Related Experiment Video
Updated: Jul 25, 2025
Dosimetry for Cell Irradiation using Orthovoltage 40-300 kV X-Ray Facilities
Published on: February 20, 2021
Assessment of a self-inspection method and reporting measured electrometer correction factors for reference-class
Motohiro Kawashima1, Maria Varnava1, Shuichi Ozawa2,3,4
1Gunma University Heavy Ion Medical Center, Maebashi, Gunma, Japan.
Background And Purpose:
The standard dosimetry system of medical accelerators in radiotherapy consists of an ionization chamber, an electrometer, and cables. Guidance for TG-51 reference dosimetry reported that the electrometer correction factor (Pelec ) should be checked every few years. Therefore, continuous Pelec measurements have not been reported. The purpose of this study is to measure the Pelec with a charge generator at our institution and to evaluate variations over time. The measurements are compared with calibration data given by an Accredited Dosimetry Calibration Laboratory (ADCL).
Materials And Methods:
We used four reference-class electrometers: RT521R (RTQM system/EMF Japan), Model 35040 (FLUKE), RAMTEC Duo (Toyo medic), and UNIDOS-E (PTW). Each electrometer was connected to the charge generator, and the required charge was applied. The measurement points used were the same as those used for calibration by the ADCL. From the measured charges at each point, the Pelec was obtained from the slope of the linear regression function. The measurements were repeated over a 3-month period to evaluate variations over time for each electrometer. Additionally, error budgets for the Pelec measurements were estimated, and the overall uncertainty was determined.
Results:
The measured Pelec values were 1.0000, 0.9995, 1.0009/0.9999, and 0.9995/0.9998 for RT521R, Model 35040, the low/medium (L/M) ranges of RAMTEC Duo, and the L/M ranges of UNIDOS-E, respectively. The measured Pelec values agreed within 0.1% with those given by the ADCL. We found a small drift in the measurements for one electrometer. Additionally, the uncertainty considered was 0.26% for k = 2 (k, coverage factor).
Conclusion:
In this study, stable Pelec values were obtained for four electrometers using a charge generator over a three-month period. The measured Pelec values were within the overall uncertainty stated in the electrometer guidelines. However, performing periodic measurements for the Pelec was able to help in detecting small errors.
More Related Videos
06:20Irradiator Commissioning and Dosimetry for Assessment of LQ α and β Parameters, Radiation Dosing Schema, and in vivo Dose Deposition
Published on: March 11, 2021
07:31Characterization of Recombination Effects in a Liquid Ionization Chamber Used for the Dosimetry of a Radiosurgical Accelerator
Published on: May 9, 2014
Related Concept Videos
01:15Distance Corrections
02:59Biological Effects of Radiation
01:30Potentiometer
Suppose the emf of a battery needs to be measured. If the battery is directly connected to a standard voltmeter, the measured quantity is...
01:17Common Leveling Mistakes and Errors
01:14Assessing Body Temperature - Axilla
Step 1: Perform hand hygiene and put on clean gloves to maintain infection control and prevent cross-contamination.
Step 2: Prepare the patient by explaining the procedure to ensure understanding and cooperation. Ensure privacy, expose the axilla, and inform the patient that minimal movement is crucial for an accurate reading.
Step 3: Adjust the patient’s clothing to expose only the axilla. It minimizes...