Evaluation of the Effect of Attenuation Correction by External CT in a Semiconductor SPECT.

The discovery of NM530c with a cadmium-zinc-telluride detector (CdZnTe-SPECT) is superior to the conventional Anger-type SPECT with a sodium-iodide detector (NaI-SPECT) in terms of sensitivity and spatial resolution. However, in the clinical example, even in CdZnTe-SPECT, a count decrease in myocardium due to the attenuation of the gamma ray is an issue. This study was conducted to evaluate the effect of computed tomography attenuation correction (CTAC) in CdZnTe-SPECT with the help of external CT. We evaluated the revision effect of uniformity, influence by the difference in attenuation distance, contrast ratio, an uptake rate using the heart phantom. As a result of the phantom studies, a good revision effect was obtained. In the clinical study, there was a statistical significant difference between the contrast ratio before and after CTAC in the inferior wall. In addition, the contrast ratio before and after CTAC in CdZnTe-SPECT image was equal to those of NaI-SPECT image. It was suggested that CTAC using external CT in CdZnTe-SPECT was clinically useful for inferior wall.

Evaluation of Resolution Recovery for Each Collimator in Brain Perfusion Image.

PURPOSE: This study aimed to verify the resolution recovery for each collimator in the brain perfusion image. METHOD: To verify the effect of the resolution recovery for each collimator, we evaluated via the three-dimensional brain phantom (phantom) and the normal brain perfusion single photon emission computed tomography (SPECT) data. These data were reconstructed using the three-dimensional ordered subset expectation maximization method (3D-OSEM) (Evolution for boneTM) that was performed with scatter correction, attenuation correction, and resolution recovery (RR). The performance of resolution recovery was evaluated in the two collimator systems (ELEGP and MEGP) reconstruction condition via the contrast value, mean counts, normalized mean square error (NMSE), and regional brain activity. RESULT: In the "with resolution recovery (+RR)", the NMSE indicated minimum value with SI (subset×iteration) = 100, cut-off frequency (Fc) = 0.50 cycles/cm. The contrast value in the "+RR" increased 20% for the cortical region and decreased 28% and 6% at ELEGP collimator and MEGP collimator for the central region, as compared to the "without resolution recovery (-RR)". In the phantom study, the error of the brain activity using MEGP collimator at the temporal lobe and sub-lobar decreased 15%, compared with ELEGP collimator in the + RR. In the clinical study, the error of the regional brain activity using MEGP collimator in the "+RR" increased from 3% to 8%, compared with "-RR". DISCUSSION: The accurate resolution recovery was obtained at SI = 100 and Fc = 0.50 cycles/cm. The contrast value and regional brain activity at the central region decreased due to incomplete resolution recovery by use of ELEGP collimator.

[Influence of a radioisotope from out of the effective field of view in a semiconductor single photon emission computed tomography scanner].

Discovery NM 530c (CZT SPECT) is a new single photon emission computed tomography (SPECT) scanner using a cadmium-zinc-telluride (CZT) solid-state semiconductor detector technology. Due to multi-pinhole collimator design of this system, each CZT detector facing different direction and be able to get incidence radioactivity from radioisotopes (RIs) existing outside of effective field of view (EFOV). The purpose of this study is to verify its impact and compare it to a conventional Anger-type SPECT scanner (Discovery NM/CT 670 pro). We used (99m)TcO4(-) as radiation source and set it outside of the EFOV at several different positions (height and angle) and scanned by both the cameras. As a result, CZT SPECT got more influence compared to Anger-type SPECT. The impact was different according to its height. When using other RIs in CZT SPECT room, it is important to confirm the appropriate position against CZT SPECT during scan.

[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).

Prediction of survival benefit using an automated bone scan index in patients with castration-resistant prostate cancer.

UNLABELLED: What's known on the subject? and What does the study add? A bone scan index (BSI) can quantify the extent of bone involvement and response to treatment, but it has not been widely accepted, because of its time-consuming nature. The study is the first to demonstrate that automated BSI calculated with a computer-assisted diagnosis system is effective in judging the chemotherapeutic response of bone metastatic lesions in patients with castration-resistant prostate cancer. OBJECTIVE: • To evaluate the value of an automated bone scan index (aBSI), calculated using a computer-assisted diagnosis system, to indicate chemotherapy response and to predict prognosis in patients with castration-resistant prostate cancer (CRPC) with bone metastasis. PATIENTS AND METHODS: • Forty-two consecutive CRPC patients underwent taxane-based chemotherapy between November 2004 and March 2011 at our institution. • The aBSIs were retrospectively calculated at the diagnosis of CRPC and 16 weeks after starting chemotherapy. • Cox proportional hazards regression models were applied to multivariate analyses with and without aBSI response in addition to the basic model. • Based on the difference in the concordance index (c-index) between each model, the prognostic relevance of adding the aBSI response was determined. RESULTS: • A decrease in aBSI was found in 28 patients (66.7%), whereas a response was shown by bone scan in only 23.8% of patients. • Patients with a reduction in aBSI had longer overall survival (OS) in comparison with the other patients (P= 0.0157). • Multivariate analysis without aBSI response showed that performance status (P= 0.0182) and PSA response (P= 0.0375) were significant prognosticators. • By adding the aBSI response to this basic model, the prognostic relevance of the model was improved with an increase in the c-index from 0.621 to 0.660. CONCLUSIONS: • The aBSI reflected the chemotherapy response in bone metastasis. • The index detected small changes of bone metastasis response as quantified values and was a strong prognostic indicator for patients with CRPC.

[Quantitative assessment of the usefulness of MR-fusion Tl-SPECT image in the diagnosis of brain tumor].

201Tl-SPECT (single photon emission computed tomography) had a disadvantage of low spatial resolution with a limited ROI (region of interest) setting. Recently, the diagnosis of brain tumors has been improved by fusion-imaging employing MRI (magnetic resonance imaging) with Tl-SPECT. In order to assess the usefulness of MR-fusion Tl-SPECT quantitatively, we have compared non-fusion (NF) and MR-fusion (MR-F) imaging with Tl-SEPCT in patients with brain tumors. A total of 38 patients (M/F=14/24) hospitalized at our institution during a 5-year period, each with a histologically confirmed brain tumor, were studied. The index of Tl was used for the early ratio (ER), delayed ratio (DR), and retention index (RI), There was no significant difference between NF and MR-F, which were examined using the test-retest method by 2 observers (N&H), but the Pearson's correlation coefficient was higher for MR-F than for NF. The RI value for MR-F was significantly correlated with the WHO histological grading (r=0.605, n=38, p<0.00l). The DR value for MR-F was significantly correlated with MIB-1 index (r=0.464, n=24, p=0.022). We estimated the RI cut-off value for both NF and MR-F in malignancy by ROC analysis. A cut-off value of RI=0.63 and RI=0.70 was good for NF and MR-F, respectively. The likelihood ratio (LR) of RI was higher for MR-F (LR=6.897) than for NF (LR=2.978), suggesting that RI=0.7 for MR-F was suitable for diagnosis of malignant brain tumor. We conclude that MR-fusion Tl-SPECT is better for quantitative analysis of brain tumors than non-fusion Tl-SPECT.

Effect of resolution recovery using graph plots on regional cerebral blood flow in healthy volunteers.

PURPOSE: We evaluated the effect of resolution recovery (RR) using graph plots on regional cerebral blood flow (rCBF) in brain perfusion single-photon emission computed tomography (SPECT) images derived from healthy volunteers and patients diagnosed with probable Alzheimer's disease. METHOD: We acquired brain perfusion SPECT images with scatter correction (SC), computed tomography-based attenuation correction (CTAC), and RR from a three-dimensional brain phantom and from healthy volunteers. We then compared contrast-to-noise ratio, count density ratios, increase maps, and rCBF using statistical parametric mapping 8. RESULTS: Regional brain counts were significantly increased from 20-24% with SC, CTAC, and RR compared with SC and CTAC. Mean CBF in healthy volunteers was 42.5 ± 5.4 mL/100 g/min. Average rCBF determined using SC, CTAC and RR increased 7.5, 2.0, and 3.7% at the thalamus, posterior cingulate, and whole brain, respectively, compared with SC and CTAC. CONCLUSION: Resolution recovery caused variations in normal rCBF because counts increased in cerebral regions.

Does applying resolution recovery to normal databases confer an advantage over conventional 3D-stereotactic surface projection techniques?

We evaluated a novel normal database (NDB) generated using single photon emission computed tomography (SPECT) data obtained from healthy brains by using a SPECT/CT system, analyzed using a resolution recovery (RR) technique applied to the three-dimensional stereotactic surface projection (3D-SSP) technique. We used a three-dimensional ordered subset expectation maximization method (3D-OSEM) with applied scatter correction (SC), attenuation correction, and RR to reconstruct the data. We verified the accuracy of the novel NDB's values (Z, extent, and error scores), and compared the novel NDB to the 3D-SSP technique by using simulated misery perfusion-related patient data from a conventional NDB. In addition, Z, extent, and error scores at the precuneus, cuneus, and posterior cingulate were compared under different reconstruction conditions by using the patient data. In the simulation, Z scores decreased when using the novel NDB corrected using computed tomography-based attenuation correction (CTAC), SC, and RR. The extent scores of the posterior cingulate increased using the novel NDB, relative to the other NDBs. The error score with the novel NDB without RR decreased by 15% compared to that of the conventional NDB. Z scores generated from patient data decreased in the novel NDB with RR. The extent scores tended to decrease in the novel NDB with RR. The extent scores in the novel NDB with RR improved at the posterior cingulate, compared to the scores with the other NDBs. However, applying RR to the novel NDB conferred no advantage because the cut-off of the current Z score must be reconsidered when using the additive RR technique.

[Examination of retention index in brain tumor 201Tl scintigraphy using iNRT].

The retention index (R.I.) in Thalliun-201-chloride (201Tl-Cl) brain tumor single photon emission computed tomography (SPECT) imaging analysis is useful in assessing grades of malignancy. When the T/N ratio that influences the R.I. is calculated, it is ideal to draw an ROI on the same slices and coordinates of both early and delayed transaxial images. However, in many institutions, the image slice and ROI are determined manually by operators (i.e., by the conventional method). The Co-registration function within iNRT software enables an ROI to be automatically drawn. In this study, we obtained the R.I. from six brain tumor patients employing two different methods (i.e., Co-registration and the conventional method). Each R.I. was obtained from the same personal computer that was used to transfer the transaxial images. We then compared and evaluated the six R.I. values of seven operators. (2 radiologists and 5 radiological technologists). The results showed that the R.I. values did not differ significantly between the two methods, except in two cases. Furthermore, the coefficient of variation (CV) of the R.I. obtained from the Co-registration method was lower than the conventional method in all cases. The variations among operators were also smaller in the Co-registration method. These outcomes may have been due to the fact that in the conventional method it is difficult to identify the same slices of early and delayed images. Therefore, there were differences among operators in their ways of specifying positions of the ROI. This may have resulted in differences in the number of counts/pixel of the ROI. In conclusion, the R.I. obtained by using the Co-registration method would be more useful for improving diagnostic accuracy in (201)Tl-Cl brain tumor SPECT imaging than the conventional method.

[Examination of normal database in three-dimensional SSP].

The results of statistical image analyses, such as three-dimensional stereotactic surface projection (3D-SSP), are affected by the normal database (NDB) used. As a general rule, each institution must establish its own NDB for analysis. However, the numbers of institutions with the ability to establish their own NDB are limited. Therefore, it would be ideal if an NDB suitable for other institutions could be established from standard volunteer data gathered at a single institution. In this study, we examined the validity of establishing an NDB suitable for other institutions from the standard volunteer data gathered at our institution, using E.CAM (used as a reference) and IRIX. We established three NDBs. One was established from E.CAM, and the other two were from IRIX (in which overall FWHM was the same as that of E.CAM with Butterworth filter cutoff frequency and using an identical algorithm for image-reconstruction of E.CAM). We then compared the mean values and standard deviations of the NDBs, and also examined the effects on the Z-score map. We determined that the NDB that had been established was suitable for other institutions, using identical FWHM (resolution of SPECT imaging) and an algorithm for image-reconstruction.

[Study of the normal database that affects 3D-SSP Z-score mapping].

The effects of image reconstruction conditions and devices used on 3D-SSP analysis (Z-score mapping) were investigated. Images of the 3D Hoffman brain phantom were taken with the IRIX device or E.CAM. Using two methods of image reconstruction (FBP and OSEM), several kinds of phantom normal databases (PNDB) and signal data, with or without correction for attenuation, were obtained at varying Butterworth filter cutoff frequencies. The results of 3D-SSP analyses were compared between combinations of PNDB and signal data obtained under the same conditions of image reconstruction and combinations obtained under different conditions. The results of PNDB obtained with different devices were also analyzed. For combinations of PNDB and signal data both obtained with OSEM, the Z-score of signals was high. When FBP was used to obtain both PNDB and signal data, the Z-score and signal size tended to become greater and the false-positive rate tended to decrease as the Butterworth filter cutoff frequency became lower. Whether or not correction for attenuation was incorporated did not affect the results of analysis when the same method was used to collect both PNDB and signal data. If the method for image reconstruction differed between PNDB and signal data, the false-positive rate was relatively high. Using a different device to obtain PNDB resulted in a relatively high false-positive rate. We therefore recommend that the conditions for image reconstruction from signal data should be matched to the conditions for image reconstruction from PNDB. It seems impossible to share the same NDB among different devices.

Evaluation of the difference-correction effect of the gamma camera systems used by easy Z-score Imaging System (eZIS) analysis.

OBJECTIVE: We examined the difference of the effect by data to revise a gamma camera difference. The difference-correction method of the camera is incorporated in eZIS analysis. METHODS: We acquired single photon emission computed tomography (SPECT) data from the three-dimensional (3D) Hoffman brain phantom (Hoffman), the three-dimensional brain phantom (3D-Brain), Pool phantom (pool) and from normal subjects (Normal-SPECT) to investigate compensating for a difference in gamma camera systems. We compared SPECT counts of standard camera with the SPECT counts that revised the difference of the gamma camera system (camera). Furthermore, we compared the "Z-score map (Z-score)". To verify the effect of the compensation, we examined digitally simulated data designed to represent a patient with Alzheimer's dementia. We carried out both eZIS analysis and "Specific Volume of interest Analysis (SVA)". RESULTS: There was no great difference between the correction effect using Hoffman phantom data and that using 3D-Brain phantom data. Furthermore, a good compensation effect was obtained only over a limited area. The compensation based on the pool was found to be less satisfactory than any of the other compensations according to all results of the measurements examined in the study. The compensation based on the Normal-SPECT data resulted in a Z-score map (Z-score) for the result that approximated that from the standard camera. Therefore, we concluded that the effect of the compensation based on Normal-SPECT data was the best of the four methods tested. CONCLUSIONS: Based on eZIS analysis, the compensation using the pool data was inferior to the compensations using the other methods tested. Based on the results of the SAV analysis, the effect of the compensation using the Hoffman data was better than the effect of the compensation using the 3D-Brain data. By all end-point measures, the compensation based on the Normal-SPECT data was more accurate than the compensation based on any of the other three phantoms.

Novel method for quantitative evaluation of cardiac amyloidosis using (201)TlCl and (99m)Tc-PYP SPECT.

OBJECTIVE: The degree of myocardial technetium-(99m)-pyrophosphate ((99m)Tc-PYP) accumulation in cardiac amyloidosis is conventionally evaluated by the PYP score. This method involves qualitative visual evaluation on two-dimensional images. Here, we performed three-dimensional quantitative analysis using software developed in our laboratory. METHODS: We performed dual myocardial imaging using thallium-(201)-chloride ((201)Tl-Cl) and (99m)Tc-PYP in cases of suspected cardiac amyloidosis and calculated the PYP accumulation rates of all myocardial pixels showing (99m)Tc-PYP accumulation. We defined this procedure as quantitative evaluation of the degree of (99m)Tc-PYP accumulation in the myocardium. Patients were divided into two groups with and without a diagnosis of cardiac amyloidosis, and we examined the PYP accumulation rates in both groups. In addition, we examined the PYP scores of the two groups by conventional qualitative evaluation. RESULTS: The PYP scores of the cardiac amyloidosis group were significantly higher than those of the other group. The PYP accumulation rates of the cardiac amyloidosis group were significantly higher than those of the other group. There were significant differences in the PYP accumulation rate and PYP score between the two groups. There was considered to be a threshold between the two groups in the case of the PYP accumulation rate. CONCLUSIONS: When the threshold of the PYP score was defined as 3+ and that of the PYP accumulation rate as 41.5 %, the sensitivity of the PYP score and PYP accumulation rate was 84.6 %. However, the specificity of the PYP accumulation rate was higher than that of the PYP score. Quantitative evaluation by the PYP accumulation rate of the degree of (99m)Tc-PYP accumulation in the myocardium may be useful in the diagnosis of cardiac amyloidosis.

[Evaluation of shortened protocol of graph plot method with ¹²³I-IMP].

The (123)I-IMP Graph Plot is a convenient method of analyzing cerebral blood flow without blood sampling. Data acquisition requires 45 minutes after the infusion of (123)I-IMP because the method is matched to the protocol of autoradiography (conventional method). However, we think that those protocols do not have to be matched because those theories are different. Therefore, we contrived a protocol for shortening that time by beginning SPECT data acquisition earlier and shortening the acquisition time compared to the conventional method. We compared count ratios of the decreased area to an area of the healthy side, quantitative values, and results of statistical analysis of the shortened protocol and the conventional method for cases of cerebral infarction and of dementia with Lewy bodies (DLB). Some count ratios of the shortened protocol were inferior to those of the conventional method, but the degrees did not affect the clinical diagnosis. In the other areas and cases also, the differences did not affect the clinical diagnosis. In addition to the results of this study, some previous reports have described that early SPECT images after infusion show the true cerebral blood flow. Therefore, we judged that this shortened protocol can be used as a clinical protocol.