A simple calibration routine for small inorganic scintillation detectors for in vivo dosimetry during brachytherapy.

Background: In vivo dosimetry (IVD) is rarely performed in brachytherapy (BT), allowing potential dose misadministration to go unnoticed. This study presents a clinical routine-calibration method of detectors for IVD in high (HDR) and pulsed dose rate (PDR) Ir-192 BT.

Purpose: To evaluate the dosimetric precision and feasibility of an in-clinic calibration routine of detectors for IVD in afterloading BT.

Establishing a fingerprinting method for fast catheter identification in HDR brachytherapy in vivo dosimetry.

Purpose: To use quantities measurable during in vivo dosimetry to build unique channel identifiers, that enable detection of brachytherapy errors.

Materials And Methods: Treatment plan of 360 patients with prostate cancer who underwent high-dose-rate brachytherapy (range, 16-25 catheters; mean, 17) were used. A single point virtual dosimeter was placed at multiple positions within the treatment geometry, and the source-dosimeter distance and dwell time were determined for each dwell position in each catheter.

Time-resolved dose rate measurements in pencil beam scanning proton FLASH therapy with a fiber-coupled scintillator detector system.

Background: The spatial and temporal dose rate distribution of pencil beam scanning (PBS) proton therapy is important in ultra-high dose rate (UHDR) or FLASH irradiations. Validation of the temporal structure of the dose rate is crucial for quality assurance and may be performed using detectors with high temporal resolution and large dynamic range.

Purpose: To provide time-resolved in vivo dose rate measurements using a scintillator-based detector during proton PBS pre-clinical mouse experiments with dose rates ranging from conventional to UHDR.

Monte Carlo characterization of high atomic number inorganic scintillators for in vivo dosimetry in Ir brachytherapy.

Background: There is increased interest in in vivo dosimetry for Ir brachytherapy (BT) treatments using high atomic number (Z) inorganic scintillators. Their high light output enables construction of small detectors with negligible stem effect and simple readout electronics. Experimental determination of absorbed-dose energy dependence of detectors relative to water is prevalent, but it can be prone to high detector positioning uncertainties and does not allow for decoupling of absorbed-dose energy dependence from other factors affecting detector response .

Toward 3D dose verification of an electronic brachytherapy source with a plastic scintillation detector.

Background: Electronic brachytherapy (eBT) is considered a safe treatment with good outcomes. However, eBT lacks standardized and independent dose verification, which could impede future use.

Purpose: To validate the 3D dose-to-water distribution of an electronic brachytherapy (eBT) source using a small-volume plastic scintillation detector (PSD).

Time structure of pencil beam scanning proton FLASH beams measured with scintillator detectors and compared with log files.

Purpose: Key factors in FLASH treatments are the ultra-high dose rate (UHDR) and the time structure of the beam delivery. Measurement of the time structure in pencil beam scanning (PBS) proton FLASH treatments is challenging for many types of detectors since high temporal resolution is needed. In this study, a fast scintillator detector system was developed and used to measure the individual spot durations as well as the time when the beam moves between two positions (transition duration) during PBS proton FLASH and UHDR treatments.

3D dose reconstruction based on in vivo dosimetry for determining the dosimetric impact of geometric variations in high-dose-rate prostate brachytherapy.

Introduction: In vivo dosimetry (IVD) can be used for source tracking (ST), i.e., estimating source positions, during brachytherapy.

A high-Z inorganic scintillator-based detector for time-resolved in vivo dosimetry during brachytherapy.

Purpose: High-dose rate (HDR) and pulsed-dose rate (PDR) brachytherapy would benefit from an independent treatment verification system to monitor treatment delivery and to detect errors in real time. This paper characterizes and provides an uncertainty budget for a detector based on a fiber-coupled high-Z inorganic scintillator capable of performing time-resolved in vivo dosimetry during HDR and PDR brachytherapy.

Method: The detector was composed of a detector probe and an optical reader.

Accuracy of an in vivo dosimetry-based source tracking method for afterloading brachytherapy - A phantom study.

Purpose: To report on the accuracy of an in vivo dosimetry (IVD)-based source tracking (ST) method for high dose rate (HDR) prostate brachytherapy (BT).

Methods: The ST was performed on a needle-by-needle basis. A least square fit of the expected to the measured dose rate was performed using the active dwell positions in the given needle.

dosimetry in brachytherapy: Requirements and future directions for research, development, and clinical practice.

Brachytherapy can deliver high doses to the target while sparing healthy tissues due to its steep dose gradient leading to excellent clinical outcome. Treatment accuracy depends on several manual steps making brachytherapy susceptible to operational mistakes. Currently, treatment delivery verification is not routinely available and has led, in some cases, to systematic errors going unnoticed for years.

3D source tracking and error detection in HDR using two independent scintillator dosimetry systems.

Purpose: The aim of this study is to perform three-dimensional (3D) source position reconstruction by combining in vivo dosimetry measurements from two independent detector systems.

Methods: Time-resolved dosimetry was performed in a water phantom during HDR brachytherapy irradiation with Ir source using two detector systems. The first was based on three plastic scintillator detectors and the second on a single inorganic crystal (CsI:Tl).

Cross-validation of a non-invasive positron detector to measure the arterial input function for pharmacokinetic modelling in dynamic positron emission tomography.

Kinetic modeling of positron emission tomography (PET) data can assess index rate of uptake, metabolism and predict disease progression more accurately than conventional static PET. However, it requires knowledge of the time-course of the arterial blood radioactivity concentration, called the arterial input function (AIF). The gold standard to acquire the AIF is by invasive means.

Inorganic scintillation detectors for Ir brachytherapy.

Many brachytherapy (BT) errors could be detected with real-time in vivo dosimetry technology. Inorganic scintillation detectors (ISDs) have demonstrated promising capabilities for BT, because some ISD materials can generate scintillation signals large enough that (a) the background signal emitted in the fiber-optic cable (stem signal) is insignificant, and (b) small detector volumes can be used to avoid volume averaging effects in steep dose gradients near BT sources. We investigated the characteristics of five ISD materials to identify one that is appropriate for BT.

Characterization of scintillating fibers for use as positron detector in positron emission tomography.

Purpose: Manual and automatic blood sampling at different time intervals is considered the gold standard to determine the arterial input function (AIF) in dynamic positron emission tomography (PET). However, blood sampling is characterized by poor time resolution and is an invasive procedure. The aim of this study was to characterize the scintillating fibers used to develop a non-invasive positron detector.

Dwell time verification in brachytherapy based on time resolved in vivo dosimetry.

Purpose: This paper presents a method to verify dwell times during High Dose Rate (HDR) Brachytherapy (BT) by means of in vivo dosimetry (IVD), and reports on an afterloader's stability in dwell time control.

Methods: In vivo dosimetry was performed during 20 HDR prostate cancer treatments using a point detector based on a radio-luminescence crystal (AlO:C) coupled to a fiber-optic cable. The dose rate was recorded at either 10 Hz or 20 Hz during the treatments.

Time-resolved in vivo dosimetry for source tracking in brachytherapy.

Purpose: The purpose of this article is to demonstrate that brachytherapy source tracking can be realized with in vivo dosimetry. This concept could enable real-time treatment monitoring.

Methods: In vivo dosimetry was incorporated in the clinical routine during high-dose-rate prostate brachytherapy at Aarhus University Hospital.

Inorganic scintillation detectors based on Eu-activated phosphors for Ir brachytherapy.

The availability of real-time treatment verification during high-dose-rate (HDR) brachytherapy is currently limited. Therefore, we studied the luminescence properties of the widely commercially available scintillators using the inorganic materials Eu-activated phosphors YO:Eu, YVO:Eu, YOS:Eu, and GdOS:Eu to determine whether they could be used to accurately and precisely verify HDR brachytherapy doses in real time. The suitability for HDR brachytherapy of inorganic scintillation detectors (ISDs) based on the 4 Eu-activated phosphors in powder form was determined based on experiments with a Ir HDR brachytherapy source.

Ruby-based inorganic scintillation detectors for Ir brachytherapy.

We tested the potential of ruby inorganic scintillation detectors (ISDs) for use in brachytherapy and investigated various unwanted luminescence properties that may compromise their accuracy. The ISDs were composed of a ruby crystal coupled to a poly(methyl methacrylate) fiber-optic cable and a charge-coupled device camera. The ISD also included a long-pass filter that was sandwiched between the ruby crystal and the fiber-optic cable.

Use of novel fibre-coupled radioluminescence and RADPOS dosimetry systems for total scatter factor measurements in small fields.

A dosimetry system based on Al2O3:C radioluminescence (RL), and RADPOS, a novel 4D dosimetry system using microMOSFETs, were used to measure total scatter factors, (S(c,p))(f(clin))(det), for the CyberKnife robotic radiosugery system. New Monte Carlo calculated correction factors are presented and applied for the RL detector response for the 5, 7.5 and 10 mm collimators in order to correct for the detector geometry and increased photoelectric cross section of Al2O3:C relative to water.

In vivo dosimetry: trends and prospects for brachytherapy.

The error types during brachytherapy (BT) treatments and their occurrence rates are not well known. The limited knowledge is partly attributed to the lack of independent verification systems of the treatment progression in the clinical workflow routine. Within the field of in vivo dosimetry (IVD), it is established that real-time IVD can provide efficient error detection and treatment verification.

Adaptive error detection for HDR/PDR brachytherapy: guidance for decision making during real-time in vivo point dosimetry.

Purpose: This study presents an adaptive error detection algorithm (AEDA) for real-time in vivo point dosimetry during high dose rate (HDR) or pulsed dose rate (PDR) brachytherapy (BT) where the error identification, in contrast to existing approaches, does not depend on an a priori reconstruction of the dosimeter position. Instead, the treatment is judged based on dose rate comparisons between measurements and calculations of the most viable dosimeter position provided by the AEDA in a data driven approach. As a result, the AEDA compensates for false error cases related to systematic effects of the dosimeter position reconstruction.

In vivo dosimetry in brachytherapy.

In vivo dosimetry (IVD) has been used in brachytherapy (BT) for decades with a number of different detectors and measurement technologies. However, IVD in BT has been subject to certain difficulties and complexities, in particular due to challenges of the high-gradient BT dose distribution and the large range of dose and dose rate. Due to these challenges, the sensitivity and specificity toward error detection has been limited, and IVD has mainly been restricted to detection of gross errors.

Sci-Fri PM: Delivery - 07: Cyberknife relative output factor measurements using fiber-coupled luminescence, MOSFETS and RADPOS dosimetry system.

Novel dosimetry systems based on Al O :C radioluminescence (RL) and a 4D dosimetry system (RADPOS) from Best Medical Canada were used to measure the relative output factor (ROF) on Cyberknife. Measurements were performed in a solid water phantom at the depth of 1.5 cm and SSD = 78.

Poster - Thur Eve - 03: LDR to HDR: RADPOS applications in brachytherapy.

The RADPOS in vivo dosimetry system combines an electromagnetic positioning sensor and either one or five MOSFET dosimeters. The feasibility of using the system for quality control has been explored for a range of radiotherapy treatment techniques including most recently transperineal interstitial permanent prostate brachytherapy and high dose rate (HDR) treatments. Dose and position information was collected by a RADPOS array detector inside a Foley catheter within patients' urethra during permanent seed implantation.