Iranian Journal of Nuclear Medicine
Volume:15 Issue: 1, 2007

Filtering can greatly affect the quality of clinical images. Determining the best filter and the proper degree of smoothing can help to ensure the most accurate diagnosis. Forty five patient’s data aquired during brain phantom SPECT studies were reconstructed using filtered back-projection technique. The ramp, Shepp-Logan, Cosine, Hamming, Hanning, Butterworth, Metz and Wiener filters were examined to find the optimum condition for each filter. For each slice image, 6200 reconstruction options were considered. The corresponding planar image of each slice was used as the reference image. The quality of reconstructed images was determined using universal image quality index (UIQI). Four nuclear medicine physicians evaluated the images to choose the best of the filters. Images with best resolution, contrast, smoothness and overall quality were selected by nuclear medicine physicians depending on filters used to generate the best image. A significant difference (p<0.05) between the filters regarding these parameters were observed. The results of this study revealed that maximum resolution and contrast could be obtained using both Metz and Wiener filters. However, the best quality images were generated by using Butterworth filter.

In this study the evaluation of a Platelet-based Maximum Penalized Likelihood Estimation (MPLE) for denoising SPECT images was performed and compared with other denoising methods such as Wavelets or Butterworth filtration. Platelet-based MPLE factorization as a multiscale decomposition approach has been already proposed for better edges and surfaces representation due to Poisson noise and inherent smoothness of this kind of images.
We applied this approach on both simulated and real SPECT images. Monte Carlo simulations were generated with the SIMSET package to model the physical processes and instrumentation used in emission imaging. Cardiac, brain and NEMA phantom SPECT images were obtained using a single-head, Argus model SPECT system. The performance of this method has been evaluated both qualitatively and quantitatively with power spectrum, SNR and noise level measurements on simulated and real SPECT images.
For NEMA phantom images, the measured noise levels before (Mb) and after (Ma) denoising with Platelet-based MPLE approach were Mb=2.1732, Ma=0.1399. In patient study for 32 cardiac SPECT images, the difference between noise level and SNR before and after the approach were (Mb=3.7607, SNRb=9.7762, Ma=0.7374, SNRa=41.0848) respectively. Thus the Coefficient of variance (C.V) of SNR values for denoised images with this algorithm as compared with Butterworth filter, (145/33%) was found. For 32 brain SPECT images the Coefficient Variance of SNR values, (196/17%) was obtained.
Our results shows that, Platelet-based MPLE is a useful method for denoising SPECT images considering better homogenous image, improvements in SNR, better radioactive uptake in target organ and reduction of interfering activity from background radiation in comparison to that of other conventional denoising methods.

64Cu-pyruvaldehyde-bis(N4-methylthiosemicarbazone) (64Cu-PTSM)‍ is one of the most important copper radiopharmaceuticals used in clinical experiments. In this work, copper-64 (T1/2=12.33 h) production has been presented followed by the synthesis of the complexing agent, PTSM, and its structure was confirmed by common spectroscopic methods followed by radiolabeling with 64Cu-actetate. The tracer was finally administered to fibrosarcoma-bearing rats and the biodistribution was determined in critical tissues as well as tumor. The final radiopharmaceutical solution underwent common quality control tests for animal injection a radiochemical purity >95% was determined. A significant tracer tumor uptake was observed 2 hours post injection. Tumor:muscle and tumor:blood ratios were shown to be 8 and 6 respectively. 64Cu-PTSM prepared in this report is a good candidate for tumor therapy as well as diagnosis for national use.

This paper presents four cases of abnormal soft tissue activity in the bone scan of patients with different lesions (lung inflammatory pseudotumor, pulmonary fibrosis, pulmonary metastatic osteosarcoma and metastatic hepatic carcinoma of colon).

In patients with coronary artery disease (CAD) noninvasive evaluation for detection of ischemia is important to avoid invasive interventions like angiography. Exercise stress test is conventionally the first study used in evaluation of CAD. Considering the noninvasive nature of the myocardial perfusion scan, we decided to compare its accuracy with stress test. Patients with chest pain, and intermediate risk for CAD underwent stress test with Bruce standard method by treadmill, and myocardial perfusion SPECT scan with Tc-99m MIBI and the results were compared to the angiography as the gold standard. Analysis of the data was performed by SPSS11.5 soft ware. The study was performed on 89 patients (mean age: 55.5, min: 29 max: 80) including 53 man and 36 women. Exercise stress test had 54% sensitivity, 65% specificity, 68% PPV, 50% NPV, while for myocardial perfusion scan sensitivity was 94%, specificity 94%, PPV 96%, and NPV 92%. Correlation between involved walls in myocardial perfusion scan with stenotic artery in angiography was 77.6%, while this value was 32.7% for exercise stress test. There was also relationship between degree of stenosis determined by angiography and severity of ischemia detected by myocardial perfusion scan. Myocardial perfusion scan is of great value in detection of CAD with sensitivity and specificity far better than exercise stress test. It is suggested that this noninvasive study being considered the first diagnostic method for patient at risk for coronary artery disease.

Despite the long history of the worldwide use of Bacillus Calmette-Guerin (BCG) vaccine, a wide spectrum of adverse reactions has been observed in a small proportion of immunized infants; the most severe complication, disseminated BCGitis, is often fatal but exceedingly rare and is considered to result from host immunodeficiency. At present, CT scan, ultrasound, X-ray and bone marrow aspirations are the investigations used to diagnose this disease. This is the case report of a 6 months old female infant with disseminated BCGitis. This paper aims to highlight the advantages of the use of nuclear medicine imaging and pattern of bone scan for diagnosis of disseminated BCGitis.

Due to the large number of PET systems available in the market, it is not very easy to decide about the scanner of choice. Conducting a research in order to compare all different PET scanners is very time consuming and expensive and practically impossible. However, such comparison may be conducted using PET simulators. In this study, the performance of 6 different PET scanners in cardiology is evaluated using a dedicated PET simulator. In this study only the design of the system were evaluated. Activity and attenuation phantoms were produced using 4D-NCAT phantom. ECAT EXACT HR+, ECAT 953B, ECAT 966, ECAT ART, GE Advance and 16HI-REZ scanners were simulated using Eidolon PET simulator and the output sinograms were reconstructed using STIR software. The reconstructed images were processed using Interview software installed on the Mediso cardiac imaging system. Counts of pixels determined by ROI were used to drawn curves and then the correlations of these curves calculated using SPSS. True coincidences 2D was 4651791±5900 for ECAT 966, 4651965±5660 for ECAT ART, 4742731±5328 for ECAT EXACT HR+, 6018435±5167 for ECAT 953B, 6566769±4734 for GE Advance and 6846339±51850 for 16HI-REZ. Resulted correlations calculated for these scanners were 0.806, 0.795, 0.718, 0.858, 0.726 and 0.896 respectively. There was a considerable different in scatter fractions of different scanners. Curves drawn using count of pixels determined by ROI and correlations of these curves showed differences in performances of scanners in cardiology. The results showed that the 16HI-REZ scanner is the best scanner of the six scanners for simulating of cardiac PET images.

We investigated the difference in left ventricular ejection fraction (LVEF) and end-systolic volume(ESV) measured by gated myocardial perfusion SPECT (GSPECT) in the post-dipyridamole stress and rest periods, and compared the results with the perfusion patterns found in the conventional non-gated tomograms.
297 consecutive patients were studied with post-stress and rest 99mTc-sestamibi GSPECT using a two-day protocol. Stress images were obtained 90 min after dipyridamole infusion and radiotracer injection. All acquisitions were analyzed visually, semi-quantitatively and quantitatively using QGS software.
Patients were divided into 4 groups according to the perfusion patterns: Group-1 = no perfusion defects (n= 129, 43.4%); Group-2 = reversible perfusion defects (n = 85, 28.6%); Group-3=Fixed defects (n =52, 17.5%); Group 4 = partially reversible perfusion defects (n =31, 10.4%). Differences between post-stress LVEF (SEF) and rest LVEF (REF) (DEF=SEF-REF) were .39, -6.45, -1.61, and -0.70 for groups 1, 2, 3 and 4 respectively. Post-stress stunning (>5% decrease in LVEF) was present in 49 patients (16.5%). SEF was significantly more than REF in patients with summed difference score (SDS) LVEF as measured by GSPECT decreased slightly in post-stress period when an ischemic insult was present, while it has a mild tendency to increase when the myocardial perfusion is normal. Not only exercise stress but also dipyridamole can cause a transient decrease in LVEF in stunned patients. It was concluded that gated study be performed in both stress and rest phases of the procedure.