis of prostate brachytherapy. , 2006, International journal of radiation oncology, biology, physics.

[21]  C C Ling,et al.  A CT-based evaluation method for permanent implants: application to prostate. , 1993, International journal of radiation oncology, biology, physics.

[22]  R. Stock,et al.  Importance of post-implant dosimetry in permanent prostate brachytherapy. , 2002, European urology.

[23]  P L Roberson,et al.  Comparison of MRI pulse sequences in defining prostate volume after permanent implantation. , 2002, International journal of radiation oncology, biology, physics.

[24]  N. Yue,et al.  Edema associated with I-125 or Pd-103 prostate brachytherapy and its impact on post-implant dosimetry: an analysis based on serial CT acquisition. , 1998, International Journal of Radiation Oncology, Biology, Physics.

[25]  J. Cosset,et al.  PSA bounce after permanent implant prostate brachytherapy may mimic a biochemical failure: a study of 295 patients with a minimum 3-year followup. , 2006, Brachytherapy.

[26]  J Blackall,et al.  Using combined x-ray and MR imaging for prostate I-125 post-implant dosimetry: phantom validation and preliminary patient work , 2006, Physics in medicine and biology.

[27]  A. Meigooni,et al.  A Monte Carlo evaluation of the dosimetric characteristics of the EchoSeed Model 6733 (125)I brachytherapy source. , 2002, Brachytherapy.

[28]  D. Altman,et al.  STATISTICAL METHODS FOR ASSESSING AGREEMENT BETWEEN TWO METHODS OF CLINICAL MEASUREMENT , 1986, The Lancet.

[29]  Kawal S. Rhode,et al.  A system for real-time XMR guided cardiovascular intervention , 2005, IEEE Transactions on Medical Imaging.

[30]  D. Ash,et al.  ESTRO/EAU/EORTC recommendations on permanent seed implantation for localized prostate cancer. , 2000, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[31]  D. Gladstone,et al.  Prostate seed implant quality assessment using MR and CT image fusion. , 1999, International journal of radiation oncology, biology, physics.

[32]  Kenneth B. Thornton,et al.  Toward a dynamic real-time intraoperative permanent prostate brachytherapy methodology. , 2003, Brachytherapy.

[33]  J J Prete,et al.  Comparison of MRI- and CT-based post-implant dosimetric analysis of transperineal interstitial permanent prostate brachytherapy. , 1998, Radiation oncology investigations.