Yield of abdominal radiographs in children with suspected intussusception; rate of pneumoperitoneum and other abdominal pathology

OBJECTIVES

Ultrasound is the criterion standard imaging modality for the diagnosis of intussusception. However, to our knowledge the utility of abdominal radiographs to concurrently screen for pneumoperitoneum or other abdominal pathology that could have a similar presentation has not been studied. Our institutional protocol requires the performance of AP supine and left lateral decubitus views of the abdomen prior to ultrasound evaluation for intussusception, providing an opportunity to examine the yield of abdominal radiographs in this setting. Our primary objective was to determine the rate of pneumoperitoneum on screening abdominal radiographs in children undergoing evaluation for intussusception. Our secondary objective was to determine the rate that other clinically significant pathology is found on these screening abdominal radiographs.

METHODS

We performed a retrospective chart review of all patients under 6 years of age who had any imaging ordered in our large urban pediatric emergency department to evaluate for suspected intussusception during the calendar years 2018-2020.

RESULTS

1115 patient encounters met our inclusion criteria. Among 1090 who had screening abdominal radiographs, 82 (8%) had findings concerning for intussusception. Of those not concerning for intussusception, 635 (58%) were read as normal, 263 (24%) showed moderate to large stool burden, 107 (10%) showed generalized bowel distention, and 22 (2%) showed abnormal gastric distention. Individually the remainder of all other findings compromised <1% of encounters and included radiopaque foreign body (8), intraabdominal calcification (4), pneumonia/effusion (3), pneumatosis intestinalis, abdominal mass (2), diaphragmatic hernia (1), rib fracture (1), appendicolith (1), feeding tube malposition (1), and bowel wall thickening (1). In one encounter the patient had a bowel perforation with pneumoperitoneum present secondary to ingestion of multiple magnets.

CONCLUSIONS

Our study indicates that radiograph-detected pneumoperitoneum is rare in children with suspected intussusception. Constipation is the most common abnormal finding on screening radiographs. Other findings occur in approximately 15% of total cases, some of which require further workup.

Oncology-specific radiation dose and image noise reference levels in adult abdominal-pelvic CT

OBJECTIVES

To provide our oncology-specific adult abdominal-pelvic CT reference levels for image noise and radiation dose from a high-volume, oncologic, tertiary referral center.

METHODS

The portal venous phase abdomen-pelvis acquisition was assessed for image noise and radiation dose in 13,320 contrast-enhanced CT examinations. Patient size (effective diameter) and radiation dose (CTDIvol) were recorded using a commercial software system, and image noise (Global Noise metric) was quantified using a custom processing system. The reference level and range for dose and noise were calculated for the full dataset, and for examinations grouped by CT scanner model. Dose and noise reference levels were also calculated for exams grouped by five different patient size categories.

RESULTS

The noise reference level was 11.25 HU with a reference range of 10.25-12.25 HU. The dose reference level at a median effective diameter of 30.7 cm was 26.7 mGy with a reference range of 19.6-37.0 mGy. Dose increased with patient size; however, image noise remained approximately constant within the noise reference range. The doses were 2.1-2.5 times than the doses in the ACR DIR registry for corresponding patient sizes. The image noise was 0.63-0.75 times the previously published reference level in abdominal-pelvic CT examinations.

CONCLUSIONS

Our oncology-specific abdominal-pelvic CT dose reference levels are higher than in the ACR dose index registry and our oncology-specific image noise reference levels are lower than previously proposed image noise reference levels.

ADVANCES IN KNOWLEDGE

This study reports reference image noise and radiation dose levels appropriate for the indication of abdomen-pelvis CT examination for cancer diagnosis and staging. The difference in these reference levels from non-oncology-specific CT examinations highlight a need for indication-specific, dose index and image quality reference registries.

Diagnostic values of supine and erect abdominal radiographs for patients with acute abdomen: which is better for decision making?

BACKGROUND

Plain abdominal radiography including supine and erect abdominal radiographs (SAR and EAR) is a frequently used image modality for preliminary evaluation of acute abdomen. We aimed to explore which one of the SAR or EAR has a higher diagnostic value in overall diagnosis of acute abdomen, including their respective advantages over each other for the various underlying diseases.

METHODS

We retrospectively analyzed the imaging findings of plain abdominal radiography of patients with acute abdomen who received abdominal computed tomography (CT) within 24 hours at the emergency department of a medical center in northern Taiwan between October 2019 and February 2020. Final diagnosis was made by CT reports and clinical data. The relevance between the imaging findings and clinical diagnosis in the groups of SAR and EAR were compared.

RESULTS

A total of 1009 cases with acute abdomen were included, of which 341 (33.8%) underwent EAR and 668 (66.2%) underwent SAR. Among them, 820 cases had final diagnosis confirmed by CT and clinical data. In comparison of the diagnostic relevance of SAR and EAR, there were no significant difference in the overall acute abdomen, but EAR showed a better diagnostic relevance in cases with bowel obstruction than SAR did (100% vs 87.2%, p < 0.05). No statistical difference in other abdominal diseases.

CONCLUSION

There is no significant difference between SAR and EAR in evaluation of overall acute abdomen. However, EARs has a diagnostic advantage over SAR for evaluation of suspected bowel obstruction.

Clinical Artificial Intelligence Applications in Radiology: Chest and Abdomen

Organ segmentation, chest radiograph classification, and lung and liver nodule detections are some of the popular artificial intelligence (AI) tasks in chest and abdominal radiology due to the wide availability of public datasets. AI algorithms have achieved performance comparable to humans in less time for several organ segmentation tasks, and some lesion detection and classification tasks. This article introduces the current published articles of AI applied to chest and abdominal radiology, including organ segmentation, lesion detection, classification, and predicting prognosis.

Evaluation of Abdominal Computed Tomography Scans for Differentiating the Discrepancies in Abdominal Adipose Tissue Between Two Major Subtypes of Primary Aldosteronism

The aim of this study was to analyze the differences in the distribution of abdominal adipose tissue between the two subtypes of primary aldosteronism (PA) using abdominal computed tomography. We retrospectively analyzed patients diagnosed as having essential hypertension (EH) or PA from the prospectively collected Taiwan Primary Aldosteronism Investigation (TAIPAI) database. Patients with PA were divided into the subgroups of idiopathic hyperaldosteronism (IHA) and unilateral aldosterone-producing adenoma (APA). Patients' basic clinicodemographic data were collected, and a self-developed CT-based software program was used to quantify the abdominal adiposity indexes, including visceral adipose tissue (VAT) area, VAT ratio, waist circumference (WC), subcutaneous adipose tissue (SAT) area, and SAT ratio. We included 190 patients with EH and 436 patients with PA (238 with IHA and 198 with APA). The APA group had significantly lower abdominal adiposity indexes than the other groups. We also found negative correlations of aldosterone-to-renin ratio (ARR) with VAT area, VAT ratio, WC, and body mass index (BMI) in the APA group. After propensity score matching (which left 184 patients each in the IHA and APA groups), patients in the APA group still had significantly lower WC, SAT area, SAT ratio, and VAT ratio than those in the IHA group. Furthermore, logistic regression analysis indicated that lower probability of abdominal obesity was significantly related to patients with APA. Our data revealed that the distribution of abdominal adipose tissue was similar in patients with IHA and those with EH, but the abdominal adiposity indexes were significantly lower in patients with APA than in those with IHA and EH.

Abdominopelvic CT findings in patients with novel coronavirus disease 2019 (COVID-19)

PURPOSE

Some patients with novel coronavirus disease 2019 (COVID-2019) present with abdominal symptoms. Abdominal manifestations of COVID on imaging are not yet established. The goal of this study was to quantify the frequency of positive findings on abdominopelvic CT in COVID-positive patients, and to identify clinical factors associated with positive findings to assist with imaging triage.

MATERIALS AND METHODS

This retrospective study included adult COVID-positive patients with abdominopelvic CT performed within 14 days of their COVID PCR nasal swab assay from 3/1/2020 to 5/1/2020. Clinical CT reports were reviewed for the provided indication and any positive abdominopelvic findings. Demographic and laboratory data closest to the CT date were recorded. Multivariate logistic regression model with binary outcome of having no reported positive abdominopelvic findings was constructed.

RESULTS

Of 141 COVID-positive patients having abdominopelvic CT (average age 64 years [± 16], 91 [64%] women), 80 (57%) had positive abdominopelvic findings. Abdominal pain was the most common indication, provided in 54% (43/80) and 74% (45/61) of patients with and without reported positive abdominopelvic findings, respectively (p = 0.015). 70% (98/141) of patients overall had reported findings in the lung bases. Findings either typical or intermediate for COVID were reported in 50% (40/80) and 64% (39/61) of patients with and without positive abdominopelvic findings, respectively (p = 0.099). Of 80 patients with positive abdominopelvic findings, 25 (31%) had an abnormality of gastrointestinal tract, and 14 (18%) had solid organ infarctions or vascular thromboses. In multivariate analysis, age (OR 0.85, p = 0.023), hemoglobin (OR 0.83, p = 0.029) and male gender (OR 2.58, p = 0.032) were independent predictors of positive abdominopelvic findings, adjusted for race and Charlson comorbidity index.

CONCLUSION

Abdominopelvic CT performed on COVID-positive patients yielded a positive finding in 57% of patients. Younger age, male gender, and lower hemoglobin were associated with higher odds of having reportable positive abdominopelvic CT findings.

Extraction of radiographic findings from unstructured thoracoabdominal computed tomography reports using convolutional neural network based natural language processing

Background

Heart failure (HF) is a major cause of morbidity and mortality. However, much of the clinical data is unstructured in the form of radiology reports, while the process of data collection and curation is arduous and time-consuming.

Purpose

We utilized a machine learning (ML)-based natural language processing (NLP) approach to extract clinical terms from unstructured radiology reports. Additionally, we investigate the prognostic value of the extracted data in predicting all-cause mortality (ACM) in HF patients.

Materials and methods

This observational cohort study utilized 122,025 thoracoabdominal computed tomography (CT) reports from 11,808 HF patients obtained between 2008 and 2018. 1,560 CT reports were manually annotated for the presence or absence of 14 radiographic findings, in addition to age and gender. Thereafter, a Convolutional Neural Network (CNN) was trained, validated and tested to determine the presence or absence of these features. Further, the ability of CNN to predict ACM was evaluated using Cox regression analysis on the extracted features.

Results

11,808 CT reports were analyzed from 11,808 patients (mean age 72.8 ± 14.8 years; 52.7% (6,217/11,808) male) from whom 3,107 died during the 10.6-year follow-up. The CNN demonstrated excellent accuracy for retrieval of the 14 radiographic findings with area-under-the-curve (AUC) ranging between 0.83–1.00 (F1 score 0.84–0.97). Cox model showed the time-dependent AUC for predicting ACM was 0.747 (95% confidence interval [CI] of 0.704–0.790) at 30 days.

Conclusion

An ML-based NLP approach to unstructured CT reports demonstrates excellent accuracy for the extraction of predetermined radiographic findings, and provides prognostic value in HF patients.

First case of paralytic ileus after endoscopic mucosal resection of caecal polyp

Endoscopic mucosal resection (EMR) is a technique developed for the removal of sessile or flat neoplastic lesions confined to the superficial layers (mucosa and submucosa) of the gastrointestinal tract. Bleeding and perforation are well-known complications of EMR. Here we report the first case of paralytic ileus after EMR of a caecal polyp. A 66-year-old man was scheduled for elective EMR of a 3.5-cm caecal polyp under general anaesthesia after a screening colonoscopy. The procedure was performed by an expert endoscopist, and air was insufflated during the procedure because of the unavailability of CO₂. The polyp was successfully removed; the procedure duration was 81 min. After the procedure, the patient complained of abdominal pain and dyspnoea. He developed tachypnoea and tachycardia as well as oxygen desaturation with SpO₂ 84%. He was administered oxygen therapy via a non-rebreather mask, following which his oxygenation improved. His abdominal X-ray findings were consistent with ileus. Therefore, a nasogastric tube was placed, and the patient was admitted to our hospital. He was managed conservatively and underwent serial abdominal X-rays that showed improvement of the ileus. On the fourth day of admission, he was started on an oral diet; on the sixth day of admission, he was discharged with resolving ileus. Computed tomography enterography performed 1 week after discharge showed complete resolution of the ileus. Factors that may have contributed to the occurrence of ileus in our patient include the use of air during the procedure, location of the polyp (caecal), duration of the procedure, effect of electrocautery, use of general anaesthesia and possibility of aspiration pneumonitis. This case report will make endoscopists aware of the abovementioned factors while performing EMR as this procedure can lead to the complication of paralytic ileus with significant patient morbidity. Conservative treatment should be attempted first before any other intervention.

Occurrence of lymphoplasmacytic lymphoma in a chronic myeloid leukemia patient following long-term treatment with tyrosine kinase inhibitors: A case report

INTRODUCTION

After tyrosine kinase inhibitors (TKIs) targeting BCR-ABL1 were introduced for the treatment of chronic myeloid leukemia, clinical outcomes have improved dramatically. However, together with the increase in the survival rate, a more frequent occurrence of secondary malignancies has been observed as well. TKIs have been demonstrated to be a risk factor of malignancies such as non-Hodgkin lymphoma, prostate cancer, and skin cancer. However, lymphoplasmacytic lymphoma (LPL) has never been reported as a secondary malignancy after TKI treatment in chronic myeloid leukemia (CML).

PATIENT CONCERNS

An 81-year-old male patient diagnosed with CML and treated with TKIs for a long period (15 years) was admitted due to a chief complaint of abdominal pain. A large abdominal mass was detected by imaging that included computed tomography.

DIAGNOSIS

LPL was confirmed from biopsies after ultrasonography and sigmoidoscopy. Serum IgM level was increased and M protein and monoclonal gammopathy, IgM_kappa light chain type were detected.

INTERVENTIONS

The patient received six cycles of R-CHOP chemotherapy.

OUTCOMES

After chemotherapy, he showed response. The sizes of the abdominal mass and lymph nodes decreased; moreover, serum M protein and IgM levels decreased, as well.

CONCLUSION

Herein, for the first time, we describe a patient who developed LPL as a secondary malignancy after administration of TKIs for the treatment of CML. Our observations indicate the importance of awareness of this secondary malignancy that can develop in CML patients treated with TKIs.

Intestinal Obstruction of Congenital Origin: A Case Report

Congenital bands are rare causes of intestinal obstruction and often leads to diagnostic challenges. Diagnostic delays in cases of mechanical obstruction might lead to irreversible bowel ischemia and perforation. Presently described is a case of an 18 month young child with severe vomiting developed for one day. The child was initially thought to have acute viral enteritis and treated accordingly. Due to the severity, an X-Ray and computed tomography scan were sent which pointed towards the possibility of having congenital bands. He was treated operatively. The child was kept under observation for eleven days and was discharged. Although rare, intestinal obstruction due to congenital bands must be considered when treating a child with severe vomiting.

Multiphase abdomen-pelvis CT in women of childbearing potential (WOCBP): Justification and radiation dose

To assess justification and radiation doses of abdomen-pelvis CT in women of childbearing potential (WOCBP) scanned in 2 tertiary hospitals in Qatar.The local ethical committee approved retrospective study of 451 WOCBP (14-55 years) who underwent abdomen-pelvis CT examinations. Patients' age, clinical indications for ordered CT, scanner types and vendors, number and type of scan phases (non-contrast, arterial, portal venous, and/or delayed phases), and radiation dose descriptors (CT dose index volume - CTDIvol and dose length product- DLP) were recorded. Patients undergoing simultaneous chest-abdomen-pelvis CT were excluded. We classified the clinical indications for all 451 CT into indicated and unindicated based on the ACR Appropriateness Criteria. Information regarding the date of last menstrual period, likelihood of pregnancy, and if available, results of the pregnancy test were recorded. Data were analyzed with descriptive statistics (median and inter-quartile range) and analysis of variance (ANOVA).None of the patients were pregnant at the time of their scanning. Amongst the 673 phases acquired for multiphase abdomen-pelvis CT in 451 patients, the 47% unindicated phases (315/673) included non-contrast (122/673, 18%), arterial (33/673, 5%), portal venous (125/673, 19%) and delayed (35/673, 5%) phases. The respective median DLP for indicated and unindicated phases were 266 and 758 mGy.cm (P < .0001).Multiphase abdomen-pelvis CT exams are frequent but seldom justified in WOCBP. They lead to a substantial increase in unindicated radiation dose compared to a single-phase CT.

'Hepato-diaphragmatic fat interposition' and 'increased right hemi-diaphragmatic thickness': new imaging signs for early diagnosis of hepatic cirrhosis on routine CT abdomen

BACKGROUND

Cirrhosis of liver is often a silent disease and need early diagnosis for effective treatment strategy.

OBJECTIVES

The present article aims to describe new imaging signs for early diagnosis of cirrhosis on routine CT. These are 'hepato-diaphragmatic fat interposition' (HDFI) and 'increased right hemi-diaphragmatic thickness' (increased r-DT sign).

MATERIALS AND METHODS

This was a retrospective study based on the presence or absence of cirrhosis of liver (n = 100). 'HDFI sign' was labeled as positive if F is more than 50% of D; where F is the medio-lateral extent of the intra-abdominal fat along the postero-medial margin of liver and D is the distance from the lateral vertebral margin to the medial margin of the outer-most rib in the same axial image. Increased 'r-DT sign' is labeled when the dimension on right side exceeds left side by at least 0.2 cm. Pearson χ² was performed to calculate the p value. A p value of < 0.05 was considered to indicate a significant difference.

RESULTS

There was a significant difference between cirrhotic and normal group, The sensitivity, specificity, positive predictive value and the negative predictive value of HDFI sign was found to be 94%, 62%, 71.21% and 91.17%, while that of increased r-DT sign was found to be 96%,52%, 66.66% and 92.85%. The area under the ROC curve for the HDFI sign was found to be 0.78 as compared to 0.74 for the increased r-DT sign.

CONCLUSION

Both these new signs should be used as additional imaging signs for early diagnosis of cirrhosis.

LOCAL DRLS FOR PAEDIATRIC CT EXAMINATIONS BASED ON SIZE-SPECIFIC DOSE ESTIMATES IN KERMANSHAH, IRAN

Due to the radiosensitivity of paediatric patients to X-ray, it is necessary to survey the paediatric DRLs using size-specific dose estimates (SSDE). In the present study, we determined the local diagnostic reference levels (DRLs) for paediatric chest, head and abdomen-pelvis CT examinations and their Surview scans in Kermanshah city, Iran. For ≤1 year, 1-5 years, 5-10 years and 10-15 years the DRLs (mGy) based on SSDE were determined N/A, 6.00, 6.25, 8.27 for abdomen-pelvis, and 8.74, 7.45, 11.15, 10.45 for chest and 19.05, 18.33, 18.22, 20.14 for head examinations, respectively. The differences between body size and default phantom defined in CT scanners are significant and should be considered when determining the DRLs. Based on our findings, use of CTDIv and SSDE parameters for determining DRLs leads to significant different results in children; thus SSDE is suggested as a more accurate index than CTDIV for establishing DRLs in paediatric CT examinations.

PATIENT DOSE SURVEY BASED ON SIZE-SPECIFIC DOSE ESTIMATE AND ACCEPTABLE QUALITY DOSE IN CHEST AND ABDOMEN/PELVIS CT EXAMINATIONS

The practical aspects of two recently developed patient dose optimization methods in computed tomography (CT) examinations, size-specific dose estimate (SSDE) and acceptable quality dose (AQD), were verified for the chest and abdomen/pelvis examinations. A dose survey was performed in a CT institute by considering patients lateral diameter, weight and body mass index (BMI). The AQD tables for weight and BMI groups and SSDE threshold curves were obtained. The mean of volume CT dose index and dose length product for standard-size patients were compared with the national diagnostic reference levels (NDRLs) of Iran. The results show that patient doses are below the NDRLs. It is more reliable to report the AQDs based on SSDE and for BMI groups which can well take into account patient size in the dose optimization process. The SSDE threshold curves can be determined with more precision by including dose data of all possible sizes in the curves.

THE IMPACT OF OBESITY ON ABDOMINAL CT RADIATION DOSE AND IMAGE QUALITY

The aim of this study was to evaluate how iterative reconstruction can compensate for the noise increase in low radiation dose abdominal computed tomography (CT) technique for large size patients and the general impact of obesity on abdominal organ doses and image quality in CT. An anthropomorphic phantom layered with either none or a single layer of 3-cm- thick circumferential animal fat packs to simulate obese patients was imaged using a 128MDCT scanner. Abdominal protocols (n = 12) were applied using automatic tube current modulation (ATCM) with various quality reference mAs (150, 200, 250 and 300). kVs of 100, 120 and 140 were used for each mAs selection. Metal oxide semiconductor field effect transistor dosimeters (MOSFET) measured internal organ dose. All images produced were reconstructed with filtered back projection (FBP) and sinogram affirmed iterative reconstruction (SAFIRE) (3, 4 and 5) and objective noise was measured within three regions of interest at the level of L4-L5. Organ doses varied from 0.12 to 41.9 mGy, the spleen received the highest doses for both phantom sizes. Compared to the phantom simulating average size, the obese phantom was associated with up to twofold increase in delivered mAs, dose length product (DLP) and computed tomography dose index (CTDIvol) for the matched mAs selection (p < 0.05). However, organ dose increased by 50% only. The use of 100 kV resulted in a 40% lower dose (p < 0.05) compared to 120 kV and the associated noise increase was improved by SAFIRE (5) use, which resulted in 60% noise reduction compared to FBP (p < 0.05). When combined with iterative reconstruction, low kV is feasible for obese patients to optimise radiation dose and maintain objective image quality.

A phantom study of the performance of model-based iterative reconstruction in low-dose chest and abdominal CT: When are benefits maximized?

INTRODUCTION

The aim of this study was to assess and compare the effects of CT image reconstruction techniques on low-dose CT image quality using phantoms.

METHODS

Anthropomorphic torso and spatial/contrast-resolution phantoms were scanned at decreasing tube currents between 400 and 10 mA. CT thorax and abdomen/pelvis series were reconstructed with filtered back projection (FBP) alone, combined 40% adaptive statistical iterative reconstruction & FBP (ASIR40), and model-based iterative reconstruction (MBIR) [(resolution-preference 05 (RP05) and RP20 in the thorax and RP05 and noise-reduction 05 (NR05) in the abdomen)]. Two readers rated image quality quantitatively and qualitatively.

RESULTS

In thoracic CT, objective image noise on MBIR RP05 data sets outperformed FBP at 200, 100, 50 and 10 mA and outperformed ASIR40 at 50 and 10 mA (p < 0.001). MBIR RP20 outperformed FBP at 50 and 10 mA and outperformed ASIR40 at 10 mA (p < 0.001). Compared with both FBP and ASIR40, MBIR RP05 demonstrated significantly better signal-to-noise ratio (SNR) at 10 mA. In abdomino-pelvic CT, MBIR RP05 and NR05 outperformed FBP and ASIR at all tube current levels for objective image noise. NR05 demonstrated greater SNR at 200, 100, 50 and 10 mA and RP05 demonstrated greater SNR at 50 and 10 mA compared with both FBP and ASIR. MBIR images demonstrated better subjective image quality scores. Spatial resolution, low-contrast detectability and contrast-to-noise ratio (CNR) were comparable between image reconstruction techniques.

CONCLUSION

CTs reconstructed with MBIR have lower image noise and improved image quality compared with FBP and ASIR. These effects increase with reduced radiation exposure confirming optimal use for low-dose CT imaging.

"Cystamatic" Review: Is Surgery Mandatory for Pneumatosis Cystoides Intestinalis?

INTRODUCTION

Pneumatosis cystoides intestinalis (PCI) is a rare condition characterized by the presence of intramural gas cysts within the small and large intestines. We describe a case of a 70-year-old man admitted to the Emergency Surgery Department for PCI who was treated conservatively.

AREAS COVERED

We reviewed 60 cases of PCI described in the international literature over the last 5 years. From our analysis, it appears that the etiology of the gas production within the submucosa or the subserosa of the gastrointestinal tract is still unknown. The rupture of the cysts can lead to pneumoperitoneum that can simulate a surgical emergency.

EXPERT COMMENTARY

For patients with PCI, a conservative approach is the treatment of choice, with surgery mandatory only for complicated disease.

Acute non-traumatic abdominal pain by quadrant: relative yield of CT and clinical evaluation for diagnosis in 1000 patients

OBJECTIVE

To determine the relative diagnostic yield of contrast-enhanced CT in adults presenting with symptoms referable to a specific abdominal quadrant.

METHODS

Electronic health records review systematically identified patients meeting the following inclusion criteria: adults (≥ 18 years) undergoing IV contrast-enhanced abdominopelvic CT for acute non-traumatic symptoms referable to a specific abdominal quadrant (RLQ/LLQ/LUQ/RUQ). The CT-based diagnosis and any clinical diagnosis in the absence of CT diagnosis were recorded. The final cohort of 1000 subjects (mean age, 48.1 years; 647F/353M) consisted of consecutive sub-cohorts of 250 patients for each abdominal quadrant. Positive oral contrast was utilized in 91.6% (916/1000) of cases.

RESULTS

A positive CT diagnosis was provided in 47.3% (473/1000) of all patients, and was highest for LLQ (58.8%) and RLQ (58.0%) symptoms, including diverticulitis and appendicitis in 23.6% and 24.8% cases, respectively. CT positivity was lower for the LUQ (34.4%) and RUQ (38.0%) (p < 0.0001), with no single diagnosis representing > 5% of cases. However, all quadrants provided valuable triage of 218 hospital admissions (21.8%), 83.0% were CT positive, whereas 62.7% of 782 discharged patients were CT negative. Only 7.0% of CT-negative patients were admitted. A clinical-only diagnosis was provided in 9.3% of the total cohort (93/1000), representing 17.6% of the CT-negative cohort (93/527).

CONCLUSION

The rate of positive CT diagnosis is considerably higher for the lower abdominal quadrants, predominately due to appendicitis and diverticulitis. However, CT results (positive vs. negative) for all four quadrants strongly correlated with hospital admission versus discharge. Clinical-only diagnosis represented < 10% of all cases.

How have advances in CT dosimetry software impacted estimates of CT radiation dose and cancer incidence? A comparison of CT dosimetry software: Implications for past and future research

Objective

Organ radiation dose from a CT scan, calculated by CT dosimetry software, can be combined with cancer risk data to estimate cancer incidence resulting from CT exposure. We aim to determine to what extent the use of improved anatomical representation of the adult human body “phantom” in CT dosimetry software impacts estimates of radiation dose and cancer incidence, to inform comparison of past and future research.

Methods

We collected 20 adult cases for each of three CT protocols (abdomen/pelvis, chest and head) from each of five public hospitals (random sample) (January-April inclusive 2010) and three private clinics (self-report). Organ equivalent and effective dose were calculated using both ImPACT (mathematical phantom) and NCICT (voxelised phantom) software. Bland-Altman plots demonstrate agreement and Passing-Bablok regression reports systematic, proportional or random differences between results. We modelled the estimated lifetime attributable risk of cancer from a single exposure for each protocol, using age-sex specific risk-coefficients from the Biologic Effects of Ionizing Radiation VII report.

Results

For the majority of organs used in epidemiological studies of cancer incidence, the NCICT software (voxelised) provided higher dose estimates. Across the lifespan NCICT resulted in cancer estimates 2.9%-6.6% and 14.8%-16.3% higher in males and females (abdomen/pelvis) and 7.6%-19.7% and 12.9%-26.5% higher in males and females respectively (chest protocol). For the head protocol overall cancer estimates were lower for NCICT, but with greatest disparity, >30% at times.

Conclusion

When the results of previous studies estimating CT dose and cancer incidence are compared to more recent, or future, studies the dosimetry software must be considered. Any change in radiation dose or cancer risk may be attributable to the software and phantom used, rather than—or in addition to—changes in scanning practice. Studies using dosimetry software to estimate radiation dose should describe software comprehensively to facilitate comparison with past and future research.

PATIENT DOSE IN DIGITAL RADIOGRAPHY UTILISING BMI CLASSIFICATION

Dose audit is important towards optimisation of patients' radiation protection in diagnostic radiography. In this study, the effect of the body mass index (BMI) on radiation dose received by 1869 adult patients undergoing chest, abdomen, lumbar spine, kidneys and urinary bladder (KUB) and pelvis radiography in an X-ray room with a digital radiography system was investigated. Patients were categorised into three groups (normal, overweight and obese) based on the BMI values. The patients' entrance surface air kerma (ESAK) and the effective dose (ED) were calculated based on the X-ray tube output, exposure parameters and technical data, as well as utilising appropriate conversion coefficients of the recorded kerma area product (KAP) values. The local diagnostic reference levels (LDRLs) were established at the 75th percentile of the distribution of ESAK and KAP values. Statistically, a significant increase was found in ESAK, KAP and ED values, for all examinations, both for overweight and obese patients compared to normal patients (Mann-Whitney test, p < 0.0001). Regarding the gender of the patients, a statistically significant increase was found in the dose values for male patients compared to female patients, except for the chest LAT examinations (Mann-Whitney test, p = 0.06). The percentage increase for chest PA, chest LAT, abdomen AP, lumbar spine AP, lumbar spine LAT, pelvis AP and KUB AP in overweight patients was 75%, 100%, 136%, 130%, 70%, 66% and 174% for median ESAK, 67%, 81%, 135%, 134%, 85%, 63% and 172% for median KAP, as well as 89%, 54%, 146%, 138%, 82%, 57% and 183% for median ED values, respectively. For obese patients, the corresponding increases were 200%, 186%, 459%, 345%, 203%, 150% and 785% for median ESAK, 200%, 185%, 423%, 357%, 227%, 142% and 597% for median KAP, as well as 222%, 156%, 446%, 363%, 218%, 136% and 625% for median ED. The corresponding LDRLs for overweight patients were 0.17 mGy, 1.21 mGy, 3.74 mGy, 7.70 mGy, 7.99 mGy, 4.07mGy, 5.03 mGy and 0.13 Gy cm2, 0.69 Gy cm2, 2.35 Gy cm2, 2.10 Gy cm2, 2.59 Gy cm2, 2.13 Gy cm2, 2.49 Gy cm2 in terms of ESAK and KAP values, respectively, while in the case of obese patients were 0.28 mGy, 1.82 mGy, 7.26 mGy, 15.10 mGy, 13.86 mGy, 6.89 mGy, 13.40 mGy and 0.21 Gy cm2, 1.10 Gy cm2, 4.68 Gy cm2, 4.01 Gy cm2, 4.80 Gy cm2, 3.27 Gy cm2, 6.02 Gy cm2, respectively. It can be concluded that overweight and obese patients received a significantly increased radiation dose. Careful adjustment of imaging protocols is needed for these patients to reduce patient dose, while keeping the image quality at an acceptable level. Additional studies need to be conducted for these patient groups, that could further contribute to the development of radiation protection culture in diagnostic radiography.

PATIENTS DOSE ESTIMATION IN CT EXAMINATIONS USING SIZE SPECIFIC DOSE ESTIMATES

The present work reports data of radiation exposure to the patients during head, chest, pelvis and abdomen CT examinations performed on a third-generation 16-slice CT machine. Radiation exposure was estimated using size specific dose estimates (SSDE) method, which takes into account patient's physical dimensions in phantom measured computed tomography dose index (CTDI) value. The reported median CT dose volume index CTDIvol values in head, chest, pelvis and abdomen examinations were 26.76, 16.27, 29.81 and 14.74 mGy, respectively. The median doses evaluated using SSDE methodology for the above mentioned procedure were 54.1, 23.1, 42.8 and 20.1 mGy, respectively. Our results showed variation in dose values estimated using CTDI and SSDE methods in all examinations. The evaluated SSDE values were also compared to the values derived from data reported by the American Association of Physicist in Medicine (AAPM). SSDE values in present measurements are 4-8% lower than AAPM values. The present results show that CTDI parameters recorded on CT console should not be used to specify patient dose during CT procedures.

RADIATION DOSE DETERMINATION IN ABDOMINAL CT EXAMINATIONS OF CHILDREN AT SUDANESE HOSPITALS USING SIZE-SPECIFIC DOSE ESTIMATES

In this study, we thought to estimate the radiation exposure of children undergoing multi-detector CT examinations using size-specific dose estimates (SSDE). Console-displayed volume computed tomography dose index (CTDIvol) were recorded for a total of 78 paediatric abdominal CT examinations performed in six hospitals. Measurements of the patient diameters were taken from the mid-slice location on the transverse and scout CT images. Size-specific conversion coefficients were used to translate CTDIvol to the SSDE, according AAPM Report 204. For children aged 0-1 y, CTDIvol, SSDEtrans (from transverse images) and SSDEsco (from scout images) were: 12.80 ± 16.10, 14.43 ± 13.22; and 14.37 ± 13.03 mGy; respectively. For children aged 1-5 y, CTDIvol, SSDEtrans and SSDEsco were: 12.11 ± 14.47, 18.8 ± 18.61 and 16.51 ± 13.55 mGy; respectively. The obtained doses are higher than the corresponding diagnostic reference levels. SSDE increase with patient size as results of tube current modulation and is therefore a valuable tool for dose optimisation.

Orthopedic metallic hardware in routine abdomino-pelvic CT scans: occurrence and clinical significance

PURPOSE

To study the occurrence of orthopedic metallic hardware in routine abdomen/pelvic computed tomography (CT) scans and their impact on image quality (IQ) and diagnostic evaluation.

MATERIAL AND METHODS

In this retrospective single institution study, we analyzed 3500 consecutive abdomen/pelvis CT scans for occurrence of orthopedic metallic hardware. In the cohort of patients with metallic hardware detected on CT scans, subjective and objective IQ analysis was performed to estimate diagnostic acceptability (DA, 4-point scale), subjective noise (SN, 3-point scale), presence of artifacts (PA, 4-point scale) and objective noise. The clinical significance of metallic hardware was determined by evaluating the impact of artifacts on radiological diagnosis according to the clinical indication and disease type.

RESULTS

Orthopedic metallic hardware was encountered in 4.97% of abdomino-pelvic CT scans (n = 174/3500), and artifacts related to the hardware in the region of clinical interest were identified in 82% (n = 144/174) of scans. The overall mean DA was 2.66 (n = 174), and it was severely limited (score < 2) in 32% of cases particularly affecting patients with bilateral hip implants (92.6%, n = 25/27). The artifacts due to hardware significantly limited diagnostic evaluation in 58.6% of cases (PA score ≥ 3), and the image noise was unacceptable in 71% of cases (SN score > 2) in the region of clinical interest.

CONCLUSION

Orthopedic metallic hardware is encountered in nearly 5% of abdomino-pelvic CT scans and causes significant image degradation limiting diagnostic evaluation in the region of clinical interest.

Attention gated networks: Learning to leverage salient regions in medical images

We propose a novel attention gate (AG) model for medical image analysis that automatically learns to focus on target structures of varying shapes and sizes. Models trained with AGs implicitly learn to suppress irrelevant regions in an input image while highlighting salient features useful for a specific task. This enables us to eliminate the necessity of using explicit external tissue/organ localisation modules when using convolutional neural networks (CNNs). AGs can be easily integrated into standard CNN models such as VGG or U-Net architectures with minimal computational overhead while increasing the model sensitivity and prediction accuracy. The proposed AG models are evaluated on a variety of tasks, including medical image classification and segmentation. For classification, we demonstrate the use case of AGs in scan plane detection for fetal ultrasound screening. We show that the proposed attention mechanism can provide efficient object localisation while improving the overall prediction performance by reducing false positives. For segmentation, the proposed architecture is evaluated on two large 3D CT abdominal datasets with manual annotations for multiple organs. Experimental results show that AG models consistently improve the prediction performance of the base architectures across different datasets and training sizes while preserving computational efficiency. Moreover, AGs guide the model activations to be focused around salient regions, which provides better insights into how model predictions are made. The source code for the proposed AG models is publicly available.

A technique to establish fistuloclysis for high-output jejunocutaneous fistula through percutaneous enterostomy: A case report

RATIONALE

Currently, fistucolysis helps to establish intestinal nutrition and succus entericus reinfusion in the case of controllable mature high-output enterocutaneous fistula. However, if the tube cannot reach the distal limb of a fistula, fistuloclysis is not achieved. We proposed a strategy to establish succus entericus reinfusion for intractable intestinal fistula through percutaneous enterostomy.

PATIENT CONCERNS

A 43-year-old man was transferred to our facility for postoperative enterocutaneous fistulae, sepsis, malnutrition, and electrolyte and fluid imbalance. The contrast X-ray demonstrated the breakdown of the primary anastomosis, with fistula output ranging from 1500 to 2000 mL/d, despite the administration of medications to reduce gastrointestinal secretions.

DIAGNOSES

The patient was diagnosed with high-output anastomosis fistula by gastrointestinal radiography.

INTERVENTIONS

We used percutaneous enterostomy to establish fistuloclysis.

OUTCOMES

Fistuloclysis was established by percutaneous enterostomy successfully. No complications were found during the past 4-month follow-up after percutaneous enterostomy. He is waiting for reconstruction surgery after 6 months' enteral nutrition (EN).

LESSONS

Fistuloclysis-assisted EN, if used appropriately, avoids the complications of long-term parenteral nutrition (PN) and may promote faster fistula healing.

Reliability of Radiomic Features Across Multiple Abdominal CT Image Acquisition Settings: A Pilot Study Using ACR CT Phantom

We studied the reliability of radiomic features on abdominal computed tomography (CT) images reconstructed with multiple CT image acquisition settings using the ACR (American College of Radiology) CT Phantom. Twenty-four sets of CT images of the ACR CT phantom were attained from a GE Discovery 750HD scanner using 24 different image acquisition settings, combinations of 4 tube currents (25, 50, 100, 200 Effective mAs), 3 slice thicknesses (1.25, 2.5, 5 mm), and 2 convolution kernels (STANDARD and SOFT). Polyethylene (-95 HU) and acrylic (120 HU) of the phantom model were selected for calculating real feature value; a noise-free, computer-generated phantom image series that reproduced the 2 objects and the background was used for calculating reference feature value. Feature reliability was defined as the degree of predicting reference feature value from real feature value. Radiomic features mean, std, skewness, kurtosis, gray-level co-occurrence matrix (GLCM)-energy, GLCM-contrast, GLCM-correlation, GLCM-homogeneity were investigated. The value of R2 ≥ 0.85 was considered to be of high reliability. The reliability of mean and std were high across all image acquisition settings. At 200 Effective mAs, all features except GLCM-homogeneity showed high reliability, whereas at 25 Effective mAs, most features (except mean and std) showed low reliability. From high to low, reliability was ranked in the following order: mean, std, skewness, kurtosis, GLCM-energy, correlation, contrast and homogeneity. CT image acquisition settings affected the reliability of radiomic features. High reliable features were attained from images reconstructed at high tube current and thick slice thickness.

VACTERL Association with Situs Inversus Totalis: A Unique Combination

BACKGROUND

VACTERL association is a sporadic, nonrandom series of congenital malformations diagnosed by the presence of three or more of the following: vertebral malformations, anal atresia, cardiac defects, tracheoesophageal fistula, renal malformations, and limb malformations. Situs inversus totalis (SIT) and esophageal malformations are rarely associated. This is the first reported case in North America of VACTERL association with SIT.

IMPLICATIONS FOR PRACTICE

Respiratory distress in the term infant requires full exploration of all possible causes because the etiology may be far more complex than routinely diagnosed respiratory distress syndrome. This particular case demonstrates physical exam findings and supportive imaging that would be observed in infants with VACTERL association and with SIT, highlighting considerations when, rarely, both occur simultaneously.

Virtual monoenergetic reconstruction of contrast-enhanced CT scans of the abdomen and pelvis at 40 keV improves the detection of peritoneal metastatic deposits

PURPOSE

To evaluate the role of virtual monoenergetic imaging (VMI) in the detection of peritoneal metastatic disease in contrast-enhanced computed tomography (CT) of the abdomen and pelvis and to compare this technique to the conventional 120 kV mixed dataset.

MATERIALS AND METHODS

Institutional review board approval was obtained with no informed consent required for this retrospective analysis. 43 consecutive patients with histopathologically confirmed peritoneal disease were scanned using a standard protocol on a 128-section dual-source, dual-energy CT system (100/140 keV). Scans were retrospectively reconstructed at VMI energy levels from 40-110 keV in 10 keV increments and were analyzed both quantitatively and qualitatively. CNR values for peritoneal metastatic deposits were recorded using region of interest (ROI) analysis at each energy level for all VMI datasets. Subjective analysis was performed by two independent fellowship-trained readers with combined experience of greater than 15 years. Qualitative parameters included diagnostic acceptability, subjective noise, and contrast resolution and confidence.

RESULTS

The contrast-to-noise ratios (CNRs) for peritoneal metastatic deposits at the different VMI energy levels were compared using a one-way ANOVA with Tukey Post Test, and the optimal CNR was observed at 40 keV (p < 0.0001). Qualitative parameters were compared using a Paired T Test. Subjective noise, diagnostic acceptability, and contrast resolution was significantly better on the conventional images, but readers reported increased confidence on VMI at 40 keV (p < 0.001).

CONCLUSION

VMI reconstruction of contrast-enhanced dual-energy CT scans of the abdomen and pelvis at 40 keV maximizes the conspicuity of metastatic peritoneal deposits and improves radiologists' diagnostic confidence compared with conventional CT images. We recommend using virtual monoenergetic datasets at 40 keV as a tool for improving the detection of these lesions in routine clinical practice.

Dual-energy CT in the obese: a preliminary retrospective review to evaluate quality and feasibility of the single-source dual-detector implementation

PURPOSE

To determine the feasibility of performing dual-energy CT with a single-source spectral detector system in obese patients.

MATERIALS AND METHODS

Retrospective, IRB-approved review of 28 patients weighing ≥ 270 lbs (122 kg) who underwent CT of the abdomen on a single-source spectral detector system was performed. Two blinded, independent radiologists rated relative preference between conventional CT images taken at 120 kVp (CCT120) and monoenergetic 70 keV equivalent (MonoE70) as well as iodine map image quality in the spleen, pancreas, kidneys, and liver. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were compared between conventional CT and MonoE70 images and correlated with body habitus markers of weight, height, and abdominal diameter.

RESULTS

MonoE70 images were preferred by radiologists 100% of the time (1-sample t test, p < 0.0001) over conventional CCT120 images. Noise was significantly lower; SNR and CNR were significantly higher in MonoE70 images than in CCT120 images (paired t tests, p < 0.0001). Mean iodine map rating (scale 1-5) was 4.54 ± 0.58, denoting near homogenous and complete iodine mapping through the spleen, pancreas, kidneys, and liver for the majority of patients. Body habitus markers were not significantly correlated with image preference score; noise; MonoE70 SNR; MonoE70 CNR; change in noise, SNR, or CNR from CCT120 to MonoE70, or iodine map quality; ordinal and linear regression, p = 0.2547, p = 0.6837, p =  0.1888, p = 0.5489, p = 0.9830, p = 0.8849, p = 0.8741, p = 0.1522, respectively.

CONCLUSION

The single-source spectral detector implementation of dual-energy CT provides viable, high-quality imaging for obese patients.

Type 1 gallbladder perforation: A rare cause of acute abdomen

Gallbladder perforation is rare. Diagnosis is usually made during operative intervention. Delay in recognition is associated with high morbidity and mortality. We report a case of type 1 gall bladder perforation in a male patient with no previous complaints related to gallstones.

Abdominal CT Scan Findings of Decompression Sickness: A Case Report

This case report depicts the radiologic findings of a 51-year-old male presenting with Decompression Sickness. Decompression Sickness is diagnosed clinically, therefore radiologic imaging of this disease entity is limited. Our patient's history includes a scuba dive to depth of 110 feet with a descending time of 24 minutes and an ascending time of 8 minutes. The patient subsequently presented to the Emergency Room with symptoms of shortness of breath and abdominal pain. The abdominal pain prompted physicians to explore further, and hence computed tomography (CT) imaging of the abdomen and pelvis was performed. This case report demonstrates a striking and unique gas pattern in both the systemic and portal venous system of our patient and provides an excellent example of the imaging findings of Decompression Sickness in the literature.

Recurrent Acute Abdomen as the Main Manifestation of Hereditary Angioedema

A diagnosis of hereditary angioedema is usually made with recurrent episodes of swelling of the subcutaneous tissue with a family history. We herein report a case in which recurrent acute abdomen was the main manifestation of hereditary angioedema. A 45-year-old womon presented with a 10-year history of recurrent severe abdominal pain. Abdominal computed tomography revealed remarkable submucosal edema of the ileum. A blood examination revealed grossly reduced complement C4 and CH50 with deficiency of C1-inhibitor. Genetic testing revealed a heterozygous nonsense mutation of the SERPING1 gene, and a diagnosis of hereditary angioedema was made. Hereditary angioedema should be listed as a differential diagnosis of recurrent acute abdomen.

A comparison of two different software packages for analysis of body composition using computed tomography images

OBJECTIVES

The analysis of body composition from computed tomography (CT) imaging has become widespread. However, the methodology used is far from established. Two main software packages are commonly used for body composition analysis, with results used interchangeably. However, the equivalence of these has not been well established. The aim of this study was to compare the results of body composition analysis performed using the two software packages to assess their equivalence.

METHODS

Triphasic abdominal CT scans from 50 patients were analyzed for a range of body composition measures at the third lumbar vertebral level using OsiriX (v7.5.1, Pixmeo, Switzerland) and SliceOmatic (v5.0, TomoVision, Montreal, Canada) software packages. Measures analyzed were skeletal muscle index (SMI), fat mass (FM), fat-free mass (FFM), and mean skeletal muscle Hounsfield Units (SMHU).

RESULTS

The overall mean SMI calculated using the two software packages was significantly different (SliceOmatic 51.33 versus OsiriX 53.77, P < 0.0001), and this difference remained significant for non-contrast and arterial scans. When FM and FFM were considered, again the results were significantly different (SliceOmatic 33.7 versus OsiriX 33.1 kg, P < 0.0001; SliceOmatic 52.1 versus OsiriX 54.2 kg, P < 0.0001, respectively), and this difference remained for all phases of CT. Finally, when analyzed, mean SMHU was also significantly different (SliceOmatic 32.7 versus OsiriX 33.1 HU, P = 0.046).

CONCLUSIONS

All four body composition measures were statistically significantly different by the software package used for analysis; however, the clinical significance of these differences is doubtful. Nevertheless, the same software package should be used if serial measurements are being performed.

Computed tomographic features of abdominal tuberculosis: unmask the impersonator!

PURPOSE

Abdominal tuberculosis (ATB) mimics various infectious, inflammatory, and neoplastic conditions and hence requires a high index of suspicion for accurate diagnosis, especially in low prevalence areas. It is difficult to consistently establish a histopathological diagnosis of ATB which underlines the importance of supportive evidences for institution of prompt empirical therapy to prevent associated morbidity and mortality.

METHODS

We retrospectively evaluated clinical and imaging features of 105 ATB cases and classified their CT findings based on peritoneal, lymph node, bowel, and solid organ involvement. Concomitant pulmonary and extra-pulmonary involvement was assessed.

RESULTS

Abdominal pain (78.1%) followed by fever (42.9%) were the commonest presenting symptoms. Peritoneal TB (77.14%) most commonly presented with a mix of ascites (49.38%), peritoneal (28.40%), and omental involvement (27.16%). Lymphadenopathy (57.1%) most commonly presented as necrotic nodes (81.67%) at mesenteric, peripancreatic, periportal, and upper paraaortic regions. Commonest site of bowel involvement (cumulative of 62.85%) was ileocecal region, with the commonest pattern of involvement being circumferential bowel wall thickening without bowel stratification with mild luminal narrowing. Hepatic (13.33%) and splenic (16.2%) involvement predominantly presented as multiple microabscesses. Adrenal and pancreatic involvement was noted in 4.7% and 1.9% of patients, respectively. 38.1% patients showed concomitant pulmonary and extra-pulmonary TB.

CONCLUSION

ATB has varied radiological features; however, peritoneal involvement in the form of mild ascites, smooth peritoneal thickening, smudgy omentum, multi-focal bowel involvement, necrotic nodes, and multiple visceral microabscesses point towards a diagnosis of ATB in appropriate clinical setting.

Comparison of image noise and image quality between full-dose abdominal computed tomography scans reconstructed with weighted filtered back projection and half-dose scans reconstructed with improved sinogram-affirmed iterative reconstruction (SAFIRE*)

PURPOSE

To retrospectively compare the image noise, signal-to-noise ratio (SNR), and subjective image quality between CT images acquired with a dual-source, split-dose imaging protocol reconstructed at full and half doses with weighted filtered back projection (wFBP) and an improved sinogram-affirmed iterative reconstruction algorithm (SAFIRE*).

METHODS

Fifty-three consecutive patients underwent contrast-enhanced CT of the abdomen using a standardized dual-source, single energy CT protocol. Half-dose images were retrospectively generated using data from one detector only. Full-dose datasets were reconstructed with wFBP, while half-dose datasets were reconstructed with wFBP and SAFIRE* strengths 1-5. Region of interest analysis was performed to assess SNR and noise. Diagnostic acceptability, subjective noise, and spatial resolution were graded on a 10-point scale by two readers. Statistical analysis was carried out with repeated measures analysis of variance, Wilcoxon signed rank test, and Cohen's κ test.

RESULTS

With the increasing strengths of SAFIRE*, a progressive reduction in noise and increase in SNR (p < 0.01) was observed. There was a statistically significant decrease in objective noise and increase in SNR in half-dose SAFIRE* strength 4 and 5 reconstructions compared to full-dose reconstructions using wFBP (p < 0.01). Qualitative analysis revealed a progressive increase in diagnostic acceptability, decrease in subjective noise and increase in spatial resolution for half-dose images reconstructed with the increasing strengths of SAFIRE* (p < 0.01).

CONCLUSIONS

Half-dose CT images reconstructed with SAFIRE* at strength 4 and 5 have superior image quality compared to full-dose images reconstructed with wFBP. SAFIRE* potentially allows dose reductions in the order of 50% over wFBP.

Development of an algorithm to automatically compress a CT image to visually lossless threshold

BACKGROUND

To develop an algorithm to predict the visually lossless thresholds (VLTs) of CT images solely using the original images by exploiting the image features and DICOM header information for JPEG2000 compression and to evaluate the algorithm in comparison with pre-existing image fidelity metrics.

METHODS

Five radiologists independently determined the VLT for 206 body CT images for JPEG2000 compression using QUEST procedure. The images were divided into training (n = 103) and testing (n = 103) sets. Using the training set, a multiple linear regression (MLR) model was constructed regarding the image features and DICOM header information as independent variables and regarding the VLTs determined with median value of the radiologists' responses (VLTrad) as dependent variable, after determining an optimal subset of independent variables by backward stepwise selection in a cross-validation scheme. The performance was evaluated on the testing set by measuring absolute differences and intra-class correlation (ICC) coefficient between the VLTrad and the VLTs predicted by the model (VLTmodel). The performance of the model was also compared two metrics, peak signal-to-noise ratio (PSNR) and high-dynamic range visual difference predictor (HDRVDP). The time for computing VLTs between MLR model, PSNR, and HDRVDP were compared using the repeated ANOVA with a post-hoc analysis. P < 0.05 was considered to indicate a statistically significant difference.

RESULTS

The means of absolute differences with the VLTrad were 0.58 (95% CI, 0.48, 0.67), 0.73 (0.61, 0.85), and 0.68 (0.58, 0.79), for the MLR model, PSNR, and HDRVDP, respectively, showing significant difference between them (p < 0.01). The ICC coefficients of MLR model, PSNR, and HDRVDP were 0.88 (95% CI, 0.81, 0.95), 0.85 (0.79, 0.91), and 0.84 (0.77, 0.91). The computing times for calculating VLT per image were 1.5 ± 0.1 s, 3.9 ± 0.3 s, and 68.2 ± 1.4 s, for MLR metric, PSNR, and HDRVDP, respectively.

CONCLUSIONS

The proposed MLR model directly predicting the VLT of a given CT image showed competitive performance to those of image fidelity metrics with less computational expenses. The model would be promising to be used for adaptive compression of CT images.

EFFECTIVE DOSE ESTIMATION FROM ORGAN DOSE MEASUREMENTS IN FAST-kV SWITCH DUAL ENERGY COMPUTED TOMOGRAPHY

The purpose of this study was to validate a novel approach to estimating effective dose (E) in 'fast-kV switch dual energy computed tomography' using MOSFET detectors. The effective energy of the combined dual energy environment was characterized with the dual energy CT scanner and then MOSFETs were calibrated matching to the effective energy of the dual energy CT beam with a conventional CT beam. The calibration method was then experimentally validated by comparing the dose between MOSFET and an ion chamber (IC) using a standard CTDI body phantom. The measured doses of the MOSFET and IC were 17.1 mGy ± 3.8% and 17.1 mGy ± 0.4%, respectively. To measure organ doses, an adult anthropomorphic phantom loaded with 18 MOSFET detectors was scanned using a standard fast-kV switch dual energy abdomen/pelvis CT protocol. E was calculated by applying ICRP 103 tissue weighting factors as well as partial volume correction factors for organs that were not completely covered by the protocol field-of-view. E from the dual energy abdomen/pelvis CT was calculated to be 17.8 mSv ± 11.6%. This calculation was then compared to E from dose length product method, which yielded 14.62 mSv.

Automatic Multiorgan Segmentation via Multiscale Registration and Graph Cut

We propose an automatic multiorgan segmentation method for 3-D radiological images of different anatomical contents and modalities. The approach is based on a simultaneous multilabel graph cut optimization of location, appearance, and spatial configuration criteria of target structures. Organ location is defined by target-specific probabilistic atlases (PA) constructed from a training dataset using a fast (2+1)D SURF-based multiscale registration method involving a simple four-parameter transformation. PAs are also used to derive target-specific organ appearance models represented as intensity histograms. The spatial configuration prior is derived from shortest-path constraints defined on the adjacency graph of structures. Thorough evaluations on Visceral project benchmarks and training dataset, as well as comparisons with the state-of-the-art confirm that our approach is comparable to and often outperforms similar approaches in multiorgan segmentation, thus proving that the combination of multiple suboptimal but complementary information sources can yield very good performance.

Surgical management of retroperitoneal schwannoma complicated with severe hydronephrosis: A case report

RATIONALE

Schwannomas are usually benign tumors arising from well-differentiated schwann cells, which rarely occur in the retroperitoneal space. The lack of specific signs and radiologic imaging characteristics makes preoperative diagnosis rather difficult. Most retroperitoneal schwannomas are benign and the primary treatment choice for retroperitoneal schwannomas is surgical excision, however, the involvement of the urinary system is scarcely reported.

PATIENT CONCERNS

A 34-year-old woman presented with progressive left abdominal pain and rebound abdominal mass at the left lower quadrant for 1 month. Radiological imaging suggested capsulated solid mass with cystic and necrotic areas in the retroperitoneum accompanied by severe left kidney hydronephrosis and preoperative biopsy result was inconclusive.

DIAGNOSES

We believe this is a rare case of retroperitoneal schwannoma complicated with severe hydronephrosis.

INTERVENTIONS

After preparation, the patient underwent laparoscopy exploration and converted to open surgical exploration. The patient accepted complete surgical excision of the retroperitoneal tumor and left kidney. Postoperative pathology diagnosis of the mass was proven to be benign retroperitoneal schwannoma.

OUTCOMES

Postoperative course of the patient was uneventful and the left abdominal pain was greatly improved. After 12-month follow up, no evidence of recurrence or any other complication including renal failure was observed.

LESSONS

Preoperative imaging and preoperative ultrasound-guided biopsy are helpful to make accurate diagnosis. The final diagnosis is based on postoperative histological and immunohistochemical findings. The primary treatment option is complete surgical resection of the retroperitoneal schwannoma and the involved upper urinary system when severe hydronephrosis occured. Local recurrence and overall survival are closely correlated with negative resection margins and pathology types.

Effect of gantry rotation speed and scan mode on peristalsis motion artifact frequency and severity at abdominal CT

PURPOSE

The purpose of the study was to understand the effect of CT gantry speed and axial vs. helical scan mode on the frequency and severity of bowel peristalsis artifacts.

METHOD

We retrospectively identified 150 oncologic abdominopelvic CT scans obtained on a 256 slice CT scanner: 50 scans obtained with Axial mode and 0.5-s gantry rotation time (Slow-Axial); 50 with Axial mode and 0.28-s gantry rotation time (Fast-Axial); and 50 scans with Helical mode and 0.28-s gantry rotation time (Fast-Helical). The patients included 74 women and 76 men with a mean age of 61 years (range 22-85 years). Two readers viewed all CT scans to record the presence and severity of bowel peristalsis artifact, location of artifact (stomach, duodenum/jejunum, ileum, and colon) and artifact location relative to bowel interface (gas-bowel, fluid-bowel, and gas-fluid). The severity of artifacts was recorded subjectively on a 3-point scale, and objectively based on maximum length of the artifact.

RESULTS

Peristalsis artifact was more commonly seen with Slow-Axial scan acquisition (37 of 50 patient scans, or 74%) than Fast-Axial (15 in 50 patient scans, or 30%, p < 0.001) and Fast-Helical (22 of 50 patient scans, or 44%, p < 0.005). The bowel segment distribution and severity of peristalsis artifacts were not significantly different between scan techniques.

CONCLUSION

Peristalsis artifacts are common at abdominopelvic CT scans. Fast gantry rotation speed significantly reduces the frequency of bowel peristalsis artifacts and should be a consideration when imaging of bowel and structures near bowel is critical.

Automatic Multi-Organ Segmentation on Abdominal CT With Dense V-Networks

Automatic segmentation of abdominal anatomy on computed tomography (CT) images can support diagnosis, treatment planning, and treatment delivery workflows. Segmentation methods using statistical models and multi-atlas label fusion (MALF) require inter-subject image registrations, which are challenging for abdominal images, but alternative methods without registration have not yet achieved higher accuracy for most abdominal organs. We present a registration-free deep-learning-based segmentation algorithm for eight organs that are relevant for navigation in endoscopic pancreatic and biliary procedures, including the pancreas, the gastrointestinal tract (esophagus, stomach, and duodenum) and surrounding organs (liver, spleen, left kidney, and gallbladder). We directly compared the segmentation accuracy of the proposed method to the existing deep learning and MALF methods in a cross-validation on a multi-centre data set with 90 subjects. The proposed method yielded significantly higher Dice scores for all organs and lower mean absolute distances for most organs, including Dice scores of 0.78 versus 0.71, 0.74, and 0.74 for the pancreas, 0.90 versus 0.85, 0.87, and 0.83 for the stomach, and 0.76 versus 0.68, 0.69, and 0.66 for the esophagus. We conclude that the deep-learning-based segmentation represents a registration-free method for multi-organ abdominal CT segmentation whose accuracy can surpass current methods, potentially supporting image-guided navigation in gastrointestinal endoscopy procedures.

Delayed manifestations of abdominal trauma: follow-up abdominopelvic CT in posttraumatic patients

PURPOSE

Our study aims to investigate the frequency and patterns of delayed manifestations of abdominal and pelvic injuries which may not be identified or which fail to manifest on the initial abdominopelvic CT in posttraumatic patients.

METHODS

For our institutional review board (IRB)-approved retrospective study, our hospital trauma registry was queried for patients with blunt multitrauma and Injury Severity Score (ISS) ≥ 16 between January 2010 and August 2016, yielding 3735 patients. A total of 203 patients received a follow-up abdominopelvic CT within six months from the initial scan and those with new findings on follow-up CT were identified. A retrospective blinded review of the initial CT examinations was performed by two experienced radiologists. The retrospective readings and original reports were compared to categorize the new abnormalities detected on follow-up CT scans. The categories included missed injuries, late presentations and sequelae of trauma, and complications of surgery, hospital admission, and invasive procedures. The patients' notes were reviewed for the clinical indications, time interval for repeat CT examination, and subsequent clinical management. The software used for statistical analysis of the extracted data was Microsoft Excel for Mac (version 15.33).

RESULTS

Out of 3735 patients, 203 patients received 232 follow-up abdominopelvic CTs. The average elapsed time between the initial CT and the follow-up CT was 15 ± 27 days. Evaluation for an abdominal fluid collection was the most common clinical indication, accounting for 40% of the total number (n = 243) of indications. Delayed manifestations and complications of trauma were present in 41 patients due to 47 abnormalities, most commonly related to solid organ injury, followed by abdominal collections and hematoma. Twenty-nine CT findings (62%) were only detectable on follow-up CT, while nine injuries (19%) were missed on initial CT. The findings on repeated CT warranted eight surgical and 15 interventional procedures.

CONCLUSION

A small percentage of traumatic injuries may be unidentified or fail to manifest on the initial CT, resulting in delayed manifestations of abdominopelvic trauma, which may lead to subsequent readmission, delayed management, and more severe medical complications.

Assessment of image quality in abdominal CT: potential dose reduction with model-based iterative reconstruction

PURPOSE

To estimate potential dose reduction in abdominal CT by visually comparing images reconstructed with filtered back projection (FBP) and strengths of 3 and 5 of a specific MBIR.

MATERIAL AND METHODS

A dual-source scanner was used to obtain three data sets each for 50 recruited patients with 30, 70 and 100% tube loads (mean CTDIvol 1.9, 3.4 and 6.2 mGy). Six image criteria were assessed independently by five radiologists. Potential dose reduction was estimated with Visual Grading Regression (VGR).

RESULTS

Comparing 30 and 70% tube load, improved image quality was observed as a significant strong effect of log tube load and reconstruction method with potential dose reduction relative to FBP of 22-47% for MBIR strength 3 (p < 0.001). For MBIR strength 5 no dose reduction was possible for image criteria 1 (liver parenchyma), but dose reduction between 34 and 74% was achieved for other criteria. Interobserver reliability showed agreement of 71-76% (κw 0.201-0.286) and intra-observer reliability of 82-96% (κw 0.525-0.783).

CONCLUSION

MBIR showed improved image quality compared to FBP with positive correlation between MBIR strength and increasing potential dose reduction for all but one image criterion.

KEY POINTS

• MBIR's main advantage is its de-noising properties, which facilitates dose reduction. • MBIR allows for potential dose reduction in relation to FBP. • Visual Grading Regression (VGR) produces direct numerical estimates of potential dose reduction. • MBIR strengths 3 and 5 dose reductions were 22-34 and 34-74%. • MBIR strength 5 demonstrates inferior performance for liver parenchyma.

Cystic Liver Metastases from Lung Adenocarcinoma: A Case Report

Cystic hepatic metastases arising from lung cancer are rare. We herein describe a case of a 71-year-old women admitted to our hospital for abdominal pain 6 months after the resection of a lung adenocarcinoma. Two cystic lesions of the liver were discovered at abdominal ultrasonography and computerized tomography scan. An ERCP excluded a biliary adenoma or adenocarcinoma, and an ultrasound-guided liver biopsy was negative for malignant cells. For persistence of symptoms and lack of a diagnosis, the patient underwent an exploratory laparotomy, a surgical biopsy with a diagnosis of adenocarcinoma, and a consequent right hepatectomy. After 2 years of follow-up, the patient is well and disease free. Although cystic liver metastasis are rare and a differential diagnosis difficult, the malignant nature should always be considered in the differential diagnosis of hepatic cysts to offer the patient the best treatment.