Radiology MOC

To improve clinical three-dimensional (3D) MR spectroscopic imaging with more accurate localization and faster acquisition schemes.

Institutional review board approval and patient informed consent were obtained. Data were acquired with a 3-T MR imager and a 32-channel head coil in phantoms, five healthy volunteers, and five patients with glioblastoma. Excitation was performed with localized adiabatic spin-echo refocusing (LASER) by using adiabatic gradient-offset independent adiabaticity wideband uniform rate and smooth truncation (GOIA-W[16,4]) pulses with 3.5-msec duration, 20-kHz bandwidth, 0.81-kHz amplitude, and 45-msec echo time. Interleaved constant-density spirals simultaneously encoded one frequency and two spatial dimensions. Conventional phase encoding (PE) (1-cm3 voxels) was performed after LASER excitation and was the reference standard. Spectra acquired with spiral encoding at similar and higher spatial resolution and with shorter imaging time were compared with those acquired with PE. Metabolite levels were fitted with software, and Bland-Altman analysis was performed.

Clinical 3D MR spectroscopic images were acquired four times faster with spiral protocols than with the elliptical PE protocol at low spatial resolution (1 cm3). Higher-spatial-resolution images (0.39 cm3) were acquired twice as fast with spiral protocols compared with the low-spatial-resolution elliptical PE protocol. A minimum signal-to-noise ratio (SNR) of 5 was obtained with spiral protocols under these conditions and was considered clinically adequate to reliably distinguish metabolites from noise. The apparent SNR loss was not linear with decreasing voxel sizes because of longer local T2* times. Improvement of spectral line width from 4.8 Hz to 3.5 Hz was observed at high spatial resolution. The Bland-Altman agreement between spiral and PE data is characterized by narrow 95% confidence intervals for their differences (0.12, 0.18 of their means). GOIA-W(16,4) pulses minimize chemical-shift displacement error to 2.1%, reduce nonuniformity of excitation to 5%, and eliminate the need for outer volume suppression.

The proposed adiabatic spiral 3D MR spectroscopic imaging sequence can be performed in a standard clinical MR environment. Improvements in image quality and imaging time could enable more routine acquisition of spectroscopic data than is possible with current pulse sequences.

© RSNA, 2011

To determine the precision of a three-dimensional (3D) method for measuring the growth rate of solid and subsolid nodules and its ability to detect abnormal growth rates.

This study was approved by the Institutional Research Board and was HIPAA compliant. Informed consent was waived. The growth rates of 123 lung nodules in 59 patients who had undergone lung cancer screening computed tomography (CT) were measured by using a 3D semiautomated computer-assisted volume method. Clinical stability was established with long-term CT follow-up (mean, 6.4 years ± 1.9 [standard deviation]; range, 2.0–8.5 years). A mean of 4.1 CT examinations per patient ± 1.2 (range, two to seven CT examinations per patient) was analyzed during 2.4 years ± 0.5 after baseline CT. Nodule morphology, attenuation, and location were characterized. The analysis of standard deviation of growth rate in relation to time between scans yielded a normative model for detecting abnormal growth.

Growth rate precision increased with greater time between scans. Overall estimate for standard deviation of growth rate, on the basis of 939 growth rate determinations in clinically stable nodules, was 36.5% per year. Peripheral location (P = .01; 37.1% per year vs 25.6% per year) and adjacency to pleural surface (P = .05; 38.9% per year vs 34.0% per year) significantly increased standard deviation of growth rate. All eight malignant nodules had an abnormally high growth rate detected. By using 3D volumetry, growth rate–based diagnosis of malignancy was made at a mean of 183 days ± 158, compared with radiologic or clinical diagnosis at 344 days ± 284.

A normative model derived from the variability of growth rates of nodules that were stable for an average of 6.4 years may enable identification of lung cancer.

© RSNA, 2011

Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11100878/-/DC1

To quantify a pseudoenhancement phenomenon observed during dynamic contrast material–enhanced ultrasonography (US) of the carotid artery, both in vitro and in vivo.

Ethical approval was obtained prior to commencing this prospective case series, and each patient gave written informed consent. Thirty-one patients with 50%–99% internal carotid artery stenosis underwent dynamic contrast-enhanced US of the carotid bifurcation with use of 2 mL of microbubbles. In the final 10 patients, an additional 1 mL bolus was administered after 15 minutes. Raw linear digital imaging and communications in medicine data were analyzed offline. Regions of interest were drawn within the common carotid artery lumen and immediately adjacent to the lumen in the near and far wall adventitia. Peak intensity was measured. An in vitro experiment with a single–channel flow phantom was also performed. This apparatus consisted of an 8-mm-diameter latex tube placed in a tissue-mimicking fluid. Microbubble concentrations of 0.02%, 0.1%, 0.5%, 1%, and 2% were pumped into the tube. Regions of interest were drawn in a similar fashion to the in vivo experiments, and peak intensity was measured. The Wilcoxon signed rank and paired t tests were used to compare the difference between the near and far wall signal intensities at each dose; a multiplication factor comparing near and far wall signal intensity was derived.

The far wall of the common carotid artery was significantly more echogenic than the near wall at 2 mL contrast agent doses (P < .0001, n = 31), and the far wall signal intensity increased synchronously with that of the lumen. The difference in signal intensity between near and far wall regions was significantly greater at 2 mL than at 1 mL (P = .012, n = 10). In vitro, the phantom tubing demonstrated a similar pattern and magnitude of enhancement to that seen in vivo.

A dose-dependent, nonlinear propagation artifact known as pseudoenhancement occurs in the far wall adventitia of the carotid artery and should not be mistaken as a marker of plaque vulnerability.

© RSNA, 2011

To quantitatively assess microvascular activation in the thickened ileal walls of patients with Crohn disease (CD) by using contrast-enhanced ultrasonography (US) and evaluate its correlation with widely used indexes of CD activity.

This prospective study was approved by the ethics committee, and written informed consent was obtained from all patients. The authors examined 54 consecutively enrolled patients (mean age, 35.29 years; age range, 18–69 years; 39 men, 15 women) with endoscopically confirmed CD of the terminal ileum. Ileal wall segments thicker than 3 mm were examined with low-mechanical-index contrast-enhanced US and a second-generation US contrast agent. The authors analyzed software-plotted time–enhancement intensity curves to determine the maximum peak intensity (MPI) and wash-in slope coefficient (β) and evaluated their correlation with (a) the composite index of CD activity (CICDA), (b) the CD activity index (CDAI), and (c) the simplified endoscopic score for CD (SES-CD, evaluated in 37 patients) for the terminal ileum. Statistical analysis was performed with the Mann-Whitney test, Spearman rank test, and receiver operating characteristic (ROC) analysis.

MPI and β coefficients were significantly increased in the 36 patients with a CICDA indicative of active disease (P < .0001 for both), the 33 patients with a CDAI of at least 150 (P < .032 and P < .0074, respectively), and the 26 patients with an SES-CD of at least 1 (P < .0001 and P < .002, respectively). ROC analysis revealed accurate identification (compared with CICDA) of active CD with an MPI threshold of 24 video intensity (VI) (sensitivity, 97%; specificity, 83%) and a β coefficient of 4.5 VI/sec (sensitivity, 86%; specificity, 83%).

Contrast-enhanced US of the ileal wall is a promising method for objective, reproducible assessment of disease activity in patients with ileal CD.

© RSNA, 2011

To compare prospectively the effects of radiofrequency (RF) ablation after transcatheter arterial chemoembolization (TACE) with those of RF ablation alone in the treatment of recurrent hepatocellular carcinoma (HCC).

This study was approved by the institutional ethics committee, and all patients gave written informed consent. From January 2002 to December 2006, 139 patients with recurrent HCC measuring 5 cm in diameter or smaller were randomized to receive either sequential TACE and RF ablation (sequential treatment group, n = 69) or RF ablation alone (RF ablation group, n = 70). The survival curves were constructed with the Kaplan-Meier method and compared by using the log-rank test. Bonferroni correction was applied when multiple comparisons were performed. P < .0083 (.05 ÷ 6) was considered indicative of a statistically significant difference.

The 1-, 3-, and 5-year overall survival rates were 94%, 69%, and 46%, respectively, for the sequential treatment group and 82%, 47%, and 36% for the RF ablation group (P = .037). The corresponding recurrence-free survival rates were 80%, 45%, and 40% for the sequential treatment group and 64%, 18%, and 18% for the ablation group (P = .005). At subgroup analyses, the overall survival for the sequential treatment group was better than that for the RF ablation group for patients with tumor recurrence 1 year or less after initial treatment (P = .004) and those with tumors measuring 3.1–5.0 cm (P = .002) but not for those with tumor recurrence more than 1 year after initial treatment (P = .421) and those with tumors 3.0 cm or smaller (P = .478). The recurrence-free survival in the sequential treatment group was better than that in the RF ablation group for patients with tumors measuring 3.1–5.0 cm (P < .001) but not for those with tumors 3.0 cm or smaller (P = .204). For recurrence-free survival, there was no significant difference between the two groups for patients with tumor recurrence 1 year or less or more than 1 year after initial treatment (P = .020 and P = .111, respectively). Logistic regression analysis showed that treatment allocation and the interval between initial treatment and tumor recurrence were significant prognostic factors for overall survival, whereas the interval between initial treatment and tumor recurrence, treatment allocation, and tumor size were significant prognostic factors for recurrence-free survival.

The efficacy of sequential TACE-RF ablation is better than that of RF ablation alone for recurrent HCC.

© RSNA, 2011

To evaluate the feasibility and efficacy of computed tomography (CT)-guided radiofrequency (RF) neurolysis (RFN) in the management of refractory inguinal neuralgia.

Local institutional review board approval was obtained and written informed consent was waived. Twelve patients 26–75 years of age with chronic (>6 months) inguinal pain refractory to specific medication were included between 2005 and 2011. Data on patient demographics, clinical history, and pain management history were retrospectively assessed. Pain was measured on a visual analog scale (VAS) from 0 to 10 before and immediately after the procedure and at 1, 3, 6, 9 and 12 months. Diagnosis was always confirmed by a positive nerve block test result. Ambulatory CT-guided RF was the rule.

Sixteen RFN procedures were performed. Pain was present for an average of 3.2 years (range: 2–8 years) prior to initial RFN. Mean VAS score before the procedure was 7.75 of 10. Immediate pain relief of 100% was achieved in all patients. Pain reduction at 1-, 3-, 6-, 9-, and 12-month follow-up was statistically significant. Important pain reduction (≥80%) was obtained in 75% of RFN procedures at 6-month follow-up and in 50% of cases at 12 months. The mean duration of pain relief was 11.8 months after RFN, with a maximum average pain reduction of 84.5%. No complications were noted during or after the procedure.

RFN with CT guidance is an effective technique in the management of refractory inguinal pain with lasting satisfactory pain reduction; it may be considered as an alternative treatment to surgery. These results should be confirmed in a controlled trial with a larger series of patients.

© RSNA, 2011

To identify differences in radiologic assessment methods and determine optimal imaging criteria for response evaluation in hepatocellular carcinoma (HCC) patients treated with chemoembolization.

Institutional review board approval was obtained, and patient informed consent was waived. The present study included 332 patients with intermediate stage HCC and Child-Pugh A cirrhosis who underwent serial chemoembolization. All measurable target lesions of 1 cm or larger in diameter were uni- and bidimensionally measured both at baseline and during follow-up. Intermodel agreement among the guidelines of the World Health Organization (WHO), Response Evaluation Criteria in Solid Tumors (RECIST), the European Association for the Study of the Liver (EASL), and modified RECIST (mRECIST) were examined. The most reliable model was selected on the basis of the correlation with survival prediction.

The values of comparisons among WHO, RECIST, and mRECIST guidelines were less than 0.20, whereas the value for the comparison of EASL and mRECIST guidelines was 0.94. In patients with a partial response (PR), stable disease (SD), or progressive disease (PD), compared with patients with a complete response (CR), hazard ratios (HRs) for survival were 2.99 (95% confidence interval [CI]: 2.14, 4.17), 3.49 (95% CI: 1.71, 7.10), and 15.63 (95% CI: 9.51, 25.69), respectively, for EASL criteria. In patients with a PR, SD, or PD, compared with patients with a CR, the HRs were 2.75 (95% CI: 1.96, 3.87), 6.32 (95% CI: 3.67, 10.90), and 16.06 (95% CI: 9.76, 26.43), respectively, for mRECIST guidelines (P < .001). The C index for the multivariate model was 0.76 (95% CI: 0.72, 0.79) for both EASL and mRECIST guidelines, thus exhibiting satisfactory capability to help predict survival. The Cox regression model revealed that both mRECIST and EASL guidelines were independent predictors of overall survival (P < .001 for both).

The enhancement models more accurately helped predict long-term survival in HCC patients treated with chemoembolization.

© RSNA, 2011

To determine the effect of evidence-based clinical decision support (CDS) on the use and yield of computed tomographic (CT) pulmonary angiography for acute pulmonary embolism (PE) in the emergency department (ED).

Institutional review board approval was obtained for this HIPAA-compliant study, which was performed between October 1, 2003, and September 30, 2009, at a 793-bed quaternary care institution with 60 000 annual ED visits. Use (number of examinations per 1000 ED visits) and yield (percentage of examinations positive for acute PE) of CT pulmonary angiography were compared before and after CDS implementation in August 2007. The authors included all adult patients presenting to the ED and developed and validated a natural language processing tool to identify acute PE diagnoses. Linear trend analysis was used to assess for variation in CT pulmonary angiography use. Logistic regression was used to determine variation in yield after controlling for patient demographic and clinical characteristics.

Of 338 230 patients presenting to the ED, 6838 (2.0%) underwent CT pulmonary angiography. Quarterly CT pulmonary angiography use increased 82.1% before CDS implementation, from 14.5 to 26.4 examinations per 1000 patients (P < .0001) between October 10, 2003, and July 31, 2007. After CDS implementation, quarterly use decreased 20.1%, from 26.4 to 21.1 examinations per 1000 patients between August 1, 2007, and September 30, 2009 (P = .0379). Overall, 686 (10.0%) of the CT pulmonary angiographic examinations performed during the 6-year period were positive for PE; subsequent to CDS implementation, yield by quarter increased 69.0%, from 5.8% to 9.8% (P = .0323).

Implementation of evidence-based CDS in the ED was associated with a significant decrease in use, and increase in yield, of CT pulmonary angiography for the evaluation of acute PE.

© RSNA, 2011

To retrospectively determine whether extrinsic warming of the low-osmolality contrast material iopamidol to 37°C prior to intravenous administration at computed tomography (CT) affects extravasation and allergic-like reaction rates.

The need to obtain informed patient consent was waived for this HIPAA-compliant and institutional review board–approved analysis. All adverse events related to the intravenous administration of iopamidol during CT examinations occurring 200 days before (period 1) and 200 days after (period 2) the cessation of extrinsic contrast material warming (37°C) for intravenous injections of less than 6 mL/sec at Duke University Medical Center (Durham, NC) were retrospectively reviewed. Adverse event rates were compared by using 2 statistics.

There were 12 682 injections during period 1 (10 831 injections of iopamidol 300 and 1851 injections of iopamidol 370) and 12 138 injections (10 064 injections of iopamidol 300 and 2074 injections of iopamidol 370) during period 2. Adverse event rates for iopamidol 300 were not affected by extrinsic warming (extravasation rates: 0.30% [32 of 10 831] in period 1 vs 0.23% [23 of 10 064] in period 2, P = .64; allergic-like reaction rates: 0.39% [42 of 10 831] in period 1 vs 0.46% [46 of 10 064] in period 2, P = .74; overall adverse events: 0.68% [74 of 10 831] in period 1 vs 0.69% [69 of 10 064] in period 2, P = .99). Discontinuation of extrinsic warming was associated with significantly increased extravasation and overall adverse event rates for iopamidol 370 (extravasation rates: 0.27% [five of 1851] vs 0.87% [18 of 2074], P = .05; allergic-like reaction rates: 0.16% [three of 1851] vs 0.39% [eight of 2074], P = .42; overall adverse events: 0.43% [eight of 1851] vs 1.25% [26 of 2074], P = .02).

Extrinsic warming (to 37°C) does not appear to affect adverse event rates for intravenous injections of iopamidol 300 of less than 6 mL/sec but is associated with a significant reduction in extravasation and overall adverse event rates for the more viscous iopamidol 370.

© RSNA, 2011

To critically evaluate the current literature in an effort to establish the current role of radiologic imaging (computed tomography, magnetic resonance imaging, ultrasonography [US], fluoroscopy, conventional film radiography) in irritable bowel syndrome (IBS).

The term "irritable bowel syndrome" was used to search Clinical Evidence, UpToDate, Cochrane Library, TRIP, and National Institute for Health and Clinical Excellence databases and the American College of Physicians Journal Club and Evidence-Based Medicine online. PubMed was searched by using medical subject headings ("irritable bowel syndrome;" "colonic diseases, functional;" "diagnosis;" "colonography;" "computed tomographic (CT)") and the dates January 1, 1985 to July 1, 2010. Appraisal was independently performed by two reviewers who followed the Oxford Centre for Evidence Based Medicine practice criteria.

No systematic review (SR) specifically examined radiologic imaging in IBS; however, in the secondary literature, five relevant SRs or guidelines partially addressed this topic. A PubMed search identified 1451 articles, 111 of which at least partially addressed radiologic imaging. Of these, seven valid articles (two SRs and five primary research articles) were identified. The five primary research articles examined either colonic investigations (colonoscopy and barium enema examination) (n = 5) or US (n = 2) or both (n = 2). Structural disease found infrequently in patients with IBS-type symptoms included diverticulosis, colorectal cancer, celiac disease, inflammatory bowel disease, and ovarian cancer. The incidence of structural disease in patients with concerning symptoms was low.

Although widely used, there is a surprising paucity of evidence guiding radiologic imaging in IBS. Radiologic imaging may not be required in patients with IBS without potentially concerning symptoms but should be considered where such symptoms exist, and choice of imaging study should be influenced by predominant symptoms. Definitive recommendations must await further research.

© RSNA, 2011

To analyze the contribution of the transverse relaxation parameter (T2), macroscopic field inhomogeneities (B0), and blood volume fraction (BVf) to blood oxygen level–dependent (BOLD)-based magnetic resonance (MR) measurements of blood oxygen saturation (SO2) obtained in a brain tumor model.

This study was approved by the local committee for animal care and use. Experiments were performed in accordance with permit 380 820 from the French Ministry of Agriculture. The 9L gliosarcoma cells were implanted in the brain of eight rats. Fifteen days later, 4.7-T MR examinations were performed to estimate T2*, T2, BVf, and T2*B0corrected in the tumor and contralateral regions. MR estimates of SO2 were derived by combining T2, BVf, and T2*B0corrected according to a recently described quantitative BOLD approach. Scatterplots and linear regression analysis were used to identify correlation between parameters. Paired Student t tests were used to compare the tumor region with the contralateral region.

No significant correlations were found between T2* and any parameter in either tumor tissue or healthy tissue. T2* in the tumor and T2* in the uninvolved contralateral brain were the same (36 msec ± 4 [standard deviation] vs 36 msec ± 5, respectively), which might suggest similar oxygenation. Adding T2 information (98 msec ± 7 vs 68 msec ± 2, respectively) alone yields results that suggest apparent hypo-oxygenation of the tumor, while incorporating BVf (5.3% ± 0.6 vs 2.6% ± 0.3, respectively) alone yields results that suggest apparent hyperoxygenation. MR estimates of SO2 obtained with a complete quantitative BOLD analysis, although not correlated with T2* values, suggest normal oxygenation (68% ± 3 vs 65% ± 4, respectively). MR estimates of SO2 obtained in the contralateral tissue agree with previously reported values.

Additional measurements, such as BVf, T2, and B0, are needed to obtain reliable information on oxygenation with BOLD MR imaging. The proposed quantitative BOLD approach, which includes these measurements, appears to be a promising tool with which to map tumor oxygenation.

© RSNA, 2011