Empirical planning target volume modeling for high precision MRI guided intracranial radiotherapy.

Purpose: Magnetic resonance image-guided radiotherapy for intracranial indications is a promising advance; however, uncertainties remain for both target localization after translation-only MR setup and intrafraction motion. This investigation quantified these uncertainties and developed a population-based planning target volume (PTV) model to explore target and organ-at-risk (OAR) volumetric coverage tradeoffs.

Methods: Sixty-six patients, 49 with a primary brain tumor and 17 with a post-surgical resection cavity, treated on a 1.

Control charts for evaluation of quality of low-dose-rate brachytherapy for prostate cancer.

Purpose: Variations in dosimetric outcomes among patients treated with low-dose-rate brachytherapy for prostate cancer exist, even when implants are within dose constraints. Here, we used control charts to investigate reasons for intra-patient dosimetric variability.

Material And Methods: Univariate and multivariate control charts for prostate V (percentage of prostate volume that received 100% of prescribed radiation dose), D (radiation dose to 90% of prostate volume), and RV (rectal wall volume that received 100% of prescribed radiation dose) were generated for 212 consecutive prostate cancer patients implanted with iodine-125 (I) radioactive seeds at the Princess Margaret Cancer Centre.

4D-CT Attenuation Correction in Respiratory-Gated PET for Hypoxia Imaging: Is It Really Beneficial?

Previous literature has shown that 4D respiratory-gated positron emission tomography (PET) is beneficial for quantitative analysis and defining targets for boosting therapy. However the case for addition of a phase-matched 4D-computed tomography (CT) for attenuation correction (AC) is less clear. We seek to validate the use of 4D-CT for AC and investigate the impact of motion correction for low signal-to-background PET imaging of hypoxia using radiotracers such as FAZA and FMISO.

[F]DCFPyL PET-MRI/CT for unveiling a molecularly defined oligorecurrent prostate cancer state amenable for curative-intent ablative therapy: study protocol for a phase II trial.

Introduction: The oligometastatic (OM) disease hypothesis of an intermediate metastatic state with limited distant disease deposits amenable for curative therapies remains debatable. Over a third of prostate cancer (PCa) patients treated with radical prostatectomy and postoperative radiotherapy experience disease recurrence; these patients are considered incurable by current standards. Often the recurrence cannot be localised by conventional imaging (CT and bone scan).

Image registration assessment in radiotherapy image guidance based on control chart monitoring.

Image guidance with cone beam computed tomography in radiotherapy can guarantee the precision and accuracy of patient positioning prior to treatment delivery. During the image guidance process, operators need to take great effort to evaluate the image guidance quality before correcting a patient's position. This work proposes an image registration assessment method based on control chart monitoring to reduce the effort taken by the operator.

Brachytherapy patient safety events in an academic radiation medicine program.

Purpose: To describe the incidence and type of brachytherapy patient safety events over 10 years in an academic brachytherapy program.

Methods And Materials: Brachytherapy patient safety events reported between January 2007 and August 2016 were retrieved from the incident reporting system and reclassified using the recently developed National System for Incident Reporting in Radiation Treatment taxonomy. A multi-incident analysis was conducted to identify common themes and key learning points.

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.

Technical challenges of sparing infrahyoid swallowing organs at risk in oropharynx squamous cell cancer treated with IMRT.

This study reports clinical performance in the sparing of infrahyoid swallowing organs at risk (SWOARs) in oropharynx cancer intensity-modulated radiation therapy (IMRT) plans. Rates of meeting dose-volume planning goals are reported and compared with geometry-based estimates of what is achievable. This study also develops 3 measures of target-SWOAR geometry and tests their usefulness in providing geometry-based dose-volume planning goals.

A Practice-based Taxonomy for Radiation Treatment Errors.

Purpose: An absence of a common language for incident classification limits knowledge sharing within and between organizations in the radiotherapy community. This challenge provided the motivation to develop a clinically relevant taxonomy for radiotherapy errors.

Materials And Methods: This was a multicenter, prospective study that consisted of three phases: (1) an initial version of the taxonomy was developed based on the World Health Organization Conceptual Framework for the International Classification for Patient Safety and taxonomy models from radiotherapy and other industries; (2) the taxonomy was evaluated using actual incident data from a single practitioner and revised; and (3) face validity testing of the taxonomy was performed by two additional practitioners from different radiotherapy centers using simulated incident cases.

The Effect of Registration Volume Extent on Residual Errors Assessed Using Cone-Beam Computed Tomography in Radiation Treatment of Head and Neck Cancer.

Purpose: The objective of this study was to investigate the effect of the varying extent of cone-beam computed tomography (CBCT) registration volumes (RVs) on setup errors for head and neck (H&N) radiotherapy.

Methods And Materials: Daily CBCT images for 31 patients receiving H&N intensity-modulated radiotherapy (IMRT) were reviewed. Registrations using anatomically defined RVs with a fixed superior border at base of sella and varying inferior extent were used retrospectively to evaluate patient setup.

Implementation of remote 3-dimensional image guided radiation therapy quality assurance for radiation therapy oncology group clinical trials.

Purpose: To report the process and initial experience of remote credentialing of three-dimensional (3D) image guided radiation therapy (IGRT) as part of the quality assurance (QA) of submitted data for Radiation Therapy Oncology Group (RTOG) clinical trials; and to identify major issues resulting from this process and analyze the review results on patient positioning shifts.

Methods And Materials: Image guided radiation therapy datasets including in-room positioning CT scans and daily shifts applied were submitted through the Image Guided Therapy QA Center from institutions for the IGRT credentialing process, as required by various RTOG trials. A centralized virtual environment is established at the RTOG Core Laboratory, containing analysis tools and database infrastructure for remote review by the Physics Principal Investigators of each protocol.

A national survey of the availability of intensity-modulated radiation therapy and stereotactic radiosurgery in Canada.

Background: The timely and appropriate adoption of new radiation therapy (RT) technologies is a challenge both in terms of providing of optimal patient care and managing health care resources. Relatively little is known regarding the rate at which new RT technologies are adopted in different jurisdictions, and the barriers to implementation of these technologies.

Methods: Surveys were sent to all radiation oncology department heads in Canada regarding the availability of RT equipment from 2006 to 2010.

Auto-segmentation of normal and target structures in head and neck CT images: a feature-driven model-based approach.

Purpose: Intensity modulated radiation therapy (IMRT) allows greater control over dose distribution, which leads to a decrease in radiation related toxicity. IMRT, however, requires precise and accurate delineation of the organs at risk and target volumes. Manual delineation is tedious and suffers from both interobserver and intraobserver variability.

Biomechanical-based image registration for head and neck radiation treatment.

Deformable image registration of four head and neck cancer patients has been conducted using a biomechanical-based model. Patient-specific 3D finite element models have been developed using CT and cone-beam CT image data of the planning and a radiation treatment session. The model consists of seven vertebrae (C1 to C7), mandible, larynx, left and right parotid glands, tumor and body.

Audit of an automated checklist for quality control of radiotherapy treatment plans.

Purpose: To assess the effect of adding an automated checklist to the treatment planning process for head and neck intensity-modulated radiotherapy.

Methods: Plans produced within our treatment planning system were evaluated at the planners' discretion with an automated checklist of more than twenty planning parameters. Plans were rated as accepted or rejected for treatment, during regular review by radiation oncologists and physicists as part of our quality control program.

Cone-beam CT assessment of interfraction and intrafraction setup error of two head-and-neck cancer thermoplastic masks.

Purpose: To prospectively compare setup error in standard thermoplastic masks and skin-sparing masks (SSMs) modified with low neck cutouts for head-and-neck intensity-modulated radiation therapy (IMRT) patients.

Methods And Materials: Twenty head-and-neck IMRT patients were randomized to be treated in a standard mask (SM) or SSM. Cone-beam computed tomography (CBCT) scans, acquired daily after both initial setup and any repositioning, were used for initial and residual interfraction evaluation, respectively.

Statistical process control for IMRT dosimetric verification.

Patient-specific measurements are typically used to validate the dosimetry of intensity-modulated radiotherapy (IMRT). To evaluate the dosimetric performance over time of our IMRT process, we have used statistical process control (SPC) concepts to analyze the measurements from 330 head and neck (H&N) treatment plans. The objectives of the present work are to: (i) Review the dosimetric measurements of a large series of consecutive head and neck treatment plans to better understand appropriate dosimetric tolerances; (ii) analyze the results with SPC to develop action levels for measured discrepancies; (iii) develop estimates for the number of measurements that are required to describe IMRT dosimetry in the clinical setting; and (iv) evaluate with SPC a new beam model in our planning system.

A method to analyze the cord geometrical uncertainties during head and neck radiation therapy using cone beam CT.

We developed a method to analyze quantitatively the residual cord geometrical uncertainties after image registration during head and neck radiation therapy by using sequential cone beam CT (CBCT). The geometrical centroid line of cervical spinal canal was computed to serve as a cord surrogate. We found that the cord motions were non-uniform from C1 to C6, and that the patterns of motion were variable across patients.

Dosimetric comparison of IMRT vs. 3D conformal radiotherapy in the treatment of cancer of the cervical esophagus.

Background And Purpose: Radiotherapy planning for cervical esophageal cancer is challenging. We compared IMRT and 3D conformal radiotherapy (CRT) with respect to conformality of target coverage and normal tissue sparing.

Materials And Methods: We selected five patients with cervical esophagus cancer, who represented the heterogeneity of clinical cases, treated to radical dose and planned with Pinnacle v6.

The importance of obtaining conjugate views on renographic evaluation of large hydronephrotic kidneys: an in vitro and ex vivo analysis.

Purpose: It is postulated that significant obstruction leads to decreased ipsilateral renal function. However, maintained or even increased differential renal function is often seen in patients with large hydronephrotic kidneys. The reason for such a phenomenon is unclear.

Quantitative PET comparing gated with nongated acquisitions using a NEMA phantom with respiratory-simulated motion.

Unlabelled: This study evaluated the use of gated versus nongated PET acquisitions for absolute quantification of radioisotope concentration (RC) in a respiratory motion-simulated moving phantom filled with radioactive spheres and background for both 2-dimensional (2D) and 3-dimensional (3D) acquisitions.

Methods: An image-quality phantom with all 6 spheres filled with the same (18)F RC (range, 19-62 kBq/mL) was scanned with PET/CT at rest and in motion with and without gating. The background was filled with (18)F solution to yield sphere-to-background ratios of approximately 5, 10, 15, and 20 to 1.

Intraobserver and interobserver variability in GTV delineation on FDG-PET-CT images of head and neck cancers.

Purpose: To determine if the addition of fluorodeoxyglucose positron emission tomography (FDG-PET) data changes primary site gross tumor volumes (GTVs) in head and neck cancers.

Methods And Materials: Computed tomography (CT), contrast-enhanced CT, and FDG-PET-CT scans were obtained in 10 patients with head and neck cancers. Eight experienced observers (6 head and neck oncologists and 2 neuro-radiologists) with access to clinical and radiologic reports outlined primary site GTVs on each modality.

Spinal cord planning risk volumes for intensity-modulated radiation therapy of head-and-neck cancer.

Purpose: To assess planning organ at risk volume (PRV) margins of the spinal cord in intensity-modulated radiotherapy (IMRT) of oropharyngeal cancers, by modeling the effect of geometric uncertainties to estimate the probability of the spinal cord receiving a particular dose.

Methods And Materials: Five patients with oropharyngeal cancer were treated by IMRT with simultaneous doses of 66 Gy (gross disease) and 54 Gy (subclinical disease) in 30 fractions. Spinal cord doses were limited to 45 Gy.