Background: To find the effect of CarekV on image quality & effective radiation dose (R.D) in PET/CT examination.Materials and Methods: This study included 37 patient who had another PET/CT scan done on the same machine (Seimens Biograph mCT, without CarekV) with the same CT parameters except CarekV. R.D in CT was calculated. Both scans of these pt were analysed for image quality grading score (G.S) on scale of 1-4 (1-Non diagnostic to 4-excellent). Images were compared fornoise, contrast resolution, edge definition, overall quality & 4 organs. G.S was calculated & compared.Result: Using CkV, mean R.D significantly reduced from 11.7 to 11.0 mSv (p value-0.002) & mean G.S significantly increased from 20.24 to 22.36 (p value- 0.0117).Conclusion: Using CkV in PET/CT examination, CT R.D to the patient can be reduced significantly without compromising the image quality.

Background: Exposure conditions in CT examinations are quite different from conventional X-ray. In CT examination higher dose is given to patient in comparison with the dose in other diagnostic examinations. In order to calculate organ effective dose in chest CT, Monte Carlo simulation has been used in this study. Materials and Methods: The Impact survey data were used to determine the parameters related to patient dose. This was done by correlating the measurements from the NRPB scanners with the effective dose calculated, using the CTDOSE software. Patient dose index in air (CTDIair) was measured as function of tube exposure ranged from 90 to 225mAs at constant kVp and slice thickness, using a stack of TLD chips which as long enough to fully encompass the dose profile that could have been used. Results: Dose profile of each exposure was measured with approximately Gaussian distribution shape. The full width at half maximum (FWHM) of these profiles was nearly equal, and on average it was equal to 8 cm. Also the maximum CTDIair for these profiles, as expected increased with mAs ranging from 29.2 to 50.606 mGy.  TDIair was measured by two methods using conversion coefficient established by using software, based on Monte Carlo simulations (CTDOSE) and the other was measured in the area under the dose profile distribution. Conclusion: The slice thickness measured from FWHM and those thicknesses set by the operator were nearly equal proving that the measurements using TLD were accurate. The effective dose for chest increased with increasing mAs. By these measurements, it was also noted that the maximum equivalent dose and sharpest slope variation were for lungs, heart and breast respectively, whereas the minimum equivalent dose with lowest slope variation was related to thyroid, liver, spleen, stomach wall and kidneys respectively.

Introduction: Nowadays with the advent of 64-slice CT modules associated with PET scanners, full clinical cardiac assessment is possible. But, the use of CT for AC of PET image can introduce misalignment artifacts due to time discrepancy between CT and PET data acquisition and produce the artifactual distribution uptake values in all segments of the myocardial wall. The aim of this study is to evaluate the misalignment effect induced by spurious patient motion in-between the two modalities on regional uptake value in the myocardial wall.Methods: The study was performed using 3 patients including one NH3 perfusion and two 18Ffluorodeoxyglucose viability examinations acquired on the Biograph TP 64 PET/CT scanners using routine cardiac PET/CT protocol. For accurate quantitative analysis, attenuation and emission data were also obtained using RSD thorax phantom. Manual shifts between the CT and PET images ranging from 0 to 20 mm in six different directions were applied. Thereafter, attenuation correction was applied to the emission data using the manually shifted CT images. The reconstructed PET images using shifted CT images for attenuation correction were compared with the reference PET image (PET image corrected with misalignment free original CT image). VOI-based analysis, regression and Box and Whisker plots were determined using 500 VOIs located within the myocardial wall in each PET dataset. For accurate assessment of the activity distribution in myocardium wall, 17-segment bull’s eye view analysis was evaluated for PET images.Results: The absolute percentage relative difference in uptake value increased in all simulated movements with increasing misalignments for both phantom and clinical studies. In patient studies, in reference to the bull’s eye view models, VOI-based analysis and visual analysis of PET images in standard axes as evaluated by expert clinicians, the significant variation in uptake value in comparion with the reference PET images were observed in the anteroseptal (23.55±9.92) and lateroinferior (32.96±9.74) segments in backward and forward directions respectively.Conclusion: although misalignment can introduce artifactual nonuniformities in myocardial wall but the anterior, lateral and septal regions were more vulnerable by misalignment. The variation were more significant for right, backward and forward directions.so that were caused erroneous clinical interpretation even in little misalignment (5 mm).but the significant errors can observe in medium (10mm) mismatch for PET image corrected using shifted CT in the left, down and up directions.

Introduction: The optimization of radiation exposure when exploring small and complex anatomical structures is the most important issue for temporal bone CT. The objective of this study is to use single-shot volume acquisition in order to minimize the dose and compare the obtained image quality to a conventional helical technique. Material and Methods: Twenty patients (8 males, 12 females) were scanned using the 135kVp single-shot volume mode (VMCT135-kVp) whereas other twenty patients (9 males, 11 females) were examined using the 120kVp helical mode (HMCT120-kVp). A physician-interpreter evaluated the subjective conspicuity of 53 structures in the temporal bone on a 5-point scale using multiplanar reconstruction (MPR). In addition, the image noise in both techniques was quantified by analyzing it in three diff, erent regions of interest (ROIs). Radiation dose reduction was noted and compared with literature-based effective dose dosimetry data. Results: The mean dose-length-product (DLP) for the VMCT135-kVp was (69. 6±, 2. 5 mGy. cm), which was significantly lower (p<0. 001), compared to (186. 4±, 4. 3 mGy. cm) for HMCT120-kVp. Similarly, the effective dose (0. 15±, 0. 01 mSv) for VMCT135-kVp was reduced by approximately 61. 5% relative to (0. 39±, 0. 05 mSv) for HMCT120-kVp. In contrast, there was no significant difference in the image noise average between the two protocols (p> 0. 05). Indeed, the overall analysis of the 53 anatomic structures revealed no differences between the two protocols, and most anatomic structures were identified. Conclusion: For temporal bone, the VMCT135-kVp scan significantly reduces radiation exposure compared to the HMCT120-kVp. The obtained dose was lower compared to the literature-based protocol while maintaining image visualization quality.

Background: This study intended to measure radiation doses to various organs and calculate the risk of cancer incidence from neck computed tomography and head computed tomography scans of trauma patients by using a thermoluminescent dosimeter. Methods: We assessed 93 patients who presented to the Emergency Department. Based on their health conditions, different computed tomography scans were performed. We used a fixed tube current of 200 mAs and tube voltage of 120 kVp for all patients. Next, we derived the effective radiation dose by multiplying the dose length product and conversion factor of each computed tomography scan based on the International Commission on Radiological Protection 103. Organ dose estimations were calculated from the dosimeter readout. We calculated the life attributable risk for cancer incidence based on the Committee on the Biological Effects of Ionizing Radiation VII preferred models. Results: Neck computed tomography scans had a mean effective dose of 2. 18 mSv. The mean effective dose for head computed tomography scans was 1. 53 mSv. The highest mean equivalent organ dose was for the thyroid with the neck computed tomography scan and the lenses of the eyes with the head computed tomography scan. There was no significant difference between scan lengths in each computed tomography acquisition. There was a noticeable correlation observed between effective radiation dose and tube current. As anticipated, young people had a higher life attributable risk of cancer compared to the elderly. This amount was less than 0. 011 per 100 persons for both computed tomography studies. Conclusion: Our data showed a significant organ radiation dose in both neck and head computed tomography scans, not only for the thyroid and the lenses of the eyes, but also for the chest.

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.

Positron emission tomography/computed tomography (PET/CT) with radioactive Fluorine-18 fluorodeoxyglucose (FDG) is a highly sensitive tool that is used for detecting malignancy. However, it can sometimes produce false positive results if done after vaccination. To prove this, we present two cases of individuals who received pneumococcal polysaccharide vaccination (PPV) and later showed FDG accumulation in the axillary lymph nodes during PET/CT scans. The first case involves a 69-year-old man who underwent a PET/CT scan for a health checkup. The scan revealed low-grade FDG uptake in the left axillary lymph nodes. A thorough examination of his medical history revealed that the patient had received PPV in his left upper arm eight days prior to the checkup. The vaccination was suspected to have caused left axillary lymphadenopathy. The second case involves a 66-year-old woman who also underwent a PET/CT scan for a health checkup. The scan showed FDG-avid lymph nodes in the left axillary region and increased FDG uptake in the spleen. After further questioning, it was discovered that the patient had received PPV in her left upper arm eight days prior to the checkup. Seven days after the PET/CT scan, when a complete blood count with differential was performed on the second case, it revealed that all data were within normal limits. Further, an abdominal ultrasound was conducted, which showed normal findings in the spleen. Based on these results, the medical team concluded that the prior vaccination was the cause of the observed benign findings and emphasized the importance of carefully reviewing patient history to differentiate between benign findings and malignant lesions.

Background: Computed Tomography (CT) is main contributor of population dose from diagnostic X-ray examinations. Children are more radiosensitive than adults, thus optimization of CT examination in these patients is essential. The purpose of this study was to evaluate dose delivered to pediatric patients’ undergoing CT examination of the common examinations and also establishing local Diagnostic Reference Levels (DRLs). Materials and Methods: Questionnaires were designed for data collection at seven public hospitals and information about patient, protocol and CT system were recorded during 2013 and 2014. Dose measurement was performed in four age groups: 0-1, 1-5, 5-10 and 10-15 years old and two CT dose quantity including CTDIw and DLP were calculated.Results: Values of 40, 48, 59.5, 59.5 mGy; 16.9, 16.9, 17.14, 17.14 mGy; 17, 17, 17, 17 mGy; 17, 17, 19.2, 19.2 mGy in terms of CTDIw and 448, 538, 758, 758 mGy cm; 129, 129, 154, 167 mGy cm; 184, 225, 306, 315 mGy cm; 289, 408, 595, 670 mGy cm in terms of DLP as regional DRL for brain, sinus, chest, abdomen and pelvic examinations were obtained respectively.Conclusion: The variations in dose of some examination were considerable. As the role and usage of CT technology continues to expand, it is important that all practitioners adapt optimized protocols, especially for pediatrics scanning, following proposed reference levels.