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Accuracy in planned radiation dose delivery in cancer treatments forms one of the prime responsibility of medical physicists. Various protocols recommend the desired steps to estimate absorbed dose in suitable phantoms, guidelines of delivering radiation doses and quality assurance(QA). Complex treatment delivery options with newer technology using medical linear accelerators, make patient management very crucial. International Atomic Energy Agency(IAEA)1, International Commission on Radiological Protection (ICRP)2 documented treatment errors and mis-administrations of dose in global context, brought out the nature of their occurance and complexity of situations encountered. The overall treatment process involves many stages and chain of events, and treatment outcome in individual patient therefore depends on the professional involvement of staff and execution accuracy at various steps. It was identified that critical areas are the interfaces in staff groups between different processes. Most of the immediate causes of accidental exposures appear to be related to lack of adequate quality assurance (QA) programme or failure in their routine applications. General human causes of errors include complacency in attention, lack of knowledge, overconfidence, pressures of time, lack of resources and failures in communication. A recent report3 highlighted a few ‘incidents’ involving treatment errors in focal delivery of large quanta of absorbed dose in ‘stereotactic treatments’ with linac, This generated a big apprehension in the minds of health administrators and regulatory bodies.
IAEA4 summarized a few mishaps in radiotherapy which occurred during years 2004-2007. They involved a) incorrect manual parameter transfer b) reversal of images in treatment planning c) use of inappropriate measuring detector d) erroneous calculation for soft wedge e) incorrect IMRT planning and f) mis-calibration of a stereotactic unit. During December, 2010, the New York Times3 enumerated misadministration of radiation doses under heading ‘harming instead of healing’. Delivery of wrong doses in ‘small field treatment plans with stereotactic equipment’ were highlighted. This report included the incidents enumerated by IAEA4 also, describe them occurred due to a) lack of proper communication between electronic components b) non-integration of retrofitted devices from different vendors c) user error combineds with safety flaws in a ‘mix and match’ of radiation delivery system d) X,Y jaws not confining to cone attachment, and non-identifcation of flaws by operators during treatment execution e) treatment planning system, verification system and control computers had mismatch and altered information through chain of ‘devices’ f) manually fed information made machine to think as different wrong attachment. All these resulted in an overdosing as high as 25 to 100% as per estimates by professional experts. When we go into review of occurance of a mis-administration of dose resulting in morbidity or mortality, the arguments lead to: 1) When millions of patients are treated, there is an insignificant risk factor associated with the delivery process. 2) In presence of era of computers, human link becomes a weak component, and the attitude of ‘to err is human’ and develop an optimistic approach to go ahead with developments 3) Document the occurance, and come out with implementation of methods overcoming the least possible nature of such incidents. Both options 1 and 2 are not acceptable as a policy, because it is projected by press3 as ‘harming instead of healing’. For pencil beam data beam configuration in treatment planning systems, small detectors (either diode or diamond detector) are recommended and therefore acquisition of beam profiles and central axis depth dose (CADD) data are to be carried out accordingly to have accuracy with high spatial resolution. Pre-treatment verifications by phantom measurements have been advocated in literature 5,6,7 for documentation of safe delivery of treatment to patients and QA method for dynamic dose delivery methods also reported8. Dose validation methods using MU verification softwares9 in addition to film scanners or matrix detectors are found very useful for treatment verifications. The accuracy of ion chamber measurements vis-à-vis Monte Carlo theoretical estimations for different detectors were highlighted10 along with the correction required when segmental fields are measured by thimble ion chambers, for IMRT dose verifications. The errors involved in non-equilibrium measuring conditions especially when large ion chambers are employed in assessment of very small radiation fields as encountered in stereotactic treatment irradiations are explained in earlier reports10,11,12.They highlighted the need for caution in configuring small fields for treatments. In our experience7, a perspex cylindrical tool validated dose delivery in SRS/SRT treatments within -0.4+0.9% (n=15), with any of the component arc fields assessment of dose within very small deviations -0.2 + 1.0 % (maximum) and -0.9+2.0 % (minimum). Also for dynamic field IMRT, the high energy linac functioning measured by the ratios8 of 4 mm/10 mm and 10 mm/20 mm integrated dynamic slit outputs, were within ±0.3% and ±0.03% respectively over the period of 3 years validating their proper functioning. It is being concluded by experts in the field, that though there are multiple aspects to the occurance of these adverse events, there are some broad conclusions and guiding principles that evolve out of the review of past accidents. Four key components for quality assurance are identified viz. a) education b) documentation c) verification and d) communication. Incident reporting and developing data base is therefore becomes part of regulatory agency’s advisory role in all the countries. From patient’s point of view, legal infrastructure, corporate approach of medical industry, even one rare occurance of ‘an event’ generates a very high cost factor for the institution, industry and overall to the profession. Though this type of topic have been discussed in many forums with recommendation to resort for correct human support in the treatment delivery aspects a need for such editorial was brought out to emphasize to develop local infrastructural strategy, easy solutions for difficult problems, sound training requirements and methods for developing effective communication, because these are the only pathways and the morals learnt from the ‘high cost incidents to patients community.’ Type approval of equipments by national regulatory authority and annual reports on safe working of machines will help as surveillance to achieve desired goals in radiation safety. In addition, dose validations and on-going quality assurance programme are the only solutions to avert possible mishaps. Like radiation safety implementation to have ‘cost incurred in implementation’, these incidents make high cost factors. Though ‘regulation’ will bring out ‘policies and guidelines’ it is the professional organizations of individuals encourage development of ‘attitudes in human mind’ to be all the time alert, vigilant and look for establishment of methods to document pre-treatment verifications for all the individual complex procedures. MU verification software and phantom measurement protocols will be of immense help in the department because when we rely on inverse planning and export information digitally. No doubt that sometimes it may not be feasible to achieve this objective because of bulk patient loads, but it appears to be mandatory. We have to work on in this directions to achieve ‘no accidents’ era and catch up with high technology developments.
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