Cleaning the dose falloff in lung SBRT plan.

Purpose: To investigate a planning technique that can possibly reduce low-to-intermediate dose spillage (measured by R50%, D2cm values) in lung SBRT plans.

Materials And Methods: Dose falloff outside the target was studied retrospectively in 102 SBRT VMAT plans of lung tumor. Plans having R50% and/or D2cm higher than recommended tolerances in RTOG protocols 0813 and 0915 were replanned with new optimization constraints using novel shell structures and novel constraints.

A Dose Falloff Gradient Study in RapidArc Planning of Lung Stereotactic Body Radiation Therapy.

Introduction: Radiation Therapy Oncology Group (RTOG) report #0813 and 0915 recommends using D and R as plan quality metrics for evaluation of normal tissue sparing in stereotactic body radiation therapy (SBRT) of lung lesion. This study introduces dose falloff gradient (DFG) as a tool for analyzing the dose beyond the planning target volume (PTV) extending into normal tissue structures. In ascertaining the impact of PTV size and SBRT planning techniques in DFG, this study questions the independence of the RTOG recommended metrics.

Diffuse optical measurements of head and neck tumor hemodynamics for early prediction of chemoradiation therapy outcomes.

This study used a hybrid near-infrared diffuse optical instrument to monitor tumor hemodynamic responses to chemoradiation therapy for early prediction of treatment outcomes in patients with head and neck cancer. Forty-seven patients were measured once per week to evaluate the hemodynamic status of clinically involved cervical lymph nodes as surrogates for the primary tumor response. Patients were classified into two groups: complete response (CR) (n=29) and incomplete response (IR) (n=18).

Noninvasive diffuse optical monitoring of head and neck tumor blood flow and oxygenation during radiation delivery.

This study explored using a novel diffuse correlation spectroscopy (DCS) flow-oximeter to noninvasively monitor blood flow and oxygenation changes in head and neck tumors during radiation delivery. A fiber-optic probe connected to the DCS flow-oximeter was placed on the surface of the radiologically/clinically involved cervical lymph node. The DCS flow-oximeter in the treatment room was remotely operated by a computer in the control room.

Dosimetric evaluation of parallel opposed spatially fractionated radiation therapy of deep-seated bulky tumors.

Application of a single fraction of parallel opposed GRID beams as a means of increasing the efficiency of radiation delivery to deep-seated tumors has been investigated. This evaluation was performed by measurement of dosimetric characteristics of the GRID radiation field in parallel opposed and single beam geometry. The limitations of the parallel opposed technique in terms of field size and tumor thickness have been evaluated for the conditions of acceptable spatial modulation.

Dosimetric validation of the MCNPX Monte Carlo simulation for radiobiologic studies of megavoltage grid radiotherapy.

Purpose: To validate the MCNPX Monte Carlo simulation for radiobiologic studies of megavoltage grid radiotherapy.

Methods And Materials: EDR2 films, a scanning water phantom with microionization chamber and MCNPX Monte Carlo code, were used to study the dosimetric characteristics of a commercially available megavoltage grid therapy collimator. The measured dose profiles, ratios between maximum and minimum doses at 1.

Dosimetric characteristics of a newly designed grid block for megavoltage photon radiation and its therapeutic advantage using a linear quadratic model.

Grid radiation therapy with megavoltage x-ray beam has been proven to be an effective technique for management of large, bulky malignant tumors. The clinical advantage of GRID therapy, combined with conventional radiation therapy, has been demonstrated using a prototype GRID block [Mohiuddin, Curtis, Grizos, and Komarnicky, Cancer 66, 114-118 (1990)]. Recently, a new GRID block design with improved dosimetric properties has become commercially available from Radiation Product Design, Inc.