Background: Brain perfusion SPECT imaging has been a useful way to evaluate cerebro‐vascular diseases and other neuro diseases. Two‐day PROTOCOL brain perfusion SPECT is more accurate but not convenient for most patients. This is the reason why a one – day PROTOCOL using SPECT/CT was designed.Materials and Methods: Both rest and acetazolamide was done by SPECT/CT system. A 2 minute ‐ dynamic acquisition was carried out immediately after injection of 99mTc ‐ HMPAO. Then, the 1st rest SPECT study was done for 30 min after 3 min post injection of 370 MBq (10 mCi) of 99mTc ‐ HMPAO. Immediately after the 1st SPECT, 1g of acetazolamide was given intravenously. Ten minutes later, 740 MBq (20 mCi) of 99mTc – HMPAO was additionally injected. Three minutes later the 2nd SPECT study was carried out for 30 min. To measure regional cerebral blood flow (rCBF) non‐invasively, the Patlak plot analysis was applied to time–activity data on radionuclide angiography. Then reconstructed images from 1st SPECT were converted to 1st rCBF map. Base on the increased count ratio in cerebellum between decay corrected 1st and 2nd SPECT images, acetazolamide increasing ratio was calculated, and then 2nd rCBF map was generated. Region of interest (ROI) in 1st and 2nd images were set, then %increase values were calculated.Results: Thirty‐three patients were performed. The rest cortices showed rCBF values by 49.3±3.3 ml/100g brain/min, acetazolamide enhanced cortices show rCBF values by 53.8±4.0 ml/100g brain/min and % increase value by 8.9±3.7 on average.Conclusion: This method of imaging would be significant for evaluating cerebral perfusion reserve in the routine cerebro‐vascular disease for a comfortable method to patient because they do not have to come to hospital in 2 days for scanning.

Background/Objective: Hepatic lesions may be missed in the routine abdominal computed tomography (CT) scan PROTOCOL using soft tissue window setting. The ability to find these lesions is very important in the assessment of metastasis and follow-up of patients.Patients and Methods: In this study, 411 patients who underwent abdominal CT for various causes were evaluated separately by two radiologists blindly. All liver images were viewed in two different window settings, soft tissue window setting: window width (WW) of 350–400 Hounsfield units (HU), window level (WL) of 35–50 HU, and liver window setting: WW of 150 HU, WL of 50–100 HU, at the workstation.Results: Out of 411 patients, 181 (44%) were referred for cancer follow-up and 230 (56%) for evaluation of abdominal discomfort. Soft tissue window setting revealed no lesion in 334 (81.26%) patients, single lesion in 30 (7.31%), and multiple lesions in 47 (11.43%) patients. Liver window setting revealed no lesion in 313 (76.2%) patients, single lesion in 35 (8.5%), and multiple liver lesions in 63 (15.3%) patients. Compared to liver window, soft tissue window setting revealed 77.77% of all detectable liver lesions. Liver window showed new lesions in 22 (6.6%) of patients in whom no lesion had been found in soft tissue window setting. Therefore, liver window setting brought 5.3% increase in the diagnostic yield of CT in our series, and changed the decision for treatment in 2.4% of patients studied.Conclusion: Liver window setting added to the standard soft tissue setting PROTOCOL of abdominal CT at the workstation can improve the diagnosis and follow-up of patients, especially for those who have known cancer. Image review with this new setting takes a few minutes and the cost is also low; there is no added radiation exposure to patients.

Background: Currently computed tomography pulmonary angiography (CTPA) has become a widely accepted clinical tool in the diagnosis of acute pulmonary embolism (PE).Objectives: To report split-bolus single-pass 64-multidetector-row CT (MDCT) PROTOCOL for diagnosis of PE.Patients and Methods: MDCT split-bolus results in 40 patients suspicious of PE were analyzed in terms of image quality of target pulmonary vessels (TPVs) and occurrence and severity of flow-related artifact, flow-related artifact, false filling defect of the pulmonary veins and beam hardening streak artifacts. Dose radiation to patients was calculated.Results: MDCT split-bolus PROTOCOL allowed diagnostic images of high quality in all cases. Diagnosis of PE was obtained in 22 of 40 patients. Mean attenuation for target vessels was higher than 250 HU all cases: 361±98 HU in pulmonary artery trunk (PAT); 339±93 HU in right pulmonary artery (RPA); 334±100 HU in left pulmonary artery (LPA). Adequate enhancement was obtained in the right atrium (RA): 292±83 HU; right pulmonary vein (RPV): 302±91 HU, and left pulmonary vein (LPV): 291±83 HU. The flow related artifacts and the beam hardening streak artifacts have been detected respectively in 4 and 25 patients. No false filling defect of the pulmonary veins was revealed.Conclusion: MDCT split-bolus technique by simultaneous opacification of pulmonary arteries and veins represents an accurate technique for diagnosis of acute PE, removes the false filling defects of the pulmonary veins, and reduces flow related artifacts.

In modern PET/CT systems, the CT provides a fast and relatively noise-free attenuation map and improving lesions localization and the possibility of accurate quantitative analysis. In cardiac imaging, there is a strong attenuation gradient along the myocardial free wall, with muscle next to the air of the lung space and heart has movement and located in the place that move due to breathing cause misalignment increases in this area. If misalignments occur along these boundaries, the attenuation correction factors are potentially inaccurate, causing as much as a 60% error in the PET tracer emission image in the critical regions of diagnostic interest. Artifacts caused by misalignment are particularly disconcerting in cardiac imaging because they can present themselves as perfusion abnormalities or erroneous information on myocardial viability. In This paper the accuracy of some CT PROTOCOLs such as gated, normal (a high-pitch helical CT), slow ct, low-temporalresolution helical CT, time-averaged CT (ACT), ultra low dose CT that normally used for attenuationcorrection in PET/CT were compared, moreover the image quality and dose that induced to patient from each PROTOCOLs. Acquiring a slow CT improved registration between the transmission and emission. Potential for a heightened radiation dose delivered by the slow CT was compensated by doubling the default noise index and increasing the slice thickness to 5 mm. In the low-dose average cine CT, Further reduction in dose is possible by lowering the upper threshold of the auto-mA settings or modulation of the CT tube current based on anatomy. ACT PROTOCOLs consist of multiple images acquired sequentially (also referred to as cine or axial) along the bed length over the span of one or more respiratory cycles. 2% average increase in ACT-PET rest reconstruction values compared the HCT-PET rest reconstruction values was slightly higher than the bias calculated. Contrary to the HCT PROTOCOL, the ACT PROTOCOL provides more flexibility in addressing artifacts such as varying the respiratory phases used to create the time-averaged CT to suppress respiratory artifacts. In addition, photon starvation can be addressed by optimizing the acquisition parameters, such as increasing the tube voltage and current in patients with high BMI values. Ultra-low-dose CT’s shorter duration and the lower radiation and revealed no severe shift of the myocardium between the CT-based transmission and the emission in the patients.

Background and purpose: Coronal CT scan of paranasal sinuses with contiguous images is the gold standard technique in diagnosis of sinusitis. Considering the expense and high dose of radiation in conventional CT scan, clinical measurements and simple radiography is not enough sensitive and specific, some workers have suggested limited screening (non contiguous) instead of conventional CT image. This study compared the diagnostic accuracy of coronal CT with limited screening (4 screens) to conventional CT in diagnosis of sinusitis.Materials and methods: On 100 patients suspected of sinusitis referred to Emam Khomeini hospital. Coronal CT scan (with 16 screens) was performed. And on the basis of relevant scout view, four images of limited screenings (non contiguouse images) were selected and printed. Images of the both CT techniques were reported seperately by two radiologists. (Totally, four CT reports for each patients were given) The results of standard and limited screening CT reports given from the first radiologist were compared with the reports of the same, given by the second radiologist.Results: The comparitive results for the standard and limited screening techniques reported by two radiologists referred to as kappa value were 0.95 and 0.97 respectively. Which indicate a good aggreement between two radiologists in giving the reports of the images. Limited screening technique generally had the rate of 94.1% and 93.5% for sensitivity and accuracy respectively. General prevalence of sinusitis in the patients under study was 67%. Maxillar sinus was the most involved one with result of 98.7%.Conclusion: Limited screening CT technique for paranasal sinuses can be a proper technigue as a first evaluative measurement in the patients suspected for sinusitis. For this, can replace simple radiography. Advantage of this technique can be due to use of less dose of radiation, more speed of radiography and less expenses.