Quantification of [123I]FP-CIT SPECT brain images: an accurate technique for measurement of the specific binding ratio

[Optimization of Reformatting Angle Using Orbitomeatal Base Line in Dopamine Transporter Scintigraphy]

Recently, dopamine transporter (DaT) scintigraphy, which contributes to the early diagnosis of Parkinson's disease and Lewy body dementia, has been widely spread. It has been revealed that analytical results can be affected by the image-reformatting angle, and a horizontal section is recommended for the anterior commissure-posterior commissure (AC-PC) line according to the clinical guidelines for ioflupane. However, it is difficult to identify AC-PC line visually, as there is no remarkable accumulation in the cerebral parenchyma in DaT scintigraphy with poor contrast resolution. The objective of this study was to establish and optimize an adjustment method for the image-reformatting angle by using orbitomeatal base line (OM line). Evaluations were made on items such as comparison of image reformatting angles by an analyst, comparison of measurement angles of OM line, the angle formed by the intersection of OM line and AC-PC line, and the change in specific biding ratio (SBR) according to the difference in the image-reformatting angle. Consequently, the difference in analytical results among technicians became smaller, and consistent results were obtained by adjusting the image-reformatting angle.

[Optimized Acquisition Time for Dopamine Transporter Imaging]

Excess acquisition counts were often obtained by the current image acquisition of 30 minutes after ¹²³I-ioflupane administration in a dopamine transporter study. The purpose of this study was to calculate the minimum acquisition time while retaining sufficient image quality, which could be adjusted for individual characteristics. Fifty patients who underwent dopamine transporter imaging were included in this retrospective study. The brain count density, determined by a striatum phantom, was compared to the participant's characteristics. The individual characteristics were divided into five categories of gender, age, height, weight, and body mass index. The values of 40 counts / voxel (brain count density) were set as the image quality criteria by the striatum phantom study. Weight was the characteristic that most correlated with brain count density in the 50 patients (correlation coefficient: -0.728). The acquisition time for the 50 patients was calculated as 23.4±2.6 minutes using the following formula: 0.332×W+5.42 minutes (W kg (individual weight)). A shorter acquisition time with sufficient image quality can be achieved by adjusting for individual patient weight.

Test-retest reproducibility of extrastriatal binding with 123I-FP-CIT SPECT in healthy male subjects

¹²³I-labeled 2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl) nortropane (¹²³I-FP-CIT) is used to assess striatal dopamine transporter (DAT) expression, but it can also quantify extrastriatal serotonin transporter (SERT) expressions. While FP-CIT uptake in extrastriatal regions has been quantified, no information exists on the reproducibility of the ¹²³I-FP-CIT specific uptake ratio (SUR) in extrastriatal regions. We investigated test-retest reproducibility of ¹²³I-FP-CIT binding in the striatum, the midbrain, and cortical regions in eight healthy male subjects. All subjects underwent two ¹²³I-FP-CIT SPECT scans, and SUR was calculated using the cerebellum as the reference. We found good test-retest reproducibility of ¹²³I-FP-CIT SUR in the midbrain, and in the lateral frontal/temporal cortex and combined cortical regions. The overall variability and intraclass correlation of SUR were, respectively, 4.9-7.8% and 0.90-0.96 in striatal regions, 8.6% and 0.79 in the midbrain, and 3.6-9.1% and 0.84-0.95 in the lateral frontal/temporal cortex and combined cortical regions. Our results provide evidence that ¹²³I-FP-CIT SPECT is a valid technique for analyzing striatal DAT, as well as extrastriatal SERT in areas such as the SERT-enriched midbrain. In addition, our data suggest that ¹²³I-FP-CIT could be used for analyzing SERT in regions with relatively low SERT expression (e.g., temporal or frontal cortices).

Imaging analysis of Parkinson's disease patients using SPECT and tractography

Parkinson's disease (PD) is a degenerative disorder that affects the central nervous system. PD-related alterations in structural and functional neuroimaging have not been fully explored. This study explored multi-modal PD neuroimaging and its application for predicting clinical scores on the Movement Disorder Society-sponsored Unified Parkinson's Disease Rating Scale (MDS-UPDRS). Multi-modal imaging that combined 123I-Ioflupane single-photon emission computed tomography (SPECT) and diffusion tensor imaging (DTI) were adopted to incorporate complementary brain imaging information. SPECT and DTI images of normal controls (NC; n = 45) and PD patients (n = 45) were obtained from a database. The specific binding ratio (SBR) was calculated from SPECT. Tractography was performed using DTI. Group-wise differences between NC and PD patients were quantified using SBR of SPECT and structural connectivity of DTI for regions of interest (ROIs) related to PD. MDS-UPDRS scores were predicted using multi-modal imaging features in a partial least-squares regression framework. Three regions and four connections within the cortico-basal ganglia thalamocortical circuit were identified using SBR and DTI, respectively. Predicted MDS-UPDRS scores using identified regions and connections and actual MDS-UPDRS scores showed a meaningful correlation (r = 0.6854, p < 0.001). Our study provided insight on regions and connections that are instrumental in PD.

(123)I-Meta-iodobenzylguanidine Sympathetic Imaging: Standardization and Application to Neurological Diseases

¹²³I-meta-iodobenzylguanidine (MIBG) has become widely applied in Japan since its introduction to clinical cardiology and neurology practice in the 1990s. Neurological studies found decreased cardiac uptake of ¹²³I-MIBG in Lewy-body diseases including Parkinson's disease and dementia with Lewy bodies. Thus, cardiac MIBG uptake is now considered a biomarker of Lewy body diseases. Although scintigraphic images of ¹²³I-MIBG can be visually interpreted, an average count ratio of heart-to-mediastinum (H/M) has commonly served as a semi-quantitative marker of sympathetic activity. Since H/M ratios significantly vary according to acquisition and processing conditions, quality control should be appropriate, and quantitation should be standardized. The threshold H/M ratio for differentiating Lewy-body disease is 2.0-2.1, and was based on standardized H/M ratios to comparable values of medium-energy collimators. Parkinson's disease can be separated from various types of parkinsonian syndromes using cardiac ¹²³I-MIBG, whereas activity is decreased on images of Lewy-body diseases using both ¹²³I-ioflupane for the striatum and ¹²³I-MIBG. Despite being a simple index, the H/M ratio of ¹²³I-MIBG uptake is reproducible and can serve as an effective tool to support a diagnosis of Lewy-body diseases in neurological practice.

123I-FP-CIT SPECT findings and its clinical relevance in prodromal dementia with Lewy bodies

PURPOSE

Evidence for the prodromal stage of dementia with Lewy bodies (DLB) is very limited. To address this issue, we investigate the ¹²³I-FP-CIT SPECT measure of dopamine transporter binding finding and its clinical relevance.

METHODS

We enrolled subjects into a prodromal DLB group (PRD-DLB) (n = 20) and clinical DLB group (CLIN-DLB) (n = 18) and compared these groups with an Alzheimer's disease control group (AD) (n = 10). PRD-DLB was defined as patients having the non-motor symptoms associated with Lewy body disease (LBD) [i.e. REM sleep behavior disorder (RBD), olfactory dysfunction, autonomic dysfunction, and depression] and showing characteristic diffuse occipital hypometabolism in ¹⁸F-FDG PET. CLIN-DLB was defined as patients fulfilling the established criteria of probable DLB. Striatal specific binding ratio (SBR) of ¹²³I-FP-CIT SPECT was used for objective group comparisons. The correlations between SBR and cognitive function (MMSE), motor symptoms (UPDRS3), and duration of LBD-associated non-motor symptoms were compared between the two DLB groups.

RESULTS

Mean SBR scores of both PRD-DLB and CLIN-DLB were significantly lower than those of AD. No correlation was found between SBR and MMSE scores. Both in the CLIN-DLB and total DLB groups, SBR scores were negatively correlated with UPDRS3 scores, whereas no correlation was found in PRD-DLB. Among the LBD-related non-motor symptoms, duration of olfactory dysfunction, and RBD demonstrated negative correlation with SBR scores in PRD-DLB.

CONCLUSION

¹²³I-FP-CIT SPECT may play a role for detecting DLB among the subjects in prodromal stage. During this stage, long-term olfactory dysfunction and/or RBD may indicate more severe degeneration of the nigro-striatal dopaminergic pathway.

Optimal ROI setting on the anatomically normalized I-123 FP-CIT images using high-resolution SPECT

Objective

The aim of this study is to establish the optimal regions of interest (ROIs) in anatomically normalized I-123 FP-CIT SPECT images for the quantification of dopamine transporter binding.

Methods

The subjects comprised 16 normal controls and 14 Parkinsonian patients. All of the normal control subjects underwent I-123 FP-CIT SPECT and MRI. The SPECT device used in this study was a Toshiba GCA-9300R with triple head detectors. I-123 FP-CIT (148 MBq) was intravenously administered as a bolus, and the SPECT scan started 4 h after the administration. The data were collected over 20 min for each subject, and reconstructed using a 3D-OSEM algorithm. The data were analyzed using SPM8. I-123 FP-CIT SPECT images were anatomically normalized to the MNI space using an I-123 FP-CIT template, and then divided by the background counts automatically measured using the ROIs set for the cerebral cortices.

Results

In the normal control subjects, the specific binding ratios of the MRI-based ROIs were lowest in the caudate nucleus, while the ratios of the I-123 FP-CIT-based ROIs were almost the same throughout all three parts. In contrast, in Parkinsonian patients, the specific binding ratios of the I-123 FP-CIT-based ROIs revealed rostrocaudal decline, while those of the MRI-based ROIs were highest in the anterior putamen.

Conclusion

We created an ROI template on the anatomically normalized MRI and I-123 FP-CIT images, and concluded that I-123 FP-CIT-based ROIs are more suitable for obtaining quantitative values than MRI-based ones.

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

PURPOSE

This study evaluates the effect of reconstruction strategies for the quantification and diagnostic accuracy of (123)I-FP-CIT SPECT.

METHODS

We evaluated the quantification of (123)I-FP-CIT SPECT obtained by several combinations of reconstruction using the striatal phantom. The phantom images were reconstructed using FBP and OSEM with/without attenuation correction (AC) and scatter correction (SC). We calculated the specific binding ratio (SBR) using volume of interest (VOI) analysis on each reconstructed images. For the clinical study, 40 patients who underwent (123)I-FP-CIT SPECT were selected. We grouped the patients into the normal binding group and decreased binding group according to their clinical diagnosis. The clinical images were reconstructed under the same conditions as the phantom study. The SBRs were calculated, and a receiver operating characteristic (ROC) analysis was performed to evaluate the diagnostic accuracy.

RESULTS

The SBRs with AC and SC significantly increased compared with no corrections. In the clinical study, although ROC analysis showed no significant difference in the all combinations of reconstruction, the area under the curve using SC and AC tended to be higher than that obtained by other reconstruction.

CONCLUSIONS

Quantification of (123)I-FP-CIT SPECT was affected by reconstruction strategies. In addition, both the AC and SC improved the diagnostic accuracy of (123)I-FP-CIT SPECT. Our results suggest that both the AC and SC are recommended for the improving the quantification and diagnostic accuracy in (123)I-FP-CIT SPECT.

[(123)I]-Ioflupane SPECT in combination with MIBG myocardial scintigraphy in Parkinson's disease: a case series study

Metaiodobenzylguanidine (MIBG) myocardial scintigraphy is widely accepted as a beneficial tool for differentiating Parkinson's disease (PD) from other Parkinson-related disorders (PRD). In Japan, dopamine transporter (DAT) imaging, which can evaluate presynaptic degeneration of dopamine neurons, has been applied in clinics since 2014. The present study investigated the utility of [(123)I]-Ioflupane single photon emission computed tomography (SPECT) combined with MIBG myocardial scintigraphy for the diagnosis of PD. We performed [(123)I]-Ioflupane SPECT and MIBG myocardial scintigraphy in 63 PD patients, 8 PRD patients and 1 essential tremor patient, and obtained the specific binding ratio (SBR [cut-off: 4.5]) and the heart-to-mediastinum ratio (H/M [cut-off: 2.2]). In 70% of the PD patients, both parameters were significantly reduced. In 22% of the PD patients, the SBR was smaller than 4.5 with normal H/M, and H/M was less than 2.2 with normal SBR in 5% of all subjects. Either the SBR or H/M was significantly reduced in 97% of the study population. The SBR showed low disease specificity to PD (11%), and the SBR and H/M negatively correlated with disease duration. These findings indicate that [(123)I]-Ioflupane SPECT combined with MIBG myocardial scintigraphy can improve the detection rate of PD. However, careful interpretation of these results is required because [(123)I]-Ioflupane SPECT poorly differentiates PD from PRD. Progression of PD may reflect the gradual reduction of isotope accumulation, hence, both [(123)I]-Ioflupane SPECT and MIBG myocardial scintigraphy should be tested repeatedly even in clinically suspected PD cases showing negative results.

Dysfunctional counting of mental time in Parkinson's disease

Patients with Parkinson’s disease (PD) often underestimate time intervals, however it remains unclear why they underestimate rather than overestimate them. The current study examined time underestimation and counting in patients with PD, in relation to dopamine transporter (DaT) located on presynaptic nerve endings in the striatum. Nineteen non-dementia patients with PD and 20 age- and sex-matched healthy controls performed two time estimation tasks to produce or reproduce time intervals with counting in the head, to examine dysfunctional time counting processing. They also performed tapping tasks to measure cycles of counting with 1 s interval with time estimation. Compared to controls, patients underestimated time intervals above 10 s on time production not reproduction tasks, and the underestimation correlated with fast counting on the tapping task. Furthermore, striatal DaT protein levels strongly correlated with underestimation of time intervals. These findings suggest that distortion of time intervals is guided by cumulative output of fast cycle counting and that this is linked with striatal DaT protein deficit.

Cingulate island sign on FDG-PET is associated with medial temporal lobe atrophy in dementia with Lewy bodies

OBJECTIVE

The cingulate island sign (CIS), which refers to sparing of the posterior cingulate relative to the precuneus and cuneus, has been proposed as an FDG-PET imaging feature of dementia with Lewy bodies (DLB). The sign is reportedly associated with Alzheimer's disease (AD) type neurofibrillary tangle (NFT) pathology in autopsy cases. To confirm this relationship using neuroimaging modalities in vivo, we investigated associations between CIS and the medial temporal lobe (MTL) atrophy in DLB.

METHODS

Twenty-four patients each of DLB and AD underwent both (18)F-FDG-PET and MRI with voxel-based morphometry. Dopamine transporter (DAT) density was also measured by DAT-SPECT in all those with DLB and in five with AD. The accumulation of FDG in the posterior cingulate ROI was divided by that in the precuneus plus cuneus ROI to derive the CIS ratio from the FDG-PET images. Values for cognitive function of Mini-Mental State Examination (MMSE), Frontal Assessment Battery (FAB) and Ray Auditory Verbal Learning Test (RAVLT) and scores for the core-feature triad of fluctuation, hallucination and parkinsonism were also statistically analyzed.

RESULTS

The CIS ratio was higher in DLB than in AD (p < 0.001). The degree of MTL atrophy was lower in DLB than in AD (p < 0.001). The CIS ratio and the degree of MTL atrophy were inversely correlated with DLB (p < 0.001) and with AD (p < 0.05). The CIS ratio did not significantly correlate with DAT density in DLB or with MMSE, FAB, fluctuation score and parkinsonism score. However, the CIS ratio significantly correlated with RAVLT and hallucination scores (both, p < 0.05).

CONCLUSIONS

The CIS on FDG-PET in DLB was associated with MTL atrophy but not with striatal DAT density, suggesting that the CIS is a useful neuroimaging biomarker to evaluate coexisting AD-type NFT pathology in vivo. The CIS was also associated with memory impairment and visual hallucination in DLB.

[Comparison of Quantitative Value of Dopamine Transporter Scintigraphy Calculated from Different Analytical Software]

In the dopamine transporter scintigraphy there are two quantitative analysis softwares, DaTView and DaTQUANT. The quantitative value of both software has to be treated independently because there is a difference between them in the point of how to set the region of interest on the striatum and the background, calculation formula of quantitation. And also DaTQUANT has a capability of performing anatomical standardization which DaTView does not have. The aim of this study was to evaluate the accuracy of registration on DaTQUANT using a phantom, and to evaluate the correlation between the quantitative values between DaTView and DaTQUANT using clinical data. As a result, the accuracy of registration was acceptable. Regardless of the degree of accumulation in the striatum, there was a high correlation to each analysis software (r>0.85).

CADA-computer-aided DaTSCAN analysis

Background

Dopamine transporter (DaT) imaging (DaTSCAN) is useful for the differential diagnosis of parkinsonian syndromes. Visual evaluation of DaTSCAN images represents the generally accepted diagnostic method, but it is strongly dependent on the observer’s experience and shows inter- and intra-observer variability. A reliable and automatic method for DaTSCAN evaluation can provide objective quantification; it is desirable for longitudinal studies, and it allows for a better follow-up control. Moreover, it is crucial for an automated method to produce coherent measures related to the severity of motor symptoms.

Methods

In this work, we propose a novel fully automated technique for DaTSCAN analysis that generates quantitative measures based on striatal intensity, shape, symmetry and extent. We tested these measures using a support vector machine (SVM) classifier.

Results

The proposed measures reached 100 % accuracy in distinguishing between patients with Parkinson’s disease (PD) and control subjects. We also demonstrate the existence of a linear relationship and an exponential trend between pooled structural and functional striatal characteristics and the Unified Parkinson’s disease Rating Scale (UPDRS) motor score.

Conclusions

We present a novel, highly reproducible, user-independent technique for DaTSCAN analysis producing quantitative measures directly connected to striatum uptake and shape. In our method, no a priori assumption is required on the spatial conformation and localization of striatum, and both uptake and symmetry contribute to the index quantification. These measures can reliably support a computer-assisted decision system.

Electronic supplementary material

The online version of this article (doi:10.1186/s40658-016-0140-9) contains supplementary material, which is available to authorized users.

Importance of (123)I-ioflupane SPECT and Myocardial MIBG Scintigraphy to Determine the Candidate of Deep Brain Stimulation for Parkinson's Disease

¹²³I-ioflupane SPECT (DaTscan) is an examination that detects presynaptic dopamine neuronal dysfunction, and has been used as a diagnostic tool to identify degenerative parkinsonism. Additionally, myocardial ¹²³I-metaiodobenzyl guanidine (MIBG) scintigraphy measures the concentration of cardiac sympathetic nerve fibers and is used to diagnose Parkinson’s disease (PD). These exams are used as adjuncts in the diagnosis of parkinsonism, however, the relationship of these two examinations are not well-known. We investigated the relationship of these two scanning results specifically for determining the use of deep brain stimulation therapy (DBS). Subjects were Japanese patients with suspected striatonigral degeneration, including PD; DaTscans and myocardial MIBG scintigraphy were performed. The mean values of the left-right specific binding ratios (SBRs) from the DaTscan, and the early/delayed heart-to-mediastinum ratios (HMRs) from the MIBG scintigraphy were calculated. Using simple linear regression analysis, we compared the SBR and early/delayed HMR values. Twenty-four patients were enrolled in this study. Twenty-one patients were positive via the DaTscan, and the MIBG scintigraphy results showed 14 patients were positive. SBR and both early and delayed HMR were positively correlated in cases of PD, but negative in non-PD cases. A mean SBR value less than 3.0 and a delayed HMR value less than 1.7 indicated a Hoehn-Yahr stage 3 or 4 for PD, which is commonly regarded as a level appropriate for initiating DBS therapy. Our results indicate that performing both DaTscan and MIBG scintigraphy is useful for the evaluation of surgical intervention in PD.

Semiquantitative slab view display for visual evaluation of 123I-FP-CIT SPECT

OBJECTIVE

Dopamine transporter single-photon emission computed tomography (SPECT) with I-FP-CIT is used widely in the diagnosis of clinically uncertain parkinsonian syndromes. In terms of the evaluation of FP-CIT SPECT, some practice guidelines state that visual interpretation alone is generally sufficient in clinical patient care, whereas other guidelines consider semiquantitative analysis of striatal dopamine transporter availability mandatory. This discrepancy might be because of a relative lack of widely available display tools for FP-CIT SPECT. In this study, we evaluate a semiquantitative slab view display optimized for visual evaluation of FP-CIT SPECT that might resolve the discrepancy.

PATIENTS AND METHODS

The reconstructed FP-CIT SPECT image was stereotactically normalized and scaled voxel by voxel to the mean uptake in the entire brain without striata. From the resulting distribution volume ratio image, a 12-mm-thick transversal slice (slab) through the striata was displayed with a standard colour table with predefined fixed thresholds on the distribution volume ratio. Visual scoring of the semiquantitative slab view was performed twice by four independent readers in 235 unselected patients. The specific binding ratio in the caudate and putamen was computed by fully automated semiquantitative analysis with predefined standard regions of interest in template space.

RESULTS

Intrarater and inter-rater agreement of binary visual categorization as 'normal' or 'reduced' was excellent (mean Cohen's κ=0.88 and 0.83, respectively). The area under the receiver-operator characteristic curve of the specific putamen-binding ratio for differentiation between visually normal and visually reduced (majority read) was 0.96.

CONCLUSION

Visual interpretation of FP-CIT SPECT on the basis of the semiquantitative slab view display provides excellent stability within and between readers as well as very high agreement with semiquantitative analysis. This suggests that the slab view display enables reliable visual interpretation of FP-CIT SPECT in clinical routine patient care.

Fully Automated Quantification of the Striatal Uptake Ratio of [(99m)Tc]-TRODAT with SPECT Imaging: Evaluation of the Diagnostic Performance in Parkinson's Disease and the Temporal Regression of Striatal Tracer Uptake

Purpose. We aimed at improving the existing methods for the fully automatic quantification of striatal uptake of [^99mTc]-TRODAT with SPECT imaging. Procedures. A normal [^99mTc]-TRODAT template was first formed based on 28 healthy controls. Images from PD patients (n = 365) and nPD subjects (28 healthy controls and 33 essential tremor patients) were spatially normalized to the normal template. We performed an inverse transform on the predefined striatal and reference volumes of interest (VOIs) and applied the transformed VOIs to the original image data to calculate the striatal-to-reference ratio (SRR). The diagnostic performance of the SRR was determined through receiver operating characteristic (ROC) analysis. Results. The SRR measured with our new and automatic method demonstrated excellent diagnostic performance with 92% sensitivity, 90% specificity, 92% accuracy, and an area under the curve (AUC) of 0.94. For the evaluation of the mean SRR and the clinical duration, a quadratic function fit the data with R² = 0.84. Conclusions. We developed and validated a fully automatic method for the quantification of the SRR in a large study sample. This method has an excellent diagnostic performance and exhibits a strong correlation between the mean SRR and the clinical duration in PD patients.

Utility of the combination of DAT SPECT and MIBG myocardial scintigraphy in differentiating dementia with Lewy bodies from Alzheimer's disease

Purpose

¹²³I-2β-Carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl) nortropane (¹²³I-FP-CIT) dopamine transporter single photon emission computed tomography (DAT SPECT) and ¹²³I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy can be used to assist in the diagnosis of patients with dementia with Lewy bodies (DLB). We compared the diagnostic value of these two methods in differentiating DLB from Alzheimer’s disease (AD). Furthermore, we evaluated whether a combination of DAT SPECT and MIBG myocardial scintigraphy would provide a more useful means of differentiating between DLB and AD.

Methods

Patients with AD (n = 57) and patients with DLB (n = 76) who underwent both DAT SPECT and MIBG myocardial scintigraphy were enrolled. The sensitivity, specificity, and accuracy of both methods as well as their combination for differentiating DLB from AD were calculated. Moreover, we examined whether symptoms of the patients with DLB were associated with the patterns of the abnormalities displayed on DAT SPECT and MIBG myocardial scintigraphy.

Results

The sensitivity and specificity of differentiating DLB from AD were 72.4 and 94.4 % by the heart to mediastinum ratio of MIBG uptake, 88.2 and 88.9 % by the specific binding ratio on DAT SPECT, and 96.1 and 90.7 % by their combination, respectively. The combined use of DAT SPECT and MIBG myocardial scintigraphy enabled more accurate differentiation between DLB and AD compared with either DAT SPECT or MIBG myocardial scintigraphy alone. There was a significantly higher frequency of parkinsonism in the abnormal DAT SPECT group than the normal DAT SPECT group. On the other hand, there was a higher frequency of the appearance of rapid eye movement (REM) sleep behavior disorder in the abnormal MIBG uptake group than the normal MIBG uptake group.

Conclusion

These results suggested that using a combination of these scintigraphic methods is a useful and practical approach to differentiate DLB from AD.

[Assessment of Inspection Technology of Dopamine Transporter Imaging with ¹²³I-Ioflupane]

Imaging start time of single-photon emission computed tomography (SPECT) scan is recommended between 3 hours and 6 hours after injection of ¹²³I-ioflupane in Ioflupane clinical practice guidelines. But image includes the effect of physiological actions of the human body and the attenuation at 13.27 hours physical half-life of ¹²³I. Therefore, we evaluated the effect of the image by the elapsed time of imaging start time. Optimal cut-off frequency of Butterworth filter were examined phantom by normalized mean square error. Count was reduced by 23.1% in 5 hours, but cut-off frequency of Butterworth filter was 0.11 cycle/pixel in 0-5 hours from phantom data. Ten subjects (age 55-85 years) were injected with ¹²³I-ioflupane of 110-199 MBq into the vein only once. And we examined the specific binding ratio (SBR) in inspection of injection after 5. 5 hours and 3 hours. Decrease of counts value increased the coefficient of variance (CV) between 3 hours and 5.5 hours after injection, but the improvement of statistical noise by pre-processing filter reduced the CV. No significant difference in the result of SBR was found between 3 hours and 5. 5 hours after injection. Our results suggest that imaging start time of SPECT scan is recommended between 3 hours and 5.5 hours after injection of ¹²³I-ioflupane.

Multipinhole collimator with 20 apertures for a brain SPECT application

PURPOSE

Several new technologies for single photon emission computed tomography (SPECT) instrumentation with parallel-hole collimation have been proposed to improve detector sensitivity and signal collection efficiency. Benefits from improved signal efficiency include shorter acquisition times and lower dose requirements. In this paper, the authors show a possibility of over an order of magnitude enhancement in photon detection efficiency (from 7.6 × 10(-5) to 1.6 × 10(-3)) for dopamine transporter (DaT) imaging of the striatum over the conventional SPECT parallel-hole collimators by use of custom-designed 20 multipinhole (20-MPH) collimators with apertures of 0.75 cm diameter.

METHODS

Quantifying specific binding ratio (SBR) of (123)I-ioflupane or (123)I-iometopane's signal at the striatal region is a common brain imaging method to confirm the diagnosis of the Parkinson's disease. The authors performed imaging of a striatal phantom filled with aqueous solution of I-123 and compared camera recovery ratios of SBR acquired between low-energy high-resolution (LEHR) parallel-hole collimators and 20-MPH collimators.

RESULTS

With only two-thirds of total acquisition time (20 min against 30 min), a comparable camera recovery ratio of SBR was achieved using 20-MPH collimators in comparison to that from the LEHR collimator study.

CONCLUSIONS

Their systematic analyses showed that the 20-MPH collimator could be a promising alternative for the DaT SPECT imaging for brain over the traditional LEHR collimator, which could give both shorter scan time and improved diagnostic accuracy.

Comparison between Different Intensity Normalization Methods in 123I-Ioflupane Imaging for the Automatic Detection of Parkinsonism

Intensity normalization is an important pre-processing step in the study and analysis of DaTSCAN SPECT imaging. As most automatic supervised image segmentation and classification methods base their assumptions regarding the intensity distributions on a standardized intensity range, intensity normalization takes on a very significant role. In this work, a comparison between different novel intensity normalization methods is presented. These proposed methodologies are based on Gaussian Mixture Model (GMM) image filtering and mean-squared error (MSE) optimization. The GMM-based image filtering method is achieved according to a probability threshold that removes the clusters whose likelihood are negligible in the non-specific regions. The MSE optimization method consists of a linear transformation that is obtained by minimizing the MSE in the non-specific region between the intensity normalized image and the template. The proposed intensity normalization methods are compared to: i) a standard approach based on the specific-to-non-specific binding ratio that is widely used, and ii) a linear approach based on the α-stable distribution. This comparison is performed on a DaTSCAN image database comprising analysis and classification stages for the development of a computer aided diagnosis (CAD) system for Parkinsonian syndrome (PS) detection. In addition, these proposed methods correct spatially varying artifacts that modulate the intensity of the images. Finally, using the leave-one-out cross-validation technique over these two approaches, the system achieves results up to a 92.91% of accuracy, 94.64% of sensitivity and 92.65 % of specificity, outperforming previous approaches based on a standard and a linear approach, which are used as a reference. The use of advanced intensity normalization techniques, such as the GMM-based image filtering and the MSE optimization improves the diagnosis of PS.

Computer-aided diagnosis of Parkinson's disease based on [(123)I]FP-CIT SPECT binding potential images, using the voxels-as-features approach and support vector machines

OBJECTIVE

The aim of the present study was to develop a fully-automated computational solution for computer-aided diagnosis in Parkinson syndrome based on [(123)I]FP-CIT single photon emission computed tomography (SPECT) images.

APPROACH

A dataset of 654 [(123)I]FP-CIT SPECT brain images from the Parkinson's Progression Markers Initiative were used. Of these, 445 images were of patients with Parkinson's disease at an early stage and the remainder formed a control group. The images were pre-processed using automated template-based registration followed by the computation of the binding potential at a voxel level. Then, the binding potential images were used for classification, based on the voxel-as-feature approach and using the support vector machines paradigm.

MAIN RESULTS

The obtained estimated classification accuracy was 97.86%, the sensitivity was 97.75% and the specificity 98.09%.

SIGNIFICANCE

The achieved classification accuracy was very high and, in fact, higher than accuracies found in previous studies reported in the literature. In addition, results were obtained on a large dataset of early Parkinson's disease subjects. In summation, the information provided by the developed computational solution potentially supports clinical decision-making in nuclear medicine, using important additional information beyond the commonly used uptake ratios and respective statistical comparisons. (ClinicalTrials.gov Identifier: NCT01141023).

Improving quantitative dosimetry in (177)Lu-DOTATATE SPECT by energy window-based scatter corrections

PURPOSE

Patient-specific dosimetry of lutetium-177 ((177)Lu)-DOTATATE treatment in neuroendocrine tumours is important, because uptake differs across patients. Single photon emission computer tomography (SPECT)-based dosimetry requires a conversion factor between the obtained counts and the activity, which depends on the collimator type, the utilized energy windows and the applied scatter correction techniques. In this study, energy window subtraction-based scatter correction methods are compared experimentally and quantitatively.

MATERIALS AND METHODS

(177)Lu SPECT images of a phantom with known activity concentration ratio between the uniform background and filled hollow spheres were acquired for three different collimators: low-energy high resolution (LEHR), low-energy general purpose (LEGP) and medium-energy general purpose (MEGP). Counts were collected in several energy windows, and scatter correction was performed by applying different methods such as effective scatter source estimation (ESSE), triple-energy and dual-energy window, double-photopeak window and downscatter correction. The intensity ratio between the spheres and the background was measured and corrected for the partial volume effect and used to compare the performance of the methods.

RESULTS

Low-energy collimators combined with 208 keV energy windows give rise to artefacts. For the 113 keV energy window, large differences were observed in the ratios for the spheres. For MEGP collimators with the ESSE correction technique, the measured ratio was close to the real ratio, and the differences between spheres were small.

CONCLUSION

For quantitative (177)Lu imaging MEGP collimators are advised. Both energy peaks can be utilized when the ESSE correction technique is applied. The difference between the calculated and the real ratio is less than 10% for both energy windows.

A novel, fully automated, observer-independent program for semiquantifying striatal ¹²³I-FP-CIT uptake

OBJECTIVE

To describe and validate a novel, fully automated program specifically designed for the semiquantification of striatal (123)I-FP-CIT uptake using volumes of interest (VOI) analysis.

MATERIAL AND METHODS

The proposed algorithm is based on a template that mimics the striatal (123)I-FP-CIT uptake in a healthy subjects, derived from defined anatomical VOIs available from WFU PickAtlas. Four SPECT studies of the anthropomorphic Alderson phantom filled with variable radioactive concentrations were acquired for the experimental validation. Experimental SPECT images were spatially normalized with respect to the previously created template. The binary VOIs corresponding to left caudate and putamen and right caudate and putamen, which were used to construct the template, were projected onto the experimental images to obtain the counts for these regions. To minimize the partial volume effect, a percentage of the voxels in these regions (threshold), rather than all of them, was used. A binary occipital VOI was used to quantify the non-specific uptake. Experimental binding potentials (BPs) were calculated from the counts in these regions. True BPs were calculated from aliquots taken from the solutions used to fill the phantom.

RESULTS

There were statistically significant differences in the experimental BP values (p<0.002) according to the percentage of voxels used. A highly significant correlation was achieved between true and experimental BP values, regardless of the percentage of voxels included for quantification.

CONCLUSIONS

Our novel, observer-independent program automatically performs the semiquantification of striatal (123)I-FP-CIT uptake in experimental studies.

Radius dependence of FP-CIT quantification: a Monte Carlo-based simulation study

OBJECTIVE

Dopamine transporter imaging with SPECT is a valuable tool for both clinical routine and research studies. Semi-quantitative analysis plays a key role in interpreting the scans, but is dependent on numerous factors, rotational radius being one of them. This study systematically evaluates the potential influence of radius of rotation on apparent tracer binding and describes methods for correction.

METHODS

Monte Carlo simulation scans of a digital brain phantom with various disease states and various radii of rotation ranging from 13 to 30 cm were analyzed using 4 different methods of semi-quantification. Different volumes of interest as well as a method with partial volume correction were applied.

RESULTS

For conventional 3D semi-quantification methods the decrease of measured striatal binding per cm additional radius rotation lied in the range between 2.5 and 3.1 %, whereas effects were negligible when applying recovery-corrected quantification. Effects were independent of disease state.

CONCLUSION

Partial volume effects with increasing radius of rotation can lead to considerable decrease of measured binding ratios, particularly when applying dopamine transporter imaging in a research setting. Standardization of acquisition radius can avoid the effect; correction seems feasible, but the correction factors depend on the quantification approach applied.

A simple algorithm for subregional striatal uptake analysis with partial volume correction in dopaminergic PET imaging

OBJECTIVE

In positron emission tomography (PET) of the dopaminergic system, quantitative measurements of nigrostriatal dopamine function are useful for differential diagnosis. A subregional analysis of striatal uptake enables the diagnostic performance to be more powerful. However, the partial volume effect (PVE) induces an underestimation of the true radioactivity concentration in small structures. This work proposes a simple algorithm for subregional analysis of striatal uptake with partial volume correction (PVC) in dopaminergic PET imaging.

METHODS

The PVC algorithm analyzes the separate striatal subregions and takes into account the PVE based on the recovery coefficient (RC). The RC is defined as the ratio of the PVE-uncorrected to PVE-corrected radioactivity concentration, and is derived from a combination of the traditional volume of interest (VOI) analysis and the large VOI technique. The clinical studies, comprising 11 patients with Parkinson's disease (PD) and 6 healthy subjects, were used to assess the impact of PVC on the quantitative measurements. Simulations on a numerical phantom that mimicked realistic healthy and neurodegenerative situations were used to evaluate the performance of the proposed PVC algorithm. In both the clinical and the simulation studies, the striatal-to-occipital ratio (SOR) values for the entire striatum and its subregions were calculated with and without PVC.

RESULTS

In the clinical studies, the SOR values in each structure (caudate, anterior putamen, posterior putamen, putamen, and striatum) were significantly higher by using PVC in contrast to those without. Among the PD patients, the SOR values in each structure and quantitative disease severity ratings were shown to be significantly related only when PVC was used. For the simulation studies, the average absolute percentage error of the SOR estimates before and after PVC were 22.74% and 1.54% in the healthy situation, respectively; those in the neurodegenerative situation were 20.69% and 2.51%, respectively.

CONCLUSIONS

We successfully implemented a simple algorithm for subregional analysis of striatal uptake with PVC in dopaminergic PET imaging. The PVC algorithm provides an accurate measure of the SOR in the entire striatum and its subregions, and improves the correlation between the SOR values and the clinical disease severity of PD patients.

3D-OSEM and FP-CIT SPECT quantification: benefit for studies with a high radius of rotation?

OBJECTIVES

Dopamine transporter imaging with single-photon emission computed tomography (SPECT) is a valuable tool for both clinical routine and research studies. Recently, it was found that the image quality could be improved by introduction of the three-dimensional ordered subset expectation maximization (3D-OSEM) reconstruction algorithm, which provides resolution recovery. The aim of this study was to systematically evaluate the potential benefits of 3D-OSEM in comparison with 2D-OSEM under critical imaging conditions, for example, scans with a high radius of rotation.

MATERIALS AND METHODS

Monte Carlo simulation scans of a digital brain phantom with various disease states and different radii of rotation ranging from 13 to 30 cm were reconstructed with both 2D-OSEM and 3D-OSEM algorithms. Specific striatal binding and putamen-to-caudate ratios were determined and compared with true values in the phantom.

RESULTS

The percentage recovery of true striatal binding was similar between both reconstruction algorithms at the minimum rotational radius; however, at the maximum rotational radius, it decreased from 53 to 43% for 3D-OSEM and from 52 to 26% for 2D-OSEM. 3D-OSEM matched the true putamen-to-caudate ratios more closely than did 2D-OSEM in scans with high SPECT rotation radii.

CONCLUSION

3D-OSEM offers a promising image quality gain. It outperforms 2D-OSEM, particularly in studies with limited resolutions (such as scans acquired with a high radius of rotation) but does not improve the accuracy of the putamen-to-caudate ratios. Whether the benefits of better recovery in studies with higher radii of rotation could potentially increase the diagnostic power of dopamine transporter SPECT in patients with borderline striatal radiotracer binding, however, needs to be further examined.

[Elaboration of the SPM template for the standardization of SPECT images with 123I-Ioflupane]

PURPOSE

Statistical parametric mapping (SPM) is a widely used produced for normalization of functional images. This study has aimed to develop a normalization template of (123)I-Ioflupane SPECT-imaging DaTSCAN(®), GE Healthcare), not available in SPM5, and to validate it compared to other quantification methods.

MATERIAL AND METHODS

In order to write the template we retrospectively selected 26 subjects who had no evidence of nigrostriatal degeneration and whose age distribution was similar to that of the patients in the usual practice of our Department: 2 subjects (7.6%) were < 35 years, 9 between 35-65 years (34.6%) and 15 > 65 years (57.7%). All the studies were normalized with the T1-template available in SPM5 and an average image of the value was obtained for each voxel. For validation we analyzed 60 patients: 30 with idiopathic Parkinson's disease patients (iPD) with right involvement (66.83±12.20 years) and 30 with essential tremor patients (ET) (67.27±8.33 years). Specific uptake rates (SUR) of different striatal regions were compared after image normalization with our template and the application of a semiautomated VOIs-map created with Analyze v9.0 ((©)BIR, Mayo Clinic), against two quantification methods: a) manual adjustment of a ROIs-map drawn in Analyze, and b) semi-automated method (HERMES-BRASS) with normalization and implementation of VOIs-map.

RESULTS

No statistically significant differences in the iPD/ET discriminatory capacity between the three methods analyzed were observed (p<0,001). The correlation of SUR after normalization with our «template» was higher than that obtained by method b) (R>0,871, p<0,001). This difference was greater in patients with PD.

CONCLUSIONS

Our study demonstrates the efficacy of our SPM «template» for (123)I-Ioflupane SPECT-imaging, obtained from normalization with «T1-template».

Feasibility of PET Template-Based Analysis on F-18 FP-CIT PET in Patients with De Novo Parkinson's Disease

PURPOSE

The aim of this study was to evaluate the feasibility of FP-CIT PET template-based quantitative analysis on F-18 FP-CIT PET in patients with de novo Parkinson's disease (PD), compared with MR-based and manual methods. We also assessed the correlation of quantitative parameters of those methods with clinical severity of the disease.

METHODS

Forty patients with de novo PD underwent both MRI and F-18 FP-CIT PET. Images were spatially normalized to a standardized PET template. Mean counts of 4 ROIs: putamen, caudate, occipital cortex and cerebellum, were obtained using the quantification program, Korean Statistical Probabilistic Anatomical Map (KSPAM). Putamen-to-caudate ratio (PCR), asymmetry index (ASI), specific-to-nonspecific ratios with two different references: to occipital cortex (SOR) and cerebellum (SCR) were compared. Parameters were also calculated from manually drawn ROI method and MR-coregistrated method.

RESULTS

All quantitative parameters showed significant correlations across the three different methods, especially between the PET-based and manual methods. Among them, PET-based SOR and SCR values showed an excellent correlation and concordance with those of manual method. In relationship with clinical severity, only ASI achieved significantly inverse correlations with H&Y stage and UPDRS motor score. There was no significant difference between the quantitative parameters of both occipital cortex and cerebellum in all three methods, which implied that quantitation using PET-based method could be reproducible regardless of the reference region.

CONCLUSIONS

Quantitative parameters using FP-CIT PET template-based method correlated well with those using laborious manual method with excellent concordance. Moreover, PET-based quantitation was less influenced by the reference region than MR-based method. It suggests that PET-based method can provide objective and quantitative parameters quickly and easily as a feasible analysis in place of conventional method.

A comparison of different energy window subtraction methods to correct for scatter and downscatter in I-123 SPECT imaging

OBJECTIVE

One of the main problems in quantification of single photon emission computer tomography imaging is scatter. In iodine-123 (I-123) imaging, both the primary 159 keV photons and photons of higher energies are scattered. In this experimental study, different scatter correction methods, based on energy window subtraction, have been compared with each other.

METHODS AND MATERIALS

Iodine-123 single photon emission computed tomography images of a phantom with a known intensity ratio between background and hollow spheres were acquired for three different collimators (low energy high resolution, low energy general purpose, and medium energy general purpose). The hollow spheres were filled with a higher activity concentration than the uniform background activity concentration, resulting in hot spots. Counts were collected in different energy windows, and scatter correction was performed by applying different methods such as effective scatter source estimation, triple and dual energy window (TEW and DEW), double peak window (DPW) and downscatter correction. The intensity ratio between the spheres and the background was used to compare the performance of the different methods.

RESULTS

The results revealed that the efficiency of the scatter correction techniques vary depending on the collimator used. For the low energy high resolution collimator, all correction methods except the effective scatter source estimation and the DPW perform well. For the medium energy general purpose collimator, even without scatter correction, the calculated ratio is close to the real ratio. The DEW and DPW methods tend to overestimate the ratio. For the low energy general purpose collimator, only the DEW and the combined DEW and downscatter correction methods perform well.

CONCLUSION

The only correction method that provides a ratio that differs by less than 5% from the real ratio for all the collimators is the combined DEW and downscatter correction method.

Improved parkinsonism diagnosis using a partial least squares based approach

PURPOSE

An accurate and early diagnosis of Parkinsonian syndrome (PS) is nowadays a challenge. This syndrome includes several pathologies with similar symptoms (Parkinson's disease, multisystem atrophy, progressive supranuclear palsy, corticobasal degeneration and others) which make the diagnosis more difficult. (123)I-ioflupane allows to obtain in vivo images of the brain that can be used to assist the PS diagnosis and provides a way to improve its accuracy.

METHODS

In this paper, we show a novel method to automatically classify (123)I-ioflupane images into two groups: controls or PS. The proposed methodology analyzes separately each hemisphere of the brain by means of a novel approach based on partial least squares (PLS) and support vector machine.

RESULTS

A database with 189 (123)I-ioflupane images (94 controls and 95 pathological images) was used for evaluation purposes. The application of the proposed method based on PLS yields high accuracy rates up to 94.7% with sensitivity = 93.7% and specificity = 95.7%, outperforming previous approaches based on singular value decomposition, which are used as a reference.

CONCLUSIONS

The use of advanced techniques based on classical signal analysis and their application to each hemisphere of the brain separately improves the (assisted) diagnosis of PS.

Experimental determination of the weighting factor for the energy window subtraction-based downscatter correction for I-123 in brain SPECT studies

Correction for downscatter in I-123 SPECT can be performed by the subtraction of a secondary energy window from the main window, as in the triple-energy window method. This is potentially noise sensitive. For studies with limited amount of counts (e.g. dynamic studies), a broad subtraction window with identical width is preferred. This secondary window needs to be weighted with a factor higher than one, due to a broad backscatter peak from high-energy photons appearing at 172 keV. Spatial dependency and the numerical value of this weighting factor and the image contrast improvement of this correction were investigated in this study. Energy windows with a width of 32 keV were centered at 159 keV and 200 keV. The weighting factor was measured both with an I-123 point source and in a dopamine transporter brain SPECT study in 10 human subjects (5 healthy subjects and 5 patients) by minimizing the background outside the head. Weighting factors ranged from 1.11 to 1.13 for the point source and from 1.16 to 1.18 for human subjects. Point source measurements revealed no position dependence. After correction, the measured specific binding ratio (image contrast) increased significantly for healthy subjects, typically by more than 20%, while the background counts outside of all subjects were effectively removed. A weighting factor of 1.1–1.2 can be applied in clinical practice. This correction effectively removes downscatter and significantly improves image contrast inside the brain.

SPECT imaging evaluation in movement disorders: far beyond visual assessment

Single photon emission computed tomography (SPECT) imaging with (123)I-FP-CIT is of great value in differentiating patients suffering from Parkinson's disease (PD) from those suffering from essential tremor (ET). Moreover, SPECT with (123)I-IBZM can differentiate PD from Parkinson's "plus" syndromes. Diagnosis is still mainly based on experienced observers' visual assessment of the resulting images while many quantitative methods have been developed in order to assist diagnosis since the early days of neuroimaging. The aim of this work is to attempt to categorize, briefly present and comment on a number of semi-quantification methods used in nuclear medicine neuroimaging. Various arithmetic indices have been introduced with region of interest (ROI) manual drawing methods giving their place to automated procedures, while advancing computer technology has allowed automated image registration, fusion and segmentation to bring quantification closer to the final diagnosis based on the whole of the patient's examinations results, clinical condition and response to therapy. The search for absolute quantification has passed through neuroreceptor quantification models, which are invasive methods that involve tracer kinetic modelling and arterial blood sampling, a practice that is not commonly used in a clinical environment. On the other hand, semi-quantification methods relying on computers and dedicated software try to elicit numerical information out of SPECT images. The application of semi-quantification methods aims at separating the different patient categories solving the main problem of finding the uptake in the structures of interest. The semi-quantification methods which were studied fall roughly into three categories, which are described as classic methods, advanced automated methods and pixel-based statistical analysis methods. All these methods can be further divided into various subcategories. The plethora of the existing semi-quantitative methods reinforces the feeling that visual assessment is still the base of image interpretation and that the unambiguous numerical results that will allow the absolute differentiation between the known diseases have not been standardized yet. Switching to a commonly agreed-ideally PC-based-automated software that may take raw or mildly processed data (checked for consistency and maybe corrected for attenuation and/or scatter and septal penetration) as input, work with basic operator's inference and produce validated numerical results that will support the diagnosis is in our view the aim towards which efforts should be directed. After all, semi-quantification can improve sensitivity, strengthen diagnosis, aid patient's follow-up and assess the response to therapy. Objective diagnosis, altered diagnosis in marginal cases and a common approach to multicentre trials are other benefits and future applications of semi-quantification.

Tracer Kinetic Modeling in PET

Molecular imaging using PET provides a unique tool for noninvasively investigating the biochemistry of living organs. The wide range of radiolabeled molecules makes it possible to explore various biochemical, physiologic, and pharmacologic processes in vivo. Because each radiotracer is characterized by its particular kinetic behavior in the human body, the quantification of this behavior is a critical component for the improvement of imaging protocols and for rapid translation from research and development to the clinic. Suitable image reconstruction algorithms combined with tracer kinetic modeling techniques are needed to assess parametric or quantitative biologic images from the available fourdimensional images. An appropriate mathematical model is generally used to fit the time-activity curves of a region or volume of interest, thus allowing the assessment of biologic parameters.