IAEA confirmed high quality operation of the radiation therapy department of Medicina Clinics Sofia Oncology Center


IAEA confirmed high quality operation of the radiation therapy department of Medicina Clinics Sofia Oncology Center

The IAEA, together with the World Health Organization (WHO), conducts bi-annual checks of gamma-ray and linear accelerator beams, as well as the quality of work of medical physicists. To date, 1,850 clinics have been audited in 126 countries.

For TrueBeam linear accelerators used at the Radiation Therapy Department of Medicina Clinic, mean deviation for photon energies of 6, 10 and 15 MV was less than 0.5% (0, 0.4 and 0.6 percent, respectively), with an acceptable deviation of 5%. And one energy demonstrated an absolute 100% correspondence. This confirms high quality of radiation therapy delivered at Medicina Clinic’s Sofia Oncology Center.

Radiation therapy is one of the most advanced, most effective and at the same time most complex types of therapies provided to cancer patients. A good outcome of treatment can be achieved only provided that the tumor is exposed to a precisely defined dose of ionizing radiation. In this connection, the issue of correspondence between the dose released by a linear accelerator (“delivered dose”) and the dose determined by the radiotherapist (planned dose") becomes of particular importance. Therefore, a team of medical physicists calibrates the linear accelerator before delivering radiotherapy. That is to say, they find a correspondence between the accelerator operation time and the dose to be delivered. Subsequently, all calculations of patients individual irradiation rely on the values obtained. The quality and accuracy of such calibration largely depends on the experience and knowledge of medical physicists.

Audit is voluntary, says Stanislav Zakharov, Senior Radiotherapist of the Radiation Therapy Department at Sofia Oncology Center, Medicina Clinic. They mailed us thermoluminescent dosimeters (TLD). The work of such dosimeters is based on the ability of certain substances to accumulate energy when exposed to ionizing radiation. Then, medical physicists expose the dosimeters to a dose of 2 Gy using linear accelerators. Following the exposure, the dosimeters are mailed back to the IAEA, and there, when heated to a temperature of about 200-400°C, the dosimeters release the accumulated energy in the form of light. This phenomenon is known as thermoluminescence, and the number of photons emitted is proportional to the absorbed dose of ionizing radiation. Based on the results of this test, a report is sent to the clinic on compliance or non-compliance of linear accelerator calibration with the IAEA requirements. The IAEAs high opinion about our work is the result of responsible and systematic work of the whole team of the Radiation Therapy Department and, of course, our medical physicists also made a great contribution.

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The Radiation Therapy Department at Sofia Oncology Center, Medicina Clinic,has two linear accelerators, new revolutionary TrueBeam models designed by Varian (USA), with innovative tables having 6 degrees of freedom, which enables the delivery of radiation therapy with a guidance accuracy of up to 0.75 mm. The department applies the latest methods. For example, prostate cancer is treated with 5 sessions of large-fraction remote radiation therapy, while lung cancer therapy can be delivered in 1 session with exposure to a single high dose of radiation.

The Radiation Therapy Department of Medicina Clinic successfully treats breast cancer, head and neck tumors, lung cancer, prostate cancer, cerebral tumors, colon cancer, and distant metastases of various localizations. The department is located at a depth of 8 meters and has a floor area of 748 m2.

In addition to its Radiation Therapy Department, Sofia Oncology Center has a polyclinic department, a chemotherapy department, a surgical department and a radionuclide diagnostics department.