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放射治療設備品質保證原理 Comprehensive QA for radiation onlology Class date/time: Thursdays, 8:20-10:05 AM, 2002/2/28~6/27 References: Quality Assurance in Radiotherapy Physics. Comprehensive QA for radiation oncology: Report of AAPM Radiation Therapy Committee Task Group 40. Med. Phys. 21 (4), April 1994. Grading: Roll call and reports: 50%, Examinations: 50% PREFACE QA activities cover a very broad range, and the work of medical physicists in this regard extends into a number of areas in which the actions of radiation oncologists, radiation therapist, dosimetrists, accelerator engineers, and medical physicists are important. If quality of care is to be improved, enlightened leadership by hospital management and clinical leaders is required. Within radiation oncology itself, coordination is critical among radiation oncology physicists, dosimetrists, accelerator engineers, radiation oncologists, radiation therapists, and administrators. The various groups are brought into coordinated efforts through well-documented QA procedures administrated by a multidisciplinary QA committee. CONTENTS Information for radiation oncology administrators Code of practice Comprehensive QA program QA of external beam radiation therapy equipment Treatment planning computer system External beam treatment planning Brachytherapy QA of clinical aspects Information for radiation oncology administrators In treating patients with radiation, the radiation oncologist prescribes a treatment regimen ( including the radiation dose ) whose goal is to cure or control the disease while minimizing complications to normal tissue. The response of tumors and normal tissue t radiation is highly variable. The radiation dose must be delivered accurately and consistently. Radiation therapy process is a complex interweaving of a number of related tasks. Information for radiation oncology administrators Radiation therapy process : Initial consultation Determination of patient-specific parameters. ( Acquired from a number of diagnostic imaging sources ) Treatment planning ( determine the size, extent, and location of the tumor in relation to the normal organs. Distribution of radiation dose to patient ) Simulating the planned treatment ( Simulator ) To treat the patient as planned Verifying the correct delivery of treatment ( portal and verification radiographs, in vivo dosimetry, and record-andverify systems. Information for radiation oncology administrators ICRU has recommended that the dose be delivered to within 5% of the prescribed dose. Each step of radiation therapy process must be performed with an accuracy much better than 5%. To meet such standards required the availability of the necessary facilities and equipment including treatment and imaging units, radiation measuring devices, computer planning systems and the appropriate staffing levels of qualified radiation oncologists, radiation oncology physicists, dosimetrists, and radiation therapists. Furthermore, the complexity of treatment modalities is increasing. Information for radiation oncology administrators For Example : Linacs contain computer control system. High and low dose-rate remote afterloaders have sophisticated control systems. Treatment planning systems become larger and more complex. Several sophisticated options have become standard on commercial and locally developed systems. ( 3-D BEV planning, DRR, 3-D dose computation and display, DVH …) The commissioning and quality assurance of such complex systems requires increasing personnel training and time. Increasing expectations on the quality of treatment which lead to greater and more complex. Information for radiation oncology administrators These expectations have arisen from a growing appreciation of the importance of QA, and from the regulations of national, state, and local authorities and accreditation bodies. QA processes and procedures emanate from a QA committee. QA committee should include nurses, the department administrator, and Radiation oncologist may be responsible for Consultation Dose prescription On-treatment supervision Treatment summary reports Information for radiation oncology administrators Radiation oncology physicist is responsible for Calibration of the therapy equipment. Directs the determination of radiation dose distributions in patients undergoing treatment. Weekly review of the dose delivered to the patient. Certifies that the treatment machine is performing according to specifications after it is installed. Generate the beam data. Outlines written QA procedures, tolerances, and frequency of the tests. Understands and appropriately responses to machine malfunctions and related safety issues. Information for radiation oncology administrators Radiation therapist Be responsible for Accurately delivering a planned course of radiation therapy as prescribed by a radiation oncologist. Be expected to recognized any change in the patient’s condition and determine when treatment should be withheld until a physician is consulted. Be able to detect any equipment deviations or malfunctions, understand the safe operating limit of the equipment. Be able to judge when, due to equipment problems , to withhold or terminate treatment until the problem has been resolved. Information for radiation oncology administrators Medical radiation dosimetrist Be responsible for accurate patient data acquisition Radiation treatment design. ( In consultation with the physicist and oncologist ) Manual/computer-assisted calculations of radiation dose distribution. Assist with machine calibrations and ongoing QA under the supervision of the physicist. Information for radiation oncology administrators It is also important to provide the appropriate dosimetry instrumentation for commissioning and QA of these devices. Daily QA device Ion chamber Electrometer/dosimeter Barometer Thermometer Level Ruler Film scanner/ densitometer Information for radiation oncology administrators Water phantom scanning system Solid phantom Survey meter A comprehensive QA program should not focus just on the analysis of a narrow set of treatment variables, but rather should attempt to understand the cumulative effects of uncertainties. Medical linear accelerator QA of external beam radiation therapy equipment A. General QA of radiation therapy equipment is primarily an ongoing evaluation of functional performance characteristics. The function performance of radiotherapy equipment can change suddenly due to Electronic malfunction Component failure Mechanical breakdown Or can change slowly due to deterioration and aging of the component. QA of external beam radiation therapy equipment A. General Therefore, two essential requirement emerge: QA measurements should be performed periodically on all therapy equipments, including the dosimetry and other QA measurement devices. There should be regular preventive maintenance monitoring and correction of the performance of therapy machines and measurement equipment. The overall responsibility for a machine QA program be assigned to one individual : the radiation oncology physicist. QA of external beam radiation therapy equipment A. General The QA program should be based on a thorough investigation for baseline standards at the time of the acceptance an commissioning of the equipment for clinical use. Acceptance procedures should be followed to verify the manufacture’s specifications and to establish baseline performance values for new or refurbished equipment, or for equipment following major repair. Once a baseline standard has be established, a protocol for periodic QA tests should be developed. QA of external beam radiation therapy equipment A. General Tests for a typical QA program. Frequency of tests ( daily, weekly, and so on ) Tolerance values. Ensuring that the equipment is suitable for high quality and safe radiation treatment. Machine QA test procedures should be able to distinguish parameter changes smaller than tolerance or action levels. Within these limits, the tests should also be developed to minimize the test time. QA of external beam radiation therapy equipment B. Test Frequency Daily tests include those could seriously affect patient positioning and therefore the registration of the radiation field and target volume (lasers, ODI ); patient dose ( output constancy ) and safety ( door interlock and audiovisual contact ) Monthly include those either have a smaller impact on the patient ( e.g., treatment couch indicators ) or have lower likelihood of changing over a month ( e.g., light and radiation field or beam flatness ). QA of external beam radiation therapy equipment B. Test Frequency AAPM recommend adherence to the program outlined in the tables unless there is demonstrable reason to modify them. At this stage there is no accepted method of systematically defining the type and frequency of QA tests that should be performed. The best guidance that can be given at present is that the QA program should be flexible enough to take into account quality, costs, equipment condition, and institutional needs. QA of external beam radiation therapy equipment C. Guideline for Tolerance Values The tolerance values are intended to make it possible to achieve an overall dosimetric uncertainty of ±5% and an overall spatial uncertainty of ±5mm. The tolerances listed in the tables mean that if a parameter either exceeds the tabulated value ( e.g., the measured isocenter under gantry rotation exceeds 2 mm diameter ) or that the change in the parameter exceeds the tabulated value ( e.g., the output changes by more than 2% ), then an action is required. QA of external beam radiation therapy equipment C. Guideline for Tolerance Values It is important to realize that the tolerance levels presented in this document reflects standards of practice which have evolved in the practice of radiation oncology physics over the past decades, or even longer. These standards may, and probably will to be modified as newer techniques are introduced. QA of external beam radiation therapy equipment Daily QA of medical accelerator Dosimetry 3% 3% Mechanical X-ray output constancy Electron output constancy Localizing lasers Distance indicator ( ODI ) 2 mm 2 mm Safety Door interlock Audiovisual monitor Functional Functional QA of external beam radiation therapy equipment Monthly QA of medical accelerator Dosimetry X-ray output constancy 2% Electron output constancy 2% X-ray central axis dosimetry parameter ( TPR) constancy 2% Electron central axis dosimetry parameter ( PDD) constancy 2mm X-ray beam flatness constancy 2% Electron beam flatness constancy 3% X-ray and electron symmetry 3% QA of external beam radiation therapy equipment Monthly QA of medical accelerator The beam uniformity and dose stability should be check at different angular positions of the gantry, since recent reports indicate that accelerator beam characteristics can vary with gantry position. Beam scanners which mount directly on the treatment head of the machine are useful in measuring beam output and symmetry as a function of gantry angle. Instruments for daily “spot checks” use arrays of ionization chambers or solid state detectors which can be perform multiple tests with one radiation exposure. QA of external beam radiation therapy equipment Monthly QA of medical accelerator Monthly output checks are performed by a physicist with an ionometric dosimetry system that is acceptable for calibration by an Accredited Dosimetry Calibration Laboratory. For daily output checks, clinical action level = 5%. If exceeded, no further Tx. should be given. If the output difference is within 3% and 5%, then Tx. may continue and the radiation oncology physicist is notified. It is essential that the physicist review these daily measurements and keep the output under surveillance. QA of external beam radiation therapy equipment Monthly QA of medical accelerator Field symmetry and flatness may be affected by both mechanical and electronic parameters. Small changes in beam energy, beam alignment, bending magnet function, target position, flattening filter selection and position, as well as other machine parameters, may result in unacceptable beam profile. Field symmetry and flatness are both characteristics of a beam profile measures either in air or at some given depth in water. QA of external beam radiation therapy equipment Monthly QA of medical accelerator Flatness Defined as the max. difference from the dose on the central axis over 80% of the field dimension ( length or width ). 80% of Field Width Ymax 100% Y0 50% Field Width Ymin ( Ymax-Y0 ) / Y0 100 % Flatness = ± ( Ymin-Y0 ) / Y0 100 % QA of external beam radiation therapy equipment Monthly QA of medical accelerator Symmetry Defined as the difference in dose rate between any two symmetric points within 80% of the field size ( length or width ). 80% of Field Width Y1 100% Y0 50% Field Width Y2 Symmetry = ( Y1-Y2 ) / Y0 100 % QA of external beam radiation therapy equipment Monthly QA of medical accelerator Safety Interlocks Emergency off switches Wedge, Electron cone interlocks Functional Functional Mechanical Checks Light/Radiation field coincidence Gantry/Collimator angle indicator Wedge position Tray position Applicator position 2mm or 1% on a side 1 deg 2 mm ( or 2% change in transmission factor ) 2 mm 2 mm Light/Radiation field coincidence Light and radiation fields coincident Light and radiation fields not coincident QA of external beam radiation therapy equipment Monthly QA of medical accelerator Mechanical Checks Field size indicators Cross-hair centering Treatment couch position indicators Latching of Wedges, Blocking tray Jaw symmetry Field light intensity 2mm 2 mm diameter 2 mm / 1 deg Functional 2 mm Function QA of external beam radiation therapy equipment Monthly QA of medical accelerator Cross-hair centering A B Mid-point of line AB is a point on the collimator axis of rotation. A and B correspond to collimator angular positions 180 degrees apart. QA of external beam radiation therapy equipment Monthly QA of medical accelerator Jaw symmetry QA of external beam radiation therapy equipment Annual QA of medical accelerator Dosimetry X-ray/electron output calibration constancy Field size dependence of x-ray output constancy Output factor constancy for electron applicators Central axis parameter constancy ( PDD, TPR) Off-axis factor constancy Transmission factor constancy for all Tx.accessories Wedge transmission factor constancy Monitor chamber linearity X-ray output constancy vs gantry angle 2% 2% 2% 2% 2% 2% 2% 1% 2% QA of external beam radiation therapy equipment Annual QA of medical accelerator Dosimetry Safety Interlock Electron output constancy vs gantry angle 2% Off-axis factor constancy vs gantry angle 2% Arc mode Functional Follow manufacturers test procedures Functional Mechanical Checks Collimator rotation isocenter Gantry rotation isocenter Couch rotation isocenter Coincidence of collimator, gantry, couch axes with isicenter 2 mm dia. 2 mm dia. 2 mm dia. 2 mm dia. QA of external beam radiation therapy equipment Annual QA of medical accelerator Mechanical Checks Coincidence of radiation and mechanical isocenter Table top sag Vertical travel of table 2 mm 2 mm 2 mm QA of Newer Innovation on Medical Accelerators Computer controlled and monitored operation ; motorized autowedge; dynamic wedge; multileaf collimators; record and verified systems; portal imaging devices; stereotactic radiosurgery; and intraoperative radiotherapy. The guidelines of these systems that established by the manufacturers for safe operation should be strictly followed. QA of Simulators Subjected to the same mechanical checks as accelerators. In addition, the simulator should be checked for image quality. QA of CT Scanners A flat top insert on the CT table to reproduce the radiation therapy treatment couch top. A laser system mimicking that used in the simulation and treatment units should be mounted in the CT suite and the alignment of the lasers should be checked daily. QA of CT Scanners The correlation of CT numbers with electron densities and the variation of CT numbers with position and phantom size should be determined. This correlation should be checked yearly. Image quality and other parameters described in the QA protocol provided by the manufacturer should be checked. QA of Measurement Equipment As important as that of the radiation treatment equipment and should be part of a QA program. QA of Measurement Equipment Redundancy in dose calibration equipment is recommended to assure that instruments are holding their calibration. By comparing the response of the measurements equipment with an appropriate long-lived radioactive source ( Sr-90 ). A two-system redundancy method provides better accuracy than one system with check source. Documentation and Records of QA This is very important that test procedures are well documented for all units under the QA program. The results of initial baseline testing ( commissioning ) and future periodic testing be recorded and dated. QA records must be kept on file for a minimum specified time ( typically 5 years, although sometimes longer ). Calibration Record Sheet for Daily, Weekly and Monthly Checks Week I T = P = Week II Date: fTP = Rg(avg) Dose/MU T = P = Vari. Machine : fTP = Rg(avg) Dose/MU Year : Week III Date: T = Vari. P = Week IV Date: fTP = Rg(avg) Dose/MU T = Vari. P = Date: fTP = Rg(avg) Dose/MU 6X 6X 6X 6X 10X 10X 10X 10X 6E 6E 6E 6E 8E 8E 8E 8E 10E 10E 10E 10E 12E 12E 12E 12E 15E 15E 15E 15E 18E 18E 18E 18E Daily Daily Daily Daily Check Check Check Check RAL Source Position RAL Source Position RAL Source Position RAL Source Position Ci RAL Source Activity Ci RAL Source Activity RAL Source Activity RAL Timer Check Note Constancy Check Date : Uniformity Check Mode 6X 10X Date : 6E 8E 10E 12E 15E 18E Ci RAL Source Activity Date : Energy Check Keithley 617 6X Flat.G-C Victoreen500 10X L-R +PTW 30-351 Level L-R Mode L-R 6X 10X L Agre. R Simu. Mode Linac Simu. RgA Check 8E P. Check 10E Cross-hair Survey Meter 12E Isocenter Check 15E Note RgB 6E Temp. Check Note 18E Note Physicist: Physicist: Physicist: Ci Date : Rg(5) Rg.(d) Rgd/Rg5 Var. + NE 2571 Symm.G-C Vari. Physicist: RgB/RgA Var. Constancy Check Report Date : 2002/4/29 Temp.= 19.2 Pres. = 766 (mmHg) 3405.0 (day) Decay Time= Calibration date: (℃) f(T,P)=[760/P]*[(273.15+T)/295.15] 0.798273956 D.F.= 1993/1/1 = 0.9828 D.F.= 0.5^[Decay Time/(28.7*365)] Keithley 35617 + NE 2571 Victoreen 500 + 30-351 Charge(nC) Current(pA) Charge(nC) 0.000 Current(pA) Bg. -0.001 -0.006 Bg. Rg1 -6.72 -37.750 Rg1 -6.23 -0.035 Rg2 -6.80 Rg2 -6.21 Rg3 -6.74 Rg3 -6.23 Rg(avg.) -6.75 -37.750 Rg(avg.) -6.22 -34.700 Rg(cor.) -8.31 -46.467 Rg(cor.) -7.66 -42.676 Var.(%) -0.588 -0.472 Var.(%) -0.396 -0.719 -34.700 Tolerence : (+/-) 1% Victoreen Battery : Note : 300 (2001/4/27 change new bettary) Keithley 35617 + NE 2571 for annual verification. Rg.(Avg.)=Avg.(Rg.1+Rg.2+Rg.3+...) Rg.(Cor.)=[Rg.(Avg.)-Bg.] * f(T/P) / D.F. Standard Data : (average, 1/94-12/94) Keithley Sys. Charge= Current= -8.362 (nC, for 3 min.) -46.687 (pA) Victoreen Sys. Charge= Current= -7.692 (nC, for 3 min.) -42.985 (pA) Physicist: 蕭安成 Skin Kong Memorial Hospital Radiation Therapy and Oncology Treatment Planning Worksheet Name : Chart number : Diagnosis : Doctor : Localization date : _____________ Note : Physicist : Modality :□ CT Image acquistition date : _____________ Note : Recheck I date : _______________ Pre-planning center : ( , , ) □ MRI Post-planning center : ( Physicist : , Physicist : , ) , Physicist : , ) , Physicist : , ) Shift (mm) □ : H □ F _____, □ R □ L _____, □ A □ P _____ Setup depth (cm) :□ AP □ LAT _____ Setup error (mm) :□ H □ F _____, □ R □ L _____, □ A □ P _____ Note : Recheck II date : _______________ Pre-planning center : ( , , ) Post-planning center : ( Shift (mm) □ : H □ F _____, □ R □ L _____, □ A □ P _____ Setup depth (cm) :□ AP □ LAT _____ Setup error (mm) :□ H □ F _____, □ R □ L _____, □ A □ P _____ Note : Recheck III date : _______________ Pre-planning center : ( , , ) Post-planning center : ( Shift (mm) □ : H □ F _____, □ R □ L _____, □ A □ P _____ Setup depth (cm) :□ AP □ LAT _____ Setup error (mm) :□ H □ F _____, □ R □ L _____, □ A □ P _____ Note : Verification film Date : ___________ Date : ___________ Date : ___________ Date : ___________ Date : ___________ Error (mm) :□ H Error (mm) :□ H Error (mm) :□ H Error (mm) :□ H Error (mm) :□ H □F □F □F □F □F _____, _____, _____, _____, _____, □R □R □R □R □R □L □L □L □L □L ** H : head, F : feet, A : anterior, P : posterior, R : right, L : left _____, _____, _____, _____, _____, □A □A □A □A □A □P □P □P □P □P _____ _____ _____ _____ _____ RAL NEW SOURCE ACTIVITY 2001/11/16 No. Date Factory Date Today Act 23 2001/11/16 2001/11/8 10.3432 temperature 22.2 Time(hour) Time(hour) Decay(hr)204 pressure 774 1 2 1.446 1.458 5.741 5.793 Rg(60sec)CH1 CH2 Rg(240sec)CH1 CH2 exposure 23.4031 activity Var.(%) 16 4.5 Activity 11.2 CTP 0.9826 3 1.446 1.459 5.743 5.793 Ci 1.446 1.458 5.744 5.793 1.4460 1.4583 5.7427 5.7930 average 1.4522 5.7678 10.1974 -1.4 (measurement/factory-1)*100 Ir-192 exposure-rate constant = 0.459 R m^2 / Ci h Ir-192 half-life = 73.83 day Keith.+2571 (Nx)xray= 4.6178 (Nx)cs= 4.7709 reading(3min) (Nx)Ir Aion Pion Pgrad CTP 4.3157 5.4480 1 1 1.004 0.9826 Exposure = Rg * Nx * Aion * Pion * Pgrad * Ctp * Prs * Ccap (Nx)Ir = ( 1+x ) * [ (Nx)x-ray + ( Nx) Cs ] /2 x = 0.0037 * ( t /9.3*10 ^22 ) t = wall thickness ( electrons / cm^2 ), wall + buildup cap Keithley Dosimetry System, Keithley electrometer + NE 2571 0.6 cc ion chamber wall thickness= 0.0650 g/cm^2 wall material = 3.008E+23 graphite electron density ( electrons / g) cap thickness= 0.5510 g/cm^2 cap material= 3.211E+23 Delrin electron density ( electrons / g) t= 1.965E+23 electrons / cm^2 x= 0.007817 ( Nx ) Ir = 4.7310 Note: Measurements were performed with Victoreen 500 electronmeter and Victoreen 30-351 ion chamber, Nx was estimated about 1% higher than the Co-60 calibration factor, and Pion , Aion = 1. ( Nx = 5.394 *1.01 = 5.448 ) Physicist : 蕭安成 Prs Ccap 0.999 1.01 Treatment Planning Computer System Commissioning and QA for external beam : The calculation of relative dose distributions for relative machine, energy, and modality. The summation of relative doses from different beams The calculation of monitor units for a given prescribed dose. Production of clear and accurate output data, including graphical isodose distributions. Independent computer “MU” programs. Treatment Planning Computer System Concerns for Brachytherapy : The dose distribution is correct for the source type in use. The spatial reproduction of the implant is appropriate Dose summations are calculated correctly. A treatment planning system should be tested over a range of parameters which would be typical of those used in the clinic, and should be tested on a periodic basis. Treatment Planning Computer System Program Documentation Beam Data Library The manufacturer should provide clear documentation on the procedures for acquiring and transferring beam and other necessary data to the treatment planning system’s data library. Users should acquire their own basic beam data sets Dose Calculation Models The documentation should describe the required dosimetric input data set and the expected accuracy of the dosimetric calculations for various conditions. Treatment Planning Computer System Program Documentation Dose Calculation Models Discuss the limitations of the dose calculation models. Operating Instructions and Data I/O Test Procedures Initial Manufacturer’s Tests Initial User Test Procedures Commissioned for each treatment machine. Energy. Modality and for each isotope at the time of purchase of the software, annually, and every time a software upgrade is installed. Treatment Planning Computer System Test Procedures Initial User Test Procedures Calculated dose distributions for a select set of treatment conditions in standard phantoms be compared to measured dose distributions for the same phantoms. A reference set of treatment planning test cases should be established. This set should be used for yearly recommissioning of the treatment planning system. Treatment Planning Computer System Test Procedures Tests After Program Modification QA tests always be performed on the treatment planning system after program modification. The results should be compared to the initial acceptance test results. External Beam Treatment Planning Nongraphical planning Single or parallel opposed fields. Traditional graphical planning Target volume is defined from CT or orthogonal simulation films. The field arrangements are designed and dose distributions calculated on one or a limited number of axial cross sections using a computerized planning system. External Beam Treatment Planning 3D treatment planning Target volume, normal tissue volumes, and surface contours are obtained directly from CT. Field design, the field apertures are defined using BEV Prescribed dose to a point, isodose curve, isodose surface, or dose volume histogram( DVH ). Treatment Planning QA for individual Patients Treatment Plan Review All graphical treatment plans should be signed and dated by individual who formulated the plan, and by the radiation oncologist. External Beam Treatment Planning Treatment Planning QA for individual Patients Treatment Plan Review Assure that the monitor units are correct, that all machine parameters used for patient setup are correct. The quality of the plan meets department standards All signatures, prescriptions, etc. are recorded. Independent calculation of the dose at one point in the plan. If the independent calculation differs by more than 5% from the treatment plan, the disparity should be resolved before commencing. External Beam Treatment Planning Treatment Planning QA for individual Patients Monitor Unit Calculation Review Initial calculation be signed and dated by the individual who performed it and reviewed by physicist. Plan Implementation All parameters in the treatment plan should be verified during first setup. Port films Radiation oncologist be present at the treatment machine for first setup and for major changes. External Beam Treatment Planning Treatment Planning QA for individual Patients A check of the setup by the physicist will minimize errors. In Vivo Dosimetry In vivo dosimerty can be used to identify major deviations in the delivery of treatment and to verify and document the dose to critical structures. TLD or other in vivo systems. Brachytherapy Brachytherapy is the use of encapsulated radioactive sources to deliver radiation dose within a distance of a few centimeters by surface, intracavitary, interstitial or intraluminal applications. One goal of QA is to achieve a desired level of accuracy and precision in the delivery of dose. For external beam therapy dose delivery < 5% For intracavitary brachytherapy, an uncertainty of 15% in the delivery of prescribed dose is a more realistic level. Sealed Sources Description of Sources The radiation characteristics of an encapsulated source are strongly dependent upon the distribution of the activity within the source and the details of the source encapsulation. Physical and chemical form The chemical composition of the radionuclide and inert filler material should be provided by the manufacturer. Sealed Sources Source encapsulation Source encapsulation can influence the source calibration, the dose distribution, and the physical integrity of the source. This information should be available by the manufacturer. Source identification It is essential to be able to distinguish between sources that have the same radionuclide and capsule design but different activities. Sealed Sources Calibration of sources Although commercial suppliers of brachytherapy sources provide a measure of source strength, it is unwise to rely solely on this value for patient dose calculations. Each institution should have the ability to independently verify the source strength provided by the manufacturer. Sealed Sources Calibration of sources Specification of Source Strength AAPM recommend that the quantity of radiation emanating from a source be expressed as “ airkerma strength”. Traceability of Source Calibration Direct traceability Secondary traceability Sealed Sources Brachytherapy Source Calibrators Well ionization or reentrant chambers are preferred for conventional strength brachytherapy sources. Thimble chambers are preferred for high dose rate sources. The radiation oncology physicist should identify a single dosimetry system that will be used for brachytherapy calibration. Remote Afterloading Accuracy of source selection Spatial positioning. Control of treatment time. QA of Clinical Aspects New Patient Planning Conference Should be attended by radiation oncologists, radiation therapists, dosimetrists, and medical physicists. The pertinent medical history, physical and diagnostic findings, tumor staging, and treatment strategy ( including the prescription and considerations of normal organ dose limits ) should be presented by the attending radiation oncologists and residents. For each patient, the prescribed dose, critical organ doses, possible patient positioning, possible field arrangements, and special instructions should also be discussed. QA of Clinical Aspects Chart Review --- Basic Component of a Chart Patient identification Initial physical evaluation of patient and pertinent clinical information Treatment planning Signed and witness consent form Treatment execution Clinical assessment during treatment Treatment summary and follow-up QA check lists QA of Clinical Aspects Chart Review --- Overview of Chart Checking The items recording in the radiation chart are reviewing by a number of individuals at different times during the patient’s treatment. Charts be reviewed At least weekly Before the third fraction following the start of each new treatment field or field modification At the completion of treatment The review be signed and dated by the reviewer. All errors be reviewed and discussed by the QA committee. QA of Clinical Aspects Chart Check Protocol --- Review of New or Modified Treatment Field The first task of the chart reviewer is to identify any changes in the treatment (e.g., changes in field size, dose per fraction, etc.) or new treatment fields since the previous weekly chart review. Chart Check Protocol --- Weekly Chart Review As part of the weekly chart review, the reviewer should determine for each patient whether any new fields have been created or any previously treated fields modified. QA of Clinical Aspects Film Review --- Types of Film Portal-localization images. Verification-localization images On-line imaging devices ( electronic portal imaging ) Initial portal imaging To verify that the radiation field isocenter is correctly registered with respect to the patient’s anatomy. The aperture ( blocks or MLC ) has been properly produced and registered with respect to the isocenter. QA of Clinical Aspects Initial portal imaging Portal films be obtained for all treatment fields prior to first treatment. Where oblique or noncoplanar fields are used, orthogonal films imaging isocenter should be obtained. If first day setup modification are not made, positioning errors may persist as systematic deviation throughout the course of treatment. QA of Clinical Aspects Ongoing Portal and Verification Images Day-to-day variations in patient setup are likely to be random and smaller in magnitude than first-day variations. Patient position observed on one day may be simply a random error which cannot be controlled. Such potential setup errors should be monitored for a few consecutive days and the patient’s position should be modified only if they persist. The relative frequency of localization errors diminishes as the frequency of portal and localization films increases.