Accuracy analysis of intrahepatic fat density measurements using dual-energy computed tomography: Validation using a test phantom.

BACKGROUND: Currently, no standardized method for measuring intrahepatic fat density via conventional computed tomography (CT) exists. OBJECTIVE: We aim to quantify intrahepatic fat density via material decomposition analysis using rapid kilovolt peak-switching dual-energy (RSDE) CT. METHODS: Homogenized porcine liver and fat (lard) were mixed in various ratios to produce phantoms for fat density verification. The actual fat density was measured on the basis of the phantom volume and weight, and these measurements were used as reference densities. The fat and liver mass attenuation coefficients, which were used as the material basis pairs, were employed in the material decomposition analysis. Then, the measured fat density of each phantom was compared with the reference densities. RESULTS: For fat content differences exceeding 2%, the measured fat density for the phantoms became statistically significant (p < 0.01). The correlation between the reference densities and RSDE-measured fat densities was reasonably high (R > 0.9997); this indicates the validity of this analysis method. CONCLUSIONS: Intrahepatic fat density can be measured using the mass attenuation coefficients of fat and liver in a material decomposition analysis. Given the knowledge of the accuracy and the limitations found in this study, our method can quantitatively evaluate fat density.

Visceral Abdominal Obesity Measured by Computed Tomography is Associated With Increased Risk of Colonic Diverticulosis.

GOALS: To investigate whether visceral obesity measured by computed tomography (CT) is a risk factor for colonic diverticulosis. BACKGROUND: The association between colonoscopy-proven diverticulosis and visceral obesity has not been studied. STUDY: A cohort of 1445 participants (1117 nondiverticulosis and 328 diverticulosis) undergoing colonoscopy and CT was prospectively analyzed. Diverticulosis was diagnosed by high-resolution colonoscopy. The associations between body mass index (BMI), visceral adipose tissue (VAT) area, subcutaneous adipose tissue (SAT) area, and diverticulosis were estimated using odds ratios (ORs) adjusted for age, sex, alcohol, smoking, medications, and comorbidities. RESULTS: In multivariate analysis, diverticulosis was significantly associated with VAT area and SAT area for both categorical data and trend (P for trend <0.001), but not BMI.Diverticulosis had a positive association with VAT area and SAT area for both categorical data and trend (P for trend <0.001) in men, but none of these associations were noted in women. In the subanalysis of normal-weight patients (BMI<25), diverticulosis was independently associated with VAT area and SAT area (P for trend <0.001). The adjusted ORs for VAT area ≥100 cm² was significantly increased in right-sided (OR, 1.8), left-sided (OR, 2.3), and bilateral (OR, 3.0) diverticula (P for trend <0.001). CONCLUSIONS: Abdominal obesity measured by CT, not BMI, is associated with colonic diverticulosis, even when body weight was normal. These findings suggest an important role for visceral fat accumulation in diverticulosis development. A high visceral fat was positively associated with the distribution of diverticula.

Visceral fat accumulation affects risk of colonic diverticular hemorrhage.

PURPOSES: Factors other than antithrombotic drugs associated with diverticular bleeding remain unknown. Visceral adiposity contributes to atherosclerosis and may affect arteriolar change at the diverticulum. We investigated whether visceral adipose tissue (VAT) measured by computed tomography (CT) is a risk factor for diverticular bleeding. METHODS: A cohort of 283 patients (184 with asymptomatic diverticulosis and 99 with diverticular bleeding) undergoing colonoscopy and CT was analyzed. Associations between body mass index (BMI), VAT, subcutaneous adipose tissue (SAT), and diverticular bleeding were assessed by logistic regression models adjusted for age, gender, alcohol, smoking, diabetes mellitus, hypertension, dyslipidemia, chronic kidney disease, and antithrombotic drugs (nonsteroidal anti-inflammatory drugs (NSAIDs), low-dose aspirin, and other antiplatelet drugs). RESULTS: In univariate analysis, hypertension, dyslipidemia, chronic kidney disease, and NSAIDs use, low-dose aspirin, non-aspirin antiplatelets, increasing BMI, and increasing VAT area were associated with diverticular bleeding. In multivariate analysis adjusted for confounding factors, VAT area (p = 0.021), but not BMI (p = 0.551) or SAT area (p = 0.635), was positively associated with diverticular bleeding. When BMI was considered simultaneously, VAT area remained positively associated with diverticular bleeding (p = 0.018). However, none of obesity indices including VAT area were associated with recurrence of diverticular bleeding or prolonged hospitalization. CONCLUSIONS: This study presents new information on risk factors for diverticular bleeding. A large volume of visceral adipose tissue, but not BMI or SAT, appears to entail a risk for diverticular bleeding, after age, gender, metabolic factors, and antithrombotic drugs use adjustments.

Abdominal visceral fat accumulation measured by computed tomography associated with an increased risk of gallstone disease.

BACKGROUND AND AIM: Visceral adiposity is a strong determinant of insulin resistance, which decreases cholecystokinin response sensitivity, and increases cholesterol saturation in the gallbladder bile; thus, it potentially relates to gallstone disease development. We aimed to investigate whether visceral fat measured by computed tomography (CT) is a risk factor for gallstone disease. METHODS: A cohort of 717 participants undergoing CT and ultrasonography was analyzed. The associations between body mass index (BMI), visceral adipose tissue (VAT) area, subcutaneous adipose tissue (SAT) area, and gallstone disease were analyzed adjusted for age, sex, hypertension, diabetes, and dyslipidemia. RESULTS: In multivariate analysis, gallstone disease was significantly associated with VAT and SAT areas for both categorical data and trend (P for trend < 0.001, 0.009), but not body mass index (BMI). Among patients with BMI < 25, gallstone disease remained significantly associated with VAT area (P for trend 0.021) and SAT area (P for trend 0.005). Interactions between the obesity indices and being elderly on the risk of gallstone disease were found; specifically BMI (P = 0.005), SAT (P < 0.001), and VAT (P = 0.154). A significant association between all obesity indices and gallstone disease was seen in patients aged < 65 but not among those aged ≥ 65. However, no significant association was noted between the obesity indices and sex. CONCLUSIONS: CT-measured adipose tissue, rather than BMI, was a better predictor for risk of gallstone disease. This finding applies to younger people or even those with normal body weight, suggesting the importance of abdominal visceral fat accumulation in the development of gallstone disease.

Abdominal Fat Accumulation, as Measured by Computed Tomography, Increases the Risk of Ischemic Colitis: A Retrospective Case-Control Study.

BACKGROUND AND AIM: Visceral fat contributes to insulin resistance and atherosclerosis. We retrospectively investigated whether abdominal fat accumulation, as measured by computed tomography, is a risk of ischemic colitis and related clinical outcomes. MATERIALS AND METHODS: Outpatient-onset ischemic colitis patients (n = 58) and age- and sex-matched controls (n = 58) underwent colonoscopy and computed tomography. Associations between body mass index, visceral adipose tissue area, subcutaneous adipose tissue area, and ischemic colitis were estimated using odds ratios adjusted for hypertension, diabetes mellitus, and dyslipidemia. RESULTS: In multivariate analysis, ischemic colitis was significantly associated with subcutaneous adipose tissue area (P for trend 0.030) and marginally associated with visceral adipose tissue area (P for trend 0.094), but was not associated with body mass index (P for trend 0.460). The adjusted odds ratios for the highest quartile of subcutaneous and visceral adipose tissue in ischemic colitis were 3.48 (1.06-11.4) and 2.43 (0.74-8.00), respectively, compared with the lowest quartile. When body mass index was considered simultaneously, ischemic colitis remained associated with subcutaneous adipose tissue (P for trend 0.016) and visceral adipose tissue (P for trend 0.077). No significant differences were noted between any of the obesity indices and the distribution type of colitis, blood transfusion requirement, or length of hospital stay. CONCLUSION: Abdominal fat accumulation measured by computed tomography, but not body mass index, was associated with outpatient-onset ischemic colitis. Ischemic colitis remained associated with abdominal fat, even when body mass index was simultaneously considered. However, clinical outcomes of ischemic colitis were not associated with abdominal fat accumulation.

Visceral abdominal fat measured by computed tomography is associated with an increased risk of colorectal adenoma.

We investigated whether visceral adipose tissue (VAT) measured by computed tomography (CT) is a risk factor for colorectal adenoma. For a total of 1,328 patients (857 without adenoma, 471 with colorectal adenoma) undergoing colonoscopy and CT, associations between colorectal adenoma and body mass index (BMI), VAT area and subcutaneous adipose tissue (SAT) were assessed using odds ratios (ORs) with 95% confidence intervals (CIs) adjusted for age, sex, family history, smoking, alcohol intake, diabetes mellitus, aspirin use and nonsteroidal anti-inflammatory drug use. Multivariate analysis showed that colorectal adenoma was marginally associated (p=0.06) with BMI, but not with SAT, while it was significantly associated with VAT and the VAT to SAT ratio (VAT/SAT) for both categorical data and trend (p<0.05). When the obesity indices were considered simultaneously, colorectal adenoma remained significantly associated with VAT and VAT/SAT (p<0.05), but not BMI and SAT. In patients with colorectal adenoma, the adjusted OR for the highest quartiles of VAT and VAT/SAT was 1.90 (95% CI 1.16-3.13) and 2.25 (95% CI 1.49-3.41), respectively, compared to the lowest quartiles. Only VAT area was significantly associated with colorectal adenoma in both men and women (p<0.05). Proximal, multiple and advanced adenomas had significantly higher VAT areas (p<0.05) than distal, solitary and nonadvanced adenomas. Our findings implicate abdominal VAT in the development and progression of colorectal adenoma, and it was better obesity index for colorectal adenoma than BMI in both sexes.

Predictors for cecal insertion time: the impact of abdominal visceral fat measured by computed tomography.

BACKGROUND: Several factors affect the risk for longer cecal insertion time. OBJECTIVE: The aim of this study was to identify the predictors of longer insertion time and to evaluate the effect of visceral fat measured by CT. DESIGN: This is a retrospective observational study. PATIENTS: Outpatients for colorectal cancer screening who underwent colonoscopies and CT were enrolled. Computed tomography was performed in individuals who requested cancer screening and in those with GI bleeding. MAIN OUTCOME MEASURES: Information on obesity indices (BMI, visceral adipose tissue, and subcutaneous adipose tissue area), constipation score, history of abdominal surgery, poor preparation, fellow involvement, diverticulosis, patient discomfort, and the amount of sedation used was collected. RESULTS: The cecal insertion rate was 95.2% (899/944), and 899 patients were analyzed. Multiple regression analysis showed that female sex, lower BMI, lower visceral adipose tissue area, lower subcutaneous adipose tissue area, higher constipation score, history of surgery, poor bowel preparation, and fellow involvement were independently associated with longer insertion time. When obesity indices were considered simultaneously, smaller subcutaneous adipose tissue area (p = 0.038), but not lower BMI (p = 0.802) or smaller visceral adipose tissue area (p = 0.856), was associated with longer insertion time; the other aforementioned factors remained associated with longer insertion time. In the subanalysis of normal-weight patients (BMI <25 kg/m), a smaller subcutaneous adipose tissue area (p = 0.002), but not a lower BMI (p = 0.782), was independently associated with a longer insertion time. Longer insertion time had a positive correlation with a higher patient discomfort score (ρ = 0.51, p < 0.001) and a greater amount of midazolam use (ρ = 0.32, p < 0.001). LIMITATIONS: This single-center retrospective study includes a potential selection bias. CONCLUSIONS: In addition to BMI and intra-abdominal fat, female sex, constipation, history of abdominal surgery, poor preparation, and fellow involvement were predictors of longer cecal insertion time. Among the obesity indices, high subcutaneous fat accumulation was the best predictive factor for easier passage of the colonoscope, even when body weight was normal.

[Decision process of Notification Value by the Dose Index Registry system in X-ray computed tomography].

A new technical standard for X-ray computed tomography (CT) has been published by the National Electrical Manufacturers Association (NEMA) that allows the Alert Value and Notification Value for cumulative dose to be configurable by CT systems operators in conjunction with the XR-25 (Dose check) standard. In this study, a decision method of the Notification Values for reducing the radiation dose was examined using the dose index registry (DIR) system, during 122 continuous days from August 1, 2012 to November 30, 2012. CT images were obtained using the Discovery CT 750HD (GE Healthcare) and the dose index was calculated using the DoseWatch DIR system. The CT dose index-volume (CTDIvol) and dose-length product (DLP) were output from the DIR system in comma-separated value (CSV) file format for each examination protocol. All data were shown as a schematic boxplot using statistical processing software. The CTDIvol of a routine chest examination showed the following values (maximum: 23.84 mGy; minimum: 2.55 mGy; median: 7.60 mGy; 75% tile: 10.01 mGy; 25% tile: 6.54 mGy). DLP showed the following values (maximum: 944.56 mGy·cm; minimum: 97.25 mGy·cm; median: 307.35 mGy·cm; 75% tile: 406.87 mGy·cm; 25% tile: 255.75 mGy·cm). These results indicate that the 75% tile of CTDIvol and DLP as an initial value proved to be safe and efficient for CT examination and operation. We have thus established one way of determining the Notification Value from the output of the DIR system. Transfer back to the protocol of the CT and automated processing each numeric value in the DIR system is desired.

USEFULNESS OF SIZE-SPECIFIC DOSE ESTIMATES IN PEDIATRIC COMPUTED TOMOGRAPHY: REVALIDATION OF LARGE-SCALE PEDIATRIC CT DOSE SURVEY DATA IN JAPAN.

The objective of this research is to calculate the organ equivalent dose and effective dose from the scanning conditions at 165 centers in Japan using computed tomography (CT) Dose software and compare the results with the CT dose index volume (CTDIvol), dose length product (DLP) and size-specific dose estimates (SSDE) to validate the usefulness of SSDE. The CTDIvol and DLP were significantly lower in infants than in children (p < 0.05). No significant differences were found in the bone marrow equivalent dose and effective dose for the torso between infants and children (p > 0.05), and the bone marrow equivalent dose and effective dose for the head were higher in infants than children (p < 0.05). No significant difference was found in SSDE for the torso between infants and children (p > 0.05). Organ equivalent and effective doses for head CT scans are higher in infants than in children (I/P ratio ≥ 1). The I/P ratios of CTDIvol and DLP for chest and abdominal CT scans are also higher in Japan than in other countries. CTDIvol and DLP are not accurate when used as a dose index, and SSDE was considered suitable for dose assessment of the torso. However, for head CT in infants, a further reduction in radiation exposure is required.

Role of urgent contrast-enhanced multidetector computed tomography for acute lower gastrointestinal bleeding in patients undergoing early colonoscopy.

BACKGROUND: The clinical significance of performing computed tomography (CT) for acute lower gastrointestinal bleeding (LGIB) remains unknown. This study aimed to evaluate the role of urgent CT in acute LGIB settings. METHODS: The cohort comprised 223 patients emergently hospitalized for LGIB who underwent early colonoscopy within 24 h of arriving at the hospital, including 126 who underwent CT within 3 h of arrival. We compared the bleeding source rate between two strategies: early colonoscopy following urgent CT or early colonoscopy alone. RESULTS: No significant differences in age, sex, comorbidities, vital signs, or laboratory data were observed between the strategies. The detection rate was higher with colonoscopy following CT for vascular lesions (35.7 vs. 20.6%, p = 0.01), leading to more endoscopic therapies (34.9 vs. 13.4%, p < 0.01). Of the 126 who underwent colonoscopy following CT, 26 (20.6%) had extravasation and 34 (27.0%) had nonvascular findings. The sensitivity and specificity of CT extravasation and nonvascular findings for predicting vascular lesions and inflammation or tumors were 37.8 and 88.9 and 81.3 and 80.9%, respectively. A high κ agreement (0.83, p < 0.01) for active bleeding locations was found between CT and subsequent colonoscopy. There were no cases of contrast-induced nephropathy after 1 week of CT. CONCLUSIONS: Urgent CT before colonoscopy had about 15% additional value for detecting vascular lesion compared to colonoscopy alone and thus enabled subsequent endoscopic therapies. Contrast-enhanced CT in acute LGIB settings was safe and correctly identified the presence and location of active bleeding, as well as severe inflammation or tumor stenosis, facilitating decision making.

Effect of body mass index and intra-abdominal fat measured by computed tomography on the risk of bowel symptoms.

BACKGROUND: This study aims to investigate the association between body mass index (BMI) or intra-abdominal fat measured by computed tomography (CT) and bowel symptoms. METHOD: A cohort of 958 Japanese adults who underwent colonoscopy and CT and completed questionnaires after excluding colorectal diseases was analyzed. Six symptoms (constipation, diarrhea, loose stools, hard stools, fecal urgency, and incomplete evacuation) using a 7-point Likert scale were evaluated between baseline and second questionnaire for test-retest reliability. Associations between BMI, visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), and symptom score were analyzed by a rank-ordered logistic model, adjusting for age, sex, smoking, and alcohol consumption, hypertension, diabetes mellitus, and dyslipidemia. RESULTS: Some bowel symptom scores were significantly (p<0.05) different between the age groups, sexes, smoking, and alcohol consumption. In multivariate analysis, constipation was associated with low BMI (p<0.01), low VAT area (p = 0.01), and low SAT area (p<0.01). Moreover, hard stools was associated with low BMI (p<0.01) and low SAT area (p<0.01). The remaining symptoms were not significantly associated with BMI or intra-abdominal fat. Test-retest reliability of bowel symptom scores with a mean duration of 7.5 months was good (mean kappa, 0.672). CONCLUSIONS: Both low BMI and low abdominal fat accumulation appears to be useful indicators of increased risk for constipation and hard stools. The long-term test-retest reliability of symptom score suggests that bowel symptoms relevant to BMI or visceral fat remain consistent over several months.