Chapter 17 Quality Assurance

An adequate QA program increased staffing and up-to-date equipment can be expensive the total cost of QA program in radiation therapy ~3% of the annual billing are QA programs voluntary? incentive for QA? a desire to practice good radiation therapy or avoid malpractice suits

QA: Goals the objective, systematic monitoring of the quality and appropriateness of patient care. is essential for all activities in Rad Onc Structure: staff, equipment and facility process: the pre- and post-treatment evaluations and the actual treatment application and outcome: the frequency of accomplishing stated objectives (TCP), and by the frequency and seriousness of NTCP all of which can be measured

A comprehensive QA program includes admin, clinical, physical, and technical aspects of rad onc Operationally, no single personnel has the expertise to cover all these areas teamwork is essential among admin, rad onc, nurses, med phys, and therapy techs For an effective QA program , all the staff must be well coordinated and committed to QA.

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 Physical therapist Maintenance engineer/electronics technician On per 2 megavoltage units or 1 megavoltage unit and a simulator if equipment serviced in-house

Additional personnel These recommendations are for clinical service only, do not include staffing for research, teaching, or administrative functions. Additional personnel required for QA of modern imaging equipment (e.g., cone-beam computed tomography [CT] system, [EPID]), CT simulators, and (PET)/CT Sophisticated and complex treatments (e.g., [IMRT], [IGRT], [HDR], prostate implants, SRS, tomo, proton therapy).

For example if 800 patients/y with 3 linacs, one 60Co, an orthovoltage, and one TPS: 2-3physicists A training program with eight residents, two tech students, and a graduate student: 1 to 1.5 full-time employees (FTEs). Administration of this group would require 0.5 FTE If the faculty had 20% time for research: a total of 5-6 physicists for direct patient care.

Many of the clinical physics tasks that have been traditionally performed by physicists can be delegated to dosimetrists or physics assistants. For example, dosimetrists can assist in routine QA checks, computer treatment planning, and monitoring unit calculations and brachytherapy source preparations. A physicist in this case has a role in establishing the procedures, directing the activities, and reviewing the results. In treatment planning, Figure 17.1 illustrates how physics support is usually organized in this country. Arrangement A, in which the physician practically works alone or does not seek consultation from the physics team, is obviously not appropriate and is contrary to the concept of a multidisciplinary approach to radiation oncology. Arrangement β is not satisfactory either but is prevalent in many institutions. There may be several reasons why an essential member of the team, the physicist, is excluded in this case from the clinical process. Economics is one reason, as physicists are usually higher salaried than the dosimetrists. Other reasons may include having physicists who lack clinical training or a well-defined role in the clinic. Nonetheless, arrangement C is probably the best approach, as it involves teamwork among personnel whose responsibilities are matched with their credentials. The Blue Book recommendation on dosimetrist staffing is 1 per 300 patients treated annually. In some institutions, dosimetrists perform physics work only, whereas in others they also do simulations. The relative proportion of a dosimetrist's efforts to various tasks is dictated by the individual needs of the department, the scope of the physics activities, and the extent of other physics and technical support available.

Training education and training of physics staffing of critical importance The greatest weakness in this regard has been the physicist's training Most physicists are hired with less than adequate clinical training Structured clinical training programs have been traditionally nonexistent

Training Certification boards residency-type clinical training nationally accredited residency programs before taking the board examinations or assuming independent clinical esponsibilitie the certifying board for radiological physicists—has decided that “Beginning in 2014… candidates must be enrolled in or have completed a accredited residency program.” CAMPEP [Commission on Accreditation of Medical Physics Educational Programs]

Radiation oncology physicist: Qualifications a M.S. or Ph.D. in physics, medical physics, or a closely related field and a certification in radiation oncology physics by the American Board of Radiology, the American Board of Medical Physics, or another appropriate certifying body.

Role of physicist: example At the University of Minnesota the physicist's consultation is made as important as other consultations, such as those sought from the medical oncologist, the surgeon, or the radiologist To prevent bypassing the physics consultation, each patient is assigned a physicist who is available at the time of simulation to assist the radiation oncologist in formulating the best possible treatment plan Subsequent physics work is the designated physicist's responsibility,although he or she may be assisted by the dosimetrist or other technical personnel. The final treatment plan is approved by the radiation oncologist after discussing the plan with the physicist. Also, the physicist is present at the time of first treatment and subsequent treatments, if needed, to ensure proper implementation of the plan.

Not all the clinical physics procedures performed by physicists Many of the technical tasks: by dosimetrists so that physicists can devote time to developmental activities Every rad onc department needs to develop new programs as well as revise the old ones to keep current with advancements in the field: Responsibility of the physicist

Acceptance Testing To satisfy all the specifications and criteria contained in the purchase contract To perform all the tests in accordance with the company’s procedure manual Any equipment to be used for patients must be tested to ensure that it meets its performance specifications and safety standards

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

Coincidence Collimator axis, light beam axis and cross-hairs The light field edges The intersection of diagonals and the position of cross-hair images Light beam with x-ray beam AAPM guidelines  3% (2%)

Mechanical Isocenter The intersection point of the axis of rotation of the collimator and the axis of rotation of the gantry Collimator rotation 2 mm diameter circle Gantry rotation ±1 mm

Radiation Isocenter Collimator2 mm diameter circle Treatment table 2 mm diameter circle Gantry 2 mm diameter circle

Multiple Beam Alignment Check Focal spot displacement Asymmetry of collimator jaws Displacement in the collimator rotation axis or the gantry rotation axis The split-field test 1 2 1 2

X-ray Beam Performance Energy 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%

X-ray Beam Performance Field 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%

X-ray Beam Performance Field 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

Electron Beam Performance Energy TG-25 Rp  (Ep)0=C1+C2Rp+C3Rp2 < ±0.5 MeV Flatness and symmetry flatness±5% (± 3%) symmetry < 2%

Wedges 1010 ±2°

Miscellaneous Checks Isocenter shift with couch motion up and down  < ±2 mm ODI  < ±2 mm Field size indicators  < ±2 mm Gantry angle and collimator angles  < 1º Laser lights aligned with the isocenter  < ±2 mm Tabletop sag with lateral or longitudinal travel under a distributed weight of 180 lb  < 0.5 cm

Simulator Checking of the geometric and spatial accuracies Performance evaluation of the x-ray generator and the associated imaging system Table 17.5

Brachytherapy Intracavitary 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

Remote Afterloaders (1) Operational testing of the afterloading unit Radiation safety check of the facility Checking of source calibration and transport Checking of treatment planning software Table 17.6

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

Commissioning After all the necessary beam data have been acquired and adopted, the machine can be released or commissioned for clinical use.

Commissioning Data for a Linear Accelerator Description Calibration 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 cones Profiles 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 photons Isodose distribution Isodose curves for all modalities and energies, all cones for electrons and selected FS for photons, all wedge filters for selected field sizes Output 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 factors Off-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 depths Inverse square law Verification of inverse square law for all photon energies,virtual source position for all electron energies, and effective SSD for all electron energies and cones TPR/TMR Direct measurement of TPRs/TMRs for all photon energies and selected FS and depths for verification of values calculated from percent depth doses Surface and buildup dose For all photon energies and selected FS, percent surface dose for all electron energies for a 1010 cm cone Treatment planning system Beam data input, generation, and verification of central axis percent depth dose and TPR/TMR 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 contours Special dosimetry Data for special techniques such as total body irradiation, total skin irradiation, stereotactic radiosurgery, intraoperative electron therapy, etc

Periodic QA of Linear Accelerator Frequency Procedure Tolerence (±) Daily X-ray output constancy 3% Localization lasers 2 mm Operational parameters recorded Biweekly Electron output constancy Weekly Light/radiation field coincidence 3 mm X-ray flatness and symmetry Electron flatness and symmetry 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 Field size indicators Gantry angle indicator 1° Collimator angle indicator Cross-hair centering 1 mm Annually Full calibration Isocenter shift Collimator rotation 2 mm diameter Gantry rotation Couch rotation Couch vertical travel Tabletop sag

Periodic QA of Simulators Frequency Procedure Tolerance (±) Daily Localization lasers 2 mm Weekly Light/radiation field coincidence Monthly ODI FS indicator Gantry angle indicator 1º Collimator angle indicator Cross-hair centering 1 mm Annually Isocenter shift collimator rotation 2 mm diameter gantry rotation Couch rotation couch vertical travel Tabletop sag

Thank you for your attention!!