[Effect of Reconstruction Strategies for the Quantification and Diagnostic Accuracy of (123)I-FP-CIT SPECT]

Verification of optimal conditions for the scattering correction of 123I-FP-CIT SPECT on a single-photon emission tomography system with a two-detector whole-body cadmium-zinc-telluride semiconductor detector

To identify the optimal scattering correction for 123I-FP-CIT SPECT (DAT-SPECT) using a two-detector whole-body cadmium-zinc-telluride semiconductor detector (C-SPECT) system with a medium-energy high-resolution sensitivity (MEHRS) collimator. The C-SPECT system with the MEHRS collimator assessed image quality and quantification using a striated phantom. Different reconstruction methods and scattering correction settings were compared, including filtered back projection (FBP) and ordered subset expectation maximization (OSEM). Higher %contrast and %CV values were observed > 10% subwindow (SW) for all conditions, with no significant differences between images without scattering correction and those < 7% SW. The FBP images show a greater increase in %CV > 10% SW than the OSEM images. The specific binding ratio in the radioactivity ratio of 8:1 was higher than the true value under all conditions. The C-SPECT system with an MEHRS collimator provided accurate scattering suppression and enabled high-quality imaging for DAT-SPECT. Careful setting of the scattering correction is essential for total count accuracy.

A new quantitative index in the diagnosis of Parkinson syndrome by dopamine transporter single-photon emission computed tomography

OBJECTIVE

Dopamine transporter single-photon emission computed tomography (DAT SPECT) has been widely used to diagnose Parkinson syndrome. Using the standardized uptake value (SUV) of DAT SPECT, we propose "functional dopamine transporter volume (f-DTV)" as a new quantitative index to evaluate the three-dimensional volume of functional dopamine transporters and assess its diagnostic ability in differentiating dopaminergic neurodegenerative diseases (dNDD) from non-dNDD.

METHODS

Seventy-nine patients were enrolled (42 dNDD, 37 non-dNDD; 38 men; age 24-88 years). We analyzed seven quantitative indices. The specific binding ratio (SBR) was calculated using a program specialized for DAT SPECT (SBR_Bolt). The SUVmax, SUVpeak, and SUVmean were calculated using a quantification program for bone SPECT. SBR_SUV was calculated by dividing striatal SUVmean by the average of background SUVmean. The cutoff value of the active dopamine transporter level was examined using three methods (threshold of 40% of SUVmax, SUV 2, and SUV 3) to calculate the active dopamine transporter volume (ADV). The f-DTV was calculated by multiplying ADV and SUV_mean. We assessed the correlations between SBR_Bolt and SBR_SUV, and compared the mean value of each index between the dNDD and non-dNDD groups. The abilities of SBR_Bolt, SBR_SUV, SUVmax, SUVpeak, SUVmean, ADV, and f-DTV in differentiating dNDD from non-dNDD were determined by the area under the receiver operating curve (AUC) generated by the receiver operating characteristics analysis.

RESULTS

The SBR_Bolt and SBR_SUV highly correlated with each other (r = 0.71). The cutoff value of the active dopamine transporter level was determined as SUV 3. All seven quantitative indices showed lower values in the dNDD group than in the non-dNDD group, and the difference between the two groups was statistically significant (p < 0.05). Sensitivity, specificity, and AUC of f-DTV were slightly lower than those of SBR_Bolt (71%, 79%, and 0.81, respectively, for f-DTV, and 81%, 84%, 0.88, respectively, for SBR_Bolt). The difference in AUC between f-DTV and SBR_Bolt was not statistically significant.

CONCLUSIONS

This study demonstrates the utility of f-DTV as a novel quantitative index for evaluating the three-dimensional volume of functional dopamine transporters, and that f-DTV has almost the same diagnostic ability to differentiate dNDD from non-dNDD using DAT SPECT.

Age-related effects and gender differences in Japanese healthy controls for [123I] FP-CIT SPECT

OBJECTIVE

Dopamine transporter (DAT) imaging with [¹²³I]FP-CIT (DaTSCAN) is a widely used diagnostic tool for Parkinsonism and dementia. Since it was approved by the Japanese Ministry of Health, Labor, and Welfare in 2013, there have been no articles focusing on a Japanese normal population. The aim of this study was to examine the effect of aging and gender on DAT availability in Japanese people.

METHODS

SPECT imaging of 30 healthy Japanese controls (17 males, 13 females; range 50-86 years, mean 70 years) was performed. SPECT images were reconstructed using a three-dimensional order subset expectation maximization (OSEM) algorithm with correction of the point spread function and scatter correction, without attenuation correction. The specific binding ratio (SBR) was calculated by DATview software. Statistical analyses were performed using linear regression analysis, analysis of variance, and multiple comparison analysis.

RESULTS

A strong correlation between the SBR and age was observed. The correlation coefficient in males and females were -0.566 and -0.502, respectively. The analysis of variance revealed that aging led to a decline of the SBR, and a significant difference (p = 0.005) was observed among generations. Gender also affected the SBR, and there was a significant difference between males and females (p = 0.036). The SBR in females was higher than in males. Consequently, the multiple comparison revealed a significant difference between 50s and 70s (p = 0.015) and 50s and 80s (p = 0.006).

CONCLUSIONS

This is the first [¹²³I]FP-CIT SPECT study on subjects with normal dopamine function in Asian countries. This study provides a database of [¹²³I]FP-CIT SPECT in Japanese healthy controls. Higher DAT availability was found in women than in men. An average age-related decline in DAT availability of 8.9% was found in both genders. The data collected in this study would be helpful for Japanese physicians to make a differential diagnosis in Parkinsonian syndrome. The registration identification number for this study is UMIN000018045.