Dose-efficiency quantification of computed tomography systems using a model-observer.

Background: Recent advances in computed tomography (CT) technology have considerably improved the quality of CT images and reduced radiation exposure in patients. At present, however, there is no generally accepted figure of merit (FOM) for comparing the dose efficiencies of CT systems.

Purpose: (i) To establish an FOM that characterizes the quality of CT images in relation to the radiation dose by means of a mathematical model observer and (ii) to evaluate the new FOM on different CT systems and image reconstruction algorithms.

Assessment of CT Image Quality Using a Bayesian Framework.

In computed tomography, there is a tradeoff between the quality of the reconstructed image and the radiation dose received by the patient. In order to find an appropriate compromise between the image quality of the reconstructed images and the radiation dose, it is important to have reliable methods for evaluating the quality of the reconstructed images. A successful family of methods for the assessment of image quality is task-based image quality assessment, which often involves the use of model observers, and which assesses the quality of the image reconstruction by deriving a figure of merit.

Feasibility study of entrance and exit dose measurements at the contra lateral breast with alanine/electron spin resonance dosimetry in volumetric modulated radiotherapy of breast cancer.

The Physikalisch-Technische Bundesanstalt has established a secondary standard measurement system for the dose to water, D , based on alanine/ESR (Anton et al 2013 Phys. Med. Biol.

Relative response of alanine dosemeters for high-energy electrons determined using a Fricke primary standard.

A significant proportion of cancer patients is treated using MeV electron radiation. One of the measurement methods which is likely to furnish reliable dose values also under non-reference conditions is the dosimetry using alanine and read-out via electron spin resonance (ESR). The system has already proven to be suitable for QA purposes for modern radiotherapy involving megavoltage x-rays.

Dose uncertainty in radiotherapy of patients with head and neck cancer measured by in vivo ESR/alanine dosimetry using a mouthpiece.

In order (i) to evaluate the dose uncertainty of the mouthpiece in daily use during intensity-modulated radiotherapy of patients with head and neck cancer, and (ii) to present a system for in vivo dosimetry of the oral mucosa, we equipped the mouthpiece with alanine dosimeter probes for in vivo dosimetry. The aim was to determine the dose uncertainty caused by the daily positioning of the mouthpiece during dynamic treatment techniques. During IMRT radiotherapy of patients with head and neck cancer, the doses accumulated next to the mucosa were measured in five patients and compared to the dose calculated by the treatment planning system.

In vivo dosimetry in the urethra using alanine/ESR during (192)Ir HDR brachytherapy of prostate cancer--a phantom study.

A phantom study for dosimetry in the urethra using alanine/ESR during (192)Ir HDR brachytherapy of prostate cancer is presented. The measurement method of the secondary standard of the Physikalisch-Technische Bundesanstalt had to be slightly modified in order to be able to measure inside a Foley catheter. The absorbed dose to water response of the alanine dosimetry system to (192)Ir was determined with a reproducibility of 1.

Is there an influence of the surrounding material on the response of the alanine dosimetry system?

In a combined experimental and Monte Carlo study the possible influence of the surrounding material on the response of the alanine dosimetry system was investigated. The aim of this work was to estimate the uncertainties induced by the surroundings with respect to quality assurance measurements for radiotherapy, for example in humanoid phantoms. Six different materials were tested.

Response of the alanine/ESR dosimetry system to MV X-rays relative to (60)Co radiation.

The measurand relevant in dosimetry for radiation therapy is the absorbed dose to water, D(W). The Physikalisch-Technische Bundesanstalt (PTB) has established a secondary standard for D(W) for high-energy photon and electron radiation based on electron spin resonance (ESR) of the amino acid alanine. Since the calibration is usually performed using (60)Co radiation while a huge part of the external radiation therapy is done with high-energy x-rays from linear accelerators, determination of the response is an important issue.

In vivo alanine/electron spin resonance (ESR) dosimetry in radiotherapy of prostate cancer: a feasibility study.

Purpose: We have developed a device to evaluate the potential of alanine/electron spin resonance (ESR) dosimetry for quality assurance in 3D conformal radiotherapy for prostate cancer. It consists of a rectal balloon carrying eight alanine dosimeter probes and two metal markers to document the exact position of the balloon. We measured the effects of an air-filled rectal balloon on the dose at the rectal wall and compared these results with the applied dose distribution of the treatment planning system.

Postirradiation effects in alanine dosimeter probes of two different suppliers.

The measurand relevant for the dosimetry for radiation therapy is the absorbed dose to water, DW. The Physikalisch-Technische Bundesanstalt (PTB) is establishing a secondary standard for DW for high-energy photon and electron radiation based on electron spin resonance (ESR) of the amino acid alanine. For practical applications, like, for example, intercomparison measurements using the ESR/alanine dosimetry system, the temporal evolution of the ESR signal of irradiated probes is an important issue.

Uncertainties in alanine/ESR dosimetry at the Physikalisch-Technische Bundesanstalt.

In radiation therapy, the effect of ionizing radiation is quantified in terms of the absorbed dose to water. Dosimetry with alanine and readout via electron spin resonance (ESR) is a method which is used as a secondary standard by several national metrology institutions. The advantages of the method are the good water-equivalence of the probes, their small size and the very weak dependence of the response on the radiation quality for MV x-rays and high-energy electrons used in radiation therapy.

Development of a secondary standard for the absorbed dose to water based on the alanine EPR dosimetry system.

The primary measurand in the dosimetry for radiation therapy is the absorbed dose to water, D(W). An alanine/EPR based secondary standard for D(W) for high-energy photon and electron radiation is presently under construction at the Physikalisch-Technische Bundesanstalt. A technique of transfer dosimetry that makes it possible to reduce the reproducibility to a level below 0.