Image Quality and Lesion Detection on Deep Learning Reconstruction and Iterative Reconstruction of Submillisievert Chest and Abdominal CT.

OBJECTIVE. The objective of this study was to compare image quality and clinically significant lesion detection on deep learning reconstruction (DLR) and iterative reconstruction (IR) images of submillisievert chest and abdominopelvic CT. MATERIALS AND METHODS. Our prospective multiinstitutional study included 59 adult patients (33 women, 26 men; mean age ± SD, 65 ± 12 years old; mean body mass index [weight in kilograms divided by the square of height in meters] = 27 ± 5) who underwent routine chest (n = 22; 16 women, six men) and abdominopelvic (n = 37; 17 women, 20 men) CT on a 640-MDCT scanner (Aquilion ONE, Canon Medical Systems). All patients gave written informed consent for the acquisition of low-dose (LD) CT (LDCT) after a clinically indicated standard-dose (SD) CT (SDCT). The SDCT series (120 kVp, 164-644 mA) were reconstructed with interactive reconstruction (IR) (adaptive iterative dose reduction [AIDR] 3D, Canon Medical Systems), and the LDCT (100 kVp, 120 kVp; 30-50 mA) were reconstructed with filtered back-projection (FBP), IR (AIDR 3D and forward-projected model-based iterative reconstruction solution [FIRST], Canon Medical Systems), and deep learning reconstruction (DLR) (Advanced Intelligent Clear-IQ Engine [AiCE], Canon Medical Systems). Four subspecialty-trained radiologists first read all LD image sets and then compared them side-by-side with SD AIDR 3D images in an independent, randomized, and blinded fashion. Subspecialty radiologists assessed image quality of LDCT images on a 3-point scale (1 = unacceptable, 2 = suboptimal, 3 = optimal). Descriptive statistics were obtained, and the Wilcoxon sign rank test was performed. RESULTS. Mean volume CT dose index and dose-length product for LDCT (2.1 ± 0.8 mGy, 49 ± 13mGy·cm) were lower than those for SDCT (13 ± 4.4 mGy, 567 ± 249 mGy·cm) (p < 0.0001). All 31 clinically significant abdominal lesions were seen on SD AIDR 3D and LD DLR images. Twenty-five, 18, and seven lesions were detected on LD AIDR 3D, LD FIRST, and LD FBP images, respectively. All 39 pulmonary nodules detected on SD AIDR 3D images were also noted on LD DLR images. LD DLR images were deemed acceptable for interpretation in 97% (35/37) of abdominal and 95-100% (21-22/22) of chest LDCT studies (p = 0.2-0.99). The LD FIRST, LD AIDR 3D, and LD FBP images had inferior image quality compared with SD AIDR 3D images (p < 0.0001). CONCLUSION. At submillisievert chest and abdominopelvic CT doses, DLR enables image quality and lesion detection superior to commercial IR and FBP images.

An overview of acquisition parameters, dose measurements and organ doses in abdominal CT scans in Brazil.

The aim of this multi-centre study was to evaluate the irradiation parameters and the radiation dose of abdomen CT exams without contrast, performed in adults In Brazil, in order to provide an overview of the CT installed base in the country and contribute for the establishment of optimization programs. Equipment of seven different models, with 16 and 64 channels, installed in 17 Brazilian states, plus the Federal District, were analyzed. The results show that the mean CTDIvol ranged from 6.60 mGy to 34.64 mGy. The results also showed that different irradiation parameters are used in equipment of the same model, resulting, in some cases, in three times higher CTDIvol values. These characteristics are not restricted to a given region of the country but distributed throughout the national territory. Repetitions of acquisitions and topograms with scan length larger than the region of interest were found in 13.5% of abdomen examinations, resulting in considerably higher absorbed doses than expected. This survey of the abdomen tomography exams, performed in about 74% of the Brazilian states, showed that in many clinics the procedures are not optimized. This study can be used for the planning of dose optimization programs and will contribute to the establishment of local diagnostic reference levels (DRL) for CT.

Development of Acceptable Quality Dose (AQD) and image quality-related diagnostic reference levels for common computed tomography investigations in a tertiary care public sector hospital of Khyber Pakhtunkhwa, Pakistan.

PURPOSE: To describe the first experience of patient dose optimization in developing AQD, SSDE and image quality-related DRLs for common CT examinations in the adult age group using the concept of AQD. MATERIALS AND METHODS: The recent published IQSC from 0 to 4 were used by radiologists for the assessment of image quality. The entire data were collected for five types (brain CT, chest CT, chest HRCT, abdomen KUB CT and abdomen + pelvic CT) CT investigations based on anatomic region (head, chest and abdomen + pelvic). The entire datasets of 264 patients were categorized into three groups based on their weights: group-1 (41-60 kg), group-2 (61-80 kg) and group-3 (81-100 kg). Only score-3 images were considered to assess median and 75th percentile values of CTDIvol and DLP to obtain AQDs and DRLs, respectively. RESULTS: Following the practical training of four radiologists on image quality scoring criteria for CT images, 264 (92%) out of 288 patient images were clinically acceptable as per IQSC for the study. The AQD (median) values in terms of CTDIvol for the mentioned weight groups were 25.8, 2.7, and 30.6 mGy, while the median DLP values for these groups were 496, 510 and 557 mGycm, respectively, for brain CT. The 75th percentile values in terms of CTDIvol were 30.2, 35.3 and 36.2 mGy, while in terms of DLP, they were 583, 619 and 781 mGycm for brain CT, respectively. Similar results are presented for the above-mentioned procedures, as well as in terms of SSDE. CONCLUSION: The first ever experience in obtaining AQD, SSDE and DRLs values for specific CT procedures couples image quality with dose indices, showing comparable values with other relevant studies. Hence, it will provide a baseline for comparison within the facility for future studies and facilitate dose optimization for other facilities aiming for improvement.

Evaluation of thyroid radiation dose during abdominal Computed Tomography procedures and dose reduction effectiveness of thyroid shielding.

INTRODUCTION: During abdominal Computed Tomography (CT) studies, vicinity organs receive a dose from scatter radiation. The thyroid is considered an organ at greater risk due to high radiosensitivity. METHODS: The primary objective of this study was to determine the entrances surface dose (ESD) to the thyroid during abdominal CT studies and to evaluate the efficiency of dose reduction by lead shielding. The calibrated thermoluminescence dosimeter (TLD) chips were used to measure the ESD during 180 contrast-enhanced (CE) and non-contrast-enhanced (NC) abdominal CT studies in the presence and absence of lead shielding. RESULTS: Thyroid shielding reduces the ESD by 72.3% (0.55 mGy), 86.5% (2.95 mGy) and 64.0% (2.24 mGy) during NC, 3-phase and 4-phase abdominal CT scans. Also, the patient height was identified as a parameter that inversely influenced the thyroid dose, proving that the taller patients receive less dose to the thyroid. Regardless, the scan parameters such as time and display field of view (DFOV) positively impact the thyroid dose. CONCLUSION: Lead shielding can prevent the external scatter reaching the thyroid region by 64%-87% during the non-vicinity scans such as abdomen CT. However, the actual dose saving lies between 0.2% and 0.4%, compared to the total effective dose of the whole CT procedure. IMPLICATIONS FOR PRACTICE: The thyroid shield can effectively reduce external scatter radiation during abdominal CT procedures. However, the dose saving is insignificant compared to the total effective dose from the whole examination. Therefore, the use of thyroid shielding should be carefully evaluated during CT abdomen procedures.

Colonic Hemostatic Clip Causing Perforated Acute Appendicitis.

Teaching Point: The advantages of CT over other imaging techniques for the diagnosis of acute appendicitis in adults include the ability to identify foreign bodies that may be involved.

Could flank pain be an indicator of COVID-19 infection?

Background: We describe the incidental detection of patients infiltrates due to COVID-19 in lung basal sections in patients undergoing abdominal computed tomography (CT) with flank pain attending the urology outpatient clinic during the current pandemic. Methods: We retrospectively analysed 276 patients admitted to the Siirt Training and Research Hospital Urology outpatients clinic between 15 March 2020 and 9 August 2020 with a complaint of flank pain and undergoing non-contrast abdominal CT. A total of 10 patients with COVID-19 compatible findings in CT were defined as the study group. A control group was formed from 10 patients with only urological pathologies (kidney stones, ureteral stones, and hydronephrosis) without a COVID-19 compatible appearance on CT. Results: Ten (3.6 %) patients were identified with COVID-19 and pneumonic infiltrations in the basal regions of the lungs; diagnosis was made by cross-sectional abdominal CT. The visual analog scale (VAS) score of flank pain was significantly higher in the control group (p<0.001); these subjects had urological pathology and no evidence of COVID-19 in the basal regions of the lungs on abdominal CT. There were no signs of COVID-19 disease detected during the admissions procedure in the urology outpatient clinic, including fever, cough, and shortness of breath. Conclusion: During the COVID-19 pandemic, it is important to consider a diagnosis of COVID_19 in patients reporting non-severe flank pain if no urological pathology is evident on abdominal CT scans.

Small bowel obstruction caused by peritoneal immunoglobulin g4-related disease mimicking carcinomatosis: case report.

We hereby report a case of diffuse pelvic peritoneal involvement by immunoglobulin G4-related disease (IgG4-RD). Numerous pelvic masses and nodules showing delayed enhancement on enhanced abdominal CT were found to congregate in the pelvic organs of a 57-year-old female presenting with intestinal subocclusion. The differentiation between peritoneal IgG4-RD and pelvic peritoneal carcinomatosis was only made by histopathology and immunohistochemistry performed after surgical resection. Autoimmune pancreatitis represents the historical prototype of IgG4-RD, but the spectrum of manifestations involving various organs has expanded during the last decade. In this report, we shortly review this clinical entity.

Follicular dendritic cell sarcoma of the abdomen: the imaging findings.

Follicular dendritic cell sarcoma is a rare neoplasm that originates from follicular dendritic cells in lymphoid follicles. This disease usually involves the lymph nodes, and especially the head and neck area. Rarely, extranodal sites may be affected, including tonsil, the oral cavity, liver, spleen and the gastrointestinal tract. We report here on the imaging findings of follicular dendritic cell sarcoma of the abdomen that involved the retroperitoneal lymph nodes and colon. It shows as a well-defined, enhancing homogenous mass with internal necrosis and regional lymphadenopathy.