Cavernous sinus haemangioma with intrasellar extension mimicking non-functioning pituitary adenoma - A case report and review of literature.

Fifty-three-year-old male suffering from a presumptive non-functioning pituitary adenoma was qualified for stereotactic radiosurgery in our institution. Two attempts of surgical treatment were taken three months before radiotherapy. Excessive bleeding did not allow to remove the tumour or to take samples for histopathological examination. Diagnosis was put on the basis of radiological assessment and lack of hypersecretion of pituitary hormones. However, radiological reevaluation in our Institute revealed the presence of a well-bounded tumour invading the cavernous sinus with high contrast enhancement in FLAIR and T2-sequence. Moreover, a constriction of the normal pituitary gland with tumour mass was seen. The imaging features of the lesion finally led to diagnosis of cavernous sinus haemangioma with intrasellar expansion. The patient received radiosurgical treatment with the use of linear accelerator (LINAC). A dose of 7 Gy in one fraction was administered to achieve satisfactory local control, prevent potential further bleeding and reduce the risk of progressive neurological deficits. Stable size of the tumour and absence of any complications are confirmed in six years of follow-up.

IMRT/VMAT dose distributions generated for HD ® and Millennium ® collimators TrueBeam ® and Clinac ® accelerators.

AIM: The aim of this study is to answer the question whether the calculated dose distributions for HD and Millennium collimators (Varian Medical Systems) are equivalent for large treatment volumes. BACKGROUND: Modern biomedical linacs are equipped with multileaf collimators where leaves can be of different widths. Thinner leaves allow better fit to desired (tumor) shape. At the same time, however, the maximum size of the field that can be obtained with the collimator is also reduced. Varian Medical Systems HD and Millennium collimators can be a good sample. They have 40 cm or 22 cm × 40 cm maximal field size at the isocenter, respectively. MATERIALS AND METHODS: This paper presents the comparison of selected statistical and dosimetric parameters achieved for treatment plans where the beams for a HD collimator had to be merged because of the size of the tumor volume. RESULTS AND DISCUSSION: Achieved results show that, independently from irradiated volume, there is no statistically significant difference for calculated dose distributions, integral doses, MU values and coefficients evaluating dose distributions for HD and Millennium collimators. CONCLUSIONS: Results show that both types of collimators can be used interchangeably for preparing the treatment plans for large tumor volume without quality reduction of the prepared treatment plan.

Primary mediastinal seminoma.

BACKGROUND: The objective of this study was to evaluate the long term treatment results of patients with primary mediastinal seminoma. METHODS: Sixteen patients aged 21-46 diagnosed with primary mediastinal seminoma between 1983 and 2014. Mean size of the tumor was 65 cm2. In all patients gonadal involvement was excluded. In 6 patients, metastases to regional lymph nodes were found and none of them presented with distant metastases. HCG was elevated in 6 patients (38%). Eight patients underwent surgery as first-line of the treatment: 7 partial and 1 complete resection of the tumor. Chemotherapy (CTH) and radiotherapy (RTH) were methods of treatment in 14 cases. Tumor was irradiated to total dose of 36.0-50.4 (median 42.5) Gy. In statistical analysis overall survival (OS) was calculated using Kaplan-Meier method. RESULTS: During median time of 11 years of the follow-up, complete or partial regression (PR) of the tumor was seen in all patients after primary treatment. Recurrence of the tumor was seen in 3 patients. The 5-, 10- and 15-year local control rates were 75%. One was treated with CTH, other two with RTH. All of them responded with complete regression (CR) of the tumor. Three patients died during the follow-up. All others are alive without disease. The 5-, 10- and 15-year OS was 100%, 91% and 91% respectively. CONCLUSIONS: Chemoradiotherapy of primary mediastinal seminoma gives satisfactory treatment results with good local control rate. The treatment outcome is comparable to primary testicular seminoma.

Integral dose: Comparison between four techniques for prostate radiotherapy.

AIM: Comparisons of integral dose delivered to the treatment planning volume and to the whole patient body during stereotactic, helical and intensity modulated radiotherapy of prostate. BACKGROUND: Multifield techniques produce large volumes of low dose inside the patient body. Delivered dose could be the result of the cytotoxic injuries of the cells even away from the treatment field. We calculated the total dose absorbed in the patient body for four radiotherapy techniques to investigate whether some methods have a potential to reduce the exposure to the patient. MATERIALS AND METHODS: We analyzed CyberKnife plans for 10 patients with localized prostate cancer. Five alternative plans for each patient were calculated with the VMAT, IMRT and TomoTherapy techniques. Alternative dose distributions were calculated to achieve the same coverage for PTV. Integral Dose formula was used to calculate the total dose delivered to the PTV and whole patient body. RESULTS: Analysis showed that the same amount of dose was deposited to the treated volume despite different methods of treatment delivery. The mean values of total dose delivered to the whole patient body differed significantly for each treatment technique. The highest integral dose in the patient's body was at the TomoTherapy and CyberKnife treatment session. VMAT was characterized by the lowest integral dose deposited in the patient body. CONCLUSIONS: The highest total dose absorbed in normal tissue was observed with the use of a robotic radiosurgery system and TomoTherapy. These results demonstrate that the exposure of healthy tissue is a dosimetric factor which differentiates the dose delivery methods.

Clinical examples of 3D dose distribution reconstruction, based on the actual MLC leaves movement, for dynamic treatment techniques.

AIM: To present practical examples of our new algorithm for reconstruction of 3D dose distribution, based on the actual MLC leaf movement. BACKGROUND: DynaLog and RTplan files were used by DDcon software to prepare a new RTplan file for dose distribution reconstruction. MATERIALS AND METHODS: FOUR DIFFERENT CLINICALLY RELEVANT SCENARIOS WERE USED TO ASSESS THE FEASIBILITY OF THE PROPOSED NEW APPROACH: (1) Reconstruction of whole treatment sessions for prostate cancer; (2) Reconstruction of IMRT verification treatment plan; (3) Dose reconstruction in breast cancer; (4) Reconstruction of interrupted arc and complementary plan for an interrupted VMAT treatment session of prostate cancer. The applied reconstruction method was validated by comparing reconstructed and measured fluence maps. For all statistical analysis, the U Mann-Whitney test was used. RESULTS: In the first two and the fourth cases, there were no statistically significant differences between the planned and reconstructed dose distribution (p = 0.910, p = 0.975, p = 0.893, respectively). In the third case the differences were statistically significant (p = 0.015). Treatment plan had to be reconstructed. CONCLUSION: Developed dose distribution reconstruction algorithm presents a very useful QA tool. It provides means for 3D dose distribution verification in patient volume and allows to evaluate the influence of actual MLC leaf motion on the dose distribution.

Significant change in the construction of a door to a room with slowed down neutron field by means of commonly used inexpensive protective materials.

The detailed analysis of nuclear reactions occurring in materials of the door is presented for the typical construction of an entrance door to a room with a slowed down neutron field. The changes in the construction of the door were determined to reduce effectively the level of neutron and gamma radiation in the vicinity of the door in a room adjoining the neutron field room. Optimisation of the door construction was performed with the use of Monte Carlo calculations (GEANT4). The construction proposed in this paper bases on the commonly used inexpensive protective materials such as borax (13.4 cm), lead (4 cm) and stainless steel (0.1 and 0.5 cm on the side of the neutron field room and of the adjoining room, respectively). The improved construction of the door, worked out in the presented studies, can be an effective protection against neutrons with energies up to 1 MeV.

Beam rate influence on dose distribution and fluence map in IMRT dynamic technique.

AIM: To examine the impact of beam rate on dose distribution in IMRT plans and then to evaluate agreement of calculated and measured dose distributions for various beam rate values. BACKGROUND: Accelerators used in radiotherapy utilize some beam rate modes which can shorten irradiation time and thus reduce ability of patient movement during a treatment session. This aspect should be considered in high conformal dynamic techniques. MATERIALS AND METHODS: Dose calculation was done for two different beam rates (100 MU/min and 600 MU/min) in an IMRT plan. For both, a comparison of Radiation Planning Index (RPI) and MU was conducted. Secondly, the comparison of optimal fluence maps and corresponding actual fluence maps was done. Next, actual fluence maps were measured and compared with the calculated ones. Gamma index was used for that assessment. Additionally, positions of each leaf of the MLC were controlled by home made software. RESULTS: Dose distribution obtained for lower beam rates was slightly better than for higher beam rates in terms of target coverage and risk structure protection. Lower numbers of MUs were achieved in 100 MU/min plans than in 600 MU/min plans. Actual fluence maps converted from optimal ones demonstrated more similarity in 100 MU/min plans. Better conformity of the measured maps to the calculated ones was obtained when a lower beam rate was applied. However, these differences were small. No correlation was found between quality of fluence map conversion and leaf motion accuracy. CONCLUSION: Execution of dynamic techniques is dependent on beam rate. However, these differences are minor. Analysis shows a slight superiority of a lower beam rate. It does not significantly affect treatment accuracy.