Morning warm-up, QA and QC procedures for Varian Linear Accelerator System - Research Paper Example

?Morning warm-up, QA and QC procedures for Varian Linear Accelerator System The Varian Clinac iX with dynamic motion management is widely employed for imaging and radiation therapy. The Clinac CX has been used by the hospitals to provide advanced treatments, where customization is possible in line with the requirements. Equipments such as Portal dosimetry for quality assurance and Argus software for effective quality control purposes are used in conjunction with these machines. In this paper Morning warm-up, QA and QC procedures to be broadly considered within any organization/hospital in relation to the Linear Accelerator System are discussed. It is stated “Daily, monthly, and annual quality control (QC) of linear accelerators are part of the major tasks of the medical physicist to verify that patients are receiving proper radiation treatment."1 The control tests consist of the measurement of beam output, verification of the beam energy, and determination of the beam flatness and symmetry in a linear accelerator parlance. However, QA and QC procedures cover wide areas aiming all- round quality in the system Introduction In a computer assisted Varian radiation therapy machine, “a computer controls the operations of the machine to automatically set the position of the gantry relative to the couch for treatment of a patient. The automated motions of the gantry and the couch are simultaneous for decreasing the setup time. In addition, the computer includes a collision avoidance program which averts collision between the couch or patient, and the gantry”. 2 A linear accelerator (LINAC) device is used for external beam radiation treatments for cancer and other radiation therapies such as Intensity-Modulated Radiation Therapy (IMRT) and Image Guided Radiation Therapy (IGRT). Daily or weekly tests are related to dosimetric and geometric parameters, audiovisual monitoring and other testing equipments. The monthly and annual tests are carried out by QMPs [Quali?ed Medical Physicist] generally. The number of patients treated using the linear accelerators are on the rise, and therefore, overall quality management in the system assumes greater significance. Morning warm-up The latest technological developments have greatly reduced human intervention in a number of technical applications, and this field is not an exception. It is stated “To overcome the problem of differential heating, it is important to slowly increase the heating of a cold tube insert. The warm-up process must be carried out first thing each morning and repeated during the day if the workload is insufficient to keep the tube warm. The manufacturer’s guidance should be followed, but in general the warm-up period will be between 10 and 20 min. "3(p146)  However, in a Varian machine, automatic warm-up program is in-built and gets activated when the temperature falls below the operating temperature. However, standard QA and QC procedures with regard to morning warm up in general is essential for quality in operations and service. Warm-up tests are carried out by the morning warm-up therapist by following standard procedures as laid down with reference to several factors and the tolerance levels. Quality Control and Quality Assurance Quality Control or Quality Assurance is a comprehensive and ongoing exercise. According to ISO definition, “Quality control is a set of activities intended to ensure that quality requirements are actually being met.” and “Quality assurance is a set of activities intended to establish confidence that quality requirements will be met” .4 Both Quality Control and Quality Assurance are the parts of Quality Management which includes direction, control and coordination in relation to quality. The efficacy of the system could be ensured through proper maintenance of records, review of the activities with reference to the objectives, periodical preventive maintenance programs and continuous monitoring of the safety measures. QC/QA Procedures for Varian linear accelerator system Varian states5 that Varian radiation therapy systems make the use of radiotherapy techniques such as Intensity Modulated Radiation Therapy (IMRT) easier and swifter by integrating software for digital data management and automating quality assurance and regulatory requirements. These devices are part of the quality assurance program. However there are several other procedures involved in carrying out a process involving a set of interrelated activities. Also, the statutory requirements of quality assurance practices vary from state to state with regard to medical linacs. Therefore, compliance with the regulations or obtaining approval for exemptions is very essential. It has been reported “A separate site plan must be developed for the location chosen for commissioning and annual QA…6(p17) Any discussion of QA for mobile linacs used for IORT [Intraoperative radiation therapy] must acknowledge the recommendations published in the Task Group 40 report regarding QA for medical linacs in general. In addition, the TG-48 report discussed specific QA issues for linacs used for IOR” 6(p29). The recommended procedures for medical linear accelerators inter alia cover Output Constancy, Depth Dose, Flatness and symmetry, Applicator output factors, Output versus gantry angle, Monitor chamber linearity and docking mechanism. “Quality assurance is a joint responsibility, especially of the radiographers and medical physics staff”3(p85) and hence coordination and cooperation among them is very important. It is pertinent to note that according to the paper “After a successful dry run of all components from the treatment simulation to the plan for delivery, we put the new electron energy beam into the clinic two years after the start of the project”.7 Therefore, these standards as evolved during this process should form the basis for comparison in the formulation, implementation and monitoring of the procedures. Secondly, the inspection of Radiation-generating and radiation-measuring units on a regular basis, say day-to-day is essential apart from the periodical tests and inspections. The third step involves the administrative aspects of the procedures. Defining the responsibilities on the part of the professionals and their area of operations, for example radiation generator, radiographers, maintenance engineers and the quality control engineers in the day-to-day operations would resolve uncertainties in the communication, which is of paramount importance. Proper documentation of these responsibilities enhances the level of interaction at all levels. In an era of intense specialization the procedures with reference to the different type of service providers or their specialties vary according to the need or requirements in each case. For example palliative care in the case of terminal patients, mitigation of pain would be the primary objective rather than cure. Therefore, prioritizing the availability of the facilities and the nature of the results expected may vary. Highlands Oncology Group states8 that the objective of radiation therapy is to kill enough cancer cells to maximize the probability of cure and minimize the side effects.  Under some circumstances, radiation therapy may also be used as palliation, or palliative care, which is aimed at reducing symptoms but not curing the disease. Recording The system of recording and the maintenance of records with reference to various activities such as radiation-generating, radiation-measuring equipment and the calibration of the dosimeters are very important on account of the radiation hazards involved. This is an integral part of the quality assurance program. The review of the records in respect of measurement of outputs, dose rates, output beam dose rate, beam quality etc. might reveal inconsistencies or need for revision of the parameters. For example, it is stated, 3(p105) that the simulator has the geometry and the movements of a linear accelerator but the tolerance are tighter and QA needs to be more carefully carried out. Also, proper maintenance of records enhances traceability in relation to history, distribution and applications. This will also be useful in comparison with the standards to bring out the deviations from the standards. Review In the review process we can measure the performance with the objectives. Proper maintenance of records will increase the effectiveness of the review. Suitability and the adequacy of the procedures are also revealed in the analysis. According to the task group 142 report 9(p4204) during the annual review of dosimetry systems, constancy factors are either established, recon?rmed, or updated. Maintenance program There are two types of maintenance programs, breakdown maintenance and preventive maintenance. Preventive maintenance is aimed at avoiding malfunctioning, nonconformities or failure of the system, whereas the breakdown maintenance is concerned with the rectification of the defects observed for the proper functioning of the machines or the equipments. Safety For radiation safety, the quality assurance programs should be consistent with the operating system and the design and content of the program need to be finalized in consultation with the Radiation Protection Adviser. Literature review It has been reported 10 “From 1989 to 1996, 29 hemangioblastomas in 13 patients with von Hippel-Lindau disease were treated with linear accelerator-based radiosurgery…Stereotactic radiosurgery provides a high likelihood of local control of hemangioblastomas and is an attractive alternative to multiple surgical procedures for patients with von Hippel-Lindau disease”. The developments in the field of radiation therapy since then have contributed to the improved results. It is stated 11(p101) that the institution of standard extended-field radiation ports with prophylactic irradiation of adjacent but uninvolved lymph node chains, the development of megavoltage linear accelerators, and the establishment of the dose-response relationshipllhave all contributed to improved results in the management of HD [Hodgkin's Disease]. The introduction of a national program for integrating IT systems within the National Health Service (NHS) has paved way for revisiting the procedures adopted so far by the hospital authorities as a whole. Naturally, this reflects in the procedural developments in the case of Linear Accelerator System as well. Computerizing the records at all levels has become necessary as it would be easy to integrate the institution at the industry and the national level. Also, the efficiency with which the data could be stored and retrieved for analysis either technically or commercially would be simplified. This system has also brought into existence the standardization in the procedures for easy understanding and interpretation by the professionals at a global level. Research and developments in the health sector is greatly facilitated in the process due to the increased storage capacity and the speed of analysis. It has been reported 12 that this would provide an immediate digital imaging solution to clinical imaging for the image intensifier-based simulator and for those linear accelerators (linacs) without amorphous silicon (aSi) electronic portal imaging devices (EPIDs). However, to have a common non-film-based system for radiotherapy equipment quality assurance purposes would be more challenging. Conclusion The latest developments have introduced an array of permutations and combinations in the operations. Consequently, the procedures are continuously required to be updated in line with the developments in the field. For example, it has been reported “Cone-beam computed tomography (CBCT) is a three-dimensional imaging modality that has recently become available on linear accelerators for radiotherapy patient position verification. This is considered to be a superior device with several advanced features. For instance as most radiotherapy treatment planning makes use of a diagnostic CT scan, the verification CBCT reproduces the same geometry imaged with the same modality as the treatment plan”. 12(p855) The continuous developments in the field underlines the need for revising the QA/QC procedures in line with the changes and training to the staff at various levels to make the system more effective to improve the level of satisfaction to the patients and safety for all. References 1. Meigooni AS, Myron G & Sowards KT Evaluation of the VeriDose QC phantom, American Association of Medical Dosimetrists, Medical Dosimery, Volume 28, Issue 1, Pages 49-54, 2002. (Spring 2003) doi:10.1016/S0958-3947(02)00249-2. . 2. Freepatentsonline. Automated Radiation Therapy Machine, http://www.freepatentsonline.com/3720817.html. Accessed February 21, 2011. 3. Bomford CK, Kunkler IH, Walter J. Textbook of Radiotherapy: Radiation Physics, Therapy and Oncology, 6th Ed. Churchhill Livingstone, Elselvier Science Ltd. 2003. 4. Paraxiom Research Group limited. ISO 9000, 9001, AND 9004 Quality Management Definitions, http://www.praxiom.com/iso-definition.htm. Accessed February 21, 2011. 5. Varian Medical Systems. Varian’s Argus IMRT Simplifies Use of State-of-the-Art Radiotherapy to Combat Cancer, http://varian.mediaroom.com/index.php?s=43&item=164. Accessed February 20, 2011. 6. Beddar AS. Intraoperative radiation therapy using mobile electron linear accelerators: Report of AAPM Radiation Therapy Committee Task Group No. 72, http://www.aapm.org/pubs/reports/RPT_92.pdf. Accessed February 20, 2011. . 7. Zhang S, Liengsawangwong P, Lindsay P et al. Clinical implementation of electron energy changes of Varian linear accelerators, Journal of Applied Clinical Medical Physics, Vol 10, No 4 (2009), http://www.jacmp.org/index.php/jacmp/article/viewArticle/2978/1725. Accessed February 20, 2011. 8. Highlands Oncology Group. Who Should Consider Early Detection Screenings? February 10, 2011. http://highlandsoncologygroup.com/blog/. Accessed February 21, 2011. 9. Klein EE, Hanley J, Bayouth J et al. Task Group 142 report: Quality assurance of medical accelerators, Medical Physics, Vol. 36, No. 9, September 2009. http://www.aapm.org/pubs/reports/RPT_142.pdf. Accessed February 21, 2011. 10. Chang SD, Peter JB, Chang S et al. Treatment of haemangioblastomas in von Hippel-Lindau disease with linear accelerator-based radiosurgery. Neurosurgery1998; 43:28-34. 11. Glen LD, Kumar PP. Radiation Therapy Alone Versus Radiation Therapy and Chemotherapy in the Management of Hodgkin’s Disease. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2625953/pdf/jnma00888-0039.pdf. Accessed February 20, 2011. 12. Patel I, Natarajan T, Hassan SS, Kirby MC. The use of computed radiography for routine linear accelerator and simulator quality control, British Journal of Radiology (2009) 82, 827-838 doi: 10.1259/bjr/98497325, http://bjr.birjournals.org/cgi/content/full/82/982/827?maxtoshow=&hits=10&RESULTFORMAT=&fulltext=Linear+Accelerator+System&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT. Accessed February 20, 2011. 13. Roxby P, Kron T, Foroudi F. et al. Simple methods to reduce patient dose in a Varian cone beam CT system for delivery verification in pelvic radiotherapy, The British Journal of Radiology, 82 (2009), 855–859, http://bjr.birjournals.org/cgi/reprint/82/982/855?maxtoshow=&hits=10&RESULTFORMAT=&fulltext=procedure+Linear+Accelerator+System&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT. Accessed February 21, 2011. . Read More