AbstractID: 8138 Title: Quality Assurance of MVCT imaging
The TomoTherapy system (TomoTherapy, Inc., Madison, WI) is designed to deliver
intensity modulated radiation therapy using a helical tomotherapy approach. In addition,
megavoltage computed tomography (MVCT) images can be acquired with the system.
MVCT images can be used to check the positioning of the patient prior to treatment. The
acquired MVCT image is registered with planning CT to determine if corrections to the
patient position are required.
Upon acceptance the registration accuracy and precision should be evaluated. Phantombased test are well suited for these tests. In addition the precision of registering clinical
images should be evaluated. Standard phantom test can be used to monitor the image
quality of MVCT images. The image noise, Hounsfield unit (HU) consistency, image
uniformity, and resolution can be tested. In addition the imaging dose should be
monitored on a routine basis.
A daily and monthly QA procedure can be implemented to monitor the consistency of all
relevant procedures. On a daily basis a phantom-based test patient can be scanned to test
the consistency of the image registration. This image can also be inspected for gross
image artifacts. On a monthly basis a scan of a modular phantom can be used to monitor
image noise, Hounsfield units, image uniformity and resolution. The imaging dose can be
measured simultaneously.
MVCT images are suitable for accurate dose recalculations. This requires the acquisition
of a MVCT HU to electron density calibration curve. The accuracy of this calibration
should be tested using an inhomogeneous rigid phantom.
Educational Objectives:
1) Identify tests to measure relevant QA parameters
2) Understand the difference between the inherent system and clinical accuracy and
precision
3) Identify and implement test procedure for routine monitoring of relevant QA
parameters
Conflict of interest: Research agreement with TomoTherapy, Inc.