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The purpose of this work is to examine physical radiation dose differences between two multileaf collimator (MLC) leaf widths (5 and 10 mm) in the treatment of CNS and head and neck neoplasms with intensity modulated radiation therapy (IMRT). Three clinical patients with CNS tumors were planned with two different MLC leaf sizes, 5 and 10 mm, representing Varian-120 and Varian-80 Millennium multileaf collimators, respectively. Two sets of IMRT treatment plans were developed. The goal of the first set was radiation dose conformality in three dimensions. The goal for the second set was organ avoidance of a nearby critical structure while maintaining adequate coverage of the target volume. Treatment planning utilized the CadPlan/Helios system (Varian Medical Systems, Milpitas CA) for dynamic MLC treatment delivery. All beam parameters and optimization (cost function) parameters were identical for the 5 and 10 mm plans. For all cases the number of beams, gantry positions, and table positions were taken from clinically treated three-dimensional conformal radiotherapy plans. Conformality was measured by the ratio of the planning isodose volume to the target volume. Organ avoidance was measured by the volume of the critical structure receiving greater than 90% of the prescription dose (V(90)). For three patients with squamous cell carcinoma of the head and neck (T2-T4 N0-N2c M0) 5 and 10 mm leaf widths were compared for parotid preservation utilizing nine coplanar equally spaced beams delivering a simultaneous integrated boost. Because modest differences in physical dose to the parotid were detected, a NTCP model based upon the clinical parameters of Eisbruch et al. was then used for comparisons. The conformality improved in all three CNS cases for the 5 mm plans compared to the 10 mm plans. For the organ avoidance plans, V(90) also improved in two of the three cases when the 5 mm leaf width was utilized for IMRT treatment delivery. In the third case, both the 5 and 10 mm plans were able to spare the critical structure with none of the structure receiving more than 90% of the prescription dose, but in the moderate dose range, less dose was delivered to the critical structure with the 5 mm plan. For the head and neck cases both the 5 and 10 x 2.5 mm beamlets dMLC sliding window techniques spared the contralateral parotid gland while maintaining target volume coverage. The mean parotid dose was modestly lower with the smaller beamlet size (21.04 Gy v 22.36 Gy). The resulting average NTCP values were 13.72% for 10 mm dMLC and 8.24% for 5 mm dMLC. In conclusion, five mm leaf width results in an improvement in physical dose distribution over 10 mm leaf width that may be clinically relevant in some cases. These differences may be most pronounced for single fraction radiosurgery or in cases where the tolerance of the sensitive organ is less than or close to the target volume prescription.

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DOI: http://dx.doi.org/10.3329/jafmc.v8i2.16342 JAFMC Vol.8(2) 2012 pp.16-21

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Major challenges in the management of mass casualty have been identified as lack of human resources, lack of material resources, lack of communication and co-ordination. Our hospital has limited resources of manpower and disposable items. The Departments of Anaesthesiology and Intensive Care have been seriously disrupted by the influx of 155 severely injured patients following the collapse of a nine storey building. Such a large, instantaneous influx of injured citizens would overwhelm even the most well resourced health care system.A multidisciplinary team approach was planned to manage the casualties. Senior anaesthesiologists took responsibility for the organisation of different staff members into medical triage team, an immediate care team, an urgent care team, a non-urgent care team and a clerical team. Different teams have accomplished casualty management by addressing four principal issues (the assessment of available resources; ensuring critical but limited care; stocking up on medicine and equipment for the patient surge; and tough rationing of decisions).Assessments of available resources were done by emphasising three #8216;S’s – staff (human resources), stuff (material resources) and structure. Additional human resources (anaesthesiologists, orthopaedic surgeons etc.) and material resources (#8216;H’ type oxygen cylinders, intravenous fluid etc.) were reinforced from nearby hospitals. Additional influxes of critical patients were supported in the postoperative ward and recovery rooms without any monitoring devices. A surgical dressing room without any basic monitoring device was used as an operating room. To do the greatest good for the greatest number of patients, we restricted ourselves to providing “essential rather than limitless critical care”.“Stocking up on medicine and equipment resources” on assessment of the constraints in managing the patient surge, was the next essential step in the management of the casualty load. Patients with life-limiting illnesses were excluded from receiving scarce critical care resources. Thus “Tough rationing of decision” was also an important element.Although the patients that were managed were not large in number, a consideration of the setup with a limited workforce and modern equipment and management experience of a mass casualty addressing the four principal issues in our department, might also help other departments in managing such events.