Red+group

=Daily CT Simulator QA:= Rachel Jacques / Adam Cohen

**Procedures:**
The CT simulator QA is done on a daily basis to ensure that the images and patient setup will be precise and accurate for planning and treatment. 1 The tests ensure that the localization of the target will also be precise. It is important to make sure that all of the information transferred to the treatment planning system is correct. This will also help ensure that the setup of the patient in the treatment room can be as accurate as possible. We need to make sure that the CT scanner is providing quality images with the proper resolution and Hounsfield unit numbers. It is also important to make sure that the lasers inside the CT room are also lining up correctly so that the patient’s setup is reproducible for treatment.

**Test 1:** Lasers: A cube is used to check if the alignment of the lasers is accurate. The cube is lined up in all directions (anteriorly to posteriorly, right to left, and superior to inferior). There is also a laser alignment tool that is sometimes used instead. It has a water bubble so that the device can be leveled on the table correctly. Lasers should be accurate within 2 mm. This ensures that the isocenter is represented correctly in planning. 1 There is also a test that is done on a phantom for the lasers. 2 Some centers do this daily and other centers do it monthly. A scan is done on the phantom to check for accuracy in the distance moved. Positional accuracy is checked by observing the laser position and QA phantom intersect on the phantom plates.


 * Test 2:** Daily warm up: If the tube is not warmed up prior to use, it can cause wear and tear on the unit and it could possibly even cause the anode to crack. Warming up the tube slowly brings it to a safe temperature so that a regular scan can then be done. This is a very simple procedure where the radiation therapist simply clicks on the daily warm up icon after the door has been closed. After the warm up a fast calibration can be done. This puts the scanner through a series of tests to ensure that all the parts are working correctly. If something is not working properly an error message will pop up and the therapist might need to call the service technician. This takes about 10 to 15 minutes to complete.


 * Test 3:** Phantom: For many centers, this test is done on a monthly basis, but other centers do it on a daily basis. A water phantom is attached to the table. A scan is taken using 1.25 mm slices. This scan is compared to the original scan done by the physicist. There are circular areas inside the phantom that are measured to ensure that the magnification is correct and that the measurements are accurate to true size. The Hounsfield unit numbers are also checked inside these circular areas and they should match the numbers for the original scan within 5 HU. There are grooves inside the phantom that are used to confirm that the resolution and spatial integrity is also within limits. 1

**Types of Equipment (provide links when possible):**
__Laser Alignment Tool__ Water Phantom GE Lightspeed Ultra 8

**Tolerances (expected):** 1
Alignment of Lasers: +/- 2 mm CT Number Accuracy - Water: 0 +/- 5 HU Image Noise: Manufacturer Specifications Spatial integrity: +/- 1 mm In-Plane Special Integrity: - 1mm Spatial Resolution: Manufacturer Specifications Contrast Resolution: Manufacturer Specifications

**Images:**

 * Figure 1.** QA components of CT simulator. 2


 * Figure 2.** Example of a CT simulator. 3

**Figure 3.** Better view of the bore and treatment table. 4

**References:**
1. Mutic S, Palta J, Butker E, et al. Quality assurance for computed tomography simulators and the computed tomography-simulation process. //Med Phys.// 2003;30(10):2762-92. 2. Shinichioro M, Toshiyuki S, Takei Y et al. Patient handling system for carbon ion beam scanning therapy. //Med Phys.// 2012;13(6). 3. Dedicated CT Simulator. Mayo Clinic Health System Web site. http://mayoclinichealthsystem.org/locations/northfield/medical-services/radiation-oncology/dedicated-ct-simulator. Accessed October 5, 2013. 4. Radiotherapy Simulators. Myradiotherapy.com Web site. http://www.myradiotherapy.com/general/Simulators/radiotherapy_simulators.html. Accessed October 5, 2013.

=Monthly CT Simulator QA:= Kevin Shun Chung Tsai

**Procedures:**
The monthly CT scanner QA procedure was performed on a Philips Brilliance CT simulator. A CT simulator is a very important tool used for planning and designing radiation treatment plans. The geometric accuracy for a simulator must maintained at he same level as the treatment machines. 1

**Test 1:** Table Vertical and Longitudinal Motion Purpose: To assure that the vertical and longitudinal table motion according to digital indicators is accurate and reproducible. Device: Stainless Steel Ruler Procedure: 1. Place the ruler longitudinally on the tabletop. 2. Move the table in and out of the gantry. 3. Measure the distance traveled and relative table position by using laser projection on the ruler. 4. Place the ruler vertically on the tabletop. 5. Move the table up and down. 6. Measure the distance traveled and relative table position by using laser projection on the ruler.

**Test 2:** Laser tracking Purpose: To assure that the external laser motion is accurate and reproducible. Device: Stainless Steel Ruler, 3-peg CIVCO Laser QA device, LAP laser PDA Procedure: 1. Align the laser QA device with lateral wall and sagittal lasers. Ensure that vertical wall laser (Z) positions read 0.0 mm. 2. Move the sagittal ceiling laser (X) to align with the left (125.9 mm), central (1 mm) and right pegs (-124.1 mm). Record the readings of the laser PDA. 3. Place the vertical ruler and lower the table to have the laser hit at the center of the ruler. Lower and raise the laser by 10 cm according to the ruler. Record the readings of the laser PDA.

Purpose: To assure that the external lasers are parallel to the table motion. Device: Two small rulers Procedure: 1. Move the table to be at the center of the vertical range of the motion. The gantry display will read 150 for the table vertical position. 2. Table has longitudinal position marks of F7 ~ H5. Place two small rulers at the zero position of the table. 3. Laser vs. Vertical table motion: a. Align the rulers to be orthogonal to the scan (axial) plane and vertical (sagittal) plane, respectively. b. Move table up and down (± y direction) over the full range of the table motion. Record the maximum longitudinal (z) and lateral (x) deviation from the center. 4. Laser vs. Longitudinal table motion: a. Tape one ruler vertical to the table. Place the other ruler orthogonal to the vertical (sagittal) plane. b. Move the table in and out (± z direction) over the full range. Record the maximum vertical (y) and lateral (x) deviation from the center.
 * Test 3:** Alignment of external lasers with table motion

Purpose: To make sure that external lasers are parallel and orthogonal with the scan plane and intersect in the center of scan plane. Devices: Laser QA device, boxes, BBs Procedure: 1. Lower the table and place a 40 cm height box. Place two BB’s at the top and bottom aligned to vertical laser. 2. Open OncoBody, OncoAbdomen axial protocol. Take axial CT scan with 16×0.75 mm collimator, 0.75 mm contiguous SW (slice width), 600 mm FOV. Evaluate if the two BB’s show up in the same plane. This confirms: 1) vertical wall laser is parallel to the scan plane; 2) gantry tilt is negligible. 3. Mount the Philips phantom at the front end of the table to apply some weight. Place the laser QA device at H2-H3 position of the table. Align it with the external lasers and zero the longitudinal table position by pressing button at the gantry control panel. Also, place two BB’s on the table, ~50 cm apart longitudinally along the sagittal laser projection. 4. Open OncoBody, OncoAbdomen protocol. Take helical CT scan enclosing two BB’s (>50 cm length), with 8×3 mm collimator, 5 mm SW. Evaluate if the two BB’s have same vertical/lateral position in the image. This confirms that the sagittal laser is orthogonal to the scan plane. 5. Take helical CT scan enclosing the three pegs of the laser QA device (~3 cm length), with 16×0.75 mm collimator, 0.8 mm SW. Evaluate if the longitudinal coordinates of the three pegs are at -500 mm. This confirms that the transverse laser is: 1) parallel to the scan plane; 2) accurately spaced from the scan plane. Evaluate if the position of the central peg is zero. This confirms that the vertical/horizontal lasers intersect in the center of the scan plane.
 * Test 4**: Alignment of external lasers with imaging plane

Purpose: To assure that the tabletop is leveled and orthogonal with respect to imaging plane Device: Laser QA device Procedure: 1. Place the laser QA device towards the foot of the table (F3-F4) and take a CT scan. 2. Using the scanner cursor tool, measure the location of the central cross and confirm the agreement with the last image taken in Test 4.
 * Test 5:** Orientation of tabletop with respect to imaging plane

Purpose: To assure spatial integrity, CT number accuracy and uniformity. Device: Philips phantom Procedure: 1. Align the body layer (diameter 30 cm) of the phantom to the external lasers and take an axial scan of the phantom. 2. Measure the diameter of the phantom in both the x- and y-directions to confirm spatial integrity. To visualize FWHM, HU level should be around the arithmetic mean of the body phantom and background (~ -450). 3. Measure the mean CT numbers for 1 cm2 region at the center and four locations in the periphery of the Nylon body to confirm uniformity. 4. Measure the area profile for CT numbers for the water hole and Teflon pin. The tolerance for spatial integrity is ±1 mm. The tolerance for CT number accuracy and uniformity are ±5 HU
 * Test 6:** Image performance

** Types of equipment **
Kevin Shun Chung Tsai

Philips Brilliance CT Simulator Stainless Steel Ruler 3-peg CIVCO Laser QA device, LAP laser PDA 2 Smaller Rulers Laser QA device, boxes, BBs Phillips Phantom

**Tolerances(expected):**
Kevin Tharp

Table Vertical and Longitudinal Motion: Both have a tolerance of 1 mm over the range of the table motion. Laser Tracking: 2 mm tolerance. Alignment of external lasers with table motion: 2 mm tolerance. Alignment of external lasers with imaging plane: 2 mm tolerance from the known dimension of -500mm. Orientation of tabletop with respect to imaging plane: The x and y coordinates of the gantry side and at the foot of the table should all be 2mm to be within tolerance. Image Performance: +/- 5HU
 * Mechanical:**

Door interlock: Functional Audio: Functioning
 * Safety:**

CT Number: 2.3 +/- 4HU CT Uniformity: 0.3+/- 4HU CT Noise: 3.7+/- 0.4 HU Water ROI: 3.5 +/- 4HU Teflon ROI: 920 +/- 50HU Nylon ROI: 1400 +/- 1000 Low contrast: 4.5+/- 1.2 HU
 * Image performance:** 1

**Images:**
Kevin Tharp


 * Figure 1**. Ruler measurement (Test 1).
 * Figure 2.** Laser QA device (Test 2, 4, 5)
 * Figure 3.** Rulers (Test 3)
 * Figure 4.** Philips Phantom (Test 6)


 * Figure 5.** Image Performance (Test 6)

**References:**
1. Khan, F. //The Physics of Radiation Therapy//. 4th ed. Baltimore, MD: Lippincott, Williams, and Wilkins; 2010: 380-403. 2. Brilliance CT Configuration. Technical Reference Guide. 2010.

=SRS QA:=

**Procedures**
Spencer Arnold

Depending on the type of machine used (treatment machine for stereotactic radiotherapy), stereotactic radiotherapy quality assurance can be slightly different. Some institutions utilize specialized machines built specifically for this type of treatment (Gamma Knife and Cyber Knife) while others equip their own linear accelerators with a particular SRS package. 1 Although the quality assurance for SRS may seem tedious, it is an important step in assuring the accuracy and safety for each and every patient that gets treatment. In order for these procedures to work, a physicist moves throughout the entire planning process (simulation through treatment), while also conducting the required QA tests. This process is done on a patient load basis, which means that the QA is completed each and every time a patient gets treatment within the clinic. The following sections provide a description on the necessary QA checks done from the time of simulation, up to the actual treatment delivery.

Depending on the tumor site within the brain, the neurosurgeon may choose a specific location to bolt the frame. In some instances, the location of the frame may cause an inadequate fit into the frame system. This causes the physicist to utilize an extension plate for and adequate fit into the framing system.
 * Simulation QA**

Check List:
 * 1) CT Localizer Bird Frame Localization – This piece of equipment sits on top of the head frame during CT simulation.
 * 2) CT Head Holder
 * 3) Laser Target Localization Frame (LTLF) – This piece of equipment is placed above head frame to take measurements of isocenter before and during treatment.

ISO Check:
 * After the simulation scan has been performed, the physicist performs an isocenter check within two separate treatment-planning systems (TPS). The x-axis, y-axis, and z-axis are verified and compared between the two TPS

After the final plan has been checked and approved by both physics and the physician, a final check of the treatment isocenter is done. The x-axis, y-axis, and z-axis are all checked over and compared within two separate planning systems.
 * Treatment Planning System QA**


 * Pre-Treatment QA**
 * 1) Accessory Check – SRS Dot Graticule is measured onset to ensure accuracy for orthogonal imaging.
 * 2) Installing Mechanical Isocenter Stand (MIS) – This piece of equipment is bolted over the pedestal with a mounting system in order to check the laser alignment accuracy. If the lasers are off on the MIS, the physicist will need to adjust the laser alignment and repeat check.
 * 3) After the MIS and lasers have been checked, the MIS is taken off of the pedestal and the SRS hardware is installed. The Rectolinear phantom pointer (RLPP) that points towards the target, and LTLF are attached to check laser alignment on the SRS hardware.
 * 4) Once this equipment had been attached to the table, the physicist zero’s the micro-positioners and roughly sets the LTLF to the laser positions. This process allows the physicist to set specific positions with regard to table sag.
 * 5) Performing Lutz-Winston test on film – This process involves using real-time film to test the accuracy of the isocenter within the frame. 3 different port films at gantry angles of 90°,0°,270° are taken to assess the variability in different positions. After the film has been exposed on all sides, the film is then scanned and digitized into a computer software system to measure the radial distance across the field. Only radial distances of less than 1.5 millimeters (mm) are passed but usually fall within less than 1mm.
 * 6) The last and final step in the pre-treatment QA process is checking the field lights for each and every field being treated. The physicist moves through each field and compares it with the beam eye view (BEV) from the treatment planning system.

During the actual SRS treatment, the physicist will take specific measurements and compare the planned results with the measured results. Before the patient begins treatment, a source to skin distance (SSD) is taken from the anterior posterior (AP) and lateral positions to be compared back to the plan. During the treatment, the physicist takes SSD measurements on every separate arc to also compare back to the plan. These measurements are taken both before and during treatment in order to maintain not only increased accuracy for radiation treatment delivery, but also to monitor the entire process for safety reassurance.
 * Treatment QA**

**Types of Equipment:** 3
Eyob Mathias Head frame: Used to immobilize the head and comfortably position the patient appropriately. Target Positioner: Used to align the isocenter accurately. Localizer: Used in the positioning of the patient. Couch Extension: Mounted on the couch to hold the head frame. Cones: Researches have proven that using cones to treat SRS significantly increases the accuracy of the treatment. Cone mount: This is inserted onto the collimator housing on the accelerator. Tighten the two knobs to secure it in place. Electronic portal imaging device (EPID): Used to assure the proper placement of the isocenter and images are taken at a vertical distance of 70 cm from the isocenter. MV images are acquired at 8 different angle arrangements (4 require room entry to preform couch kicks). A simplified QA software is used to analyze the database and generate a report.

**Tolerances (expected):** 2
Spencer Arnould CT Localization or System Verification Test: 2mm Linear Accelerator/Collimator/Couch:1mm Lasers: 1mm Patient Docking Device: 1mm Frame System: Accurate within +/- 0.6mm for each axis. Dose Delivery: The accuracy of the target should be uncertain by less than 5%, in accordance with AAPM Report 21.

**Images** 3
Eyob Mathias
 * Figure 1.** Brainlab SRS system equipments 3
 * Figure 2:** Treatment couch adjustment tolerances 3


 * Figure 3.** Head frame 3

**References:**
1. Lenards N. //QA of Treatment Planning Computer//. [SoftChalk]. La Crosse, WI: UW-L Medical Dosimetry Program; 2011. 2. American Association of Physicists in Medicine. //Stereotactic Radiosurgery.// http://www.aapm.org/pubs/reports/rpt_54.pdf. Accessed October 1, 2013. 3. Gayou O. Cranial SRS on a Siemens ArtisteTM using the BrainLab iPlan treatment planning system. Available at: http://amos3.aapm.org/abstracts/pdf/68-19924-235349-85578.pdf. Accessed on October 5, 2013. = = = = =Brachytherapy QA:= Jake Osen and Megan Whitley

A brachytherapy quality assurance (QA) program is very important in every radiation therapy clinic. The QA process helps maintain confidence that a consistent and safe dose is delivered every time radiation is administered. This is essential in minimizing damage to healthy tissue while achieving the prescribed dose to the target volume. Strong development and implementation of a QA program can help discover errors and prevent problems. This ensures the safety of the patient and protects physicians, physicists, therapists, and the hospital from potential catastrophic errors and legal consequences. Brachytherapy is much different than external beam therapy. These differences are a result of the presence of a radioactive source versus using electricity to produce a radioactive interaction. Because the radiation is constant, the principal protective measures of time, distance, and shielding are utilized. Although the brachytherapy technique is complex, the primary goals of its QA are to determine that the treatment is safe, and the source is in the correct position for the desired amount of time. In clinic, there are several QA tests performed daily, prior to a patient’s treatment. These standard procedures are also incorporated into the monthly tests to maintain consistency and accuracy. Although the brachytherapy techniques and procedures discussed within this section were all performed on a Varian Varisource iX HDR afterloader, they were done in two different clinics, providing a comparison. Both clinics use Iridium-192 as the radioactive isotope. Below is a list of the QA procedures performed.

**Procedures:**
**Test 1:** **Treatment Vault (shielding)** 1. In all facilities, prior to any brachytherapy procedure, the room should be checked for a pig unit. This container can be used if an incident or an accident occurs and the room, and a radiation free area is needed so that the room can be utilized in a normal manner.
 * Figure 1**. Verification that a pig unit is in the brachytherapy room.

2. Check to make sure the Victoreen 451#RYR functions correctly using the Cs-137 check source. Hold the Victoreen 451P # RYR survey meter next to the check source.


 * Figure 2**: Survey Meter 1

3. Check Primalert light function with check source. Light should turn on when source is placed next to Primalert.


 * Figure 3**. Primalert Light function

4. Check vault camera function. 5. Check vault intercom function. 6. Survey treatment unit (Varian Afterloader). Hold the Survey meter 10 centimeters away from the marked spot on the treatment unit. Exposure rate must be < 1mR/hr.


 * Figure 4 and 5.** Survey Meter 1 and Varian Afterloader 2

7. Check function of Afterloader/Connective tubing function lights. Green (good) or Red (bad)


 * Figure 6.** Varian Afterloader 3


 * Test 2:** **Test Plan (source travel and dwell time)**

8. Check source position using a test plan, PermaDoc, and film. Source is moved through the transfer tubing and instructed to stop at five dwell positions, 1 cm apart, on the film. Pattern on film should show three exposures 1 cm apart, then a 1 cm gap followed by two more exposures.


 * Figure 7.** Source position verification.
 * Figure 8.** Source length verification.

9. Check to make sure Primalert light is turned on when source is out of the treatment unit. 10. Check to make sure the lights mounted on the front of the afterloader are turned on when source is out of the treatment unit. 11. Push the wall mounted emergency off button. Source should retract back into the afterloader.
 * Figure 9.** Emergency off verification

12. Test door open interlock. Source should retract back into the afterloader when the door is opened. 13. Using a stop watch, manually record the length of the time the source is in a predetermined dwell position. In the first facility, the test plan has the source in a dwell position for 30 seconds. The accuracy should be within 2%. In the second facility, the dwell time is 5 minutes and it has to be accurate within 1 second, as seen in the next picture.


 * Figure 10.** Stop watch verification

14. Test the emergency off switch on the console. Source should retract.


 * Figure 11.** Emergency off switch at console

15. Using the tubing with a knot, the afterloader should recognize the obstruction and automatically retract.
 * Figure 12.** Obstruction test

16. Have the test plan try to release the source through channel 4. The afterloader should recognize no transfer tubing or improperly connected tubing and not allow the source to be transferred.




 * Figure 13**. Channel Test 3

17. With the source out in the transfer tubing, unplug the power cord to the treatment console. The backup battery power should automatically retract source.

18. At the end of the test plan, the source should be completely retracted into the afterloader housing. The Primalert light should be off and the survey meter reading should verify.


 * Test 3: Non Radiation Tests (Activity)**

19. Calculate the correct source activity using the Excel spreadsheet and compare it to the activity determined from the HDR computer. 20. Verify Date 21. Verify time of QA 22. Verify emergency procedures are posted 23. Verify emergency kit is complete and accessible.


 * Figure 14.** Check off sheet at the first clinic.


 * Figure 15.** Check off sheet at the second clinic.

The following is a decay table generated at the time of source acceptance. When the source is accepted, the activity is measured and a table is generated to designate what the activity should be each day after delivery. This allows for a comparison of the current activity tracked within the brachytherapy software.


 * Figure 16.** Decay Table

**References:**
1. Fluke Biomedical. Website.[]. Accessed September 30, 2013. 2. Varian medical systems. Website.[|http://www.varian.com/media/oncology/brachytherapy/pdf/VariSource_iX_Brochure.pdf] Accessed September 30, 2013. 3. Varian medical systems. Website.[|http://www.varian.com/media/oncology/brachytherapy/pdf/VariSource_iX_Brochure.pdf] Accessed September 30, 2013.

= IGRT QA: = Pablo Pereira

**CBCT QA:** ‍In recent years the use of different imaging modalities has become commonly used. This technique called Image Guided Radiation Therapy (IGRT) allows for very accurate and fast localization of the target area, while also helping in the protection of critical structures and organs. The use of Cone Beam Computed Tomography (CBCT) in linear accelerators produces three-dimensional images of the region of interest in a relatively short period of time, (usually 1-3 minutes) with a quality that will allow for proper patient setup. In order to ensure this level of accuracy, a comprehensive quality assurance (QA) program needs to be implemented by physics and a combination of tests performed daily, monthly and annually to ensure the proper and safely operation of the imaging equipment.

**Procedures: **
The following tests are part of a comprehensive QA for a CBCT. 1) System safety, 2) Geometric accuracy, 3) Registration and correction accuracy, 4) Image quality, and 5) x-ray tube and generator performance. The following paragraphs will provide a brief description of each one of the tests mentioned above and their functions.


 * Test 1: System safety: ** These system checks are concern mostly with gross safety issues. The prevention of physical harm to patients and motion of the CBCT system if any of the interlocks are triggered. All system interlocks including door interlocks, touch guard and collision detector must be tested and be fully functional.

**Test 2: Geometric accuracy:** Necessary to verify if the isocenter of the CBCT is in agreement with the isocenter of the linear accelerator. These tests are performed daily by a radiation therapist and monthly or after any system repairs by a qualified physicist and or service engineer. A solid structure such as a cube phantom is imaged with the CBCT system and its alignment is checked against the MV treatment beam. During daily checks this can be done with the room lasers. During a more demanding monthly check, the isocenter is checked at multiple angles.

**Test 3: Registration and correction accuracy:** This test is performed in order to verify that the calculation of different shifts (couch movements) by the system is accurate and precise. Targeting of the intended area and avoidance of certain structures is highly dependent on these shifts. A slight misalignment from the system can have dangerous consequences for the patient receiving treatment. This test is accomplished with what is called a cube phantom which contains a predetermined number of fiducial markings inside. A prepared reference image of the cube is used as a reference image. Daily, the cube phantom is setup in an off center location with reference to the rooms lasers and scanned by the operator. The fiducials marks in the reference image and the one taken daily are superimposed on one another and match by making the necessary shifts (couch movements). A second scan is then performed and the alignment of the fiducials is checked again. After the second scan, the shifts should not be greater than 2mm laterally, vertically or longitudinally.

**Test 4: Image quality:** Necessary to insure that the best possible image can be obtained with the lowest dose to the patient, following the as low as reasonable achievable (ALARA) philosophy. A Catphan phantom can be used to test the image quality of a CBCT system. The phantom is leveled and set-up isocentrically at the end of the treatment couch. After a CBCT scan is performed, the different modules and geometrical structures in the phantom are analyzed to test the quality of the image. The spatial resolution of the image can be tested by visually analyzing predetermined line pairs in the Catphan phantom. Geometric tests determined the accuracy of the distances in the phantom and the image obtained. The shifts applied to the phantom or eventually a patient are based on those obtained in an image, making this test extremely important. The CT number linearity and low contrast visibility can also be checked with the Catphan phantom. This is accomplished by checking the differences of known densities in the phantom.

**Test 5:** **X-ray tube and generator performance:** The x-ray generator, x-ray tube and the imaging digital devise are all part of the CBCT imaging equipment. For the safety of the patient and the operator, it is imperative that these components function properly and in a safely manner. The following tests are required to ensure the proper operation of the CBCT components. kVp accuracy and HVL which measure the value chosen by the operator against the generator. HVL measure setting for small and large focal spot sizes. Timer tests measure exposure time values. mA linearity test make sure that mA values remain constant over the full range of different settings. These test are all part of a baseline and acceptance test that are recorded by a qualified physicist.

**Types of Equipment: **
The two most popular systems used in clinical practice include the Varian OBI (Varian Medical Systems, Inc., Palo Alto, CA, USA) Varian Medical Systems and the Elekta XVI system (Elekta AB, Stockholm, Sweden) Elekta.

**Tolerances (expected): **
kV source to isocenter distance: 85.1cm / ±2mm. <span style="font-family: Arial,Helvetica,sans-serif;">kV detector to isocenter distance: 45.1cm / ± 2mm. <span style="font-family: Arial,Helvetica,sans-serif;">Couch movements for registration and correction accuracy: longitudinal, vertical and lateral / ± 2mm.

**<span style="font-family: Arial,Helvetica,sans-serif;">Frequency of Test: **
<span style="font-family: Arial,Helvetica,sans-serif;">Daily QA: Safety checks, geometric accuracy tests, registration and correction accuracy. <span style="font-family: Arial,Helvetica,sans-serif;">Monthly QA: Safety checks, geometric accuracy tests, registration and correction accuracy, image quality check. <span style="font-family: Arial,Helvetica,sans-serif;">Annual QA: x-ray tube and generator tests.

<span style="font-family: Arial,Helvetica,sans-serif;">‍**Images:**
<span style="font-family: Arial,Helvetica,sans-serif;">
 * Figure 1 and 2.** <span style="font-family: Arial,Helvetica,sans-serif; line-height: 1.5;">Cube phantom used at ICI. <span style="font-family: Arial,Helvetica,sans-serif; line-height: 1.5; vertical-align: super;">3

<span style="font-family: Arial,Helvetica,sans-serif;"> <span style="font-family: Arial,Helvetica,sans-serif;">**Figure 3.** Cataphan phantom <span style="font-family: Arial,Helvetica,sans-serif; vertical-align: super;">4 <span style="font-family: Arial,Helvetica,sans-serif;"> <span style="font-family: Arial,Helvetica,sans-serif;">

<span style="font-family: Arial,Helvetica,sans-serif;">**Figure 4 and 5.** Varian CBCT/OBI <span style="font-family: Arial,Helvetica,sans-serif; vertical-align: super;">5

**<span style="font-family: Arial,Helvetica,sans-serif;">References: **
<span style="font-family: Arial,Helvetica,sans-serif;">1. Journal of Applied Clinical Medical Physics. Website. []. Accessed September 23, 2013. <span style="font-family: Arial,Helvetica,sans-serif;">2. Intech Journals. Website. []. Accessed September 26, 2013. <span style="font-family: Arial,Helvetica,sans-serif;">3. Intech Journals. Website. []. Accessed September 26, 2013. <span style="font-family: Arial,Helvetica,sans-serif;">4. Journal of Applied Clinical Medical Physics. Website. []. Accessed September 25, 2013. <span style="font-family: Arial,Helvetica,sans-serif;">5. Varian medical systems. Website. []. Accessed September 25, 2013.

Pablo Pereira

<span style="font-family: Arial,Helvetica,sans-serif;">In order to ensure the proper and safely use of the all equipment used in radiation therapy for imaging purposes, institutions must comply with certain guidelines designed in the interest of safety. The use of On Board Imaging (OBI) has become one of the most useful tools in the fight against cancer. The American Association of Physics in Medicine (AAPM) task group (TG) 142 has published a report with recommendations for radiation therapy institutions to follow when using Image Guidance Radiation Therapy (IGRT) techniques. A quality assurance (QA) program must be implemented by a qualified physics department prior to use. The following paragraphs will describe the procedures and the purpose for such a QA program.
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 1.3em;">KV Imaging QA: **

**<span style="font-family: Arial,Helvetica,sans-serif;">Procedures: **
<span style="font-family: Arial,Helvetica,sans-serif;">**Test 1:Collision interlocks:** Tested by triggering the different interlocks that interrupt the motion of the imaging device. <span style="font-family: Arial,Helvetica,sans-serif;">**Test 2: Mechanical:** the x-ray source and imaging panel should be checked periodically (daily), the KVD and the KVS are to be measured with a ruler and the know differences should be compared (annually). <span style="font-family: Arial,Helvetica,sans-serif;">**Test 4:** **Image and treatment coincidence:** Similar to the positioning and repositioning test, images are taken at 0°, 90°, 180°, and 270° to check measurements and discrepancies. <span style="font-family: Arial,Helvetica,sans-serif;">**Test 5:** **Scaling accuracy:** Performed imaging a cube phantom embedded with multiple radiopaque markers and checking the distances between the central markers and the peripheral markers. These values are then compared to known predetermined distances. <span style="font-family: Arial,Helvetica,sans-serif;">**Test 6:** **Uniformity and noise:** Image intensity of a predetermined area is acquired. A deviation of ±5% should be in agreement with baseline values.
 * <span style="font-family: Arial,Helvetica,sans-serif; line-height: 1.5;">Test 3: Imaging positioning and repositioning: **<span style="font-family: Arial,Helvetica,sans-serif; line-height: 1.5;"> A cube phantom with radiopaque fiducials inside is placed on the treatment couch at the isocenter. The phantom is then shifted to a known distance from the isocenter, orthogonal KV images are then taken and the proper couch shifts are then applied to bring the cube phantom back to the isocenter location. The distances are then compared and a match of ±2 mm should be obtained.

**<span style="font-family: Arial,Helvetica,sans-serif;">Types of Equipment (provide links when possible): **
<span style="font-family: Arial,Helvetica,sans-serif;">The following equipment is included in the QA procedures. The KV x-ray Source (KVS), and KV amorphous silicon detector (KVD) which are the components of the OBI system. They can produce a 2D radiographic acquisition and or a 2D fluoroscopic image. Equipment for QA measurements include: <span style="font-family: Arial,Helvetica,sans-serif;">a) Leeds phantom: A Leeds phantom TOR 18 FG (Leeds test objects Ltd, North Yorkshire, UK) is used to quantify the spatial resolution and contrast of the planar KV OBI imaging system. <span style="font-family: Arial,Helvetica,sans-serif;">b) UnforsXi system: (Unfors Instruments AV, Billdal, Sweden), is used to measure the dosimetric characteristics of the KV 2-D OBI and also for the 3D CBCT system. It consists of several external detectors. These detectors measure values such as radioscopy/fluoroscopy (R/F). The R/F consists of two sensors, R/F low for low dose rate measurements and R/F high for high dose rate measurements.

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<span style="font-family: Arial,Helvetica,sans-serif;">Novalis treatment system Novalis Radiosurgery Varian Medical Systems (Varian, Palo Alto, CA), and the BrainLAB [|BrainLAB] (Heimstetten, Germany), are two examples of OBI imaging built into the Varian Trilogy linear accelerator for the purpose of obtaining imaging of the region of interest (ROI) prior to delivering radiation therapy to patients. =====

**<span style="font-family: Arial,Helvetica,sans-serif;">Images: **
<span style="font-family: Arial,Helvetica,sans-serif;">

<span style="font-family: Arial,Helvetica,sans-serif;">**Figure 1:** Cube Phantom with embedded fiducial markers. <span style="font-family: Arial,Helvetica,sans-serif; vertical-align: super;">3

<span style="font-family: Arial,Helvetica,sans-serif;">


 * <span style="font-family: Arial,Helvetica,sans-serif;">Figure 2. **<span style="font-family: Arial,Helvetica,sans-serif;">Varian Trilogy OBI KV Imager. <span style="font-family: Arial,Helvetica,sans-serif; vertical-align: super;">4

<span style="font-family: Arial,Helvetica,sans-serif;"> <span style="font-family: Arial,Helvetica,sans-serif;">**Figure 3.** Scaling Accuracy Equipment. <span style="font-family: Arial,Helvetica,sans-serif; vertical-align: super;">5

**<span style="font-family: Arial,Helvetica,sans-serif;">References: **
<span style="font-family: Arial,Helvetica,sans-serif; font-size: 1.033em; line-height: 1.5;">1.Journal of Applied Medical Physics. Website. []. Accessed September 22, 2013 <span style="font-family: Arial,Helvetica,sans-serif; font-size: 1.033em; line-height: 1.5;">2. American Association of Physics in Medicine. Website. []. Accessed September 28, 2013. <span style="font-family: Arial,Helvetica,sans-serif; font-size: 1.033em; line-height: 1.5;">3. Varian medical systems. Website. []. Accessed September 24, 2013. <span style="font-family: Arial,Helvetica,sans-serif; font-size: 1.033em; line-height: 1.5;">4. Journal of Applied Medical Physics. Website. []. Accessed September 26, 2013. <span style="font-family: Arial,Helvetica,sans-serif; font-size: 1.033em; line-height: 1.5;">5. Journal of Applied Medical Physics. Website. []. Accessed September 27, 2013.

- Ashley Pyfferoen
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 17px;">ExacTrac Imaging QA: **

**Procedures:**

 * 1) Imaging Positioning**:** Monthly alternating tests are performed to ensure that ExacTrac correctly identifies soft tissue anatomy.
 * **Test 1: Winston-Lutz:** A frame is mounted to the treatment couch that suspends a rod over free space (Figure 1). The couch is aligned so the room lasers perfectly intersect the rod across the cross hairs (Figure 2). Inside the rod, a BB is detected by the ExacTrac imaging system. An ExacTrac X-ray image is obtained and the image is sent to the imaging console for evaluation (Figure 3). If the BBs and cross hairs on the image do not perfectly intersect, the program provides coordinates to adjust the imaging equipment (Figure 4).
 * **Test 2: Solid Water Phantom:** The solid water phantom contains objects detectable by the ExacTrac system including radiopaque catheters and a balloon containing a contrast agent. The phantom is scanned through the CT simulator and the information is sent to ExacTrac (just like a real patient). The solid water phantom is placed on the treatment couch and aligned to isocenter with the in-room lasers. An ExacTrac image is obtained. The robotic couch makes the necessary shifts to align isocenter. The physicist shifts away from iso 1 cm longitudinal, 1 cm lateral and 1 cm vertical. Another image is obtained at those shifts. The ExacTrac system should instruct to move those coordinates to return to isocenter. The shifts should be within 1 mm in any direction.

**Types of Equipment (provide links when possible):**

 * 1) Winston-Lutz Frame and Rod
 * 2) ExacTrac Imaging Software
 * 3) Brain Lab Evaluation Software

**Tolerances (expected):**

 * 1) Winston Lutz: Less than 1 mm in any direction
 * 2) Solid Water Phantom Shifts:Less than 1 mm in any direction

**Images:**

 * Figure 1.** Frame and Winston-Lutz rod mounted on treatment couch.
 * Figure 2.** Laser alignment of Winston-Lutz ExacTrac test.
 * Figure 3.** BB and cross hair alignment.
 * Figure 4.** Shifts to isocenter are less than 1mm.

Links:

 * 1) I invite you to explore this link for a better understanding of ExacTrac imaging. (**ExacTrac Video)** 1

**References:**

 * 1) ExacTrac Snap Verification. Youtube Web Site. [] . Accessed September 30,2013.


 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 17px;">MV Imaging QA: **

**Procedures**

 * 1) **Test 1: Isocenter Alignment:** The isocenter is displayed via cross hairs in a light field emanating from the gantry head. A ruler is used to measure from the field edge in the X and Y direction to verify that isocenter is centered perfectly within the open field (Figure 1).
 * 2) **Test 2: Distance Consistency Check:** To verify the distance remains consistent between the source and the detector, the distance is manually measured to the laser intersections. The distance from the detector to the source is 150 cm. We are not able to measure to the detector manually due to the detector cover but it is measured each month to maintain a consistent distance (Figure 2).
 * 3) **Test 3: Dark and Flood Field Check:** A Sun Nuclear MV phantom is placed on the treatment table to analyze noise and radiation exposure (Figure 3). The phantom is imaged at 6MV energy and Brain Lab analyzes the background noise of the image (Figure 4). The phantom is imaged again with a "flood" of radiation (Figure 5). Brain Lab software analyzes the pixel differences between the 2 images and corrects for dead pixels.
 * 4) **Test 4: Contrast, Uniformity and Resolution:** An image of the Sun Nuclear MV phantom is taken and analyzed for contrast, uniformity and resolution using the Dose Lab Analysis Program (Figure 6). The program analyzes each of these aspects and gives a pass or fail rating (Figure 7).

**Types of Equipment (provide links when possible):**

 * 1) MV Imaging Detector
 * 2) Light Field
 * 3) Tape Measure
 * 4) Ruler
 * 5) Sun Nuclear MV-QA Phantom (Sun Nuclear Link) 1
 * 6) Brain Lab Evaluation Software

**Tolerances (expected):**

 * 1) Isocenter Alignment: Less than 1 mm in any direction
 * 2) Distance Consistency Check:Consistent measurement from month to month
 * 3) Dark and Flood Field Check: No tolerance (measured for calibration corrections in pixels)
 * 4) Contrast, Uniformity and Resolution: Baseline (Contrast = +/- 1%, Contrast-to-Nose Ratio= +/- 4, Uniformity= +/- 2%)

**Images:**

 * Figure 1**. Cross hair in light field on the image detector.


 * Figure 2.** Physicist pictured measuring the detector to laser distance.
 * Figure 3.** Sun Nuclear MV phantom.


 * Figure 4.** Noise analysis.
 * Figure 5.** Flood Field.


 * Figure 6.** Measurement of contrast, resolution and uniformity.
 * Figure 7**. Evaluation of the contrast, resolution and uniformity of the MV image by Brain Lab software.

References:

 * 1) Your Most Valuable QA & Dosimetry Tools. Sun Nuclear Web site. [] . Accessed October 2, 2013.