Impact of high dose volumetric CT on PTV margin reduction in VMAT prostate radiotherapy.

The aim of the study is to determine PTV margin for inter-observer variability in the volumetric modulated arc therapy (VMAT) prostate radiotherapy with high-dose volumetric CT (HDVCT) and conventional helical CT (CCT) for planning. Secondly to investigate the impact of geometric (PTV expansion) and dosimetric (conformity) imperfection of planning process on the PTV margin analysis. Prostate gland of ten patients were scanned with CCT and HDVCT techniques consecutively on a 320 slice volumetric CT scanner with wide field detector of 16 cm.

Evaluation of high dose volumetric CT to reduce inter-observer delineation variability and PTV margins for prostate cancer radiotherapy.

Purpose: The aim was to determine whether the enhanced soft tissue contrast provided by high-dose volumetric CT (HDVCT) can reduce inter-observer variability in delineating prostate compared to helical conventional CT (CCT) scans and 3T MRI scans for patients undergoing radical prostate cancer radiotherapy. Secondly, to quantify the potential PTV reduction with decreased inter-observer variability.

Materials And Methods: A 320 slice volumetric CT scanner was used.

'Compromise position' image alignment to accommodate independent motion of multiple clinical target volumes during radiotherapy: A high risk prostate cancer example.

Introduction: Inclusion of multiple independently moving clinical target volumes (CTVs) in the irradiated volume causes an image guidance conundrum. The purpose of this research was to use high risk prostate cancer as a clinical example to evaluate a 'compromise' image alignment strategy.

Methods: The daily pre-treatment orthogonal EPI for 14 consecutive patients were included in this analysis.

A facility for magnetic resonance-guided radiation therapy.

Magnetic resonance (MR) imaging is routinely employed in the design of radiotherapy (RT) treatment plans for many disease sites. It is evident that tighter integration of MR imaging into the RT process would increase confidence in dose placement and facilitate the integration of new MR imaging information (including anatomical and functional imaging) into the therapy process. To this end, a dedicated MR-guided RT (MRgRT) facility has been created that integrates a state-of-the-art linear accelerator delivery system, high-dose rate brachytherapy afterloader, and superconducting MR scanner to allow MR-based online treatment guidance, adaptive replanning, and response monitoring while maintaining the clinical functionality of the existing delivery systems.

Automatic Segmentation of Lung Carcinoma Using 3D Texture Features in 18-FDG PET/CT.

Target definition is the largest source of geometric uncertainty in radiation therapy. This is partly due to a lack of contrast between tumor and healthy soft tissue for computed tomography (CT) and due to blurriness, lower spatial resolution, and lack of a truly quantitative unit for positron emission tomography (PET). First-, second-, and higher-order statistics, Tamura, and structural features were characterized for PET and CT images of lung carcinoma and organs of the thorax.

A randomized comparison of interfraction and intrafraction prostate motion with and without abdominal compression.

Background And Purpose: To quantify inter- and intrafraction prostate motion in a standard VacLok (VL) immobilization device or in the BodyFix (BF) system incorporating a compression element which may reduce abdominal movement.

Materials And Methods: Thirty-two patients were randomly assigned to VL or BF. Interfraction prostate motion >3 mm was corrected pre-treatment.

Investigation of the dosimetric effect of respiratory motion using four-dimensional weighted radiotherapy.

We have developed a four-dimensional weighted radiotherapy (4DW-RT) technique. This method involves designing the motion of the linear accelerator beam to coincide with the tumour motion determined from 4D-CT imaging while including a weighting factor to account for irregular motion and limitations of the delivery system. Experiments were conducted with a moving phantom to assess limitations of the delivery system when applying this method.

Studies of the in vivo radiosensitivity of human skin fibroblasts.

Background And Purpose: To examine the radiosensitivity of skin cells obtained directly from the irradiated skin of patients undergoing fractionated radiation treatment prior to surgery for treatment of soft tissue sarcoma (STS) and to determine if there was a relationship with the development of wound healing complications associated with the surgery post-radiotherapy.

Methods: Micronucleus (MN) formation was measured in cells (primarily dermal fibroblasts) obtained from human skin at their first division after being removed from STS patients during post-radiotherapy surgery (2-9 weeks after the end of the radiotherapy). At the time of radiotherapy (planned tumor dose - 50Gy in 25 daily fractions) measurements were made of surface skin dose at predetermined marked sites.

Patient dose from kilovoltage cone beam computed tomography imaging in radiation therapy.

Kilovoltage cone-beam computerized tomography (kV-CBCT) systems integrated into the gantry of linear accelerators can be used to acquire high-resolution volumetric images of the patient in the treatment position. Using on-line software and hardware, patient position can be determined accurately with a high degree of precision and, subsequently, set-up parameters can be adjusted to deliver the intended treatment. While the patient dose due to a single volumetric imaging acquisition is small compared to the therapy dose, repeated and daily image guidance procedures can lead to substantial dose to normal tissue.

Comparative evaluation of image quality from three CT simulation scanners.

Today, radiation therapy (RT) is moving toward increased radiation dose to the tumor as a result of 3D conformal RT (3DCRT) and intensity-modulated RT (IMRT), which have been made possible by advances in volumetric-based image planning with digital imaging systems such as computed tomography (CT). Treatment planning for such RT requires superior CT image quality. Our goal in this study was to evaluate and to compare the image quality of three unique CT simulation scanners available at our center for both single- and multiple-slice helical scanners.

On-line aSi portal imaging of implanted fiducial markers for the reduction of interfraction error during conformal radiotherapy of prostate carcinoma.

Purpose: An on-line system to ensure accuracy of daily setup and therapy of the prostate has been implemented with no equipment modification required. We report results and accuracy of patient setup using this system.

Methods And Materials: Radiopaque fiducial markers were implanted into the prostate before radiation therapy.

A randomized trial of supine vs. prone positioning in patients undergoing escalated dose conformal radiotherapy for prostate cancer.

Background And Purpose: The optimal treatment position for patients receiving radical radiation therapy for prostate cancer has been a source of controversy. To resolve this issue, we conducted a randomized trial to evaluate the effects of supine and prone positioning on organ motion, positioning errors, and dose to critical organs during escalated dose conformal irradiation for localized prostate cancer and patient and therapist satisfaction with setup technique.

Patients And Methods: Twenty eight patients were randomized to commence treatment immobilized in the supine or prone position and were subsequently changed to the alternate positioning for the latter half of their treatment.

A dose-volume histogram analysis of the seminal vesicles in men treated with conformal radiotherapy to 'prostate alone'.

Background And Purpose: There is no consensus on whether the seminal vesicles should be included in the clinical target volume (CTV) for radiotherapy of localized prostate cancer. To inform the debate, we have undertaken a dose-volume histogram (DVH) analysis of the seminal vesicles in patients treated with escalated dose conformal radiation to 'prostate alone'.

Material And Methods: Twenty-five consecutive patients receiving conformal radiation to the prostate, to a dose of 75.