Radiology Quality Control and Optimization

Vocabulary flashcards for key concepts in radiology quality control and dose optimization.

Optimization in Diagnostic Radiology

A process of balancing diagnostic information (image quality) and patient dose to minimize radiation risk while maximizing information content.

Justification

Ensuring an exam is medically indicated.

Optimization (ALARA)

Performing exams using doses that are As Low As Reasonably Achievable (ALARA).

Limitation

Limiting doses to occupationally exposed individuals and patients to recommended levels.

Spatial Resolution

The degree of blurring in an image; the ability to discriminate objects of varying densities close together against a uniform background.

Line Pairs Phantom

A phantom used to measure the degree of blurring in an image, containing closely spaced metal strips.

Spatial Frequency

The number of line pairs visible per unit length.

Contrast Resolution

Also called low contrast or tissue resolution; the ability of the scanner to demonstrate small changes in tissue contrast.

Contrast Resolution Determination

Characterized by Hounsfield units or Linear Attenuation Coefficients (CT numbers).

Contrast Resolution Test

Evaluated using a phantom containing objects of varying sizes and with small differences in density (4 to 10 HU).

Slice Thickness Accuracy Test

Measured using a phantom that includes a step-wedge, containing objects with known measurements to provide a standard for comparison.

Laser Light Accuracy Test

Measured using a specific phantom designed for the purpose and provided by the scanner manufacturer.

Noise Test

Measured using a water phantom; measured by obtaining the standard deviation of CT numbers within a Region of Interest (ROI).

Uniformity

Refers to the ability of the scanner to yield the same CT number regardless of the location of an ROI within a homogeneous object.

Uniformity Test

Measured by placing several ROIs within a water phantom, aiming for all to have the same Hounsfield Unit (HU).

Linearity

The relationship between CT numbers and the linear attenuation values of the scanned object at a selected kVp value.

Linearity Test

Measured using a phantom that contains a variety of objects with known densities.

Computed Tomography Dose Index (CTDI)

A special quantity that expresses radiation dose in CT, measured with a dosimeter inserted into a phantom.

Multiple Scan Average Dose (MSAD)

The radiation dose delivered to a patient when a series of scans are performed.

CT Image Artifact

Anything appearing on the image that is not present in the object scanned.

CTDIvol and DLP

Displayed on many CT scanners to help the technologist achieve protocol optimization.

Optimization

Exams must be performed using doses that are As Low As Reasonably Achievable, consistent with the diagnostic task. ALARA acronym

Linearity

Refers to the relationship between CT numbers and the linear attenuation values of a scanned object at a selected kVp value

Linearity

The ability of the CT imager to correctly categorize the correct Hounsfield Unit (HU) to any particular tissue density.