Prostate postbrachytherapy seed distribution: comparison of high-resolution, contrast-enhanced, T1- and T2-weighted endorectal magnetic resonance imaging versus computed tomography: Initial experience

Harvard University, Cambridge, Massachusetts, United States
International Journal of Radiation OncologyBiologyPhysics (Impact Factor: 4.18). 10/2007; 69(1):70-8. DOI: 10.1016/j.ijrobp.2007.02.039
Source: PubMed

ABSTRACT To compare contrast-enhanced, T1-weighted, three-dimensional magnetic resonance imaging (CEMR) and T2-weighted magnetic resonance imaging (T2MR) with computed tomography (CT) for prostate brachytherapy seed location for dosimetric calculations.
Postbrachytherapy prostate MRI was performed on a 1.5 Tesla unit with combined surface and endorectal coils in 13 patients. Both CEMR and T2MR used a section thickness of 3 mm. Spiral CT used a section thickness of 5 mm with a pitch factor of 1.5. All images were obtained in the transverse plane. Two readers using CT and MR imaging assessed brachytherapy seed distribution independently. The dependency of data read by both readers for a specific subject was assessed with a linear mixed effects model.
The mean percentage (+/- standard deviation) values of the readers for seed detection and location are presented. Of 1205 implanted seeds, CEMR, T2MR, and CT detected 91.5% +/- 4.8%, 78.5% +/- 8.5%, and 96.1% +/- 2.3%, respectively, with 11.8% +/- 4.5%, 8.5% +/- 3.5%, 1.9% +/- 1.0% extracapsular, respectively. Assignment to periprostatic structures was not possible with CT. Periprostatic seed assignments for CEMR and T2MR, respectively, were as follows: neurovascular bundle, 3.5% +/- 1.6% and 2.1% +/- 0.9%; seminal vesicles, 0.9% +/- 1.8% and 0.3% +/- 0.7%; periurethral, 7.1% +/- 3.3% and 5.8% +/- 2.9%; penile bulb, 0.6% +/- 0.8% and 0.3% +/- 0.6%; Denonvillier's Fascia/rectal wall, 0.5% +/- 0.6% and 0%; and urinary bladder, 0.1% +/- 0.3% and 0%. Data dependency analysis showed statistical significance for the type of imaging but not for reader identification.
Both enumeration and localization of implanted seeds are readily accomplished with CEMR. Calculations with MRI dosimetry do not require CT data. Dose determinations to specific extracapsular sites can be obtained with MRI but not with CT.

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    Scientific poster presentation at the European Congress of Radiology 2013, Vienna, Austria; 03/2013
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    ABSTRACT: To assess detailed dosimetry data for prostate and clinical relevant intra- and peri-prostatic structures including neurovascular bundles (NVB), urethra, and penile bulb (PB) from postbrachytherapy computed tomography (CT) versus high resolution contrast enhanced magnetic resonance imaging (HR-CEMRI). Eleven postbrachytherapy prostate cancer patients underwent HR-CEMRI and CT imaging. Computed tomography and HR-CEMRI images were randomized and 2 independent expert readers created contours of prostate, intra- and peri-prostatic structures on each CT and HR-CEMRI scan for all 11 patients. Dosimetry data including V100, D90, and D100 was calculated from these contours. Mean V100 values from CT and HR-CEMRI contours were as follows: prostate (98.5% and 96.2%, p = 0.003), urethra (81.0% and 88.7%, p = 0.027), anterior rectal wall (ARW) (8.9% and 2.8%, p < 0.001), left NVB (77.9% and 51.5%, p = 0.002), right NVB (69.2% and 43.1%, p = 0.001), and PB (0.09% and 11.4%, p = 0.005). Mean D90 (Gy) derived from CT and HR-CEMRI contours were: prostate (167.6 and 150.3, p = 0.012), urethra (81.6 and 109.4, p = 0.041), ARW (2.5 and 0.11, p = 0.003), left NVB (98.2 and 58.6, p = 0.001), right NVB (87.5 and 55.5, p = 0.001), and PB (11.2 and 12.4, p = 0.554). Findings of this study suggest that HR-CEMRI facilitates accurate and meaningful dosimetric assessment of prostate and clinically relevant structures, which is not possible with CT. Significant differences were seen between CT and HR-CEMRI, with volume overestimation of CT derived contours compared to HR-CEMRI.
    Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, Chicago IL; 12/2013
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    ABSTRACT: MR localization of implanted devices for radiotherapy (RT) in prostatic carcinoma is critical for treatment planning. This clinical note studies the application of a multi-echo gradient recalled echo (GRE) pulse sequence with sum of squares echo combination (ME GRE) to enhance detection of seeds and fiducials. Fifteen patients who underwent MRI using fast spin echo (FSE), single-echo and ME GRE over a 9-month period were retrospectively evaluated by two readers who assessed overall image quality, depiction of seeds/fiducials and image sharpness using a 5-point scale (1 = poor, 2 = suboptimal, 3 = adequate, 4 = above average, 5 = excellent). Image scores were compared using the Wilcoxon sign rank test. In all 15 patients, both readers rated the depiction of seeds/fiducials with ME GRE as excellent. In all 15 patients, overall image quality and image sharpness with ME GRE was rated as excellent by reader 1. In 12/15 patients, overall image quality and image sharpness with ME GRE was rated as excellent and in the other patients above average by reader 2. There was a difference in depiction of seeds/fiducials comparing GRE to FSE (P < 0.001) and ME to single echo GRE (P < 0.001). Overall image quality and sharpness was higher with ME compared with single echo GRE (P < 0.001) and similar to FSE (P = 0.26 and P = 0.16). Multi-echo GRE provides better detection of implanted seeds and fiducial markers when compared with both FSE and single-echo GRE potentially improving RT treatment planning for prostate carcinoma.J. Magn. Reson. Imaging 2014. © 2014 Wiley Periodicals, Inc.
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