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Cold spot in the uniform Co-57 image may not necessarily be due to photomultiplier tube failure or variations in photomultiplier tube tuning: A technical note.

Pandey AK, Karunanithi S, Patel CD, Sharma SK, Bal C, Kumar R - Indian J Nucl Med (2015 Apr-Jun)

View Article: PubMed Central - PubMed

Affiliation: Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India.

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Sir, The reason for cold spot in the uniform Co-57 image has been reported as the variation in photomultiplier tube (PMT) tuning or PMT failure... In this report, we found that this problem can also be related with the electronic board that stores the correction maps (such as uniformity, energy, and sensitivity) and applies necessary correction on the acquisition data acquired during the static or dynamic acquisition with the gamma camera... On performing the routine daily extrinsic uniformity test on Symbia E Dual Head Gamma Camera (Symbia E, Siemens Medical Solutions, Illinious, USA), we found a cold spot on gamma camera with detector head 2... We later performed several interventions to sort the issue... The interventions we performed and the corresponding results we obtained are elaborated in Table 1... As detailed in Table 1, The PMT tuning was performed and still the cold spot persisted... Before coming to conclusion that PMT number 57 has failed and it needs replacement, the acquisition electronic board (AEB) was replaced... The variation in uniformity across the FOV can also be due to the hygroscopic nature of the NaI (Tl) detector... NaI (Tl) captures the water vapor and becomes yellow leading to decrease in light transmission in that area... That is why the AEB was replaced with the board... The appearance of hot and cold spots in the flood image may be due to the variation in PMT tuning or PMT failure... From Figure 2, it is clear that problem can also be in the AEB, or the cable that is driving the signal from the PMT to the AEB... This report highlights the importance of considering the problem with AEB can also be a reason for the cold spot in the uniform Co-57 image apart from the usual reasons like the variation in PMT tuning or PMT failure.

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Related in: MedlinePlus

The Co-57 flood image, 20% symmetric window, 256 × 256 matrix size and 500 k counts. A discrete, semicircular cold indentation can be appreciated in the lower region of the field of view. Semi-circular pattern delineated by borders of increased count. This was due to a defect in the electronic board which stores and applies correction factors on static and dynamic images
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Figure 1: The Co-57 flood image, 20% symmetric window, 256 × 256 matrix size and 500 k counts. A discrete, semicircular cold indentation can be appreciated in the lower region of the field of view. Semi-circular pattern delineated by borders of increased count. This was due to a defect in the electronic board which stores and applies correction factors on static and dynamic images

Mentions: On performing the routine daily extrinsic uniformity test on Symbia E Dual Head Gamma Camera (Symbia E, Siemens Medical Solutions, Illinious, USA), we found a cold spot on gamma camera with detector head 2. The uniformity test was performed with Co-57 flood source (Co-57, Serial Number: 1717-119, 10 mCi, Reference date: 1-February-2014, from Eckert and Ziegler Isotope Products, Medical Imaging Laboratory, 24937 Avenue Tibbitts, Valencia, California 91355, USA). The uniformity image was acquired in 256 × 256 matrix size for 500 k counts on individual detector. The image we obtained is depicted in Figure 1. Initially we thought that the cold spot might be either because of failure of one of the PMTs corresponding to that position or the corresponding PMT may be out of tune in comparison to their surrounding PMTs. We later shut down the system and restarted it. Even then the cold spot persisted. Hence, the system engineer's support was taken to resolve this issue. We later performed several interventions to sort the issue. The interventions we performed and the corresponding results we obtained are elaborated in Table 1. As detailed in Table 1, The PMT tuning was performed and still the cold spot persisted. Before coming to conclusion that PMT number 57 has failed and it needs replacement, the acquisition electronic board (AEB) was replaced. After replacing another spare electronic board, the intrinsic and extrinsic Co-57 flood source image were acquired and we obtained the uniform image without the cold spot.


Cold spot in the uniform Co-57 image may not necessarily be due to photomultiplier tube failure or variations in photomultiplier tube tuning: A technical note.

Pandey AK, Karunanithi S, Patel CD, Sharma SK, Bal C, Kumar R - Indian J Nucl Med (2015 Apr-Jun)

The Co-57 flood image, 20% symmetric window, 256 × 256 matrix size and 500 k counts. A discrete, semicircular cold indentation can be appreciated in the lower region of the field of view. Semi-circular pattern delineated by borders of increased count. This was due to a defect in the electronic board which stores and applies correction factors on static and dynamic images
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4379689&req=5

Figure 1: The Co-57 flood image, 20% symmetric window, 256 × 256 matrix size and 500 k counts. A discrete, semicircular cold indentation can be appreciated in the lower region of the field of view. Semi-circular pattern delineated by borders of increased count. This was due to a defect in the electronic board which stores and applies correction factors on static and dynamic images
Mentions: On performing the routine daily extrinsic uniformity test on Symbia E Dual Head Gamma Camera (Symbia E, Siemens Medical Solutions, Illinious, USA), we found a cold spot on gamma camera with detector head 2. The uniformity test was performed with Co-57 flood source (Co-57, Serial Number: 1717-119, 10 mCi, Reference date: 1-February-2014, from Eckert and Ziegler Isotope Products, Medical Imaging Laboratory, 24937 Avenue Tibbitts, Valencia, California 91355, USA). The uniformity image was acquired in 256 × 256 matrix size for 500 k counts on individual detector. The image we obtained is depicted in Figure 1. Initially we thought that the cold spot might be either because of failure of one of the PMTs corresponding to that position or the corresponding PMT may be out of tune in comparison to their surrounding PMTs. We later shut down the system and restarted it. Even then the cold spot persisted. Hence, the system engineer's support was taken to resolve this issue. We later performed several interventions to sort the issue. The interventions we performed and the corresponding results we obtained are elaborated in Table 1. As detailed in Table 1, The PMT tuning was performed and still the cold spot persisted. Before coming to conclusion that PMT number 57 has failed and it needs replacement, the acquisition electronic board (AEB) was replaced. After replacing another spare electronic board, the intrinsic and extrinsic Co-57 flood source image were acquired and we obtained the uniform image without the cold spot.

View Article: PubMed Central - PubMed

Affiliation: Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India.

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

Sir, The reason for cold spot in the uniform Co-57 image has been reported as the variation in photomultiplier tube (PMT) tuning or PMT failure... In this report, we found that this problem can also be related with the electronic board that stores the correction maps (such as uniformity, energy, and sensitivity) and applies necessary correction on the acquisition data acquired during the static or dynamic acquisition with the gamma camera... On performing the routine daily extrinsic uniformity test on Symbia E Dual Head Gamma Camera (Symbia E, Siemens Medical Solutions, Illinious, USA), we found a cold spot on gamma camera with detector head 2... We later performed several interventions to sort the issue... The interventions we performed and the corresponding results we obtained are elaborated in Table 1... As detailed in Table 1, The PMT tuning was performed and still the cold spot persisted... Before coming to conclusion that PMT number 57 has failed and it needs replacement, the acquisition electronic board (AEB) was replaced... The variation in uniformity across the FOV can also be due to the hygroscopic nature of the NaI (Tl) detector... NaI (Tl) captures the water vapor and becomes yellow leading to decrease in light transmission in that area... That is why the AEB was replaced with the board... The appearance of hot and cold spots in the flood image may be due to the variation in PMT tuning or PMT failure... From Figure 2, it is clear that problem can also be in the AEB, or the cable that is driving the signal from the PMT to the AEB... This report highlights the importance of considering the problem with AEB can also be a reason for the cold spot in the uniform Co-57 image apart from the usual reasons like the variation in PMT tuning or PMT failure.

No MeSH data available.


Related in: MedlinePlus