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Validation of PET/CT Measurements of Cobalt 57sheet Source Radionuclidic Impurities

L Zimmermann*, D Jordan , University Hospitals Cleveland Medical Center, Cleveland, OH


(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: In nuclear medicine, ��Co sheet sources are commonly used to check gamma camera detector uniformity. These sources typically have small amounts of ��Co and ��Co impurities which can affect detector uniformity measurements due to their high energy photon emissions, including positron emission annihilation photons. This work extends previously-published methods by validating them on an additional PET/CT scanner platform using settings available in a clinical environment.

Methods: A ��Co sheet source was scanned on a Philips Ingenuity TF PET/CT scanner to acquire annihilation photons from positron emission decays of ��Co and ��Co, over a period of 6 months. Standard whole-body PET reconstruction was used with the “high quality� option. No other special reconstruction or processing was used. In the reconstructed images, an ROI was placed over the source in each slice to measure activity concentration (Bq/mL). The concentration was multiplied by the ROI volume to obtain the activity in each slice, slice activities were summed to determine the total activity. The effectiveness of the scanner in quantifying the weak positron emissions from the ��Co and ��Co contaminants in the high single-photon background from the ��Co was also evaluated.

Results: Measurements of the ��Co and ��Co impurity activity agreed with the vendor’s specified activity and an exponential decay model with a half-life consistent with a mixture of ��Co and ��Co. The true coincidence rate for each scan versus single counts was calculated as a measure of the scanner’s effectiveness in quantifying the weak impurity positron emissions from.

Conclusion: ��Co sheet source contamination can be easily measured on a PET/CT scanner in a clinical setting by scanning the source and measuring the activity in the slices. The PET/CT scanner used in this study was effective in making these activity measurements at a ratio of true coincidences versus singles of 0.02 PPM.


Gamma Cameras, Quality Assurance, PET


IM- Nuclear Medicine General: Gamma Camera or other (other than PET/SPECT)

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