{"id":6516,"date":"2016-04-28T08:45:54","date_gmt":"2016-04-28T08:45:54","guid":{"rendered":"http:\/\/biomedpharmajournal.org\/?p=6516"},"modified":"2020-04-24T06:51:46","modified_gmt":"2020-04-24T06:51:46","slug":"quality-control-of-acuity-varian-radiotherapy-simulator-system","status":"publish","type":"post","link":"https:\/\/biomedpharmajournal.org\/staging\/vol9no1\/quality-control-of-acuity-varian-radiotherapy-simulator-system\/","title":{"rendered":"Quality Control of Acuity-Varian Radiotherapy Simulator System"},"content":{"rendered":"

Introduction <\/strong><\/p>\n

Reaching to the maximum probabilities of tumor control without severe normal tissue damage, still remains as the major challenge in radiotherapy 1<\/sup>. Amoung the many important proccess to obtain this end point of radiotherapy, one of the main and primarily phase is the localization of the tumor volume which is to receive the prescribed dose and the peripheral critical normal tissues which is to receive minimum possible dose 2<\/sup>. This process is so called as simulation. A conventional\u00a0radiotherapy simulator\u00a0is a Kv x-ray machine and detector, that is attached to a machine that emulates the movements of a\u00a0radiotherapy treatment\u00a0<\/strong>machine\u00a0<\/strong>as\u00a0linear accelerator (Linac).\u00a0Therefore it makes possible to produce x-ray images from the patient body under positioning conditions simulating a Linac and make it possible to control of all parameters on the treatment plan such as the field size, beam directions, collimator setting, etc. However in developed countries the\u00a0simulator-fluoroscopy have been replaced by the modern CT-simulator,\u00a0due to its inability to accurately distinguish the different densities of areas,\u00a0such as bone and air,\u00a0but\u00a0it is useful for checking radiotherapy plans and planning palliative treatments very quickly and efficiently\u00a03<\/sup>. Furthermore, in most centers in poor and developing countries simulating of treatment planning is still done based on surface markings or simulator-fluoroscopy in a cost viewpoint and quality of patient care 3, 4<\/sup>. Any improper functioning of the mechanical and electrical components of a simulator may cause serious errors in the entire course of radiotherapy.\u00a0Acceptance\u00a0test and quality control of different radiotherapy treatment\u00a0simulators\u00a0in order to satisfy the quality\u00a0requirements\u00a0needed in radiotherapy have been discussed in\u00a0literature 5-11<\/sup>. To the best of our knowledge from literature there is not any report of quality control on\u00a0Acuity-Varian radiotherapy treatment\u00a0simulator. The aim of this study is to check the some parameters of simulator which\u00a0affect the accuracy performance of\u00a0Acuity-Varian\u00a0simulator-fluoroscopy installed in Golestan hospital of Ahvaz-Iran.<\/p>\n

Materials And Methods <\/strong><\/p>\n

Radiotherapy\u00a0simulator<\/strong><\/p>\n

Acuity-Varian\u00a0radiotherapy simulator (figure 1) has been\u00a0installed\u00a0at\u00a0Radiotherapy\u00a0& Oncology Department\u00a0of\u00a0the Golestan Hospital of Ahvaz Jundishapour University of Medical Sciences (AJUMS) and only works in fluoroscopic mode. The\u00a0gantry and collimator (to\u00a0shape\u00a0the desired fild size\u00a0and direction) can rotate about angle of \u00b1190\u00b0 and \u00b1185\u00b0, respectively. X-ray tube and flat panel detector are mounted on the two ends of arm. It has control options to change of the focal spot to axis distance (FAD) and axis to film distance (AFD). Exposure parameters of fluoroscopic mode are 40-120 kVp with 2.5 mmAl filter.\u00a0The table of simulator is similar to the one from Linac with equal vertical, lateral and longitudinal motions.<\/p>\n\n\n\n
\"Figure<\/a><\/td>\nFigure\u00a01:<\/strong>\u00a0A phantom positioned on the treatment table top of Acuity-Varian radiotherpy simulator installed in Department of Radiotherapy and Oncology at Golestan hospital of Ahvaz-Iran.<\/strong><\/p>\n

Click here to View figure<\/a><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The Checked parameters<\/strong><\/p>\n

Accuracy of field size was preformed by fixing a\u00a0graph\u00a0sheet on the coach at isocenter and changing the\u00a0field size from 5 \u00d7 5 to 30 \u00d7 30 cm2<\/sup>. The\u00a0difference\u00a0between values from the electrical readouts\u00a0on the console system and the measured values on the\u00a0graph\u00a0sheet were compared.<\/p>\n

Gantry was set to 0\u00b0 and a\u00a0perspex\u00a0phantom of thorax (figure 1) was positioned on the table in which the\u00a0central hole of the phantom is exactly in the cross-wire. In fixed laterally position of table, the gantry was moved to 180\u00b0 and the table is adjusted longitudinally to\u00a0obtain\u00a0exactly match at the\u00a0central hole in the cross-wire. The difference between the two longitudinal values of table was reported. This check was repeated for gantry angles of 90\u00b0 and 270\u00b0 at FAD=100 cm and the difference between two table\u00a0height\u00a0to match the cross-wire in the central hole of phantom was\u00a0noted. The effect of coach rotation on isocenter was\u00a0determined\u00a0in gantry angle of 0\u00b0 and FAD=100 cm.\u00a0In first a paper sheet on the table top was fixed and centered to the field light cross-wire. Then the table and collimator were rotated separately around the angle of 0\u00b0 in clockwise and\u00a0anticlockwise\u00a0directions and for each angle the cross-wire projection was marked on a sheet; and then a circle was drawn around these points and their\u00a0deviations\u00a0were noted.<\/p>\n

The consistency between the mechanical and electrical reading of the collimator rotation angle was checked. The accuracy of the mechanical and electrical reading of the gantry\u00a0rotation\u00a0angle for angles of\u00a0\u00a00\u00b0, 90\u00b0, 180\u00b0 and 270\u00b0 was checked with a spirit level held against a true surface at the radiation head. The table rotate around an axis that passes through the isocenter. To checking the accuracy of isocentric rotation of table, the movement of the cross-hair projection on table during an isocenteric rotation was measured. Accuracy of flat panel detector movement was also checked in longitudinal and lateral directions.<\/p>\n

The matching of radiation field and optical field for 10\u00d710 cm2<\/sup>\u00a0field size at FAD= 100 cm was tested with a paper sheet putted on a film and fixed on the table in which a L-shape\u00a0wires positioned on each corner of it. The\u00a0shift\u00a0value between lateral distance of edges from the optical field\u00a0on paper and exposed region was noted. The coincidence between the point of intersection of lasers with the isocenter was\u00a0checked\u00a0\u00a0by matching of isocenter using a graph plaxiglass sheet.<\/p>\n

The table top should be exactly horizontal that was measured by a spirit level at different hieghts and rotation angles. The rigidity of table was checked by placing a mass approximately 50 kg at the end of the table top and at the outermost longitudinal or lateral position. The related sag values were measured in the\u00a0longitudinal\u00a0and lateral positions on table top. The horizontal shift of table during vertical motion was performed by determining the horizontal movement of the cross-hair with decreasing of table about 50 cm upper and around the FAD of 100 cm. The accuracy of FAD was\u00a0determined\u00a0by comparing the values of the electrical readout and the\u00a0measured\u00a0data by a photometer at gantry angle of 0\u00b0.<\/p>\n

The\u00a0resolution\u00a0of flat panel detector on fluoro mode was\u00a0checked\u00a0in horizontal and vertical\u00a0orientations\u00a0with\u00a0TOR Phantom 18FG (with resolution limit of 0.5 to 5.0 LP\/mm)\u00a0at 50 kV and 1 mA. The visible lines were counted. The low contrast sensitivity was measured with\u00a0TOR Phantom 18FG\u00a0(18 details, 8mm diameter, contrast range 0.009 to 0.167) at 70 kVp, 2 mA\u00a0and with 1mm Cu filter.\u00a0\u00a0The visible discs were counted.<\/p>\n

The accuracy of kV and its reproducibility in floroscopic mode were measured by kV meter. Each\u00a0measurement\u00a0was repeated three times. The exposure parameters of mA and mAs and also consistency of X-ray\u00a0output were not check due to the lack of radiological mode of system. It be mentioned that the checked parameters in this study are not included all needed tests for a\u00a0complete\u00a0quality\u00a0control\u00a0process.<\/p>\n

Results And Discussion <\/strong><\/p>\n

The mean difference of field sizes between readouts of digital system and\u00a0measured\u00a0values on\u00a0graph\u00a0sheet\u00a0was 1.6 mm that is acceptable within the related tolerance value of \u22642 mm per jaw by\u00a0 The resulted\u00a0diameters\u00a0of pushed circle for checking of isocenter was about 1.4 mm and 0.9 mm for gantry\u00a0positions at 0\u00b0 and 180\u00b0 and for 90\u00b0 and 270\u00b0, respectively. However the isocenter check along\u00a0longitudinal\u00a0and lateral directions are in the borderlines of acceptance but these deviations of\u00a0isocenter with gantry rotation are within the tolerance values of 1.4 mm and 1mm reported by\u00a0meijer\u00a0et al (1997)\u00a011<\/sup>, respectively. The deviation resulted of the cross-wire projections for evaluation of isocenter stability during the table and collimator rotation were\u00a0determined\u00a0about\u00a00.9 mm and 0.8 mm that is within the recommended tolerance level of 1 mm reported by Kutcher et al (1994)10<\/sup>, respectively.<\/p>\n

The accuracy of table and gantry rotation around the isoceter was 0.5\u00b0 that is in borderline of the\u00a0tolerance\u00a0level of 0.5\u00b0\u00a011<\/sup>. The longitudinal and lateral displacements of flat panel were about 1.8 mm and 1.5 mm that are within acceptable limit of 2 mm recommended by Meijer et al (1997) 11<\/sup>, respectively.<\/p>\n

The difference between the radiation field and optical field was about 1.6 mm for each edge that is within the\u00a0tolerance\u00a0level of 2 mm\u00a010<\/sup>. The slope of the treatment table top to test horizontally of table to mimic the Linacs’ table was 0.2\u00b0 (i.e. 3.6 mm\/m) that is within\u00a0tolerance\u00a0level of\u00a0\u00a00.2\u00b0\u00a011<\/sup>. The table top sag to test the rigidity of table top was\u00a04.5 and 2.1 for\u00a0longitudinal\u00a0and lateral directions that\u00a0are within recommended limits of 5 and 2.5 mm, respectively 11<\/sup>. The horizontal\u00a0displacement\u00a0of table when setting the\u00a0height\u00a0of table was about\u00a0\u00a01.8 mm that pass the recommended limit of 2 mm 11<\/sup>. The\u00a0difference\u00a0between the readout and mechanical measurement of FAD\u00a0was about 1.7 mm that is within the\u00a0tolerance\u00a0value of 2 mm recommended by Kutcher et al (1994) 10<\/sup> and Brahme et al (1988) 12<\/sup>. The laser beams\u00a0alignment\u00a0with isocenter for the four lasers was 1.5 mm that is within the acceptable limit of\u00a02 mm\u00a010<\/sup>.<\/p>\n

With checking the resolution of\u00a0simulator\u00a0with\u00a0TOR Phantom 18FG (with no filter) as shown in figure 2 a., 13 lines were detectable in both horizontal and lateral directions that is equal to 1.34 LP\/mm. This resolution is within the accepted level of 9 lines.\u00a0As sown in figure 2 b., the visible discs was about 10 discs that is lower than the\u00a0tolerance\u00a0limit of\u00a012 discs. This means that the measured low contrast\u00a0sensitivity\u00a0of 2.25%\u00a0need to be modified to pass the\u00a0tolerance\u00a0limit of 2.7%. A summary of these results is\u00a0collected in table 1.<\/p>\n

The\u00a0accuracy and reproducibility of\u00a0\u00a0kVp by averaging of tree times measurements for each nominal Kv of 70, 80, 90 and 110 were 71.033, 79.667, 91.300 and 116.267 respectively. The measured kVps are presented in table 2 and were within the acceptable limits.<\/p>\n

Table 1:<\/strong>\u00a0Verification\u00a0of different quality control parameters for quality assurance of\u00a0on the Acuity-Varian\u00a0simulator\u00a0radiotherapy.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n
Parameter<\/strong><\/td>\nDifference between electrical readout or set value with measured value by test objects<\/strong><\/td>\nTolerance<\/strong><\/td>\n<\/tr>\n
Field size (with Collimator jaws)<\/strong><\/td>\n1.6 mm<\/td>\n\u2264 2 mm 10<\/sup><\/td>\n<\/tr>\n
Isocenter<\/strong><\/td>\nLongitudinal, gantry angle 0\u00b0-180\u00b0<\/strong><\/p>\n

Lateral, gantry angle 90\u00b0-270\u00b0<\/strong><\/p>\n

Table rotation<\/strong><\/p>\n

Collimator rotation<\/strong><\/td>\n

1.4 mm<\/p>\n

0.9 mm<\/p>\n

0.9 mm<\/p>\n

0.8 mm<\/td>\n

\u2264 1.4 mm<\/p>\n

\u2264 1 mm<\/p>\n

\u2264 1 mm<\/p>\n

\u2264 1 mm 11<\/sup><\/td>\n<\/tr>\n

Movements<\/strong><\/td>\nFlat panel<\/strong><\/p>\n

Longitudinal<\/strong><\/p>\n

Lateral<\/strong><\/p>\n

Gantry rotation<\/strong><\/p>\n

Table rotation<\/strong><\/td>\n

 <\/p>\n

1.8 mm<\/p>\n

1.5 mm<\/p>\n

0.5\u00b0<\/p>\n

0.5\u00b0<\/td>\n

 <\/p>\n

\u2264 2 mm<\/p>\n

\u2264 2 mm<\/p>\n

\u2264 0.5\u00b0<\/p>\n

\u2264 0.5\u00b0 11<\/sup><\/td>\n<\/tr>\n

Difference between radiation and optical fields (For each edge)<\/strong><\/td>\n1.6 mm<\/td>\n\u2264 2 mm 10<\/sup><\/td>\n<\/tr>\n
Table top sag (rigidity of treatment table)<\/strong><\/p>\n

Longitudial<\/strong><\/p>\n

Lateral<\/strong><\/p>\n

Table top slope<\/strong><\/p>\n

Horizontal shift of table during vertical motion<\/strong><\/td>\n

 <\/p>\n

4.5 mm<\/p>\n

2.1 mm<\/p>\n

0.2\u00b0<\/p>\n

1.8 mm<\/td>\n

 <\/p>\n

\u2264 5 mm<\/p>\n

\u2264 2.5 mm<\/p>\n

\u2264 0.2\u00b0<\/p>\n

\u2264 2 mm 11<\/sup><\/td>\n<\/tr>\n

FAD<\/strong><\/td>\n1.7 mm<\/td>\n\u2264 2 mm 10, 12<\/sup><\/td>\n<\/tr>\n
Coincidence of lasers<\/strong><\/td>\n1.5 mm<\/td>\n\u2264 2 mm 10<\/sup><\/td>\n<\/tr>\n
Resolusion<\/strong><\/td>\n12 lines (i.e. 1.34 LP\/mm)<\/td>\n\u2265 9 lines (i.e. 1.25 LP\/mm)<\/td>\n<\/tr>\n
Low contrast sensitivity<\/strong><\/td>\n10 discs (i.e. 2.25%)<\/td>\n\u2265 12 discs (i.e. 2.7%)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

 <\/p>\n

Figure 2.(a)<\/strong>\u00a0: The horizontal resolusion and b. low contrast sensitivity of flat panel detector.<\/strong><\/p>\n\n\n\n
\u00a0\"Figure<\/td>\nFigure 2. a. The horizontal resolusion and b. low contrast sensitivity of flat panel detector.<\/p>\n

Click here to View figure<\/a><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

 <\/p>\n

Table 2 :\u00a0The accuracy and reproducibility of kV. Data with % error \u2264 5% for accuracy and % CV \u2264 5% for reproducibility are acceptable.<\/strong><\/p>\n\n\n\n\n\n\n\n\n
Nominal value of kV<\/strong><\/td>\nAverage of kVps<\/strong><\/td>\n% Error<\/strong><\/td>\nSTD<\/strong><\/td>\n% CV<\/strong><\/td>\n<\/tr>\n
70<\/strong><\/td>\n71.033<\/td>\n1<\/td>\n3.362<\/td>\n5<\/td>\n<\/tr>\n
80<\/strong><\/td>\n79.667<\/td>\n0<\/td>\n1.0305<\/td>\n2<\/td>\n<\/tr>\n
90<\/strong><\/td>\n91.300<\/td>\n1<\/td>\n0.624<\/td>\n1<\/td>\n<\/tr>\n
110<\/strong><\/td>\n116.267<\/td>\n5<\/td>\n2.892<\/td>\n2<\/td>\n<\/tr>\n
CV: Coefficient\u00a0 of variation; STD: Standard deviation<\/strong><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The correctly preformance of the interlock systems against unallowed actions such as interlock door, preventing of collision between gantry and floor, alarm lights and signs, emergency stop button on the wall, etc were accepted.<\/p>\n

Conclusion <\/strong><\/p>\n

Our results of various quality control tests were within the recommended\u00a0tolerance\u00a0limits. However the low\u00a0contrast resolution of flat panel detector not passed the test and need to be modified. The quality control of radiotherapy simulator is essential and must be carried out\u00a0regularly\u00a0to\u00a0ensure of correctly\u00a0transferring\u00a0of anatomical data of patients to the clinical Linac.<\/p>\n

Acknowledgment <\/strong><\/p>\n

This study was funded by the research and technology deputy of Ahvaz Jundishapur University of Medical Sciences and Arvand international University of Medical Sciences, Ahvaz, Iran.<\/p>\n

References<\/strong><\/p>\n

    \n
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    Introduction Reaching to the maximum probabilities of tumor control without […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[30],"tags":[],"class_list":["post-6516","post","type-post","status-publish","format-standard","hentry","category-vol9no1"],"_links":{"self":[{"href":"https:\/\/biomedpharmajournal.org\/staging\/wp-json\/wp\/v2\/posts\/6516","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/biomedpharmajournal.org\/staging\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/biomedpharmajournal.org\/staging\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/biomedpharmajournal.org\/staging\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/biomedpharmajournal.org\/staging\/wp-json\/wp\/v2\/comments?post=6516"}],"version-history":[{"count":5,"href":"https:\/\/biomedpharmajournal.org\/staging\/wp-json\/wp\/v2\/posts\/6516\/revisions"}],"predecessor-version":[{"id":32638,"href":"https:\/\/biomedpharmajournal.org\/staging\/wp-json\/wp\/v2\/posts\/6516\/revisions\/32638"}],"wp:attachment":[{"href":"https:\/\/biomedpharmajournal.org\/staging\/wp-json\/wp\/v2\/media?parent=6516"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/biomedpharmajournal.org\/staging\/wp-json\/wp\/v2\/categories?post=6516"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/biomedpharmajournal.org\/staging\/wp-json\/wp\/v2\/tags?post=6516"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}