The design and implementation of the radiation therapy information management system (RTIMS) based on the workflow of radiation therapy / 中华放射肿瘤学杂志

Objective To meet the special needs of the department of radiation oncology, a radiation therapy information management system ( RTIMS) has been developed as a secondary database system to supplement the Varian Varis/Aria since 2007. Methods The RTIMS server was used to run a database and web service of Apache + PHP + MySQL. The RTIMS sever's web service could be visited with Internet Explorer (IE) to input, search, count, and print informations from about 30 workstations and 20 personal computers. As some workstations were installed with Windows and IE in English only, some functions had English version. Results In past five years, as the RTIMS was implemented in the department, some further needs were met and more practical functions were developed. And now the RTIMS almost covered the whole workflow of radiation therapy ( RT) . By September 2011 , recorded patients data in the RTIMS is as follows: 3900 patients, 2600 0utpatient RT records, 6800 progress notes, 1900 RT summaries, 6700 charge records, 83000 workload records, 3900 plan application forms, 1600 ICRT records. etc. Conclusions The RTIMS hased on the workflow of RT has been successfully developed and clinically implemented. And it was demonstrated to be user-friendly and was proven to　significantly improve the efficiency of the department. Since it is an in-house developed system, more functions can be added or modified to further enhance its potentials in research and clinical practice.

Correction of manual monitor unit calculation for asymmetric fields using Varian enhanced dynamic wedge / 中华放射医学与防护杂志

Objective To investigate the correction of manual monitor unit calculation for asymmetric fields using the Varian enhanced dynamic wedge.Methods Monitor unit (MU) was calculated when the field sizes ranged from 6 cm × 6 cm to 20 cm × 20 cm at a depth of 5 cm using Varian Eclipse and both 6 MV and 10 MV X-rays data from Varian Clinac 23EX for all seven available EDW angles,including 10°15°,20°,25°,30°,45°and 60° The field size was kept fixed,and the distance between geometry center of field and isocenter was increased in increments of 1 cm,ranging from -9 cm to 4 cm.When the field size was the same,the correction factor was defined as the ratio of MU calculated for asymmetric field to monitor unit calculated for symmetric field.To ensure the correction factors obtained above could be used in routine manual calculation for EDW fields,measurements were made at a depth of 5 cm for 30°and 45°EDW with field size of 10 cm × 10 cm using 6 MV X-rays.Results The correction factor was independent of field dimensions,so the average value was adopted to make practical calculation.Without correction,the maximum error was 18% for 30°,and 30% for 45.After the results of monitor unit calculation were corrected,the largest error was - 1.8% and - 1.7% for 30° and 45°EDW,respectively.The magnitude of errors was within the clinical tolerance limits.Conclusions For asymmetric EDW fields,there is very large difference between the prescribed dose by manual calculation using EDW factors measured for symmetric fields and that delivered during treatment in order to obtain correct dose to reference point.The errors are decreased to be acceptable after correction.The method of correction is simple and independent of machine specific beam parameters.

Quality Assurance of X Knife / 中华放射肿瘤学杂志

Purpose: A comprehensive quality assurance program has been established in Beijing hospital to ensure that "radiosurgery" be carried out precisely and safetely.Materials and Methods: A film checking technique was used to verify the localization accuracy and the setting-up accuracy.Results: The figures taken from 80 cases treated show that the setting-up accuracy of the target positions be within ?1mm .Conclusion: The positional accura cies during target localization and setting-up are guaranteed by using our QA procedures.

Clinical quality assurance of intensity modulated radiation therapy / 中华放射肿瘤学杂志

Objective To evaluate the clinical feasibility of quality assurance of intensity modulated radiation therapy(IMRT) through a series of clinical case studies. Methods Helios inverse planning system was used to provide optimized IMRT treatment plans for brain tumor, nasopharyngeal carcinoma, pancreatic cancer, spinal metastatic tumor and prostatic cancer. To verify the conformation between the fluence map of each beam predicted by the planning system and that actually delivered, a piece of film under a homogeneous polystyrene phantom was irradiated vertically with each of the beams to record the deposited dose. This measured fluence map was compared with that predicted by the planning. The dose distribution was recorded by irradiating the film in an anthropomorphic phantom using patients' treatment plan, then compared with that predicted by the planning. An ionization chamber in a water phantom was used to measure the central point dose and another eccentric point dose. Results The fluence map measured by the film was well consistent with that predicted by the planning. The error between the measured dose and predicted dose in the central point was less than 3%, whereas the error of the dose in another eccentric point varied greatly. The isodose distribution (on axial plane) measured by the film was consisent with the predicted one. Conclusions The procedures for quality assurance of IMRT are feasible in our experience.

Influence of field size on electron beam central axis dose on a radiotherapy linear accelerator / 中华放射肿瘤学杂志

Objective Clinical application of electrons often involves some beam in which the field size varies with the applicators. The work was done to understand the electron beam characteristics in different field sizes. Methods Percent depth dose and the dose output factor were measured for square and rectangular fields at 100?cm source to surface distance ( SSD ) . Central axis percent depth dose (PDD) measurements were made using the RFA 300 three dimensional radiation field analyzer with a shielded p type diode detector . The dose output factors were measured with the RFA 300 three dimensional radiation field analyzer with a PTW 0.1?cm 3 chamber and a Farmer 2570/1 dosimeter with a 2571 ion chamber in a water phantom. Results The measurements showed that the depth dose curves and the output factors were sometimes dependent on how the field sizes were formed. The change in depth dose with field size was more pronounced in the high energy beams than the low energy ones. However, the output factor did not show any systematic energy dependence because each applicator had it's own X ray jaw setting at each energy. Conclusions When using small inserted apertures to treat small lesions, we should verify the conformation of depth dose and output factors. In this case, we should use applicator dependent output factors at each energy to calculate the monitor units for irradiation.