Faculty Bibliography

PRIMARY OBJECTIVE: To explore whether baseline diffusion tensor imaging (DTI) metrics are predictive of cognitive functioning 6 months post-injury in patients with mild traumatic brain injury (MTBI). RESEARCH DESIGN: Seventeen patients with MTBI and 29 sex- and age-matched healthy controls were studied. METHODS AND PROCEDURES: Participants underwent an MRI protocol including DTI, at an average of 4.0 (range: 1-10) days post-injury. Mean diffusivity (MD) and fractional anisotropy (FA) were measured in the following white matter (WM) regions: centra semiovale, the genu and the splenium of the corpus callosum and the posterior limb of the internal capsule. Participants underwent neuropsychological (NP) testing at baseline and at 6-month follow-up. Least squares regression analysis was used to evaluate the association of MD and FA with each NP test score at baseline and follow-up. MAIN OUTCOMES AND RESULTS: Compared to controls, average MD was significantly higher (p = 0.02) and average FA significantly lower (p = 0.0001) in MTBI patients. At the follow-up, there was a trend toward a significant association between baseline MD and response speed (r = -0.53, p = 0.087) and a positive correlation between baseline FA and Prioritization form B (r = 0.72, p = 0.003). CONCLUSIONS: DTI may provide short-term non-invasive predictive markers of cognitive functioning in patients with MTBI

BACKGROUND AND PURPOSE: Despite the prominent peak of N-acetylaspartate (NAA) in proton MR spectroscopy ((1)H-MR spectroscopy) of the adult brain and its almost exclusive presence in neuronal cells, the total amount of NAA, regarded as their marker, is difficult to obtain due to signal contamination from the skull lipids. This article compares the performance of 2 methods that overcome this difficulty to yield the whole-brain NAA signal, important for the assessment of the total disease load in diffuse neurologic disorders. MATERIALS AND METHODS: The heads of 12 healthy volunteers, 3 women and 9 men, 31.0 +/- 7.1 years of age, were scanned at 3T by using 2 nonlocalizing (1)H-MR spectroscopy sequences: One nulls the NAA (TI = 940 ms) every second acquisition by inversion-recovery to cancel the signals of the lipids (T1 << TI) in an add-subtract scheme. The other nulls the signal of the lipids (TI = 155 ms) directly after each acquisition, requiring half as many averages for the same signal-to-noise ratio. Each sequence was repeated 3 times back-to-back on 3 occasions, and the comparison criteria were intrasubject precision (reproducibility) and total measurement duration. RESULTS: NAA nulling is nearly twice as precise in its intrinsic back-to-back (5.8% versus 8.6%) as well as longitudinal (10.6% versus 19.7%) coefficients of variation compared with lipid nulling, but at the cost of double the acquisition time. CONCLUSION: When speed is a more stringent requirement than precision, the new lipid-nulling sequence is a viable alternative. For precision in cross-sectional or longitudinal global NAA quantification, however, NAA nulling is still the approach of choice despite its x2 ( approximately 5 minutes) time penalty compared with the lipid-nulling approach

PURPOSE: To report our initial experience implementing a noncontrast-enhanced electrocardiograph (ECG) gated fast spin echo magnetic resonance angiography (MRA) technique for assessment of the calf arteries. MATERIALS AND METHODS: Noncontrast MRA images of 36 clinical patients examined over a 6-month period were evaluated by two radiologists for length and degree of stenosis of arterial segments. Diagnostic confidence in the technique was also recorded. The reference standard was a consensus reading by both radiologists using the noncontrast technique combined with two gadolinium-enhanced techniques: bolus-chase and time-resolved imaging. RESULTS: For stenosis evaluation the noncontrast technique demonstrated accuracy 79.4% (1083/1364), sensitivity 85.4% (437/512), and specificity 75.8% (646/852). The sequence demonstrated high negative predictive value (92.3%, 646/700). The technique had serious artifacts leading to poor diagnostic confidence in 17 patients (47.2%). These included motion (n = 7) and artifacts specific to the sequence, including inaccurate trigger delays (n = 5), linear artifact (n = 7), and vessel blurring (n = 5). When only patients in whom there was satisfactory diagnostic confidence were considered, accuracy, sensitivity, and negative predictive value were 92.2% (661/717), 92.4% (158/171), and 97.5% (503/516), respectively. CONCLUSION: Our results indicate that when technically successful, noncontrast-enhanced MRA using ECG-gated fast spin echo can provide accurate imaging of the calf and pedal arteries. However, further development and optimization are needed to improve the robustness of the technique

AIM: To determine whether epiploic appendagitis occurs in the caecum. METHODS: From 2000-2006, 58 cases with classic computed tomography (CT) features of acute epiploic appendagitis (focal round or oval fat density immediately adjacent to the colon with surrounding oedema and stranding, with or without a central area of high attenuation) were identified from a radiology information system and available for review on the picture archiving and communication system (PACS). Cases were assigned to one of six colonic segments: rectum, sigmoid, descending colon, transverse colon, ascending colon, and caecum. The Blyth-Still-Casella procedure was used to derive an exact upper bound on the likelihood of epiploic appendagitis occurring within the caecum. RESULTS: Twenty-eight cases occurred in the sigmoid colon, 16 in the descending colon, four in the transverse colon, and 10 in the ascending colon. No cases of acute epiploic appendagitis were identified in the caecum. Four cases of prospectively dictated caecal epiploic appendagitis were identified from the database. Retrospective review of these cases showed two cases to be epiploic appendagitis of the ascending colon. The third case demonstrated peritoneal thickening without evidence of an inflamed epiploic appendage. The fourth case was caecal diverticulitis. Based on these findings there is 95% confidence that no more than 4.6% of patients with epiploic appendagitis will show this condition within the caecum. CONCLUSION: In the authors' experience, epiploic appendagitis does not occur in the caecum. Therefore, it is an unlikely cause for an inflammatory process in this region and other conditions should be considered

PURPOSE: To evaluate the possible radiation dose reduction facilitated by using dual-energy (DE) multidetector computed tomography (CT) after endovascular repair of abdominal aortic aneurysms (AAAs). MATERIALS AND METHODS: This prospective study was HIPAA compliant and institutional review board approved. Twenty-two patients who previously had undergone endovascular repair of AAAs underwent 24 DE multidetector CT examinations, which were performed with a 64-detector scanner. Initial nonenhanced CT was followed by arterial phase and venous phase acquisitions. Virtual nonenhanced, pure 80-kVp, and weighted-average peak voltage CT data sets were generated from the venous acquisition. Two independent readers interpreted the virtual nonenhanced and DE weighted-average CT data for the presence or absence of endoleaks. These interpretations were compared with the clinical interpretations of the data performed by a different radiologist by using true nonenhanced, arterial phase, and venous phase data. Region-of-interest measurements of the abdominal aorta and of the region of the endoleaks were obtained. Effective radiation dose was calculated. RESULTS: Both independent readers' interpretations of the virtual nonenhanced and weighted-average venous CT data revealed six type II endoleaks. There were no false-positive or false-negative findings. Aortic attenuation during the arterial, 80-kVp venous, and weighted-average data acquisitions were 288, 213, and 150 HU, respectively. The attenuation of the endoleaks was higher during the 80-kVp acquisition (P < .03) than during the arterial phase and weighted-average venous phase acquisitions. The mean effective dose for DE venous phase CT was 11.1 mSv compared with 27.8 mSv for standard triple-phase CT with a single-source configuration. CONCLUSION: Preliminary observations suggest that obtaining DE multidetector CT data by using a single 60-second contrast material-enhanced acquisition may be all that is required for surveillance after endovascular repair of AAA

OBJECTIVE: Conventional MR sequences are sometimes nonspecific in differentiating benign from pathologic fractures. To address this difficulty, diffusion-weighted images were conjectured to aid in this discrimination with variable results. As each of these studies contained somewhat small numbers of patients, we performed a meta-analysis to determine if this sequence may be used for this important diagnostic problem. MATERIALS AND METHODS: We reviewed and statistically analyzed the results of eight studies, performed between 1998 and 2003, comparing diffusion-weighted magnetic resonance signal intensity characteristics of benign and pathologic vertebral body fractures. Diffusion-weighted imaging (DWI) signal characteristics and apparent diffusion coefficient (ADC) values of 104 benign fractures and 161 combined malignant vertebral body lesions and pathologic fractures were statistically evaluated in terms of mean ADC, as well as percentage classified as either hypointense or isointense. The meta-analysis to compare benign fractures with the combined pathologic fractures and metastatic lesions in terms of mean ADC used Hedge's g statistic with a small sample bias adjustment; the comparison of the percentage hypo- or isointense used the Mantel-Haenszel method to calculate a weighted summary odds ratio. All summary effect sizes were computed under a random effects model to account for study heterogeneity. RESULTS: The mean ADC was significantly higher (p < 0.01) among benign fractures, with a standardized mean difference (SMD) of 2.8 and a 95% confidence interval (CI) for the SMD of 2.1 to 3.5. Lesions classified as hypointense were significantly more likely to be benign (p < 0.01), based on a summary odds ratio (OR) of 24.5 and 95% confidence that the OR exceeds 1.7. Lesions classified as isointense were not significantly more likely to be benign or malignant (p > 0.1), based on a summary OR of 3.6 and a 95% CI for the OR of 0.35 to 36.6. CONCLUSION: Even though the literature has been inconsistent, ADC maps appear to be a reliable method to differentiate benign from malignant fractures

Increased androgen receptor (AR) expression and activity are pivotal for androgen-independent (AI) prostate cancer (PC) progression and resistance to androgen-deprivation therapy. We show that a novel transcriptional repressor complex that binds a specific sequence (repressor element) in the AR gene 5'-untranslated region contains Pur alpha and hnRNP-K. Pur alpha expression, its nuclear localization, and its AR promoter association, as determined by chromatin immunoprecipitation analysis, were found to be significantly diminished in AI-LNCaP cells and in hormone-refractory human PCs. Transfection of AI cells with a plasmid that restored Pur alpha expression reduced AR at the transcription and protein levels. Pur alpha knockdown in androgen-dependent cells yielded higher AR and reduced p21, a gene previously shown to be under negative control of AR. These changes were linked to increased proliferation in androgen-depleted conditions. Treatment of AI cells with histone deacetylase and DNA methylation inhibitors restored Pur alpha protein and binding to the AR repressor element. This correlated with decreased AR mRNA and protein levels and inhibition of cell growth. Pur alpha is therefore a key repressor of AR transcription and its loss from the transcriptional repressor complex is a determinant of AR overexpression and AI progression of PC. The success in restoring Pur alpha and the repressor complex function by pharmacologic intervention opens a promising new therapeutic approach for advanced PC

BACKGROUND AND PURPOSE: Concurrent temporary inflation of a nondetachable balloon in the parent artery has been reported to be useful during endovascular coiling of complex, wide-neck aneurysms, facilitating truer coil reconstruction of the native vessel. Nevertheless, there exists concern that adjunctive use of balloon assistance may lead to increased adverse events during aneurysm coiling. MATERIALS AND METHODS: A literature search of all of the unassisted and balloon-remodeling studies published between 1997 and 2006 was conducted with application of strict selection criteria based on the reporting of complication incidence and outcome. The final cohort was analyzed to determine rates and clinical outcomes of iatrogenic aneurysm rupture and thromboembolism. Additional data were collected on the degree of initial and follow-up aneurysm occlusion rates. RESULTS: A total of 83 potential studies (4973 patients) were identified, from which 23 articles reporting results for 867 traditional-unassisted and 273 balloon-assisted coiled aneurysms met inclusion criteria for the analysis of thromboembolic complications, and 21 articles with 993 routinely coiled and 170 balloon-remodeled aneurysms were eligible for iatrogenic perforation analysis. No statistically significant difference was found in the rates of thromboembolism. Iatrogenic perforation rates were also comparable, though the overall numbers were too few for meaningful statistical analysis. Both initial and follow-up aneurysm occlusion rates were higher in balloon-assisted cases. CONCLUSION: This largest-to-date literature review and meta-analysis did not demonstrate a higher incidence of thromboembolic events or iatrogenic rupture with the use of adjunctive balloon remodeling compared with unassisted coiling. Balloon remodeling appears to result in higher initial and follow-up aneurysm occlusion rates

OBJECTIVE: Diffusion tensor imaging (DTI) allows in vivo delineation of brainstem white matter tracts. The purpose of this study was to determine whether or not abnormalities of DTI metrics and fiber tractography correlate with neurological deficits and clinical status in patients with primary posterior fossa tumors. METHODS: A review of patients with primary posterior fossa tumors who underwent magnetic resonance imaging with DTI was performed. Patients were stratified by tumor type (well-circumscribed or infiltrating lesions). Fractional anisotropy (FA) color maps were used to localize the corticospinal tracts within the brainstem. FA, mean diffusivity, and eigenvalues were measured. Tractography was performed. Correlations between DTI metrics and clinical status and between DTI metrics and neurological examination findings were assessed within each patient group using Bonferroni correction for multiple comparisons. Comparisons of DTI metrics were also made between patient groups (infiltrating lesions versus well-circumscribed lesions). RESULTS: Thirty patients were studied (mean age, 14.1 yr; 16 male, 14 female). Eighteen patients had infiltrating lesions and 12 had well-circumscribed lesions. Twelve patients (four well-circumscribed and eight infiltrating) demonstrated motor weakness on physical examination (four right, three left, five bilateral). Patients with well-circumscribed lesions and weakness had higher mean diffusivity and lower FA in the contralateral corticospinal tract (P < 0.05). No such association was seen in patients with infiltrating tumors. In 102 total patient-years of follow-up (average follow-up period, 4.2 yr), 17 patients (six well-circumscribed and 11 infiltrating lesions) demonstrated complete response or stable disease and six patients (three well-circumscribed and three infiltrating lesions) demonstrated progressive disease or death. No differences were seen in terms of DTI metrics between patients with infiltrating lesions and those with well-circumscribed lesions. Patients with well-circumscribed tumors and a bad outcome had significantly lower transverse eigenvalue measures in the corticospinal tracts compared with those with a more favorable clinical status (P < 0.05). CONCLUSION: In patients with well-circumscribed primary posterior fossa masses, higher mean diffusivity and lower FA in the brainstem corticospinal tract are associated with contralateral motor deficits; lower transverse eigenvalue may be observed with an unfavorable clinical outcome

OBJECTIVE: To compare the 2-dimensional time of flight, the 3-dimensional time-resolved contrast-enhanced magnetic resonance (MR) angiography, and the 3-dimensional 3-station bolus chase contrast-enhanced MR angiography in assessing distal station atherosclerosis. METHODS: Two-dimensional time of flight, 3-dimensional time-resolved contrast-enhanced MR angiography, and 3-dimensional bolus chase contrast-enhanced MR angiography were performed from the knees to the metatarsal heads of 40 patients. Blinded to the patients' identity, 2 readers independently reviewed the 3 sequences in random order; differences were resolved by consensus. Anterior tibial, peroneal, and posterior tibial arterial lengths to the talar dome were scored as follows: 1, greater than 50% of the length of a normal artery; 2, less than 50%; and 3, total occlusion. Stenoses were scored as follows: 1, less than 50%; and 2, greater than 50%. The pedal vessels (dorsalis pedis, posterior tibial, and plantar pedal arch arteries) were scored as follows: 1, less than 50% stenosis; and 2, greater than 50% stenosis. The reference standard was a combined interpretation of all 3 sequences by both readers in consensus. RESULTS: For the 240 calf segments scored for length, concordance with reference assessment was poorer for the time of flight than for either the bolus chase or time-resolved angiography (P = 0.0021 and P = 0.0082, respectively), and the latter two were statistically indistinguishable. For stenosis grading of the 461 calf and pedal segments, the time-resolved and bolus chase methods were superior to the time of flight (P = <0.0001 and P = 0.0041, respectively), and the contrast-enhanced methods were statistically indistinguishable. CONCLUSIONS: Both contrast-enhanced time-resolved and bolus chase MR angiography are superior to the time of flight in diagnosing distal station peripheral vascular disease