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Ultra-low Dose CT for Attenuation Correction of 82Rb Cardiac PET

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Aim: Myocardial perfusion imaging (MPI) using cardiac PET with tracers like 82Rb and 15O-water is substantially lower in radiation dose than classic MIBI-based SPECT. However, for cardiac PET, the dose contribution of CT for attenuation correction (CTAC) is typically 20-30% of the total dose. To reduce the total radiation dose of cardiac PET further, we set out to examine if the use of ultra-low dose CTAC (UL-CTAC) would affect the accuracy of the quantitative parameters related to MPI. Furthermore, we examined whether the low quality of the UL-CTAC would affect the technologist’s ability to perform manual adjustment for misalignment between PET and CTAC. The CT reconstruction algorithm Q.AC was used to improve quality and consistency of the CTAC. Method: 23 consecutive clinical patients (BMI: 26.9 [range: 15.4-38.8]) referred for 82Rb PET rest and stress imaging were included in the study. All patient received both a normal dose CTAC (120 kVp, 0.5s rotation, 10-100 mA (Smart mA), Noise Index 46) and an UL- CTAC (100 kVp, 0.7s rotation, 10-40 mA (Smart mA), Noise Index 125) prior to the rest PET scan. The same CTAC was used for correction of both rest and stress scans. Manual adjustment for misalignment between PET and CT was performed independently for both CTAC and UL-CTAC. Data was analyzed using QPET (Cedar Sinai). Static uptake images were analyzed (%Summed Scores, %Extend, %Reversible and Total Perfusion Deficit (TPD)), and parameters were compared by using scatter plots and linear regression. CTAC radiation dose was estimated from Dose Length Product using a conversion factor of 0.014 mSv/(mGy cm). All patients were scanned on a GE Discovery MI Digital Ready PET/CT. PET images were reconstructed using Time-of-Flight, Resolution Recovery, attenuation and scatter corrections. Results: CTAC dose was reduced from 0.5 mSv [range: 0.1-1.1] to 0.11 mSv [range: 0.1-0.2]. Manual adjustment for misalignment between PET and CTAC was performed without any difficulties on all images. Excellent correlation between normal dose CTAC and UL-CTAC was found for all MPI parameters (Summed Scores: y=0.96x+0.02, R2=0.95; %Extend: y=0.99x+0.80, R2=0.97; %Reversible: y=0.86x+0.84, R2=0.94; TPD: y=0.99x+0.76, R2=0.97). Conclusion: The CTAC dose was reduced from 0.5 mSv [range: 0.1-1.1] to 0.11 mSv [range: 0.1-0.2]. Excellent correlation between the normal dose CTAC and UL-CTAC was found for the quantitative parameters related to MPI. Therefore, it seems possible to use a UL-CTAC without affecting the quantitative accuracy.
Original languageEnglish
Publication year2017
DOIs
Publication statusPublished - 2017
EventEuropean Association of Nuclear Medicine Annual Congress - Vienna, Austria
Duration: 21 Oct 201725 Oct 2017
http://eanm17.eanm.org

Conference

ConferenceEuropean Association of Nuclear Medicine Annual Congress
CountryAustria
CityVienna
Period21/10/201725/10/2017
Internet address

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