No abstract

This article has been peer reviewed and published immediately upon acceptance.It is an open access article, which means that it can be downloaded, printed, and distributed freely, provided the work is properly cited.

Purpose: To evaluate the performance of an in‐house laser CT scanner and study its usefulness for dose verification in IMRT. Method and Materials A laser CT scanner has been developed based on the principle of a first generation X‐ray CT. This scanner consists of an aquarium, a turntable with angular graduation, photodiode as detector and laser as light source. The laser is swappable between a red laser and a green laser. The laser attenuation data acquired using a data acquisition board and a Personal computer is reconstructed using IRADON function implemented in MATLAB. The spatial accuracy of measurement, resolution and reproducibility of the scanner were investigated in this study. The spatial accuracy of the scanner was verified by scanning needles placed in phantom with known geometry. A capillary tube with 1mm bore was scanned to check the resolution of the scanner. Calibration was performed by exposing the gel for a few known doses. Three IMRT plans were verified using normoxic polymer gels and the dose distribution were compared with that of the treatment planning system. Results: The spatial measurement accuracy of the scanner was one millimeter. The scan of the 1 mm capillary showed that the resolution of the scanner was 1 mm. The repeated scanning of a gel produced identical results suggesting that the dose mapping with the scanner is reproducible. The dose distribution obtained with gel measurements agree with the treatment plans within the 5%‐3mm. Conclusion: The performance of laser CT scanner developed in‐house has been found to be adequate for reading dose distribution embedded in gel. The comparison of the IMRT plans showed that it could be used for patient specific quality assurance of IMRT plans.

Background: There are clinical scenarios when it is required to deliver Radiotherapy (RT) to patients who have implanted pacemakers and it is challenging when treatment portals are close to pacemaker. The cumulative dose to the pacemaker needs to be less than 2 to 5 Gy as per the current recommendations.Aim and Methods: To describe the steps undertaken for safe delivery of mediastinal radiotherapy for a patient with Hodgkin’s lymphoma and implanted pacemaker. Case presentation: Sixty-year-old gentleman who had implanted dual-chamber rate adaptive (DDDR), magnetic resonance imaging (MRI) compatible, permanent pacemaker for complete heart block presented with lymphadenopathy and was diagnosed with Classical Hodgkin’s Lymphoma stage IV. He received consolidation RT (30 Gy in 15 fractions) to the mediastinum after completion of chemotherapy. An algorithm was developed based on AAPM (The American Association of Physicists) report for necessary steps to be taken at various stages of radiotherapy planning and treatment delivery. This approach made it possible to reduce cumulative dose to the pacemaker to < 2Gy.Conclusion: RT can be safely delivered to the patients with cardiac pacemakers. Close follow-up of the patients in conjunction with the Cardiologist, before, during and after radiation is essential for the patient’s safety.

No abstract