Dose Tracking System Research Articles

Improved-Resolution, Real-Time Skin-Dose Mapping for Interventional Fluoroscopic Procedures.

We have developed a dose-tracking system (DTS) that provides a real-time display of the skin-dose distribution on a 3D patient graphic during fluoroscopic procedures. Radiation dose to individual points on the skin is calculated using exposure and geometry parameters from the digital bus on a Toshiba C-arm unit. To accurately define the distribution of dose, it is necessary to use a high-resolution patient graphic consisting of a large number of elements. In the original DTS version, the patient graphics were obtained from a library of population body scans which consisted of larger-sized triangular elements resulting in poor congruence between the graphic points and the x-ray beam boundary. To improve the resolution without impacting real-time performance, the number of calculations must be reduced and so we created software-designed human models and modified the DTS to read the graphic as a list of vertices of the triangular elements such that common vertices of adjacent triangles are listed once. Dose is calculated for each vertex point once instead of the number of times that a given vertex appears in multiple triangles. By reformatting the graphic file, we were able to subdivide the triangular elements by a factor of 64 times with an increase in the file size of only 1.3 times. This allows a much greater number of smaller triangular elements and improves resolution of the patient graphic without compromising the real-time performance of the DTS and also gives a smoother graphic display for better visualization of the dose distribution.

PM418 Cumulative Radiation Exposure and Peak Skin Dose Quantification using a real time dose tracking system in coronary procedures

PM418 Cumulative Radiation Exposure and Peak Skin Dose Quantification using a real time dose tracking system in coronary procedures

SU‐E‐I‐25: Extension of a Real‐Time Skin Dose Tracking System to Include Pediatric Fluoroscopic Cardiac Procedures

Purpose: To develop pediatric graphic models for a real‐time skin dose‐tracking system (DTS) and to verify the accuracy of dose and dose‐rate determination with these models for cardiac projections. Methods: A system has been developed to track skin dose during fluoroscopic interventional procedures and to provide a graphic representation of the cumulative dose distribution in real time. Accurate operation of the DTS has been verified for adult patient graphic models. To extend the application of this software to pediatric procedures, a series of 3D pediatric patient graphic models has been developed with varying heights ranging from 60 to 128 cm and with three weight ranges for each height. An open‐source software application was used for graphic development while a commercial software package was used to pose the models with arms up or down. The appropriate graphic model is selected by the operator at the beginning of the procedure to closely match the patient. To verify correct dose calculation for these models, exposures were made for typical cardiac projections using a water‐filled phantom with AP and lateral dimensions of 12 and 19 cm, respectively, corresponding to the torso of a 20 kg child. Dose (rate) was measured at the center of the field using a 6 cc ionization chamber and the readings compared to those calculated by the DTS. Results: The DTS displayed values of cumulative skin dose and of dose rate agreed with the values measured with an ionization chamber within 2 percent over a range of RAO/LAO and CRA/CAU projections on a cardiac C‐arm unit. Conclusion: The patient model size range for the DTS software has been extended to include pediatric patients down to 60 cm in height and 12 kg in weight and the DTS has been shown to be able to accurately track the skin dose for such models. Research supported in part by Toshiba Medical Systems and NIH Grant 2R01EB002873.

Current Methods of Monitoring Radiation Exposure From CT

Increased public and regulatory scrutiny of imaging-related radiation exposure requires familiarity with current dose-monitoring techniques and best practices. CT-related ionizing radiation exposure has been cited as the largest and fastest growing source of population-wide iatrogenic ionizing radiation exposure. Upcoming federal regulations require imaging centers to familiarize themselves with available dose-monitoring techniques and implement comprehensive strategies to track patient dose, with particular emphasis on CT. Because of institution-specific and vendor-specific technologies, there are significant barriers to adoption and implementation. In this article, the authors outline the core components of a universal dose-monitoring strategy and detail a few of the many available commercial platforms. In addition, the authors introduce a cloud-based hybrid model dose-tracking system with the goal of rapid implementation, multicenter scalability, real-time dose feedback for technologists, cumulative dose monitoring, and optional dose communication to patients and into the record; doing so results in improved patient loyalty, referring physician satisfaction, and opportunity for repeat business.

Updates in the real-time Dose Tracking System (DTS) to improve the accuracy in calculating the radiation dose to the patients skin during fluoroscopic procedures.

We have developed a dose-tracking system (DTS) to manage the risk of deterministic skin effects to the patient during fluoroscopic image-guided interventional cardiac procedures. The DTS calculates the radiation dose to the patient's skin in real-time by acquiring exposure parameters and imaging-system geometry from the digital bus on a Toshiba C-arm unit and displays the cumulative dose values as a color map on a 3D graphic of the patient for immediate feedback to the interventionalist. Several recent updates have been made to the software to improve its function and performance. Whereas the older system needed manual input of pulse rate for dose-rate calculation and used the CPU clock with its potential latency to monitor exposure duration, each x-ray pulse is now individually processed to determine the skin-dose increment and to automatically measure the pulse rate. We also added a correction for the table pad which was found to reduce the beam intensity to the patient for under-table projections by an additional 5-12% over that of the table alone at 80 kVp for the x-ray filters on the Toshiba system. Furthermore, mismatch between the DTS graphic and the patient skin can result in inaccuracies in dose calculation because of inaccurate inverse-square-distance calculation. Therefore, a means for quantitative adjustment of the patient-graphic-model position and a parameterized patient-graphic library have been developed to allow the graphic to more closely match the patient. These changes provide more accurate estimation of the skin-dose which is critical for managing patient radiation risk.

SU-E-I-28: Development of Graphic Patient Models for a Real-Time Skin Dose Tracking System (DTS) for Fluoroscopic Interventional Procedures.

To develop a library of graphic human models that closely match patients undergoing interventional fluoroscopic procedures in order to obtain an accurate estimate of their skin dose. A dose tracking system (DTS) has been developed that calculates the dose to the patient's skin in real time during fluoroscopic procedures based on a graphical simulation of the x-ray system and the patient. The calculation is performed using a lookup table containing values of mGy per mAs at a reference point and inverse-square correction using the distance from the source to individual points on the skin. For proper inverse-square correction, the external shape of the graphic should closely match that of the patient. We are in the process of developing a library of 3D human graphic models categorized as a function of basic body type, sex, height and weight. Two different open- source software applications are being used to develop graphic models with varying weights and heights, to 'morph' the shapes for body type and to 'pose' them for proper positioning on the table. The DTS software is being designed such that the most appropriate body graphic can be automatically selected based on input of several basic patient dimensional metrics. A series of male and female body graphic models have been developed which vary in weight and height. Matching pairs have been constructed with arms at the side and over the head to simulate the usual placement in cardiac procedures. The error in skin dose calculation due to inverse-square correction is expected to be below 5% if the graphic can match the position of the patient's skin surface within 1 cm. A library of categorized body shapes should allow close matching of the graphic to the patient shape allowing more accurate determination of skin dose with the DTS. Support for this work was provided in part by NIH grants R43FD0158401, R44FD0158402, R01EB002873 and R01EB008425, and by Toshiba Medical Systems Corporation.

SU-F-BRA-09: Comparison of Skin-Dose Distributions Calculated by a Real-Time Dose-Tracking System with That Measured by Gafchromic Film for a Fluoroscopic C-Arm Unit

Purpose: To assess the ability of a real‐time dose‐tracking system (DTS) to accurately represent the skin dose distribution for fluoroscopic interventional procedures by comparison to that measured using Gafchromic film (XR‐RV3, ISP, Wayne, NJ).Methods: We have developed a dose‐tracking system that calculates the radiation dose to the patient's skin in real‐time using the exposure parameters and imaging‐system‐geometry obtained from the digital bus on a Toshiba Infinix C‐arm unit. The DTS presents the cumulative dose values in a color mapping on a 3D graphic of the patient for immediate feedback to the interventionalist. Gafchromic film was used to verify the spatial correspondence of the mapped distribution and the accuracy of the dose accumulation on the graphic. The film was calibrated against the readings of a 6 cc ionization chamber (PTW‐Freiburg GmbH, Freiburg, Germany) over a range of exposure values from 0 to 1500 R using cine‐radiographic exposures on the same C‐arm system. A simulated cardiac‐catheterization procedure was performed with the film wrapped around an Alderson torso phantom; the density distribution and converted dose values on the film were compared to that of the DTS graphic.Results: The DTS and film distributions were compared and excellent agreement was obtained within the cm‐sized surface elements used for the patient model demonstrating proper geometric scaling of the graphic. The dose values for individual points on the phantom surface agreed within 10% between the film and DTS even with inexact contouring of the film with the phantom in the measurement Conclusions: As shown by the agreement with Gafchromic film, the DTS provides skin‐dose distribution mapping with sufficient accuracy for use in monitoring interventional fluoroscopic procedures. NIH Grants R01‐EB002873, R01‐EB002873, R43‐FD0158401, R44‐FD0158402, and Toshiba Medical Systems Corporation.

Verification of the performance accuracy of a real-time skin-dose tracking system for interventional fluoroscopic procedures.

A tracking system has been developed to provide real-time feedback of skin dose and dose rate during interventional fluoroscopic procedures. The dose tracking system (DTS) calculates the radiation dose rate to the patient's skin using the exposure technique parameters and exposure geometry obtained from the x-ray imaging system digital network (Toshiba Infinix) and presents the cumulative results in a color mapping on a 3D graphic of the patient. We performed a number of tests to verify the accuracy of the dose representation of this system. These tests included comparison of system-calculated dose-rate values with ionization-chamber (6 cc PTW) measured values with change in kVp, beam filter, field size, source-to-skin distance and beam angulation. To simulate a cardiac catheterization procedure, the ionization chamber was also placed at various positions on an Alderson Rando torso phantom and the dose agreement compared for a range of projection angles with the heart at isocenter. To assess the accuracy of the dose distribution representation, Gafchromic film (XR-RV3, ISP) was exposed with the beam at different locations. The DTS and film distributions were compared and excellent visual agreement was obtained within the cm-sized surface elements used for the patient graphic. The dose (rate) values agreed within about 10% for the range of variables tested. Correction factors could be applied to obtain even closer agreement since the variable values are known in real-time. The DTS provides skin-dose values and dose mapping with sufficient accuracy for use in monitoring diagnostic and interventional x-ray procedures.

Endovascular image‐guided interventions (EIGIs)

Minimally invasive interventions are rapidly replacing invasive surgical procedures for the most prevalent human disease conditions. X-ray image-guided interventions carried out using the insertion and navigation of catheters through the vasculature are increasing in number and sophistication. In this article, we offer our vision for the future of this dynamic field of endovascular image-guided interventions in the form of predictions about (1) improvements in high-resolution detectors for more accurate guidance, (2) the implementation of high-resolution region of interest computed tomography for evaluation and planning, (3) the implementation of dose tracking systems to control patient radiation risk, (4) the development of increasingly sophisticated interventional devices, (5) the use of quantitative treatment planning with patient-specific computer fluid dynamic simulations, and (6) the new expanding role of the medical physicist. We discuss how we envision our predictions will come to fruition and result in the universal goal of improved patient care.