Rotation effects on the target-volume margin determination.

Rotational setup errors are usually neglected in most clinical centers. An analytical formula is developed to determine the extra margin between clinical target volume (CTV) and planning target volume (PTV) to account for setup errors. The proposed formula corrects for both translational and rotational setup errors and then incorporated into margin determination for PTV.

Three independent one-dimensional margins for single-fraction frameless stereotactic radiosurgery brain cases using CBCT.

Purpose: Setting a proper margin is crucial for not only delivering the required radiation dose to a target volume, but also reducing the unnecessary radiation to the adjacent organs at risk. This study investigated the independent one-dimensional symmetric and asymmetric margins between the clinical target volume (CTV) and the planning target volume (PTV) for linac-based single-fraction frameless stereotactic radiosurgery (SRS).

Methods: The authors assumed a Dirac delta function for the systematic error of a specific machine and a Gaussian function for the residual setup errors.

Using a novel dose QA tool to quantify the impact of systematic errors otherwise undetected by conventional QA methods: clinical head and neck case studies.

Recent studies have demonstrated that per-beam planar intensity-modulated radiation therapy (IMRT) quality assurance (QA) passing rates may not predict clinically relevant patient dose errors. This work is to evaluate the effect of dose variations introduced in dynamic multi-leaf collimator (DMLC) modeling and delivery processes on clinically relevant metrics for IMRT. Ten head and neck (HN) IMRT plans were randomly selected for this study.

Feasibility study of real-time planning for stereotactic radiosurgery.

Purpose: 3D rotational setup errors in radiotherapy are often ignored by most clinics due to inability to correct or simulate them accurately and efficiently. There are two types of rotation-related problems in a clinical setting. One is to assess the affected dose distribution in real-time if correction is not applied and the other one is to correct the rotational setup errors prior to the initiation of the treatment.

Confirmation of skin doses resulting from bolus effect of intervening alpha-cradle and carbon fiber couch in radiotherapy.

In this study, we verified the treatment planning calculations of skin doses with the incorporation of the bolus effect due to the intervening alpha-cradle (AC) and carbon fiber couch (CFC) using radiochromic EBT2 films. A polystyrene phantom (25 × 25 × 15 cm(3)) with six EBT2 films separated by polystyrene slabs, at depths of 0, 0.1, 0.

Estimating dose to implantable cardioverter-defibrillator outside the treatment fields using a skin QED diode, optically stimulated luminescent dosimeters, and LiF thermoluminescent dosimeters.

The purpose of this work was to determine the relative sensitivity of skin QED diodes, optically stimulated luminescent dosimeters (OSLDs) (microStar™ DOT, Landauer), and LiF thermoluminescent dosimeters (TLDs) as a function of distance from a photon beam field edge when applied to measure dose at out-of-field points. These detectors have been used to estimate radiation dose to patients' implantable cardioverter-defibrillators (ICDs) located outside the treatment field. The ICDs have a thin outer case made of 0.

The development of a novel radiation treatment modality - volumetric modulated arc therapy.

Recent theoretical studies and clinical investigations have indicated that volumetric modulated arc therapy (VMAT) can produce equal or better treatment plans than intensity modulated radiation therapy (IMRT), while achieving a significant reduction in treatment time. Built upon the concept of aperture-based multi-level beam source sampling optimization, VMAT has overcome many engineering constraints and become a clinically viable radiation treatment modality. At this point in time, however, there are only two commercial VMAT treatment planning systems (TPS) on the market, which severely limit the dissemination of this novel technology.

Comparison of two treatment approaches for prostate cancer: intensity-modulated radiation therapy combined with 125I seed-implant brachytherapy or 125I seed-implant brachytherapy alone.

The purpose of the present study was to assess the results of two different treatment approaches for clinically localized prostate cancer: intensity-modulated radiation therapy (IMRT) followed by 125I seed-implant brachytherapy and 125I seed-implant brachytherapy alone. We studied our 30 most recent consecutive patients. The sample population consisted of 15 cases treated with IMRT (50.

A model-aided segmentation in urethra identification based on an atlas human autopsy image for intensity modulated radiation therapy.

In order to protect urethra in radiation therapy of prostate cancer, the urethra must be identified and localized as an organ at risk (OAR) for the inverse treatment planning in intensity modulated radiation therapy (IMRT). Because the prostatic urethra and its surrounding prostate tissue have similar physical characteristics, such as linear attenuation coefficient and density, it is difficult to distinct the OAR from the target in CT images. To localize the urethra without using contrast agent or additional imaging modalities other than planning CT images, a different approach was developed using a standard atlas of human anatomy image.

From intensity modulated radiation therapy to 4D radiation therapy--an advance in targeting mobile lung tumors.

Intensity modulated radiation therapy (IMRT) has been widely used in the treatment of lung cancer. The highly conformal dose distribution with steep gradients could miss the target if respiratory motion is not carefully considered during the treatment planning. The issue becomes particularly critical when dose escalation technique is used.

Femoral fracture risk assessment after intensity modulated radiation therapy (IMRT) for the treatment of soft tissue sarcoma using a novel mathematical model.

Intensity modulated radiation therapy (IMRT) is often used for the treatment of soft tissue sarcoma. Due to high radiation doses, many patients have high risk of suffering from a femoral bone fracture sometime following the IMRT treatment. The most common type of radiation treatment-related fracture is a stress fracture.

Inter-modality variation in gross tumor volume delineation in 18FDG-PET guided IMRT treatment planning for lung cancer.

Rapid advances in 18FDG-PET/CT technology and novel co-registration algorithms have created a strong interest in 18FDG-PET/CT's application in intensity modulated radiation therapy (IMRT) and image-guided radiation therapy (IGRT). Accurate target volume delineation, particularly identification of pathologically positive lymph nodes, could translate into favorable treatment outcome. However, gross tumor volume (GTV) delineation on both CT and 18FDG-PET is very sensitive to observer variation.

The treatment of extensive scalp lesions combining electrons with intensity-modulated photons.

This study was to investigate the feasibility and potential benefits of combining electrons with intensity modulated photons (IMRT+e) for patients with extensive scalp lesions. A case of a patient with an extensive scalp lesion, in which the target volume covered the entire front half of the scalp, is presented. This approach incorporated the electron dose into the inverse treatment planning optimization.

A novel radiation therapy technique for malignant pleural mesothelioma combining electrons with intensity-modulated photons.

Background And Purpose: To investigate the feasibility and potential benefits of combining electron and photon intensity modulated radiotherapy (IMRT) for patients with malignant pleural mesothelioma (MPM).

Patients And Methods: The planning CT images of 11 MPM patients, six after extrapleural pneumonectomy (EPP) and five after pleurectomy/decortication (P/D), were used for this study. These cases were planned with photon IMRT alone and photon IMRT combined with electrons (IMRT+e).

Results of a one year survey of output for linear accelerators using IMRT and non-IMRT techniques.

This paper presents the results of a one year survey of treated fields for 3 treatment machines at our New Jersey regional center. One machine predominantly treated IMRT prostate patients using a sliding window technique. The others were not equipped to deliver IMRT.

Comparison of intensity-modulated radiotherapy with three-dimensional conformal radiation therapy planning for glioblastoma multiforme.

This study was designed to assess the feasibility and potential benefit of using intensity-modulated radiotherapy (IMRT) planning for patients newly diagnosed with glioblastoma multiforme (GBM). Five consecutive patients with confirmed histopathologically GBM were entered into the study. These patients were planned and treated with 3-dimensional conformal radiation therapy (3DCRT) using our standard plan of 3 noncoplanar wedged fields.

Technological advances in external-beam radiation therapy for the treatment of localized prostate cancer.

The relative inability of conventional radiotherapy to control localized prostate cancer results from resistance of subpopulations of tumor clonogens to dose levels of 65 to 70 Gy, the maximum feasible with traditional two-dimensional (2D) treatment planning and delivery techniques. Several technological advances have enhanced the precision and improved the outcome of external-beam radiotherapy. The three-dimensional conformal radiotherapy (3D-CRT) approach has permitted significant increases in the tumor dose to levels beyond those feasible with conventional techniques.

A study of the effects of internal organ motion on dose escalation in conformal prostate treatments.

Background And Purpose: To assess the effect of internal organ motion on the dose distributions and biological indices for the target and non-target organs for three different conformal prostate treatment techniques.

Materials And Methods: We examined three types of treatment plans in 20 patients: (1) a six field plan, with a prescribed dose of 75.6 Gy; (2) the same six field plan to 72 Gy followed by a boost to 81 Gy; and (3) a five field plan with intensity modulated beams delivering 81 Gy.

Dose-volume factors contributing to the incidence of radiation pneumonitis in non-small-cell lung cancer patients treated with three-dimensional conformal radiation therapy.

Purpose: To analyze acute lung toxicity data of non-small-cell lung cancer patients treated with three-dimensional conformal radiation therapy in terms of dosimetric variables, location of dose within subvolumes of the lungs, and models of normal-tissue complication probability (NTCP).

Methods And Materials: Dose distributions of 49 non-small-cell lung cancer patients treated in a dose escalation protocol between 1992 and 1999 were analyzed (dose range: 57.6-81 Gy).

Intensity-modulated radiotherapy.

Intensity-modulated radiotherapy represents a recent advancement in conformal radiotherapy. It employs specialized computer-driven technology to generate dose distributions that conform to tumor targets with extremely high precision. Treatment planning is based on inverse planning algorithms and iterative computer-driven optimization to generate treatment fields with varying intensities across the beam section.

Fitting of tissue tolerance data to analytic function: improving the therapeutic ratio.

Response of human tissues to ionizing radiation is a complex process. It is influenced by many factors, such as use of chemotherapy drugs and underlying diseases such as diabetes and/or lung emphysema. A phenomenological model such as Lyman's is an attempt to predict the complication, for a variety of tissues, in the absence of these factors.