Use of CT simulation and 3-D radiation therapy treatment planning system to develop and validate a total-body irradiation technique for the New Zealand White rabbit.

Purpose: Well-controlled ionizing radiation injury animal models for testing medical countermeasure efficacy require robust radiation physics and dosimetry to ensure accuracy of dose-delivery and reproducibility of the radiation dose-response relationship. The objective of this study was to establish a simple, convenient, robust and accurate technique for validating total body irradiation (TBI) exposure of the New Zealand White rabbit.

Methods: We use radiotherapy techniques such as computed tomography simulation and a 3 D-conformal radiation therapy treatment planning system (TPS) on three animals to comprehensively design and preplan a TBI technique for rabbits.

A practical cyberattack contingency plan for radiation oncology.

Purpose: This article presents a solution for continuing radiation therapy without interruption in the event of a cyberattack to the radiation oncology information systems (ROIS). This process could be easily deployed to any radiation oncology practice, with little clinical overhead or burden.

Methods And Materials: The solution automatically retrieves all essential information from the clinical ROIS for each under-treatment patient and periodically (e.

Commissioning and acceptance guide for the GammaPod.

The GammaPod breast treatment device has been introduced to provide stereotactic radiation therapy to the breast to patients in the prone position. The GammaPod, using a stereotactic coordinate system, dynamically delivers dose to the target by rotating 25 non-overlapping Co-60 beams while the patient's breast is translated continuously in three axes on the couch during delivery. From simulation to treatment, the patient's breast is immobilized using mild negative pressure (150 mm Hg below atmospheric pressure) through a device-specific dual-cup system with stereotactic fiducials.

Efficacy of Neulasta or Neupogen on H-ARS and GI-ARS Mortality and Hematopoietic Recovery in Nonhuman Primates After 10-Gy Irradiation With 2.5% Bone Marrow Sparing.

A nonhuman primate model of acute, partial-body, high-dose irradiation with minimal (2.5%) bone marrow sparing was used to assess endogenous gastrointestinal and hematopoietic recovery and the ability of Neulasta (pegylated granulocyte colony-stimulating factor) or Neupogen (granulocyte colony-stimulating factor) to enhance recovery from myelosuppression when administered at an increased interval between exposure and initiation of treatment. A secondary objective was to assess the effect of Neulasta or Neupogen on mortality and morbidity due to the hematopoietic acute radiation syndrome and concomitant gastrointestinal acute radiation syndrome.

Action Levels on Dose and Anatomic Variation for Adaptive Radiation Therapy Using Daily Offline Plan Evaluation: Preliminary Results.

Purpose: This study aimed to develop action levels for replanning to accommodate dosimetric variations resulting from anatomic changes during the course of treatments, using daily cone beam computed tomography (CBCT).

Methods And Materials: Daily or weekly CBCT images of 20 patients (10 head and neck, 5 lung, and 5 prostate cancers) who underwent resimulation per physicians' clinical decisions, mainly from the comparison of CBCT scans, were used to determine action levels. The first CBCT image acquired before the first treatment was used as the reference image to rule out effects of dose inaccuracy from the CBCT.

Feasibility of CBCT-based dose with a patient-specific stepwise HU-to-density curve to determine time of replanning.

Purpose: (a) To investigate the accuracy of cone-beam computed tomography (CBCT)-derived dose distributions relative to fanbeam-based simulation CT-derived dose distributions; and (b) to study the feasibility of CBCT dosimetry for guiding the appropriateness of replanning.

Methods And Materials: Image data corresponding to 40 patients (10 head and neck [HN], 10 lung, 10 pancreas, 10 pelvis) who underwent radiation therapy were randomly selected. Each patient had both intensity-modulated radiation therapy and volumetric-modulated arc therapy plans; these 80 plans were subsequently recomputed on the CBCT images using a patient-specific stepwise curve (Hounsfield units-to-density).

AEOL 10150 Mitigates Radiation-Induced Lung Injury in the Nonhuman Primate: Morbidity and Mortality are Administration Schedule-Dependent.

Pneumonitis and fibrosis are potentially lethal, delayed effects of acute radiation exposure. In this study, male rhesus macaques received whole-thorax lung irradiation (WTLI) with a target dose of 10.74 Gy prescribed to midplane at a dose rate of 0.

Clinical implementation of an electron monitor unit dosimetry system based on task group 71 report and a commercial calculation program.

Many clinics still use monitor unit (MU) calculations for electron treatment planning and/or quality assurance (QA). This work (1) investigates the clinical implementation of a dosimetry system including a modified American Association of Physicists in Medicine-task group-71 (TG-71)-based electron MU calculation protocol (modified TG-71 electron [mTG-71E] and an independent commercial calculation program and (2) provides the practice recommendations for clinical usage. Following the recently published TG-71 guidance, an organized mTG-71E databook was developed to facilitate data access and subsequent MU computation according to our clinical need.

Optimizing the MLC model parameters for IMRT in the RayStation treatment planning system.

Unlike other commercial treatment planning systems (TPS) which model the rounded leaf end differently (such as the MLC dosimetric leaf gap (DLG) or rounded leaf-tip radius), the RayStation TPS (RaySearch Laboratories, Stockholm, Sweden) models transmission through the rounded leaf end of the MLC with a step function, in which the radiation transmission through the leaf end is the square root of the average MLC transmission factor. We report on the optimization of MLC model parameters for the RayStation planning system. This (TPS) models the rounded leaf end of the MLC with the following parameters: eaf-tip offset, leaf-tip width, average transmission factor, and tongue and groove.

The Effect of Radiation Dose and Variation in Neupogen® Initiation Schedule on the Mitigation of Myelosuppression during the Concomitant GI-ARS and H-ARS in a Nonhuman Primate Model of High-dose Exposure with Marrow Sparing.

A nonhuman primate (NHP) model of acute high-dose, partial-body irradiation with 5% bone marrow (PBI/BM5) sparing was used to assess the effect of Neupogen® [granulocyte colony stimulating factor (G-CSF)] to mitigate the associated myelosuppression when administered at an increasing interval between exposure and initiation of treatment. A secondary objective was to assess the effect of Neupogen® on the mortality or morbidity of the hematopoietic (H)- acute radiation syndrome (ARS) and concurrent acute gastrointestinal radiation syndrome (GI-ARS). NHP were exposed to 10.

Mean Organ Doses Resulting From Non-Human Primate Whole Thorax Lung Irradiation Prescribed to Mid-Line Tissue.

Multi-organ dose evaluations and the effects of heterogeneous tissue dose calculations have been retrospectively evaluated following irradiation to the whole thorax and lung in non-human primates (NHP). A clinical-based approach was established to evaluate actual doses received in the heart and lungs during whole thorax lung irradiation. Anatomical structure and organ densities have been introduced in the calculations to show the effects of dose distribution through heterogeneous tissue.

Automated compromised right lung segmentation method using a robust atlas-based active volume model with sparse shape composition prior in CT.

To resolve challenges in image segmentation in oncologic patients with severely compromised lung, we propose an automated right lung segmentation framework that uses a robust, atlas-based active volume model with a sparse shape composition prior. The robust atlas is achieved by combining the atlas with the output of sparse shape composition. Thoracic computed tomography images (n=38) from patients with lung tumors were collected.

Pegfilgrastim Improves Survival of Lethally Irradiated Nonhuman Primates.

Leukocyte growth factors (LGF), such as filgrastim, pegfilgrastim and sargramostim, have been used to mitigate the hematologic symptoms of acute radiation syndrome (ARS) after radiation accidents. Although these pharmaceuticals are currently approved for treatment of chemotherapy-induced myelosuppression, such approval has not been granted for myelosuppression resulting from acute radiation exposure. Regulatory approval of drugs used to treat radiological or nuclear exposure injuries requires their development and testing in accordance with the Animal Efficacy Rule, set forth by the U.

A six-year review of more than 13,000 patient-specific IMRT QA results from 13 different treatment sites.

Due to a lack of information regarding the current clinical experience of IMRT QA for a large and varied plan population, we reviewed our patient-specific IMRT quality assurance (QA) results for 13,003 treatment plans from 13 distinct treatment sites from a six-year period. QA records were reviewed for dose difference (single point with ion chamber measurement; ± 3% agreement criteria) and percentage of pixels passing relative dose gamma analysis (film measurement; 90% passing 5%(global)/3 mm agreement criteria) from 2005 through 2011. Plan records were analyzed for trends with measurement date and treatment site.

An analytical formalism to calculate phantom scatter factors for flattening filter free (FFF) mode photon beams.

Phantom Scatter Factors, Sp in the Khan formalism (Khan et al 1980 J. Radiat. Oncol.

The MCART radiation physics core: the quest for radiation dosimetry standardization.

Dose-related radiobiological research results can only be compared meaningfully when radiation dosimetry is standardized. To this purpose, the National Institute of Allergy and Infectious Diseases (NIAID)-sponsored Medical Countermeasures Against Radiological Threats (MCART) consortium recently created a Radiation Physics Core (RPC) as an entity to assume responsibility of standardizing radiation dosimetry practices among its member laboratories. The animal research activities in these laboratories use a variety of ionizing photon beams from several irradiators such as 250-320 kVp x-ray generators, Cs irradiators, Co teletherapy machines, and medical linear accelerators (LINACs).

A pilot study in rhesus macaques to assess the treatment efficacy of a small molecular weight catalytic metalloporphyrin antioxidant (AEOL 10150) in mitigating radiation-induced lung damage.

The objective of this pilot study was to explore whether administration of a catalytic antioxidant, AEOL 10150 (C48H56C15MnN12), could reduce radiation-induced lung injury and improve overall survival when administered after 11.5 Gy of whole thorax lung irradiation in a non-human primate model. Thirteen animals were irradiated with a single exposure of 11.

The ability of filgrastim to mitigate mortality following LD50/60 total-body irradiation is administration time-dependent.

The identification of the optimal administration schedule for an effective medical countermeasure is critical for the effective treatment of individuals exposed to potentially lethal doses of radiation. The efficacy of filgrastim (Neupogen®), a potential medical countermeasure, to improve survival when initiated at 48 h following total body irradiation in a non-human primate model of the hematopoietic syndrome of the acute radiation syndrome was investigated. Animals were exposed to total body irradiation, antero-posterior exposure, total midline tissue dose of 7.

Dosimetric and geometric evaluation of a novel stereotactic radiotherapy device for breast cancer: the GammaPod™.

Purpose: A dedicated stereotactic gamma irradiation device, the GammaPod™ from Xcision Medical Systems, was developed specifically to treat small breast cancers. This study presents the first evaluation of dosimetric and geometric characteristics from the initial prototype installed at University of Maryland Radiation Oncology Department.

Methods: The GammaPod™ stereotactic radiotherapy device is an assembly of a hemi-spherical source carrier containing 36 (60)Co sources, a tungsten collimator, a dynamically controlled patient support table, and the breast immobilization system which also functions as a stereotactic frame.

Protons offer reduced normal-tissue exposure for patients receiving postoperative radiotherapy for resected pancreatic head cancer.

Purpose: To determine the potential role for adjuvant proton-based radiotherapy (PT) for resected pancreatic head cancer.

Methods And Materials: Between June 2008 and November 2008, 8 consecutive patients with resected pancreatic head cancers underwent optimized intensity-modulated radiotherapy (IMRT) treatment planning. IMRT plans used between 10 and 18 fields and delivered 45 Gy to the initial planning target volume (PTV) and a 5.

Use of a matchline dosimetry analysis tool (MDAT) to quantify dose homogeneity in the region between abutting tangential and supraclavicular radiation fields.

In this work, we develop and test a matchline dosimetry analysis tool (MDAT) to examine the dose distribution within the abutment region of two or more adjoining radiotherapy fields that employ different blocking mechanisms and geometries in forming a match. This objective and quantitative tool uses calibrated radiographic film to measure the dose in the abutment region, and uses a frequency distribution of area versus dose (a dose-area histogram) to visualize the spatial dose distribution. We tested the MDAT's clinical applicability and parameters by evaluating the dose between adjacent photon fields incident on a flat phantom using field-matching techniques employing collimator-jaw and multileaf collimator (MLC) configurations.

Energy dependence and dose response of Gafchromic EBT2 film over a wide range of photon, electron, and proton beam energies.

Purpose: Since the Gafchromic film EBT has been recently replaced by the newer model EBT2, its characterization, especially energy dependence, has become critically important. The energy dependence of the dose response of Gafchromic EBT2 film is evaluated for a broad range of energies from different radiation sources used in radiation therapy.

Methods: The beams used for this study comprised of kilovoltage x rays (75, 125, and 250 kVp), 137Cs gamma (662 KeV), 60Co gamma (1.

Lack of correlation between external fiducial positions and internal tumor positions during breath-hold CT.

Purpose: For thoracic tumors, if four-dimensional computed tomography (4DCT) is unavailable, the internal margin can be estimated by use of breath-hold (BH) CT scans acquired at end inspiration (EI) and end expiration (EE). By use of external surrogates for tumor position, BH accuracy is estimated by minimizing the difference between respiratory extrema BH and mean equivalent-phase free breathing (FB) positions. We tested the assumption that an external surrogate for BH accuracy correlates with internal tumor positional accuracy during BH CT.

Clinical implementation of electron energy changes of varian linear accelerators.

Modern dual photon energy linear accelerators often come with a few megavoltage electron beams. The megavoltage electron beam has limited range and relative sharp distal falloff in its depth dose curve compared to that of megavoltage photon beam. Its radiation dose is often delivered appositionally to cover the target volume to its distal 90% depth dose (d90), while avoiding the normal--sometimes critical--structure immediately distal to the target.