SPECT and SPECT/CT Instrumentation

Subgroup IV: Instrument Operations and Quality Control

factors affecting SPECT image quality

• collimator

• distance

• time per stop

• image matrix

What QC procedures are used on SPECT cameras?

uniformity correction map, pixel sizing, center of rotation, SPECT phantom

SPECT uniformity correction map frequency

weekly

SPECT uniformity correction map source

Co-57 sheet source

SPECT uniformity correction map counts

64 × 64 matrix — 30 million counts
128 × 128 matrix — 120 million counts

SPECT pixel sizing procedure

two point sources 10 cm apart, measure the pixels between peaks on a count profile of the image

SPECT pixel sizing calculation

(FOV dimension) / (matrix dimension) = mm/pixel

SPECT center of rotation purpose

aligns physical axis of rotation with center of 3D image matrix, checks for effects of gravity and mechanical variations in rotation

SPECT center of rotation frequency

weekly

SPECT center of rotation source

~300 uCi Tc99m line source

SPECT center of rotation acceptable results

X-offset ≤ 0.5 pixel deviation, X-offset range < 1 pixel

SPECT phantom purpose

verify SPECT detector uniformity, resolution, contrast

SPECT phantom frequency

monthly or quarterly

SPECT phantom source

Tc99m filled phantom

SPECT cylindrical phantom evaluates

tomographic uniformity

SPECT Jaszczak phantom evaluates

overall performance

What SPECT phantom is depicted?

Jaszczak phantom

What does a ring artifact indicate?

non-uniformities in the flood, COR problems

What artifact is depicted?

ring artifact

What does a ray artifact indicate?

filtered backprojection errors