Chad M. Miller

Detection of Renal Lesion Enhancement with Dual-Energy Multidetector CT

PURPOSE To determine whether dual-energy multidetector CT enables detection of renal lesion enhancement by using calculated nonenhanced images with spectral-based extraction in a non-body weight-restricted patient population. MATERIALS AND METHODS Between January 2008 and December 2009, 139 patients were enrolled in this prospective HIPAA-compliant, institutional review board-approved study. Written informed consent was obtained from all patients. After single-energy nonenhanced 120-kVp CT images were acquired, contrast material-enhanced dual-energy multidetector CT images were acquired at 80 and 140 kVp. Calculated nonenhanced images were generated by using spectral-based iodine extraction. Lesion attenuation was measured on the acquired nonenhanced, calculated nonenhanced, and 140-kVp contrast-enhanced nephrographic images. Enhancement, defined as a 15-HU or greater increase in attenuation on the nephrographic images, was assessed by using the baseline attenuation on the acquired and calculated nonenhanced images. Acquired nonenhanced versus calculated nonenhanced image attenuation, as well as enhancement values, were compared by using paired Student t tests and Bland-Altman plots. RESULTS Hypoattenuating (n = 66) and hyperattenuating (n = 28) cysts, angiomyolipomas (n = 18), and solid enhancing lesions (n = 27) were detected. Mean attenuation values for hypoattenuating cysts on the acquired and calculated nonenhanced CT images were 6.5 HU ± 5.8 (standard deviation) and 8.1 HU ± 3.1 (P = .13), respectively, with corresponding enhancement values of 1.1 HU ± 5.2 and -0.5 HU ± 6.2 (P = .12), respectively. Mean values for hyperattenuating cysts were 29.4 HU ± 5.6 on acquired images and 31.7 HU ± 5.1 on calculated images (P = .39) (corresponding enhancement, 4.7 HU ± 3.3 and 2.3 HU ± 4.1, respectively; P = .09). Mean values for fat-containing enhancing lesions were -90.6 HU ± 24.7 on acquired images and -85.9 HU ± 23.7 on calculated images (P = .57) (corresponding enhancement, 18.2 HU ± 10.1 and 13.6 HU ± 10.7, respectively; P = .19). Mean attenuation values for solid enhancing lesions were 26.0 HU ± 15.0 on acquired images and 27.7 HU ± 14.9 on calculated images (P = .45) (corresponding enhancement, 60.3 HU ± 13.1 and 58.3 HU ± 15.5, respectively; P = .38). CONCLUSION Dual-energy CT acquisitions with spectral-based postprocessing enabled accurate detection of renal lesion enhancement across the attenuation spectrum of frequently encountered renal lesions in a non-body habitus-restricted patient population.

Practice patterns in imaging of the pregnant patient with abdominal pain : A survey of academic centers

OBJECTIVE The purpose of our study was to evaluate current practice patterns in the imaging of pregnant women with abdominal complaints. MATERIALS AND METHODS A survey was sent to the abdominal imaging division of 183 radiology residency programs in the United States. The survey asked for information regarding CT and MRI of abdominal complaints in pregnant patients. RESULTS Eighty-five surveys (46%) were returned. Sixty-three (74%) of 85 of respondents have a written departmental policy regarding imaging pregnant women. Eighty-two (96%) of 85 perform CT in pregnant women when benefits outweigh risks, with 58 (68%) obtaining written informed consent before CT examination. Eighty (94%) of 85 perform MRI in pregnant women, and 43 (51%) obtain written consent before MRI. Fifty-seven (67%) of 85 respondents do not administer gadolinium in pregnancy. In the setting of trauma, respondents choose CT over MRI for imaging in all three trimesters (75% vs 5%, 85% vs 5%, and 88% vs 4%). In the second and third trimesters, respondents prefer CT to MRI to evaluate for maternal renal calculus (35% vs 20% and 48% vs 18%, respectively), appendicitis (48% vs 38% and 58% vs 29%), and abscess (49% vs 41% and 58% vs 35%). However, MRI is preferred for imaging of appendicitis and abscesses in the first trimester (39% vs 32% and 46% vs 32%). CONCLUSION Most academic radiology departments have written policies regarding imaging of pregnant women. Academic radiologists prefer CT to MRI for imaging abdominal complaints in pregnant women, especially in the second and third trimesters.

Radiation Dose for Body CT Protocols: Variability of Scanners at One Institution

OBJECTIVE The objective of our study was to determine, using an anthropomorphic phantom, whether patients are subject to variable radiation doses based on scanner assignment for common body CT studies. MATERIALS AND METHODS Twenty metal oxide semiconductor field effect transistor dosimeters were placed in a medium-sized anthropomorphic phantom of a man. Pulmonary embolism and chest, abdomen, and pelvis protocols were used to scan the phantom three times with GE Healthcare scanners in four configurations and one 64-MDCT Siemens Healthcare scanner. Organ doses were averaged, and effective doses were calculated with weighting factors. RESULTS The mean effective doses for the pulmonary embolism protocol ranged from 9.9 to 18.5 mSv and for the chest, abdomen, and pelvis protocol from 6.7 to 18.5 mSv. For the pulmonary embolism protocol, the mean effective dose from the Siemens Healthcare 64-MDCT scanner was significantly lower than that from the 16- and 64-MDCT GE Healthcare scanners (p < 0.001). The mean effective dose from the GE 4-MDCT scanner was significantly lower than that for the GE 16-MDCT scanner (p < 0.001) but not the GE 64-MDCT scanner (p = 0.02). For the chest, abdomen, and pelvis protocol, all mean effective doses from the GE scanners were significantly different from one another (p < 0.001), the lowest mean effective dose being found with use of a single-detector CT scanner and the highest with a 4-MDCT scanner. For the chest, abdomen, and pelvis protocols, the difference between the mean effective doses from the GE Healthcare and Siemens Healthcare 64-MDCT scanners was not statistically significant (p = 0.89). CONCLUSION According to phantom data, patients are subject to different radiation exposures for similar body CT protocols depending on scanner assignment. In general, doses are lowest with use of 64-MDCT scanners.

Should Women with Obstructive Sleep Apnea Syndrome Be Screened for Hypothyroidism

ABSTRACTThis study was conducted to determine if there is a significant increase in prevalence of hypothyroidism in women with OSAS such that screening might be warranted. Women undergoing polysomnography (PSG) at Duke University between January 1, 2000 and August 21, 2001 were considered for enrollment. Those with a respiratory disturbance index (RDI) ≥ 10 were included for further analysis. Demographic data and documentation of thyroid testing was obtained. Thyroid testing obtained within 1 year of the PSG was used for this study. Demographic data of the euthyroid and hypothyroid groups were compared. Prevalence of hypothyroidism was calculated and compared with the prevalence of hypothyroidism in the Framingham study. A total of 118 women had OSAS per PSG. Seventy-five patients had thyroid function testing within 1 year of PSG evaluation. The mean age, body mass index, and RDI in the euthyroid and hypothyroid groups were not significantly different. The prevalence of hypothyroidism was 9.3%; the established prevalence of hypothyroidism in women in the general population is 5.9%. There was no statistically significant difference in the prevalence between these groups. The prevalence of hypothyroidism in women with OSAS is no higher than that seen in the general population. Screening women with symptoms of OSAS for hypothyroidism is unlikely to be useful.

Magnetic resonance (MR) cholangiography: quantitative and qualitative comparison of 3.0 Tesla with 1.5 Tesla.

Objectives:To determine quantitative and qualitative image quality in patients undergoing magnetic resonance (MR) cholangiography at 3.0 Tesla (T) compared with 1.5 T. Materials and Methods:Fifty patients (30 women; mean age, 51 years) underwent MR cholangiography at 1.5 T; another 50 patients (25 women; mean age 51 years) were scanned at 3.0 T. MR sequence protocol consisted of breath-hold single-slice rapid acquisition with relaxation enhancement (RARE) and a respiratory-triggered 3D turbo spin echo (3D TSE) sequence. Maximum intensity projections were generated from the 3D TSE datasets. Contrast-to-noise ratio (CNR) measurements between the common bile duct (CBD), left and right intrahepatic duct (LHD, RHD), and periductal tissue were performed. Three radiologists assessed qualitatively the visibility of the CBD, LHD, and RHD and the overall diagnostic quality. Results:Mean gain in CNR at 3.0 T versus 1.5 T in all 3 locations ranged for the RARE sequence from 7.7% to 38.1% and for the 3D TSE from 0.5% to 26.1% (P > 0.05 for all differences). Qualitative analysis did not reveal any significant difference between the 2 field strengths (P > 0.05). Conclusions:MR cholangiography at 3.0 T shows a trend toward higher CNR without improving image quality significantly.

Effect of Organ Enhancement and Habitus on Estimation of Unenhanced Attenuation at Contrast-Enhanced Dual-Energy MDCT: Concepts for Individualized and Organ-Specific Spectral Iodine Subtraction Strategies

OBJECTIVE The purpose of this study was to assess whether habitus and organ enhancement influence iodine subtraction and should be incorporated into spectral subtraction algorithms. SUBJECTS AND METHODS This study included 171 patients. In the unenhanced phase, MDCT was performed with single-energy acquisition (120 kVp, 250 mAs) and in the parenchymal phase with dual-energy acquisitions (80 kVp, 499 mAs; 140 kVp, 126 mAs). Habitus was determined by measuring trunk diameters and calculating circumference. Iodine subtraction was performed with input parameters individualized to muscle, fat, and blood ratio. Attenuation of the liver, pancreas, spleen, kidneys, and aorta was assessed in truly and virtually unenhanced image series. Pearson analysis was performed to correlate habitus with the input parameters. Analysis of truly unenhanced and virtually unenhanced images was performed with the Student t test; magnitude of variation was evaluated with Bland-Altman plots. Correction strategies were derived from organ-specific regression analysis of scatterplots of truly unenhanced and virtually unenhanced attenuation and implemented in a pixel-by-pixel approach. Analysis of individual organ correction and truly unenhanced attenuation was performed with the Student t test. RESULTS The correlations between habitus and blood ratio (r = 0.694) and attenuation variation of fat at 80 kVp (r = -0.468) and 140 kV (r = -0.454) were confirmed. Although overall mean attenuation differed by no more than 10 HU between truly and virtually unenhanced scans overall, these differences varied by organ and were large in individual patients. Paired comparisons of truly and virtually unenhanced measurements differed significantly for liver, spleen, pancreas, kidneys, and aortic blood pool (p < 0.001 for all comparisons), but paired comparisons of truly unenhanced and individually organ-corrected measurements did not differ when organ- and habitus-based correction strategies were applied (p > 0.38 for all comparisons). CONCLUSION Habitus and organ enhancement influence virtually unenhanced imaging and should be incorporated into spectral subtraction algorithms.

Intravenous Gadoxetate Disodium Administration Reduces Breath-holding Capacity in the Hepatic Arterial Phase: A Multi-Center Randomized Placebo-controlled Trial

Purpose To determine, in a multicenter double-blinded placebo-controlled trial, whether maximal hepatic arterial phase breath-holding duration is affected by gadoxetate disodium administration. Materials and Methods Institutional review board approval was obtained for this prospective multi-institutional HIPAA-compliant study; written informed consent was obtained from all subjects. At three sites, a total of 44 volunteers underwent a magnetic resonance (MR) imaging examination in which images were acquired before and dynamically after bolus injection of gadoxetate disodium, normal saline, and gadoterate meglumine, administered in random order in a single session. The technologist and volunteer were blinded to the agent. Arterial phase breath-holding duration was timed after each injection, and volunteers reported subjective symptoms. Heart rate (HR) and oxygen saturation were monitored. Images were independently analyzed for motion artifacts by three radiologists. Arterial phase breath-holding duration and motion artifacts after each agent were compared by using the Mann-Whitney U test and the McNemar test. Factors affecting the above outcomes were assessed by using a univariate, multivariable model. Results Arterial phase breath holds were shorter after gadoxetate disodium (mean, 32 seconds ± 19) than after saline (mean, 40 seconds ± 17; P < .001) or gadoterate meglumine (43 seconds ± 21, P < .001) administration. In 80% (35 of 44) of subjects, arterial phase breath holds were shorter after gadoxetate disodium than after both saline and gadoterate meglumine. Three (7%) of 44 volunteers had severe arterial phase motion artifacts after gadoxetate disodium administration, one (2%; P = .62) had them after gadoterate meglumine administration, and none (P = .25) had them after saline administration. HR and oxygen saturation changes were not significantly associated with contrast agent. Conclusion Maximal hepatic arterial phase breath-holding duration is reduced after gadoxetate disodium administration in healthy volunteers, and reduced breath-holding duration is associated with motion artifacts.

Prospective Double-Blinded Study of Abdominal-Pelvic Computed Tomography Guided by the Region of Tenderness: Estimation of Detection of Acute Pathology and Radiation Exposure Reduction

STUDY OBJECTIVE Computed tomography (CT) is increasingly used for emergency department (ED) patients with abdominal tenderness. CT-related radiation contributes to 2% of US cancers. We hypothesized that in the ED patient with nontraumatic abdominal tenderness, the tender region accurately delineates acute pathology. z axis-restricted CT guided by this region could detect pathology while reducing radiation dose. METHODS This was a prospective double-blinded observational trial with informed consent and was institutional review board-approved and registered with ClinicalTrials.gov. A convenience sample of ED patients undergoing abdominal CT was recruited, excluding pregnant women, patients with altered mental status or abdominal sensation, preverbal children, and patients with abdominal trauma or surgery in the previous month. Before standard CT, physicians demarcated the tender region with labels invisible to radiologists on abdominal windows. Radiologists blinded to the tender region recorded cephalad-caudad limits of pathology on CT. Personnel blinded to pathology location recorded label positions on lung windows. Two hypothetical CT strategies were then explored: CT restricted to the tender region and CT from the cephalad skin marker to the lower caudad limit of the usual CT. The percentage of the pathologic region contained within the extent of the 2 hypothetical z axis restricted CTs was calculated. z axis reduction, which is linearly related to radiation reduction, from the restricted CTs was determined. RESULTS One hundred two subjects were enrolled, 93 with complete data for analysis. Fifty-one subjects had acute pathology on CT. CT limited to the tender region would reduce z axis (radiation exposure) by 69% (95% confidence interval [CI] 60% to 78%). All acute pathology was included within these boundaries in 17 of the 51 abnormal cases (33%; 95% CI 22% to 47%). CT from the cephalad marker through the caudad abdomen and pelvis would reduce z axis (radiation exposure) by 38% (95% CI 29% to 48%). All acute pathology was included within these boundaries in 36 of 51 abnormal cases (71%; 95% CI 57% to 81%). With both strategies 1 and 2, the pathologic region was at least partially included within the CT region in the majority of cases (84% and 92%, respectively). CONCLUSION CT with z axis restriction based on abdominal tenderness could reduce radiation exposure but with a potentially unacceptably high rate of misdiagnosis, using our current methods. Further prospective study may be warranted to determine the diagnostic utility of partially visualized pathology.

Can the localization of primary colonic tumors be improved by staging CT without specific bowel preparation compared to optical colonoscopy

OBJECTIVES To investigate the ability of staging computed tomography (CT) without bowel preparation to accurately localize colonic tumors compared to optical colonoscopy. METHODS The local institutional review board approved this retrospective and HIPAA-compliant study. Forty-six patients with colonic adenocarcinoma, preoperative colonoscopy, and staging CT within 60 days of resection were included. Patients underwent contrast enhanced CT imaging without bowel preparation or oral contrast. The colon was divided into four segments with the operative reports used as the standard. Rectal and cecal cancers were excluded. CT scans were reviewed by 5 readers in a segmental binary fashion using a 5-point confidence scale in two sessions blinded and unblinded to the colonoscopy report. RESULTS At surgery 49 tumors were found in 46 patients. Readers detected 86.1%, 74.3%, and 66.9% of lesions with 92.0%, 94.1%, and 95.4% accuracy for confidence scores of ≥ 3, ≥ 4, and 5. CT interobserver agreement was good (κ=0.82) for the unblinded and moderate (κ=0.60) for the blinded read. Colonoscopic localization was only 78.7% accurate with 2 tumors undiscovered. Colonoscopic accuracy was low in the descending colon (57.1%) and the transverse colon (55.6%). CONCLUSIONS Preoperative staging CT is more accurate than colonoscopy in the localization of colonic tumors.

Comparison of Visualization Rates of LI-RADS Version 2014 Major Features With IV Gadobenate Dimeglumine or Gadoxetate Disodium in Patients at Risk for Hepatocellular Carcinoma

OBJECTIVE The purpose of this study is to compare visualization rates of the major features covered by Liver Imaging Reporting and Data System (LI-RADS) version 2014 in patients at risk for hepatocellular carcinoma using either gadobenate dimeglumine or gadoxetate disodium IV contrast agent. MATERIALS AND METHODS This retrospective study included liver MRI examinations performed with either gadobenate dimeglumine or gadoxetate disodium contrast enhancement. Using age, sex, underlying liver disease, and presence of cirrhosis, patients were placed into matched cohorts. All hepatic nodules 1 cm or larger (up to five per subject) were included, resulting in 63 subjects with 130 nodules (median nodule size, 1.9 cm) imaged with gadobenate and 64 subjects with 117 nodules (median nodule size, 2.0 cm) imaged with gadoxetate. Three radiologists reviewed the studies for LI-RADS major features independently. Bootstrap resampling with 10,000 repetitions was used to compare feature detection rates. RESULTS Arterial phase hyperenhancement was seen in a similar number of nodules with gadobenate dimeglumine (mean, 91.5% [119/130]) and gadoxetate disodium (mean, 88.0% [103/117]) (p = 0.173). Dynamic phase washout was more commonly seen with gadobenate dimeglumine (mean, 60.2% [78.3/130]) than with gadoxetate disodium (mean, 45.3% [53/117]) (p = 0.006). The capsule feature was more often visualized with gadobenate dimeglumine (mean, 50.2% [65.3/130]) than with gadoxetate disodium (mean, 33.3% [39/117]) (p < 0.001). Interreader agreement for arterial phase enhancement and dynamic phase washout was almost perfect for both contrast agents (κ > 0.83). Agreement for the capsule feature was moderate for gadobenate dimeglumine (κ = 0.52) and substantial for gadoxetate disodium (κ = 0.67). CONCLUSION The rates of visualization of arterial phase hyperenhancement are similar in studies performed with gadobenate dimeglumine and gadoxetate disodium, but dynamic phase washout and capsule appearance are more commonly visualized with gadobenate dimeglumine.