Nuclear Medicine: Gamma Camera and Radiation Units

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Questions and Answers

What is the conversion rate of 1 millicurie to megabecquerel?

37 (correct)

What is the purpose of a flood field or sheet phantom?

To measure radioactivity

To check uniformity of detector response (correct)

To measure radiation exposure

To calibrate the gamma camera

What type of radiation is used in a flood field or sheet phantom?

Gamma radiation

Cobalt-57 (57Co) (correct)

Beta radiation

Alpha radiation

What would a defective photomultiplier show as in the image?

An area of reduced counts Signup and view all the answers

What would a cracked crystal show as in the image?

A linear defect Signup and view all the answers

Why are regular checks needed for photomultipliers?

To monitor for deterioration Signup and view all the answers

What is the purpose of background radiation checks?

To identify contamination Signup and view all the answers

What does a high reading obtained with the collimator in place indicate?

Contamination on the collimator Signup and view all the answers

What type of radiation is similar to 99mTc in gamma emission?

Cobalt-57 (57Co) Signup and view all the answers

What is the primary function of a flood field or sheet phantom?

To check the uniform response of the detector Signup and view all the answers

What is the result of a non-uniform detector response?

An area of reduced counts in the image Signup and view all the answers

What is the purpose of analyzing counts in each pixel?

To compensate for non-uniform detector response Signup and view all the answers

What is indicated by a high reading obtained with the camera orientation changed?

Contamination on the crystal or camera head Signup and view all the answers

Why is cobalt-57 used in a flood field or sheet phantom?

Because it has a similar gamma emission to 99mTc Signup and view all the answers

What is the purpose of a gamma camera?

To produce a uniform image of a uniform field Signup and view all the answers

What is the result of a defective photomultiplier?

An area of reduced counts in the image Signup and view all the answers

What is the purpose of regular checks on photomultipliers?

To monitor any deterioration in the photomultipliers Signup and view all the answers

What is the result of a cracked crystal?

A linear defect in the image Signup and view all the answers

Study Notes

Converting Units

1 millicurie (mCi) is equal to 37 megabecquerel (MBq)

Characteristics and Quality Assurance of Gamma Images

A conventional gamma camera should give a uniform response to a uniform field
A flood field or sheet phantom is used to check uniformity of detector response
Flood field consists of a flat sealed plate, larger than the FOV, and usually filled with cobalt-57 (57Co)
57Co has a similar gamma emission to 99mTc but is longer-lived
Uniform image with collimator in place indicates proper functioning
Defective photomultiplier appears as an area of reduced counts in the image
Cracked crystal appears as a linear defect

Uniformity of Detector Response

Non-uniformity caused by individual photomultiplier differences can be analyzed and compensated automatically
Regular checks are necessary to monitor photomultiplier deterioration
Background radiation checks identify contamination of the gamma camera, collimator, or local unshielded source
High reading obtained regardless of camera orientation indicates contamination on the crystal or camera head
High reading obtained with collimator in place indicates collimator contamination

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Description

Test your knowledge of gamma cameras, radiation units, and quality assurance in nuclear medicine. Learn about the conversion of mCi to MBq, characteristics of gamma images, and uniformity of detector response.