INVESTIGATION OF SECONDARY MIXED RADIATION FIELD AROUND A MEDICAL LINEAR ACCELERATOR.

The aim of this study is to investigate secondary mixed radiation field around linac, as the first part of an overall assessment of out-of-field contribution of neutron dose for new advanced radiation dose delivery techniques. All measurements were performed around Varian Clinic 2300 C/D accelerator at Maria Sklodowska-Curie Memorial, Cancer Center and Institute of Oncology, Krakow Branch. Recombination chambers REM-2 and GW2 were used for recombination index of radiation quality Q4 determination (as an estimate of quality factor Q), measurement of total tissue dose Dt and calculation of gamma and neutron components to Dt. Estimation of Dt and Q4 allowed for the ambient dose equivalent H*(10) per monitor unit (MU) calculations. Measurements around linac were performed on the height of the middle of the linac's head (three positions) and on the height of the linac's isocentre (five positions). Estimation of secondary radiation level was carried out for seven different configurations of upper and lower jaws position and multileaf collimator set open or closed in each position. Study includes the use of two photon beam modes: 6 and 18 MV. Spatial distribution of ambient dose equivalent H*(10) per MU on the height of the linac's head and on the standard couch height for patients during the routine treatment, as well as relative contribution of gamma and neutron secondary radiation inside treatment room were evaluated.

Application of IMRT in adjuvant treatment of soft tissue sarcomas of the thigh-Preliminary results.

BACKGROUND: Fracture of the femur is the most frequent late complication in patients with soft tissue sarcomas (STS) who receive external beam radiotherapy after limb-sparing surgery. AIM: To reduce the risk of bone fracture following radiotherapy of STS of the thigh, we minimized the dose to the femur and to surrounding normal tissues by applying intensity modulated radiation therapy (IMRT). We report preliminary results of post-surgery IMRT of the thigh in patients with STS in this extremity. MATERIALS AND METHODS: 10 adult patients undergoing post-operative radiotherapy of STS of the thigh were treated using IMRT. Clinical IMRT plans with simultaneous integrated boost (SIB) and 3-phase three-dimensional conformal radiotherapy (3D-CRT) were designed to adequately treat the planning target volume and to spare the femur to the largest extent possible. Dose distributions and dose-volume histograms were compared. RESULTS: For either technique, a comparable target coverage was achieved; however, target volume was better covered and critical structures were better spared in IMRT plans. Mean and maximum doses to OAR structures were also significantly reduced in the IMRT plans. On average, the mean dose to the femur in 3D-CRT plans was about two times higher than that in IMRT plans. CONCLUSION: Compared with 3D-CRT, the application of IMRT improves the dose distribution within the concave target volumes and reduces dose to the OAR structures without compromising target coverage.

Comparison between intensity modulated radiotherapy (IMRT) and 3D tangential beams technique used in patients with early-stage breast cancer who received breast-conserving therapy.

BACKGROUND: The most often found complications in patients with breast cancer who received radiotherapy are cardiac and pulmonary function disorders and development of second malignancies. AIM: To compare the intensity modulated radiotherapy with the 3D tangential beams technique in respect of dose distribution in target volume and critical organs they generate in patients with early-stage breast cancer who received breast-conserving therapy. MATERIALS AND METHODS: A dosimetric analysis was performed to assess the three radiotherapy techniques used in each of 10 consecutive patients with early-stage breast cancer treated with breast-conserving therapy. Radiotherapy was planned with the use of all the three techniques: 3D tangential beams with electron boost, IMRT with electron boost, and intensity modulated radiotherapy with simultaneous integrated boost. RESULTS: The use of the IMRT techniques enables more homogenous dose distribution in target volume. The range of mean and median dose to the heart and lung was lower with the IMRT techniques in comparison to the 3D tangential beams technique. The range of mean dose to the heart amounted to 0.3-3.5 Gy for the IMRT techniques and 0.4-4.3 for the tangential beams technique. The median dose to the lung on the irradiated side amounted to 4.9-5 Gy for the IMRT techniques and 5.6 Gy for the 3D tangential beams technique. CONCLUSION: The application of the IMRT techniques in radiotherapy patients with early-stage breast cancer allows to obtain more homogenous dose distribution in target volume, while permitting to reduce the dose to critical organs.

[Choroidal metastases of malignancies. Review of treatment methods with special regard to application of radiotherapy]. / Przerzuty nowotworowe do naczyniówki galki ocznej. Przeglad metod leczenia ze szczególnym uwzglednieniem radioterapii.

Choroidal metastases are developed in 4 - 12% of patients with solid malignancies. Typical symptoms are loss of visual acuity or visual field, photophobia and floaters. In therapy of choroidal metastases are used following methods: surgery, laser photocoagulation, radiotherapy, and systemic treatment (anti-neoplastic chemotherapy or hormonotherapy). At choice of method of treatment it is taking not only features associate with choroidal metastases (as size, shape, number of changes and localization) but also: performance status of patient and the presence of metastases in any sites. The purpose of this paper is the review of treatment methods of choroidal metastases with special regard to application of radiotherapy. Radiotherapy is a conservative method of treatment, and it is used as brachytherapy or external beam irradiation (teleradiotherapy). Brachytherapy is recommended in case of single change, with base diameter below 18 mm. The positive results are observed in 90% cases. Teleradiotherapy is used in metastatic tumours which size exceed possibility successfully using of brachytherapy, and in case of multiple foci of choroidal changes, and metastases bilaterally localized. 70 - 89% patients developed regression of choroidal metastases after external beam irradiation. The preservation of bulbus oculi is observed in 98% patients. Presented paper showed application of methods of brachytherapy used in Ophthalmological Department of Jagiellonian University, and technique of teleradiotherapy used in Radiotherapy Department of Oncology Centre in Krakow, which are used in treatment of choroidal metastases.