12 chap 17 qa for kscgmh 王


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12 chap 17 qa for kscgmh 王

  1. 1. Chapter 17Quality Assurance Wang, Hui-Chuan
  2. 2. Quality assurance (QA)A program designed to control and maintain thestandard of quality set for that program For radiation oncology, to maintain the quality of patient careModel QA program in radiation oncology have beenproposed by ACR, AAPM, ACMP1. ACR Physical aspects of quality assurance. Reston, VA: American College of Radiology, 1990.2. AAPM. Physical aspects of quality assurance in radiation therapy. Report No. 13. Colchester, W: AIDC, 1984.3. AAPM. Comprehensive QA for radiation oncology: report of the Radiation Therapy Task Group 40. Med Phys 1994;21:581-618for combined technical and professional chargesTotal cost of QA program in radiation therapy amounts toapproximately 3% of the annual billing
  3. 3. The goals of a QA programThe purpose of a Quality Assurance Program is the objective,systematic monitoring of the quality and appropriateness ofpatient care. Such a program is essential for all activities inRadiation Oncology.The Quality Assurance Program should be related tostructure, process and outcome, all of which can bemeasured. Structure includes the staff, equipment and facility. Process covers the pre- and post-treatment evaluations and the actual treatment application. Outcome is documented by the frequency of accomplishing stated objectives, usually tumor control, and by the frequency and seriousness of treatment-induced sequelae.Quality assurance committee (QAC) be formed withappropriate personnel (e.g., radiation oncologist, physicist,dosimetrist, therapist, nurse, and administrator).
  4. 4. Minimum Personnel Requirements for Clinical Radiation Therapy Category Staffing Radiation oncologist-in-chief One per program Staff radiation oncologist One additional for each 200-250 patients treated annually; no more than 25-30 patients under treatment by a single physician Radiation physicist One per center for up to 400 patients annually; additional in ratio of one per 400 patients treated annually Treatment planning staff dosimetrist or physics assistant One per 300 patients treated annually physics technologist (mold room) One per600 patients treated annually Radiation therapy technologist supervisor One per center staff (treatment) Two per megavoltage unit up to 25 patients treated daily per unit; four per megavoltage unit up to 50 patients treated daily per unit staff (simulation) Two for every 500 patients simulated annually staff (brachytherapy) As needed Treatment aid As needed, usually one per 300-400 patients treated annually Nurse One per center for up to 300 patients treated annually and an additional one per 300 patients treated annually Social worker As needed to provide service Dietitian As needed to provide service Physical therapist As needed to provide service Maintenance engineer/electronics On per 2 megavoltage units or 1 megavoltage unit and a technician simulator if equipment serviced in-house
  5. 5. Physics staffing
  6. 6. Equipment• External Beam Units• Brachytherapy Sources• Simulator
  7. 7. Dosimetric accuracyAccuracy of approximately ±5% in dose delivery Uncertainties in equipment calibration, treatment planning, and patient setup Further reduction in dose accuracy limit will be not only very difficult but probably of marginal value
  8. 8. Equipment specificationsJustification of needMarket evaluation of different makes and modelsChecks of vendors’ business relations and servicerecordCalling up users for their opinionsWriting bid specificationsMaking final evaluationDoing price negotiation
  9. 9. Acceptance testingTo satisfy all the specifications and criteriacontained in the purchase contractTo perform all the tests in accordance withthe company’s procedure manualAny equipment to be used for patients mustbe tested to ensure that it meets itsperformance specifications and safetystandards
  10. 10. Linear acceleratorInstallation, acceptance testing,commisioning Commission: the machine tested to be acceptable and sufficient data have been acquired to permit treatment planning and dose calculations for patient treatments
  11. 11. Linear accelerator: Radiation survey To evaluate the exposure levels outside the room will not exceed permissible limits, considering the dose rate output, machine on time, use factors and occupancy factors for the surrounding areas A calibration of the machine output (cGy/MU) Radiation protection survey Head leakage Area survey Tests of interlocks, warning lights, and emergency switches
  12. 12. Linear accelerator: Jaw symmetryJaw symmetry A machinist’s dial indicator The symmetry error of collimator jaw: typically less than 1 mm http://www.gwrauto.com/phoenix /brake_tools.html
  13. 13. Linear accelerator: CoincidenceCollimator axis, light beam axis and cross-hairs The light field edges The intersection of diagonals and the position of cross-hair imagesLight beam with x-ray beam AAPM guidelines ⇒ ±3% (±2%)
  14. 14. Mechanical IsocenterThe intersection point of the axis of rotationof the collimator and the axis of rotation ofthe gantryCollimator rotation 2 mm diameter circleGantry rotation ±1 mm
  15. 15. Radiation IsocenterCollimator⇒2 mm diameter circleTreatment table ⇒2 mm diameter circleGantry ⇒2 mm diameter circle
  16. 16. Multiple Beam Alignment CheckFocal spot displacementAsymmetry of collimator jawsDisplacement in the collimator rotation axisor the gantry rotation axisThe split-field test 1 2 1 2
  17. 17. X-ray Beam PerformanceEnergy A central axis depth dose distribution A suitable ion chamber in a water phantom Small chamber (<3 mm) For a larger chamber, the depth dose curve should be shift to the left (toward the source) by 3/4r. Suitable depths for comparing depth dose ratios are 10 and 20 cm. 10×10, 100 cm SSD, and 10 cm depth ⇒ ±2%
  18. 18. X-ray Beam PerformanceField flatness The variation of dose relative to the central axis over the central 80% of the field size at 10 cm depth < ±3% Within the region extending up to 2 cm from the field edge at a 10 cm depth +3% ~ -5% The diagonal flatness extending up to 2.8 cm from the 50% isodose curve in a plane at a 10 cm depth +4% ~ -6%
  19. 19. X-ray Beam PerformanceField symmetry To fold the profile at the field center and the two halves of the profiles to be compared < 2% at any pair of points
  20. 20. Electron Beam PerformanceEnergy TG-25 Rp ⇒ (Ep)0=C1+C2Rp+C3Rp2 < ±0.5 MeVFlatness and symmetry TG-25 flatness⇒±5% (± 3%) symmetry⇒ < 2%
  21. 21. Monitor chambersLinearityAs a function of dose rateSpecial operating conditions Total body irradiation Total skin irradiation Arc rotationLong-term stability check
  22. 22. Wedges10×10 ±2°
  23. 23. Miscellaneous ChecksIsocenter shift with couch motion up and down ⇒< ±2 mmODI ⇒ < ±2 mmField size indicators ⇒ < ±2 mmGantry angle and collimator angles ⇒ < 1ºLaser lights aligned with the isocenter ⇒ < ±2 mmTabletop sag with lateral or longitudinal travelunder a distributed weight of 180 lb ⇒ < 0.5 cm
  24. 24. SimulatorChecking of the geometric and spatialaccuraciesPerformance evaluation of the x-raygenerator and the associated imagingsystemTable 17.5
  25. 25. BrachytherapyIntracavitary sources and applicators Source identity Physical length, diameter, serial No. Source uniformity and symmetry The superposition of the autoradiograph and transmission radiograph Source calibration A well ionization chamber ±5% Applicator evaluation Orthogonal radiographs The ease of source loading and removal
  26. 26. Remote Afterloaders (1)Operational testing of the afterloading unitRadiation safety check of the facilityChecking of source calibration andtransportChecking of treatment planning softwareTable 17.6
  27. 27. Remote Afterloaders (2)Source positioning The position of dummy sources and radioactive sources should correspond within ±1 mm.Source calibration A well ionization chamber A cylindrical lead insert for a conventional well ionization chamber for calibrating HDR sources Cylindrical ion chamber A free air geometry An interpolative method of obtaining exposure calibration factor
  28. 28. CommissioningAfter all the necessary beam data have beenacquired and adopted, the machine can bereleased or commissioned for clinical use.
  29. 29. Commissioning Data for a Linear AcceleratorData DescriptionCalibration Dose per MU calibration of all modalities and energies according to current protocol (TG21)Depth dose Central axis depth dose distribution for all modalities and energies, sufficient number of FS to allow interpolation of data and all available electron conesProfiles Tranverse, longitudinal, and diagonal dose profiles for all modalities and energies at dmax for electrons and selected depths for photons; all cones for electrons and selected FS for photonsIsodose Isodose curves for all modalities and energies, all cones for electrons and selected FS fordistribution photons, all wedge filters for selected field sizesOutput factors Sc,p, Sc, and Sp factors as a function of FS for all photon energies: output factors for all electron energies, cones, and standard inserts; tray transmission factors and wedge transmission factorsOff-axis ratios A table of off-axis ratios for all photon energies as a function of distance from central axis; these data may be obtained from those profiles for a 40×40 cm field at selected depthsInverse square Verification of inverse square law for all photon energies,virtual source position for all electronlaw energies, and effective SSD for all electron energies and conesTPR/TMR Direct measurement of TPRs/TMRs for all photon energies and selected FS and depths for verification of values calculated from percent depth dosesSurface and For all photon energies and selected FS, percent surface dose for all electron energies for abuildup dose 10×10 cm coneTreatment Beam data input, generation, and verification of central axis percent depth dose and TPR/TMRplanning system tables; sample isodose curves for unwedged, wedged, asymmetric and blocked fields; sample isodose curves for multiple field plans using rectangular and elliptical contours; electron beam depth dose data, isodose curves on rectangular and circular contoursSpecial Data for special techniques such as total body irradiation, total skin irradiation, stereotacticdosimetry radiosurgery, intraoperative electron therapy, etc
  30. 30. Periodic QA of Linear AcceleratorFrequency Procedure Tolerence (±)Daily X-ray output constancy 3% Localization lasers 2 mm Operational parameters recordedBiweekly Electron output constancy 3%Weekly Light/radiation field coincidence 3 mm X-ray flatness and symmetry 3% Electron flatness and symmetry 3%Monthly X-ray output calibration 2% X-ray energy 2% in fepth dose (2% in ionization ratio) Electron energy 3 mm in R80 (2 mm in Rp) Optical distance indicator 2 mm Field size indicators 2 mm Gantry angle indicator 1° Collimator angle indicator 1° Cross-hair centering 1 mmAnnually Full calibration 2% Isocenter shift Collimator rotation 2 mm diameter Gantry rotation 2 mm diameter Couch rotation 2 mm diameter Couch vertical travel 2 mm Tabletop sag 2 mm
  31. 31. Periodic QA of SimulatorsFrequency Procedure Tolerance (±)Daily Localization lasers 2 mmWeekly Light/radiation field coincidence 2 mmMonthly ODI 2 mm FS indicator 2 mm Gantry angle indicator 1º Collimator angle indicator 1º Cross-hair centering 1 mmAnnually Isocenter shift collimator rotation 2 mm diameter gantry rotation 2 mm diameter Couch rotation 2 mm diameter couch vertical travel 2 mm Tabletop sag 2 mm
  32. 32. 依游離輻射防護法第十七條第三項規定訂定之自中華民國九十四年七月一日施行輻射醫療曝露品質保證標準 醫用直線加速器 含鈷六十放射性物質之遠隔治療機 含放射性物質之遙控後荷式近接治療設備輻射醫療曝露品質保證組織與專業人員設置及委託相關機構管理辦法 設有醫用直線加速器者,應置二人。超過一部者 ,每增加一部,應增置一人。 設有含放射性物質之遙控後荷式近接治療設備者 ,應置一人。
  33. 33. 醫用直線加速器每日品質保證作業項目 結果或容許誤差項次 校驗項目 結果或誤差容許值A1-1 定位雷射 小於二毫米A1-2 光學距離指示器 小於二毫米A1-3 治療室門連鎖 功能正常A1-4 視聽監視器 功能正常A1-5 光子輸出劑量 小於百分之三
  34. 34. 醫用直線加速器每月品質保證作業項目結果或容許誤 差項次 校驗項目 結果或誤差容許值A2-1 光子輸出劑量 小於百分之二A2-2 緊急關閉按鈕 功能正常A2-3 楔形濾器、電子錐連鎖裝置 功能正常A2-4 電子輸出劑量 小於百分之二A2-5 光子射束中心軸於治療深度之劑量參數 每一點小於百分之二A2-6 電子射束中心軸於治療深度之劑量參數 每一點小於百分之二或於 治療深度內小於二毫米A2-7 光子平坦性 小於基準直百分之二A2-8 電子平坦性 小於基準直百分之三A2-9 光子對稱性 小於百分之三A2-10 電子對稱性 小於百分之三A2-11 光照野與輻射照野一致性 小於二毫米A2-12 旋轉臂及準直儀角度指示器 數位式小於零點五度;機 械式小於一度A2-13 十字交叉線中心位置 小於直徑二毫米圓形範圍A2-14 照野指示器 小於二毫米A2-15 準直儀對稱性 小於二毫米
  35. 35. 醫用直線加速器每年品質保證作業項目結果或容許誤差項次 校驗項目 結果或誤差容許值A3-1 光子輸出劑量 小於百分之二A3-2 緊急關閉按鈕 功能正常A3-3 楔形濾器、電子錐連鎖裝置 功能正常A3-4 電子輸出劑量 小於百分之二A3-5 光子射束中心軸於治療深度之劑量參數 每一點小於百分之二 每一點小於百分之二或於治療A3-6 電子射束中心軸於治療深度之劑量參數 深度內小於二毫米A3-7 光子平坦性 小於基準直百分之二A3-8 電子平坦性 小於基準直百分之三A3-9 光子對稱性 小於百分之三A3-10 電子對稱性 小於百分之三 小於二毫米或靶至量測距離之A3-11 光照野與輻射照野一致性 百分之一 數位式小於零點五度;機械式A3-12 旋轉臂及準直儀角度指示器 小於一度A3-13 十字交叉線中心位置 小於直徑二毫米圓形範圍A3-14 照野指示器 小於二毫米A3-15 準直儀對稱性 小於二毫米
  36. 36. 醫用直線加速器每年品質保證作業項目結果或容許誤差A3-16 準直儀機械旋轉中心 小於直徑二毫米圓形範圍A3-17 旋轉臂機械旋轉中心 小於直徑二毫米圓形範圍A3-18 治療床機械旋轉中心 小於直徑二毫米圓形範圍A3-19 準直儀輻射旋轉中心 小於直徑二毫米圓形範圍A3-20 旋轉臂輻射旋轉中心 小於直徑二毫米圓形範圍A3-21 治療床輻射旋轉中心 小於直徑三毫米圓形範圍A3-22 區域監測器 功能正常A3-23 治療床垂直升降之線性 小於百分之二A3-24 光子照野因子 小於百分之二A3-25 電子錐因子 小於百分之二 光子或電子射束中心軸百分深度劑量比,組織與A3-26 小於百分之二 空氣比A3-27 穿透因子 小於百分之二A3-28 楔形濾器穿透因子 小於百分之二A3-29 監測游離腔之線性 小於百分之二A3-30 安全連鎖 ( 含門、緊急停止與臨時中斷 ) 功能正常
  37. 37. 遙控後荷式近接治療設備每日品質保證作業項目結果或容許誤 差項次 校驗項目 結果或誤差容許值 輻射安全系統確認、警示系統、視聽監測器B1-1 系統、安全連鎖 ( 含門、緊急停止與臨時中 功能正常 斷)B1-2 檢視輻射源治療管線完整性 功能正常
  38. 38. 遙控後荷式近接治療設備每月質保證作業項目結果或容許誤差項次 校驗項目 結果或誤差容許值 輻射安全系統確認、警示系統、視聽監測器系統B2-1 功能正常 、安全連鎖 ( 含門、緊急停止與臨時中斷 )B2-2 備用電池狀況 功能正常B2-3 檢視輻射源導線完整性 功能正常 啟動輻射源由原點至最遠距離B2-4 輻射源速率 之時間誤差為小於一秒 輻射源強度(每月、每年為計算值,換輻射源為B2-5 小於百分之一 實測值)B2-6 輻射源停留位置 小於一毫米B2-7 輻射源停留時間 每分鐘小於一秒
  39. 39. 遙控後荷式近接治療設備每年質保證作業項目結果或容許誤差 項次 校驗項目 結果或誤差容許值 輻射安全系統確認、警示系統、視聽監測器 B3-1 系統、安全連鎖 ( 含門、緊急停止與臨時中 功能正常 斷) B3-2 檢視裝療器及裝療管完整性 功能正常 輻射源擦拭試驗測試值(擦拭面積至少一百 B3-3 小於七十四貝克 平方厘米)
  40. 40. Thanks for your attention!!