BACKGROUND: Organ doses in spiral CT scans depend on the tube start angle.
OBJECTIVE: To determine the effective dose in single source CT (SSCT) and dual source CT (DSCT) scans as a function of tube start angle and spiral pitch value to identify the dose reduction potential by selecting the optimal start angle.
METHODS: Using Monte Carlo simulations, dose values for different tube positions with an angular increment of 10 ∘ $10^\\circ$ and a longitudinal increment of 4.5 m m $4.5 \\,\\mathrm{m}\\mathrm{m}$ were simulated over a range of 31.5 c m $31.5 \\,\\mathrm{c}\\mathrm{m}$ with collimations of 40 mm $40\\, \\mathrm{mm}$ , 60 mm $60\\, \\mathrm{mm}$ , and 80 m m $80 \\,\\mathrm{m}\\mathrm{m}$ . The simulations were performed for the thorax region of six adult patients based on clinical CT data. From the resulting dose distributions, organ doses and effective dose were determined as a function of tube angle and longitudinal position. Using these per-view dose data, the individual organ doses, as well as the total effective dose, were determined for spiral scans with and without tube current modulation (TCM) with pitch values ranging from 0.5 to 1.5 for SSCT and up to 3.0 for DSCT. The dose of the best and worst tube start angle in terms of dose was determined and compared to the mean dose over all tube start angles.
RESULTS: With increasing pitch and collimation, the dose variations from the effective dose averaged over all start angles increase. While for a collimation of 40 m m $40 \\,\\mathrm{m}\\mathrm{m}$ , the variations from the mean dose value stay below 5 % $5 \\%$ for SSCT, we find that for a spiral scan with a pitch of 3.0 for DSCT with TCM and collimation of 80 m m $80 \\,\\mathrm{m}\\mathrm{m}$ , the dose for the best starting angle is on average 16 % $16 \\%$ lower than the mean value and 28 % $28 \\%$ lower than the maximum value.
CONCLUSIONS: Variation of the tube start angle in spiral scans exhibits substantial differences in radiation dose especially for high pitch values and for high collimations. Therefore, we suggest to control the tube start angle to minimize patient risk.

BACKGROUND: Methanol-poisoning can be a challenging cause of mortality. Identifying the epidemiological, clinical, and para-clinical determinants of outcome in methanol-poisoning patients could be a step forward to its management.
METHODS: In this hospital-based cohort study, 123 methanol-poisoning patients were included. Data on background variables, details of methanol consumption, and laboratory assessments were recorded for each patient. Patients underwent brain CT scans without contrast. We evaluated the association of all gathered clinical and para-clinical data with patients\' outcome and length of hospital stay (LOS). Independent association of potential determinants of death, and LOS were modeled applying multivariable logistic, and Ordinary Least Square regressions, respectively. Odds ratio (OR), and regression coefficient (RC), and their 95% confidence intervals (CIs) were estimated.
RESULTS: Most of the study population were male (n=107/123). The mean age of the participants was 30.3±9.1 years. Ninety patients (73.2%) were reported as being conscious on admission, and 34.3% of patients were identified with at least one abnormality in their CT scan. Level of consciousness (LOC) (OR: 42.2; 95% CI: 2.35-756.50), and blood pH (OR: 0.37; 95% CI: 0.22-0.65) were associated with death. Supratentorial edema (RC: 17.55; 95% CI: 16.95-18.16) were associated with LOS.
CONCLUSIONS: Besides LOC, patients with any abnormality in their brain CT scan on admission were found to be at higher risk of death, and patients with supratentorial edema were at risk of longer LOS. Brain CT-scan on admission should be considered as a part of the routine procedure during the management of methanol-poisoning.

Essential thrombocythemia (ET) is associated with an increased risk of thrombosis and autoimmune renal involvement. We report an extremely rare case of an acute kidney injury (AKI) in the presence of bilateral renal pelvises fibrosis in a patient with a proven diagnosis of ET. A 48-year-old male patient with a past medical history of mild chronic kidney disease and ET was admitted to our hospital with AKI. The patient discontinued his hydroxyurea treatment for the past 2 months and laboratory data showed increasing serum creatinine levels and platelet counts with increased renal sizes, severe hydrocalyx, and bilateral renal sinuses\' fibrosis in imaging. The patient started again on hydroxyurea therapy and showed improvement in all laboratory scales. ET and increased levels of platelet-derived growth factors could cause renal sinuses fibrosis and glomerulopathy. In ET patients with renal sinuses\' fibrosis and glomerulopathy, initiating cytoreductive therapy could improve the outcome.

Surgical treatment of tumours in the anterior mandible and surrounding tissues may result in defects which can be restored by a fibula free flap. The upper airway may change during this process. The purpose of this retrospective study was to evaluate upper airway changes after fibula free flap reconstruction. A total of 37 patients who underwent anterior mandibulectomy and fibula free flap reconstruction between 2012 and 2020 were recruited. Patients with benign and malignant tumours involving the anterior mandible were included. Spiral computed tomography was performed 1 week preoperatively, 1 week postoperatively, and at> 1 year (range 12-23 months) after surgery. Cross-sectional areas and volumes of the upper airway were measured. Data were analysed by two-way analysis of variance. The upper airway in the malignant tumour group showed an increasing trend, especially at the soft palate and tongue base levels (P < 0.01). In the benign tumour group, the upper airway showed no significant changes. The location of the minimum cross-sectional area moved downwards in both groups, and the area increased in the malignant tumour group during long-term follow-up. Upper airway obstruction is less likely to occur in the long term after surgical resection of anterior mandible malignancies and fibula free flap reconstruction.

Colorectal carcinoma is the third most malignant and second leading cause of death from cancer. The cruelty of this entity is that it takes decades to be symptomatic and is known to be detected late in its timeline by a screening technique. The fatality of this carcinoma only means heightened importance of screening guidelines to be laid down and strict follow-ups by the healthcare providers. A novel method, a potential competitor that could now replace the present screening techniques for colorectal carcinoma, is computed tomographic colonography (CTC) or virtual colonoscopy. Though it first came into existence in 1994, this method is yet to be deeply studied and scrutinized for it to be the next benchmark modality. This review has mainly focused on the various features of CTC. It is contrasted against the gold standard colonoscopy for its superiority, efficacy, cost-effectiveness, patient logistics, and role in detecting extra-colonic lesions. The main focus would be laid on CTC being a screening modality. The review also emphasized why there is a need for the current healthcare providers to incorporate this modality into their practice widely. Although much has been said about CTC and its various aspects of cost-effectiveness, about it being replaced or supplemented for cancer screening, a collaborative effort has to be made by both the fields of radiology and gastroenterology to investigate the outcomes of this not so new technique in daily practice and to avoid misinterpretation of the results due to lack of skill and proficiency.

OBJECTIVE: This study aimed to focus on the atlantoaxial pedicle screw placement and evaluate the effects of anatomical data and degree of surgical exposure of the atlantoaxial pedicle screw trajectory determined using spiral CT on the reference sites for pedicle screw insertion and various parameters in clinical application.
METHODS: The data of CT scan of cervical spine from individuals treated in our hospital were selected. Various anatomical parameters of the atlantoaxial pedicle screw trajectory were measured through multiplanar reconstruction (MPR) technology. Anatomical data and degree of surgical exposure of the atlantoaxial pedicle screw trajectory were obtained through spiral CT. Vernier calipers with least count of 0.01 mm was selected and the least count of the protractor was 0.2°. Prism 8.0 was adopted for graphical data analysis. The anatomical data of atlas of the local population were established. The measurement technique for pedicle screw trajectory and the method for pedicle screw insertion were mastered.
RESULTS: The results indicated that the intraoperative blood loss was between 30-280 ml with no case of excessive blood loss. Follow-up studies 10-18 months after the operations indicated stability of upper cervical spine without adverse conditions. The width of the pedicle screw was 13-24 mm, and the maximal inclination angle of the horizontal for the insertion was 17-21°.
CONCLUSIONS: The atlantoaxial pedicle screw placement was an effective surgical treatment for stabilizing the upper cervical spine. The measurement data of the atlantoaxial pedicle screw path was obtained through spiral CT and the surgical placement of pedicle screw was guided through individual data. Postoperative CT scan was adopted to evaluate the accuracy of pedicle screw placement, record the occurrence of secondary injuries, improve the stability of clinical applications, and reduce the risks for patients.

OBJECTIVE: To investigate the dependence of signal-to-noise ratio (SNR) and calculated average dose per volume of spiral breast-CT (B-CT) on breast size and breast density and to provide a guideline for choosing the optimal tube current for each B-CT examination.
METHODS: Three representative B-CT datasets (small, medium, large breast size) were chosen to create 3D-printed breast phantoms. The phantoms were filled with four different agarose-oil-emulsions mimicking differences in breast densities. Phantoms were scanned in a B-CT system with systematic variation of the tube current (6, 12.5, 25, 32, 40, 50, 64, 80, 100, 125 mA). Evaluation of SNR and the average dose per volume using Monte Carlo simulations were performed for high (HR) and standard (STD) spatial resolution.
RESULTS: SNR and average dose per volume increased with increasing tube current. Artifacts had negligible influence on image evaluation. SNR values ≥ 35 (HR) and ≥ 100 (STD) offer sufficient image quality for clinical evaluation with SNR being more dependent on breast density than on breast size. For an average absorbed dose limit of 6.5 mGy for the medium and large phantoms and 7 mGy for the small phantom, optimal tube currents were either 25 or 32 mA.
CONCLUSIONS: B-CT offers the possibility to vary the X-ray tube current, allowing image quality optimization based on individual patient\'s characteristics such as breast size and density. This study describes the optimal B-CT acquisition parameters, which provide diagnostic image quality for various breast sizes and densities, while keeping the average dose at a level similar to digital mammography.
CONCLUSIONS: • Image quality optimization based on breast size and density varying the tube current using spiral B-CT.

OBJECTIVE: To compare the clinical diagnostic value of spiral CT scan with different dose in patients with early-stage peripheral lung cancer.
METHODS: A total of 163 cases of patients with early-stage peripheral lung cancer who came to People\'s Hospital of Rizhao for treatment from June 2014 to January 2017 were retrospectively analyzed. A total of 78 cases of patients who received low-dose CT scanning were the low-dose group, another 84 cases of patients who received routine dose CT scanning were the routine dose group. Multislice helical CT (MSCT) scanning was performed in both groups, with tube voltage of 120 kV. Tube current was 25 m A in the low-dose group and 250 m A in the routine dose group. In addition, a total of 80 patients with lobar pneumonia were added as the control group of diagnostic sensitivity, specificity and accuracy. Pathological diagnosis was taken as the gold standard to compare the diagnostic sensitivity, specificity and accuracy of the two groups.
RESULTS: The image quality, nodules and signs of the two groups were compared, and the results of radiation dose of the two groups were compared. The diagnostic sensitivity, specificity and accuracy of the low-dose group were 82.05%, 87.50% and 84.81%, respectively. The diagnostic sensitivity, specificity and accuracy of the routine dose group were 85.71%, 86.25% and 85.97%, respectively. The diagnostic value of the two groups was not statistically significant (p > 0.05). However, the radiation dose in the low-dose group was significantly lower than that in the routine group.
CONCLUSIONS: Low-dose MSCT scanning can meet the clinical requirements for imaging diagnosis of peripheral lung cancer, and can reduce the radiation dose of patients.

OBJECTIVE: Emphysema and chronic obstructive lung disease were previously identified as major risk factors for severe disease progression in COVID-19. Computed tomography (CT)-based lung-density analysis offers a fast, reliable, and quantitative assessment of lung density. Therefore, we aimed to assess the benefit of CT-based lung density measurements to predict possible severe disease progression in COVID-19.
METHODS: Thirty COVID-19-positive patients were included in this retrospective study. Lung density was quantified based on routinely acquired chest CTs. Presence of COVID-19 was confirmed by reverse transcription polymerase chain reaction (RT-PCR). Wilcoxon test was used to compare two groups of patients. A multivariate regression analysis, adjusted for age and sex, was employed to model the relative increase of risk for severe disease, depending on the measured densities.
RESULTS: Intensive care unit (ICU) patients or patients requiring mechanical ventilation showed a lower proportion of medium- and low-density lung volume compared to patients on the normal ward, but a significantly larger volume of high-density lung volume (12.26 dl IQR 4.65 dl vs. 7.51 dl vs. IQR 5.39 dl, p = 0.039). In multivariate regression analysis, high-density lung volume was identified as a significant predictor of severe disease.
CONCLUSIONS: The amount of high-density lung tissue showed a significant association with severe COVID-19, with odds ratios of 1.42 (95% CI: 1.09-2.00) and 1.37 (95% CI: 1.03-2.11) for requiring intensive care and mechanical ventilation, respectively. Acknowledging our small sample size as an important limitation; our study might thus suggest that high-density lung tissue could serve as a possible predictor of severe COVID-19.

To investigate temporal changes in the utilization and patient impact of abdominal CT during duty shifts in the past 15 years.
This study included a random sample of 1761 abdominal CT scans that were made during evening and night duty shifts in a tertiary care center between 2005 and 2019.
The number of CT scans significantly increased (almost threefold) between 2005 and 2019 (Mann-Kendall tau of 0.829, P < 0.001). The proportion of negative CT scans (i.e., the absence of findings related to the reason that the CT scan was made and no disease deterioration or other new and clinically relevant findings compared to a previous imaging examination when available) was 40.0% (700/1749) in the entire 15-year study frame and did not significantly change over time (Mann-Kendall tau of - 0.219, P = 0.276). The overall frequency of same-day hospital discharge after negative CT was 20.6% (150/729) in the past 15 years and showed a significant increase over time (Mann-Kendall tau of 0.505, P = 0.010). The overall proportion of CT scans with incidental findings was 3.4% (60/1761) and remained statistically stable over the past 15 years (Mann-Kendall tau of - 0.057, P = 0.804).
Over the past 15 years, the number of CT scans and the frequency of same-day hospital discharge after negative CT have increased, while the proportions of negative CT scans and incidental findings have remained stable in our tertiary care center. The data from this study can be used for interinstitutional benchmarking to define, monitor, and improve the appropriateness of imaging utilization.