Evaluation of the Changes in the Shape and Location of the Prostate and Pelvic Organs Due to Bladder Filling and Rectal Distension
نویسندگان
1 Department of Radiology, Medical Imaging Research Center,
2 Department of Mechanical Engineering, Radiation Research Center, Shiraz University of Medical Sciences, Shiraz,
3 Department of Radiology, Medical Imaging Research Center,
4 Department of Radiotherapy, Center for Research in Medical Physics and Engineering, Nemazee Hospital,
5 Department of Medical Physics and Engineering, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
doi
چکیده
Background: A steep dose gradient between prostate and organs at risk (rectum and bladder) is ideal in treatmentmodality, so prostate displacement and deformation due to bladder filling and rectal distension play animportant role in critical organs dose. This study aims to evaluate the changes in the shape and location of theprostate and pelvic organs due to bladder filling and rectal distension.Methods: Three patients who referred for transrectal prostatic biopsy (Shahid Faghihi Hospital, Shiraz, Iran) withdifferent prostate sizes were enrolled. A 1.5-Tesla MRI system (Avanto, Siemens, Germany) and an ultrasoundsystem (Logiq 500, GE medical systems, USA) were used to collect images of patients prostate at differentstages of bladder and rectum fullness.Results: The mean displacement of the prostate after bladder filling in the supine and left decubitus positionsalong the Anterior-Posterior (AP) axis was posterior by 4.9 mm (range: 0.7-6.3 mm) and along the Superior-Inferior (SI) axis was inferior by 3.4 mm (range: 1.4-5 mm). Prostate displacement in the Left-Right (LR) axis wasnegligible. The mean prostate displacement after rectal distension was anterior by 7.1 mm in the supine position,5.1 mm anterior in the left decubitus position and along the SI axis was inferior by 2.5 mm in the supine and leftdecubitus positions. The maximum prostate deformation due to rectal distension and bladder filling in the supineposition was as large as 3.2 mm, 1.9 mm and 1.2 mm in the AP, SI and LR directions respectively. While in theleft decubitus position, it was 2.6 mm, 1.2 mm and 1.3 mm in the AP, LR and SI axis respectively.Conclusion: It is probably of importance to evaluate the influence of the changes in the shape and location ofthe prostate due to bladder filling, rectal distension and patient position in post-implant brachytherapy dosimetry.Using images of the patients in the left decubitus position with full bladder and distended rectum for planning atreatment are suggested.
