Gamma | Comprehension and appropriate use of a flood table on a gamma…

Jae Il Kim, 1 Jeom Jin Im, 1 Seong Wook Cho, 2 Jin Eui Kim, 1 and Hyun Joo Kim 1

Departments of Nuclear Medicine, Seoul National University, Seoul, Korea

Background and Purpose:  Uniformity  is the one of the important  quality control  features with respect to gamma cameras. To maintain adequate uniformity, we must acquire suitable flood table (= flood  map) data because the flood table effects energy, and the type or dose of input radiation. Therefore, in this study we evaluated the difference in uniformity when uniformity  does not match between the type of input  radiation  and the flood  table data or collimator type.

Subjects and Methods:  For input  radiation,  we prepared 10 mCi of 57Co,  99mTc, and 201Tl.

Using SKYLight (Philips) and Infinia gamma cameras (GE), we acquired nine uniformity  data that were corrected by technetium,  cobalt flood  table and did not  corrected image for the three sources. Additionally, we acquired two uniformity  images with a collimator that were corrected by intrinsic and extrinsic flood tables. Using this data, we evaluated and compared the uniformity  values.

Results: In the case of  the SKYLight  gamma camera,  the uniformities  of  the images that matched between the input  radiation  and flood  table with  respect to  99mTc and 57Co were better than the unmatched uniformity, as shown in Table 1. However, because there was no thallium   flood   table,  the  uniformities   of  images  at  Tl  were  significantly  incorrect.  The uniformities  of  the  Infinia  gamma  camera had the  same pattern  as the  SKYLight gamma camera.   Moreover,   the  uniformity   of  the  99mTc  image  acquired  with   a  collimator   and corrected by an extrinsic flood table was better than the intrinsic flood table.

Conclusion:   Correcting  an  image  by  a  suitable  flood   table  can  help  achieve  better uniformity   for  a  gamma  camera.  Therefore,   we  have  to  acquire  images  with  suitable uniformity   correction,  and  update  the  flood   table  periodically.  Whenever  we  acquire  a nuclear medicine image,  we always have to check the appropriate  flood  table according to the acquired condition.