Evaluating effectiveness of clustering algorithms in multiple target stereotactic radiosurgery.

. Single-isocenter-multiple-target technique for stereotactic radiosurgery (SRS) can reduce treatment duration but risks compromised dose coverage due to potential rotational errors. Clustering targets into two groups can reduce isocenter-target distances, mitigating the impact of rotational uncertainty.

The effects of flattening filter-free beams and aperture shape controller on the complexity of conventional large-field treatment plans.

Purpose: The purpose of this study was to investigate the impact of using flattening filter-free (FFF) beams and the aperture shape controller (ASC) on the complexity of conventional large-field treatment plans.

Methods And Materials: A total of 24 head and neck (H&N) and 24 prostate with pelvic nodes treatment plans were used in this study. Each plan was reoptimized using the original clinical objectives with both flattened and FFF beams, as well as six different ASC settings.

Knowledge-based quality control of organ delineations in radiation therapy.

Purpose: To reduce the likelihood of errors in organ delineations used for radiotherapy treatment planning, a knowledge-based quality control (KBQC) system, which discriminates between valid and anomalous delineations is developed.

Method And Materials: The KBQC is comprised of a group-wise inference system and anomaly detection modules trained using historical priors from 296 locally advanced lung and prostate cancer patient computational tomographies (CTs). The inference system discriminates different organs based on shape, relational, and intensity features.

Detection of dose delivery variations on TomoTherapy using on-board detector based verification.

A clinical case of delivery dose deviations on a TomoTherapy treatment was discovered during a patient specific treatment quality assurance (QA) verification. An in-house developed QA system, MCLogQA, for TomoTherapy has been implemented in our clinic for patient specific treatment QA. The MCLogQA system utilizes the log file and detector-based multileaf collimator (MLC) leaf opening time (LOT) to assess accuracy of treatment plan delivery.

A Novel Small-Animal Model of Irradiated, Implant-Based Breast Reconstruction.

Background: There is currently a need for a clinically relevant small-animal model for irradiated, implant-based breast reconstruction. Present models are inadequate in terms of suboptimal location of expander placement and mode of radiation delivery, correlating poorly with the human clinical scenario. The authors hypothesized that by delivering fractionated radiation and placing an expander under the scalp of the animal, they would achieve soft-tissue changes histologically analogous to those seen in human irradiated, implant-based breast reconstruction.

Quality assurance tool for organ at risk delineation in radiation therapy using a parametric statistical approach.

Purpose: To develop a quality assurance (QA) tool that identifies inaccurate organ at risk (OAR) delineations.

Methods: The QA tool computed volumetric features from prior OAR delineation data from 73 thoracic patients to construct a reference database. All volumetric features of the OAR delineation are computed in three-dimensional space.

Clinical adequacy assessment of autocontours for prostate IMRT with meaningful endpoints.

Purpose: To determine if radiation treatment plans created based on autosegmented (AS) regions-of-interest (ROI)s are clinically equivalent to plans created based on manually segmented ROIs, where equivalence is evaluated using probabilistic dosimetric metrics and probabilistic biological endpoints for prostate IMRT.

Method And Materials: Manually drawn contours and autosegmented ROIs were created for 167 CT image sets acquired from 19 prostate patients. Autosegmentation was performed utilizing Pinnacle's Smart Probabilistic Image Contouring Engine.

Fast range measurement of spot scanning proton beams using a volumetric liquid scintillator detector.

Accurate confirmation and verification of the range of spot scanning proton beams is crucial for correct dose delivery. Current methods to measure proton beam range using ionization chambers are either time-consuming or result in measurements with poor spatial resolution. The large-volume liquid scintillator detector allows real-time measurements of the entire dose profile of a spot scanning proton beam.

4D MR imaging using robust internal respiratory signal.

The purpose of this study is to investigate the feasibility of using internal respiratory (IR) surrogates to sort four-dimensional (4D) magnetic resonance (MR) images. The 4D MR images were constructed by acquiring fast 2D cine MR images sequentially, with each slice scanned for more than one breathing cycle. The 4D volume was then sorted retrospectively using the IR signal.

Internal respiratory surrogate in multislice 4D CT using a combination of Fourier transform and anatomical features.

Purpose: The purpose of this study was to develop a novel algorithm to create a robust internal respiratory signal (IRS) for retrospective sorting of four-dimensional (4D) computed tomography (CT) images.

Methods: The proposed algorithm combines information from the Fourier transform of the CT images and from internal anatomical features to form the IRS. The algorithm first extracts potential respiratory signals from low-frequency components in the Fourier space and selected anatomical features in the image space.

3D reconstruction of scintillation light emission from proton pencil beams using limited viewing angles-a simulation study.

An accurate and high-resolution quality assurance (QA) method for proton radiotherapy beams is necessary to ensure correct dose delivery to the target. Detectors based on a large volume of liquid scintillator have shown great promise in providing fast and high-resolution measurements of proton treatment fields. However, previous work with these detectors has been limited to two-dimensional measurements, and the quantitative measurement of dose distributions was lacking.

Optical artefact characterization and correction in volumetric scintillation dosimetry.

The goals of this study were (1) to characterize the optical artefacts affecting measurement accuracy in a volumetric liquid scintillator detector, and (2) to develop methods to correct for these artefacts. The optical artefacts addressed were photon scattering, refraction, camera perspective, vignetting, lens distortion, the lens point spread function, stray radiation, and noise in the camera. These artefacts were evaluated by theoretical and experimental means, and specific correction strategies were developed for each artefact.

Improved three-dimensional Look-Locker acquisition scheme and angle map filtering procedure for T1 estimation.

The three-dimensional (3D) Look-Locker (LL) acquisition is a widely used fast and efficient T1 mapping method. However, the multi-shot approach of 3D LL acquisition can introduce reconstruction artifacts that result in intensity distortions. Traditional 3D LL acquisition generally utilizes a centric encoding scheme that is limited to a single phase-encoding direction in k space.

Fast algorithm for calculation of inhomogeneity gradient in magnetic resonance imaging data.

Purpose: To develop and implement a new approach for correcting the intensity inhomogeneity in magnetic resonance imaging (MRI) data.

Materials And Methods: The algorithm is based on the assumption that intensity inhomogeneity in MR data is multiplicative and smoothly varying. Using a statistically stable method, the algorithm first calculates the partial derivative of the inhomogeneity gradient across the data.