The use of computed tomography (CT) in routine diagnostic imaging, and in conjunction with PET and MRI images for nuclear medicine,
and radiation oncology treatment planning has expanded rapidly in recent years. To obtain optimum images with a CT scanner, it is
necessary to have a detailed quality assurance (QA) and quality control (QC) program in place. Each manufacturer supplies a QC phantom
and a recommended test protocol with the its scanners. The tests involve daily and weekly measurements by the CT technologist and
monthly, semi-annual, and annual tests by the technologists, service engineers, and medical physicists. Tests for noise, CT# for water and
common plastics used to simulate tissue, uniformity, CT# linearity, low contrast sensitivity, high contrast spatial resolution, slice thickness,
beam quality, distance measurement accuracy, laser alignment, couch positioning, and couch indexing accuracy will be presented. A
variety of QC phantoms developed by medical physicists, CT manufacturers, and other interested parties will be discussed including those
with both regular and anatomical shapes. Specific measurement techniques required for helical/spiral scanners with single- or multi-row
detector elements will be presented. Image quality tests for associated peripheral devices or systems such as laser film imagers and PACS
will also be discussed. Measurement of and presentation of CT patient dose and personnel scatter information will be mentioned briefly, but
is covered in detail in another presentation in this series.
Educational objectives:
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3.
Become familiar with the many elements of a quality control program for computed tomography facilities
Understand the design and construction of various test phantoms and test instruments
Understand the test procedures required in a quality control program for CT