Download 08. Gammacamera imaging - RPOP

Radiation Protection in Nuclear Medicine
PRACTICAL SESSION 8
GAMMACAMERA IMAGING
BACKGROUND
The quality of a gamma camera image is dependent on several operational factors
such as the count density, which affects the noise level and the contrast resolution,
the distance between the detector and the patient, which affects the geometric resolution, and the window setting, which affects the registered amount of scattered radiation. A proper operation of the gammacamera by a well-trained staff is essential for a
high quality practice.
AIM
The aim of this practical section is to demonstrate how an optimised use of the
equipment will increase the image quality and hence the diagnostic quality (sensitivity
and specificity).
MATERIAL
Sources
 Tc-99m
Other equipment
 Total performance phantom for planar imaging (emission or transmission)
PROCEDURE
Fill the phantom with about 50 MBq Tc99m. Use an all purpose collimator on the
gammacamera. Acquire images in 256 x 256 matrix.
Count density
Acquire images with 50000, 100000, 200000, 500000 and 1000000 counts. Analyse
the images in terms of contrast resolution.
Distance
Acquire images (1000000 counts) with the phantom at 0, 10 and 20 cm from the collimator. Analyse the images in terms of geometric resolution.
Window setting
Acquire images (1000000 counts) with a centered energy window, with the energy
window centered 10% towards lower energy and centered 10% towards higher energy. Record the imaging times. Analyse the images in terms of contrast resolution and
geometric resolution.
1
Radiation Protection in Nuclear Medicine
PRACTICAL SESSION 8
CONCLUSIONS
2