This paper evaluates the uncertainty in the measurement of radiated disturbance by analyzing and calculating the components that influence the uncertainty. And the effectiveness of the uncertainty testing has been confirmed through the ability validation.
Radiometry ; methods ; Uncertainty

OBJECTIVETo research the method of dosimetric verification of the intensity modulated radiation therapy (IMRT).

METHODSThe IMRT treatment plans were designed by Eclipse TPS and were implemented in Varian ClinacIX LA with 6MV X-ray. The absolute point doses were measured using a PTW 0.6 cc ion chamber with UNIDOS E dosimeter and the planes dose distributions were measured using PTW 2D-Array ion chamber in the phantom.

RESULTSThe error between the measured dose and calculated dose in the interesting points was less than 3%. The points passed ratio was more than 90% in gamma analysis method (3 mm 13%) about the plane dose distribution verification.

CONCLUSIONThe method of dosimetric verification of IMRT is reliable and efficient in the implementation.

The structural principles and technical performances of different ionization chamber dosimeters used in radiotherapy have been briefly introduced in this paper. In the mean time, a comparison of technical performances of four different kinds of ionization chamber dosimeter used in hospitals in China has also been made. The data show their quality meet the required specification specified by IEC731 and JJG912-96, so they can be used as field survey dosimeters in hospitals. Some precautions in using these dosimeters are given here too.
Equipment Design ; Radiometry ; classification ; instrumentation ; methods ; Radiotherapy ; instrumentation ; Radiotherapy Dosage

OBJECTIVETo evaluate the clinical feasibility of daily quality assurance for linac radiation field by analyzing the trend of the daily testing data about parameter of radiation field.

METHODSTwo-dimensional ion chamber array Daily QA3 was used to measure the difference between the practical value and the standard value of the parameter about radiation field before commencing daily treatment. Farmer type ionization chambers from IBA Co. with DOSE1 dosimeter was used for the absolute dosimetry of photon and electron beams. Light/radiation field coincidence was checked by using films every month. The daily testing data (from 11/28/2009 to 4/8/2011) were reviewed and analyzed.

RESULTSX-ray and electron output was increasing steadily; light/radiation field coincidence, beam flatness constancy and symmetry of X- ray and electron was keeping stable.

CONCLUSIONThe procedures for daily quality assurance of linac radiation field, which will provide reference for long term linac calibration, are feasible in our experience.

Conformal radiation therapy using multi-leaf collimator (MLC) is considered as a conventional technology in the hospital nowadays. However the stepped leaf edge caused by the finite width of the leaves could influence the conformality that could be achievable. In this paper, the effect produced by rotating the collimator angle on the conformality was investigated. A method, in which multiple MLC fields of various rotation angles are applied, has been proposed to have the targets be more uniformly irradiated and thus to eliminate the cold spots on the targets and hot spots in normal tissues. By simulation, it has been shown that the multiple MLC field method can eliminate the stepped leaf edges and improve the conformality significantly, moreover, the PTV can receive a more uniform delivery with cold spot eliminated.
Humans ; Radiometry ; methods ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted ; instrumentation ; methods ; Radiotherapy, Conformal ; methods

In order to improve the diagnostic quality of X-ray device and to promote the implementation of radiation protection in accordance to the ICRU definition and ICRP classification standards for measuring radiation harm to human body, we have made a number of tests, including the kinetic energy released by ionizing air, the Half-value layer, the output dose coincidence, the High contrast resolution, the Consistency between visual light field and project X-ray field, and the Focus of X-ray tube. We have also analysed the measured data and results. The tests were conducted on the XEB150L-20 made by Shimadzu Co. in the middle of 1990s.
Quality Control ; Radiation Dosage ; Radiation Monitoring ; methods ; Radiation Protection ; methods ; Radiography ; instrumentation ; Radiometry ; methods

BACKGROUNDA novel radioactive 125I seed-loaded biliary stent has been used for patients with malignant biliary obstruction. However, the dosimetric characteristics of the stents remain unclear. Therefore, we aimed to describe the dosimetry of the stents of different lengths - with different number as well as activities of 125I seeds.

METHODSThe radiation dosimetry of three representative radioactive stent models was evaluated using a treatment planning system (TPS), thermoluminescent dosimeter (TLD) measurements, and Monte Carlo (MC) simulations. In the process of TPS calculation and TLD measurement, two different water-equivalent phantoms were designed to obtain cumulative radial dose distribution. Calibration procedures using TLD in the designed phantom were also conducted. MC simulations were performed using the Monte Carlo N-Particle eXtended version 2.5 general purpose code to calculate the radioactive stent's three-dimensional dose rate distribution in liquid water. Analysis of covariance was used to examine the factors influencing radial dose distribution of the radioactive stent.

RESULTSThe maximum reduction in cumulative radial dose was 26% when the seed activity changed from 0.5 mCi to 0.4 mCi for the same length of radioactive stents. The TLD's dose response in the range of 0-10 mGy irradiation by 137Cs γ-ray was linear: y = 182225x - 6651.9 (R2=0.99152; y is the irradiation dose in mGy, x is the TLDs' reading in nC). When TLDs were irradiated by different energy radiation sources to a dose of 1 mGy, reading of TLDs was different. Doses at a distance of 0.1 cm from the three stents' surface simulated by MC were 79, 93, and 97 Gy.

CONCLUSIONSTPS calculation, TLD measurement, and MC simulation were performed and were found to be in good agreement. Although the whole experiment was conducted in water-equivalent phantom, data in our evaluation may provide a theoretical basis for dosimetry for the clinical application.

The purpose of this study is to establish and apply a correction method for titanium alloy implant in spinal IMRT plan, a corrected CT-density table was revised from normal CT-density table to include the density of titanium alloy implant. Dose distribution after and before correction were calculated and compared to evaluate the dose deviation. Plans were also copied to a spinal cancer simulation phantom. A titanium alloy fixation system for spine was implanted in this phantom. Plans were recalculated and compared with the measurement result. The result of this study shows that the max dose of spinal cord showed significant difference after correction, and the deviation between calculation results and measurement results was reduced after correction. The method for expanding the range CT-density table, which means that the density of titanium alloy was included, can reduce the error in calculation.
Radiotherapy, Intensity-Modulated/methods* ; Titanium ; Radiotherapy Dosage ; Alloys ; Radiometry/methods* ; Radiotherapy Planning, Computer-Assisted/methods*

This paper presents a rapid searching algorithm for dose calculation based on the region growing algorithm. Using this algorithm, we can automatically and rapidly search out the dose computational region for the gamma knife, so as to reduce the computational time, and space complexity.
Algorithms ; Radiometry ; methods ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted ; methods ; Robotics ; Tomography, X-Ray Computed

BACKGROUND AND OBJECTIVETo ensure the accuracy of dose calculation for radiation treatment plans is an important part of quality assurance (QA) procedures for radiotherapy. This study evaluated the Monitor Units (MU) calculation accuracy of a third-party QA software and a 3-dimensional treatment planning system (3D TPS), to investigate the feasibility and reliability of independent verification for radiation treatment planning.

METHODSTest plans in a homogenous phantom were designed with 3-D TPS, according to the International Atomic Energy Agency (IAEA) Technical Report No. 430, including open, blocked, wedge, and multileaf collimator (MLC) fields. Test plans were delivered and measured in the phantom. The delivered doses were input to the QA software and the independent calculated MUs were compared with delivery. All test plans were verified with independent calculation and phantom measurements separately, and the differences of the two kinds of verification were then compared.

RESULTSThe deviation of the independent calculation to the measurements was (0.1 +/- 0.9)%, the biggest difference fell onto the plans that used block and wedge fields (2.0%). The mean MU difference between the TPS and the QA software was (0.6 +/- 1.0)%, ranging from -0.8% to 2.8%. The deviation in dose of the TPS calculation compared to the measurements was (-0.2 +/- 1.7)%, ranging from -3.9% to 2.9%.

CONCLUSIONSMU accuracy of the third-party QA software is clinically acceptable. Similar results were achieved with the independent calculations and the phantom measurements for all test plans. The tested independent calculation software can be used as an efficient tool for TPS plan verification.