Imaging of Brain Structural and Functional Effects in People With Human Immunodeficiency Virus.

Before the introduction of antiretroviral therapy, human immunodeficiency virus (HIV) infection was often accompanied by central nervous system (CNS) opportunistic infections and HIV encephalopathy marked by profound structural and functional alterations detectable with neuroimaging. Treatment with antiretroviral therapy nearly eliminated CNS opportunistic infections, while neuropsychiatric impairment and peripheral nerve and organ damage have persisted among virally suppressed people with HIV (PWH), suggesting ongoing brain injury. Neuroimaging research must use methods sensitive for detecting subtle HIV-associated brain structural and functional abnormalities, while allowing for adjustments for potential confounders, such as age, sex, substance use, hepatitis C coinfection, cardiovascular risk, and others. Here, we review existing and emerging neuroimaging tools that demonstrated promise in detecting markers of HIV-associated brain pathology and explore strategies to study the impact of potential confounding factors on these brain measures. We emphasize neuroimaging approaches that may be used in parallel to gather complementary information, allowing efficient detection and interpretation of altered brain structure and function associated with suboptimal clinical outcomes among virally suppressed PWH. We examine the advantages of each imaging modality and systematic approaches in study design and analysis. We also consider advantages of combining experimental and statistical control techniques to improve sensitivity and specificity of biotype identification and explore the costs and benefits of aggregating data from multiple studies to achieve larger sample sizes, enabling use of emerging methods for combining and analyzing large, multifaceted data sets. Many of the topics addressed in this article were discussed at the National Institute of Mental Health meeting "Biotypes of CNS Complications in People Living with HIV," held in October 2021, and are part of ongoing research initiatives to define the role of neuroimaging in emerging alternative approaches to identifying biotypes of CNS complications in PWH. An outcome of these considerations may be the development of a common neuroimaging protocol available for researchers to use in future studies examining neurological changes in the brains of PWH.

Evaluation of image quality of wideband single-shot late gadolinium-enhancement MRI in patients with a cardiac implantable electronic device.

INTRODUCTION: While wideband segmented, breath-hold late gadolinium-enhancement (LGE) cardiovascular magnetic resonance (CMR) has been shown to suppress image artifacts associated with cardiac-implanted electronic devices (CIEDs), it may produce image artifacts in patients with arrhythmia and/or dyspnea. Single-shot LGE is capable of suppressing said artifacts. We sought to compare the performance of wideband single-shot free-breathing LGE against the standard and wideband-segmented LGEs in CIED patients. METHODS AND RESULTS: We retrospectively identified all 54 consecutive patients (mean age: 61 ± 15 years; 31% females) with CIED who had undergone CMR with standard segmented, wideband segmented, and/or wideband single-shot LGE sequences as part of quality assurance for determining best clinical practice at 1.5 T. Two raters independently graded the conspicuity of myocardial scar or normal myocardium and the presence of device artifact level on a 5-point Likert scale (1: worst; 3: acceptable; 5: best). Summed visual score (SVS) was calculated as the sum of conspicuity and artifact scores (SVS ≥ 6 defined as diagnostically interpretable). Median conspicuity and artifact scores were significantly better for wideband single-shot LGE (F = 24.2, p < .001) and wideband-segmented LGE (F = 20.6, p < .001) compared to standard-segmented LGE. Among evaluated myocardial segments, 72% were deemed diagnostically interpretable-defined as SVS ≥ 6-for standard-segmented LGE, 89% were deemed diagnostically interpretable for wideband-segmented LGE, and 94% segments were deemed diagnostically interpretable for wideband single-shot LGE. CONCLUSIONS: Wideband single-shot LGE and wideband-segmented LGE produced similarly improved image quality compared to standard LGE.

Left ventricular extracellular volume expansion does not predict recurrence of atrial fibrillation following catheter ablation.

INTRODUCTION: A recent study reported that diffuse left ventricular (LV) fibrosis is a predictor of atrial fibrillation (AF) recurrence following catheter ablation, by measuring postcontrast cardiac T1 (an error prone metric as per the 2017 Society for Cardiovascular Magnetic Resonance consensus statement) using an inversion-recovery pulse sequence (an error prone method in arrhythmia) in AF ablation candidates. The purpose of this study was to verify the prior study, by measuring extracellular volume (ECV) fraction (an accurate metric) using a saturation-recovery pulse sequence (accurate method in arrhythmia). METHODS AND RESULTS: This study examined 100 AF patients (mean age = 62 ± 11 years, 69 males and 31 females, 67 paroxysmal [pAF] and 33 persistent [peAF]) who underwent a preablation cardiovascular magnetic resonance (CMR) exam. LV ECV and left atrial (LA) and LV functional parameters were quantified using standard analysis methods. During an average follow-up period of 457 ± 261 days with 4 ± 3 rhythm checks per patient, 72 patients maintained sinus rhythm. Between those who maintained sinus rhythm (n = 72) and those who reverted to AF (n = 28), the only clinical characteristic that was significantly different was age (60 ± 12 years vs 66 ± 9 years); for CMR metrics, neither mean LV ECV (25.1 ± 3.3% vs 24.7 ± 3.7%), native LV T1 (1093.8 ± 73.5 ms vs 1070.2 ± 115.9 ms), left ventricular ejection fraction (54.1 ± 11.2% vs 55.7 ± 7.1%), nor LA end diastolic volume/body surface area (42.4 ± 14.8 mL/m2 vs 43.4 ± 19.6 mL/m2 ) were significantly different (P ≥ .23). According to Cox regression tests, none of the clinical and imaging variables predict AF recurrence. CONCLUSION: Neither LV ECV nor other CMR metrics predict recurrence of AF following catheter ablation.

Accelerated, first-pass cardiac perfusion pulse sequence with radial k-space sampling, compressed sensing, and k-space weighted image contrast reconstruction tailored for visual analysis and quantification of myocardial blood flow.

PURPOSE: To develop an accelerated cardiac perfusion pulse sequence and test whether it is capable of increasing spatial coverage, generating high-quality images, and enabling quantification of myocardial blood flow (MBF). METHODS: We implemented an accelerated first-pass cardiac perfusion pulse sequence by combining radial k-space sampling, compressed sensing (CS), and k-space weighted image contrast (KWIC) filtering. The proposed and clinical standard pulse sequences were evaluated in a randomized order in 13 patients at rest. For visual analysis, 3 readers graded the conspicuity of wall enhancement, artifact, and noise level on a 5-point Likert scale (overall score index = sum of 3 individual scores). Resting MBF was calculated using a Fermi function model with and without KWIC filtering. Mean visual scores and MBF values were compared between sequences using appropriate statistical tests. RESULTS: The proposed pulse sequence produced greater spatial coverage (6-8 slices) with higher spatial resolution (1.6 × 1.6 × 8 mm3 ) and shorter readout duration (78 ms) compared to clinical standard (3-4 slices, 3 × 3 × 8 mm3 , 128 ms, respectively). The overall image score index between accelerated (11.1 ± 1.3) and clinical standard (11.2 ± 1.3) was not significantly different (P = 0.64). Mean resting MBF values with KWIC filtering (0.9-1.2 mL/g/min across different slices) were significantly lower (P < 0.0001) than those without KWIC filtering (3.1-4.3 mL/g/min) and agreed better with values reported in literature. CONCLUSION: An accelerated, first-pass cardiac perfusion pulse sequence with radial k-space sampling, CS, and KWIC filtering is capable of increasing spatial coverage, generating high-quality images, and enabling quantification of MBF.

Cognitive function in early HIV infection.

This study aimed to examine cognitive function in acute/early HIV infection over the subsequent 2 years. Fifty-six HIV+ subjects and 21 seronegative participants of the Chicago Early HIV Infection Study were evaluated using a comprehensive neuropsychological assessment at study enrollment and at 2-year follow-up. Cognitive performance measures were compared in the groups using t tests and mixed-effect models. Patterns of relationship with clinical measures were determined between cognitive function and clinical status markers using Spearman's correlations. At the initial timepoint, the HIV group demonstrated significantly weaker performance on measures of verbal memory, visual memory, psychomotor speed, motor speed, and executive function. A similar pattern was found when cognitive function was examined at follow-up and across both timepoints. The HIV subjects had generally weaker performance on psychomotor speed, executive function, motor speed, visual memory, and verbal memory. The rate of decline in cognitive function across the 2-year follow-up period did not differ between groups. Correlations between clinical status markers and cognitive function at both timepoints showed weaker performance associated with increased disease burden. Neurocognitive difficulty in chronic HIV infection may have very early onset and reflect consequences of initial brain viral invasion and neuroinflammation during the intense, uncontrolled viremia of acute HIV infection. Further characterization of the changes occurring in initial stages of infection and the risk and protective factors for cognitive function could inform new strategies for neuroprotection.

Analysis of the RENAL and mRENAL Scores and the Relative Importance of Their Components in the Prediction of Complications and Local Progression after Percutaneous Renal Cryoablation.

PURPOSE: To determine if modified RENAL (mRENAL) score and its individual components have superior predictive value relative to the RENAL nephrometry score in prediction of complications and recurrence after percutaneous renal cryoablation. MATERIALS AND METHODS: Primary masses treated with CT-guided percutaneous renal cryoablation between June 2007 and May 2016 were retrospectively reviewed. RENAL and mRENAL scores were used to stratify masses into low, medium, and high complexity tertiles. Complications were characterized by SIR criteria. Predictors of complications and local progression were analyzed using multivariate logistic regression and Kaplan-Meier analysis. RESULTS: There were 95 renal cryoablation procedures in 86 patients. Of ablations, 89 had at least 1 follow-up imaging study, with median follow-up of 29 months. There were 11 (12.4%) complications, including 5 (6.5%) major complications. Mass complexity, as measured by mRENAL complexity tertile, was associated with increased risk of complications on multivariate analysis (P = .045). Endophytic location was the only individual ordinal component of the RENAL and mRENAL scores associated with complications (P = .021). Local progression occurred in 7 (8.3%) masses. Complexity as measured by either scoring system was not associated with local progression. Only diameter > 3 cm was associated with increased risk of local progression (hazard ratio = 9.9, 95% confidence interval = 2.1-45, P = .003). CONCLUSIONS: mRENAL score was predictive of complications and tumor size was predictive of recurrence. Use of mRENAL score for complications and tumor size for recurrence should allow for simpler risk stratification and more accurate patient counseling.

Early suppressive antiretroviral therapy in HIV infection is associated with measurable changes in the corpus callosum.

The purpose of this study was to examine the impact of early suppressive antiretroviral therapy (ART) on brain structure and neurocognitive outcomes. We conducted an observational study of subjects within 1 year of HIV infection. Ten ART-naïve and 10 ART-suppressed individuals were matched for age and infection duration and age-matched to 10 HIV-seronegative controls. Quantitative brain imaging and neurocognitive data were analyzed. Subjects on suppressive ART had diminished corpus callosum structural integrity on macromolecular and microstructural imaging, higher cerebrospinal fluid percent, higher depression scores, and lower functional performance. Early suppressive ART may alter the trajectory of neurological progression of HIV infection, particularly in the corpus callosum.

Diffusion abnormalities of the corpus callosum in patients receiving bevacizumab for malignant brain tumors: suspected treatment toxicity.

Bevacizumab has been reported to cause diffusion restriction in the tumor bed of patients with malignant gliomas. This study evaluated prolonged diffusion restriction, in the corpus callosum (CC), of patients with malignant brain tumors treated with bevacizumab. We retrospectively reviewed our database of patients treated with bevacizumab for malignant brain tumors looking for those with restricted diffusion in the CC. CC ADC ratio measurements were obtained prior to and following treatment. Correlation was made with biopsy (n = 3) and MR perfusion (n = 7) and PET (n = 4). The temporal evolution of these changes relative to therapy was examined with mixed effects regression analysis. Nine patients (eight malignant gliomas, one malignant meningioma) out of 146 patients were found to have developed areas of diffusion restriction in the CC. These areas tended to enlarge and coalesce over serial MRIs and persisted for up to 22 months. Hypoperfusion was demonstrated in MR perfusion in 7/7. PET was hypometabolic in all 4. Biopsy of the CC showed no tumor in 3/3. ADC ratio measurements indicated a significant overall effect of time (F(16,60) = 11.2; p < 0.0001), consistent with persistent diffusion restriction over the measured time periods. Bevacizumab causes prolonged diffusion restriction in the CC. The negative MR perfusion, FDG PET and histopathology suggest this is a toxicity of bevacizumab and not active tumor. Awareness of these changes can assist in patient care.

MR imaging enables measurement of therapeutic nanoparticle uptake in rat N1-S1 liver tumors after nanoablation.

PURPOSE: To test the hypothesis that magnetic resonance (MR) imaging can quantify intratumoral superparamagnetic iron oxide (SPIO) nanoparticle uptake after nanoablation. MATERIALS AND METHODS: SPIO nanoparticles functionalized with doxorubicin were synthesized. N1-S1 hepatomas were successfully induced in 17 Sprague-Dawley rats distributed into three dosage groups. Baseline tumor R2* values (the reciprocal of T2*) were determined using 7-tesla (T) MR imaging. After intravenous injection of SPIO nanoparticles, reversible electroporation (1,300 V/cm, 8 pulses, 100-µs pulse duration) was applied. Imaging of rats was performed to determine tumor R2* values after the procedure, and change in R2* (ΔR2*) was calculated. Inductively coupled plasma mass spectrometry was used to determine intratumoral iron (Fe) concentration after the procedure, which served as a proxy for SPIO nanoparticle uptake. Mean tumor Fe concentration [Fe] and ΔR2* for each subject were assessed for correlation with linear regression, and mean [Fe] for each dosage group was compared with analysis of variance. RESULTS: ΔR2* significantly correlated with tumor SPIO nanoparticle uptake after nanoablation (r = 0.50, P = .039). On average, each 0.1-ms(-1) increase in R2* corresponded to a 0.1394-mM increase in [Fe]. There was no significant difference in mean SPIO nanoparticle uptake among dosage groups (P = .57). CONCLUSIONS: Intratumoral SPIO nanoparticle uptake after nanoablation can be successfully quantified noninvasively with 7-T MR imaging. Imaging can be used as a method to estimate localized drug delivery after nanoablation.

Matrix metalloproteinase levels in early HIV infection and relation to in vivo brain status.

Matrix metalloproteinases (MMPs) have been implicated in human immunodeficiency virus (HIV)-associated neurological injury; however, this relationship has not been studied early in infection. Plasma levels of MMP-1, MMP-2, MMP-7, MMP-9, and MMP-10 measured using Luminex technology (Austin, TX, USA) were compared in 52 HIV and 21 seronegative participants of the Chicago Early HIV Infection study. MMP levels were also examined in HIV subgroups defined by antibody reactivity, viremia, and antiretroviral status, as well as in available cerebrospinal fluid (CSF) samples (n = 9). MMPs were evaluated for patterns of relationship to cognitive function and to quantitative magnetic resonance measurements of the brain derived in vivo. Plasma MMP-2 levels were significantly reduced in early HIV infection and correlated with altered white matter integrity and atrophic brain changes. MMP-9 levels were higher in the treated subgroup than in the naïve HIV subgroup. Only MMP-2 and MMP-9 were detected in the CSF; CSF MMP-2 correlated with white matter integrity and with volumetric changes in basal ganglia. Relationships with cognitive function were also identified. MMP-2 levels in plasma and in CSF correspond to early changes in brain structure and function. These findings establish a link between MMPs and neurological status previously unidentified in early HIV infection.

Locoregional chemoembolic delivery: prediction with transcatheter intraarterial perfusion MRI.

OBJECTIVE: To our knowledge there is currently no quantitative preprocedural method for predicting the distribution and selectivity of delivery of chemoembolic material during trans-arterial chemoembolization. Transcatheter intraarterial perfusion MRI has been developed as a method of quantifying hepatic arterial perfusion. The purpose of this study was to investigate whether findings at transcatheter intraarterial perfusion MRI before chemoembolization can be used to predict uptake of the chemoembolic material delivered during chemoembolization. SUBJECTS AND METHODS: We compared quantitative prechemoembolization transcatheter intraarterial perfusion MRI parameters with analogous postchemoembolization CT chemoembolic distribution parameters and analyzed correlation using the Pearson correlation coefficient. These MRI and CT parameters included volume of distribution (a metric for volumetric liver perfusion or therapeutic agent delivery) and chemoembolic delivery selectivity factor (a ratio of volume-normalized tumor to background signal intensity that indicates the selectivity of chemoembolic delivery). RESULTS: Twenty-four hepatocellular carcinomas were targeted in 18 patients (14 men, four women; mean age, 66 years), and segmental or lobar chemoembolization with intraprocedural transcatheter intraarterial perfusion MRI was successful in all 18. Transcatheter intraarterial perfusion MRI and CT volume of distribution did not differ significantly (MRI, 233 cm(3); CT, 235 cm(3); p = 0.857). Transcatheter intraarterial perfusion MRI selectivity factor was an underestimate of CT selectivity factor (MRI, 0.20; CT, 0.25; p = 0.005). Prechemoembolization transcatheter intraarterial perfusion MRI and postchemoembolization CT volume of distribution (r = 0.93; p < 0.001) and selectivity factor (r = 0.95; p < 0.001) showed significant correlation. CONCLUSION: Tumor perfusion measured with transcatheter intraarterial perfusion MRI is predictive of uptake of chemoembolic material before delivery. This MRI technique may have utility as a method of quantifying delivery of the therapeutic agent during chemoembolization and, potentially, other liver-directed locoregional therapies.

Legacy effect on neuropsychological function in HIV-infected men on combination antiretroviral therapy.

OBJECTIVE: To determine whether combination antiretroviral therapy (cART) initiation alters the trajectory of cognitive performance in HIV+ men, and whether cognition prior to cART predicts postcART function. DESIGN: Longitudinal cohort study. Multicenter AIDS Cohort Study. METHODS: From an initial set of 3701 men with complete neuropsychological data, men with HIV infection were initially matched with men without infection on cognitive status, race, age, and timeline (T0 defined as cART initiation). Propensity score matching was then used to match pairs on depressive symptoms at T0, education, T0 cognitive scores, and recruitment cohort. There were 506 matched pairs of infected and uninfected men in the final analysis. Mixed effect models were constructed to analyze the trajectories of cognitive functions and to test the effect of cART and HIV on cognitive functions over time. RESULTS: Performance in each cognitive domain did not change following the initiation of cART among HIV-infected men with prior impairment and was comparable to the performance of their matched uninfected men. However, among the infected men who were unimpaired prior to cART, motor function declined significantly faster than it did for uninfected controls. CONCLUSIONS: Cognitive dysfunction is persistent in HIV-infected men and cART does not alter the trajectory of cognitive decline in men who were impaired prior to effective therapy. This suggests that current cognitive impairment in HIV+ men results from a legacy effect, and from factors other than the HIV itself. Furthermore, motor skills may be uniquely vulnerable to the virus, cART, or age-related co-morbidities.

Marked relationship between matrix metalloproteinase 7 and brain atrophy in HIV infection.

Circulating levels of matrix metalloproteinases (MMP-1 and 7) have been found to correlate with the severity of brain injury in HIV-infected subjects. This study used high-resolution neuroanatomic imaging and automated segmentation algorithms to clarify this relationship. Both metalloproteinases were significantly correlated with increased cerebrospinal fluid volume fraction. Comprehensive brain volumetric analysis revealed a more marked relationship with atrophy for MMP-7, which was significantly correlated with neural injury in multiple brain regions and nearly all ventricular measurements. MMP-7 was also correlated with measures of virologic and cognitive status.

Platelet decline as a predictor of brain injury in HIV infection.

An association between platelet decline and increased risk of progression to dementia has been observed in an advanced HIV infection cohort study. This investigation evaluated the prognostic significance of platelet decline for dementia, for psychomotor slowing, and for brain injury, as quantified in vivo, in a much larger population of HIV+ men. Platelet counts and neurocognitive data were available from biannual visits of 2,125 HIV+ men participating in the prospective, Multicenter AIDS Cohort Study from 1984 to 2009. Brain volumetric data were also available from an imaging substudy of 83 seropositive participants aged 50 and older. The association of platelet counts with neurocognitive outcome was assessed using Cox proportional hazard models where change in platelet count from baseline was a time-updated variable. Marked platelet decline was associated with increased risk of dementia in univariate analysis (hazard ratio [HR] = 2.5, 95% confidence interval [CI] = 1.8-3.5), but not after adjustment for CD4 cell count, HIV viral load, age, study site, hemoglobin, race, education, smoking, and alcohol use (HR = 1.4, 95% CI = 0.78-2.5). Platelet decline did not predict psychomotor slowing in either univariate (HR = 0.79, 95% CI = 0.58-1.08) or multivariate (HR = 1.10, 95% CI = 0.73-1.67) analysis. Analysis of brain volumetric data, however, indicated a relationship between platelet decline and reduced gray matter volume fraction in univariate (p = 0.06) and multivariate (p < 0.05) analyses. Platelet decline was not an independent predictor of dementia or psychomotor slowing, after adjusting for stage of disease. Findings from a structural brain imaging substudy of older participants, however, support a possible relationship between platelet decline and reduced gray matter.

MDCT bolus tracking data as an adjunct for predicting the diagnosis of pulmonary hypertension and concomitant right-heart failure.

OBJECTIVE: The purpose of this study was to investigate the utility of bolus-triggering data from pulmonary CT angiography for predicting the diagnosis of pulmonary hypertension (PH) and right ventricular dysfunction (RVD) and to test its performance against previously established CT signs of PH. MATERIALS AND METHODS: Automated bolus-triggering data from pulmonary CT angiograms of 101 patients were correlated with echocardiographic findings and a variety of CT-derived indexes of PH and RVD, including right and left ventricular minor axis diameter; pulmonary artery (PA), aortic, and superior vena caval diameters; right ventricular thickness; contrast reflux; and configuration of the interventricular septum. For bolus triggering, a region of interest was placed in the main PA. Time to threshold, defined as the time from the beginning of contrast injection to the time attenuation exceeded the threshold (100 HU), was measured. On the basis of results of two consecutive echocardiographic studies, subjects were divided into control and PH groups. The latter group was subdivided into PH without RVD and PH with RVD. Time to threshold values were compared between groups and correlated with standard CT-derived parameters. RESULTS: Significant differences between groups were found in time to threshold, PA and right ventricular diameters, and PA-to-aorta and right ventricular-to-left ventricular ratios. Time to threshold had an incremental pattern from the control group (6.6 ± 1.0 seconds) to PH without RVD (9.2 ± 2.4 seconds) and PH with RVD (12.1 ± 3.4 seconds) (p < 0.001). The optimal diagnostic performance of time to threshold for revealing the presence of PH and RVD was at cutoff values of 7.75 and 8.75 seconds, respectively. Time to threshold had a strong direct correlation with PA diameter. In multivariable analyses, time to threshold was identified as a significant predictor of PH and RVD. The specificity of time to threshold and PA diameter together was higher than that of PA diameter alone. CONCLUSION: Measurement of time to threshold of contrast enhancement derived from bolus-timing data at MDCT may be a useful adjunctive tool for diagnosing PH and consequent RVD.

Longitudinal 5-year prediction of cognitive impairment among men with HIV disease.

BACKGROUND: Although combination antiretroviral therapy reduced the prevalence of HIV-associated dementia, milder syndromes persist. Our goals were to predict cognitive impairment of the Multicenter AIDS Cohort Study (MACS) participants 5 years ahead and from a large pool of factors, select the ones that mostly contributed to our predictions. DESIGN: Longitudinal, natural and treated history of HIV infection among MSM. METHODS: The MACS is a longitudinal study of the natural and treated history of HIV disease in MSM; the neuropsychological substudy aims to characterize cognitive disorders in men with HIV disease. RESULTS: We modeled on an annual basis the risk of cognitive impairment 5 years in the future. We were able to predict cognitive impairment at individual level with high precision and overperform default methods. We found that while a diagnosis of AIDS is a critical risk factor, HIV infection per se does not necessarily convey additional risk. Other infectious processes, most notably hepatitis B and C, are independently associated with increased risk of impairment. The relative importance of an AIDS diagnosis diminished across calendar time. CONCLUSION: Our prediction models are a powerful tool to help clinicians address dementia in early stages for MACS paticipants. The strongest predictors of future cognitive impairment included the presence of clinical AIDS and hepatitis B or C infection. The fact that the pattern of predictive power differs by calendar year suggests a clinically critical change to the face of the epidemic.

MR imaging to assess immediate response to irreversible electroporation for targeted ablation of liver tissues: preclinical feasibility studies in a rodent model.

PURPOSE: To test the hypothesis that magnetic resonance (MR) imaging measurements can be used to immediately detect treated tissue regions after irreversible electroporation (IRE) ablation procedures in rodent liver tissues. MATERIALS AND METHODS: All experiments received institutional animal care and use committee approval. In four rats for preliminary studies and 18 rats for formal assessment, MR imaging-compatible electrodes were inserted into the liver and MR imaging-monitored IRE procedures were performed at one of three electrode voltages (1000, 1500, or 2500 V), with T1- and T2-weighted images acquired before and immediately after application of the IRE pulses. MR imaging measurements were compared with both finite element modeling (FEM)-anticipated ablation zones and histologically confirmed ablation zones at necropsy. Intraclass and Spearman correlation coefficients were calculated for statistical comparisons. RESULTS: MR imaging measurements permitted immediate depiction of IRE ablation zones that were hypointense on T1-weighted images and hyperintense on T2-weighted images. MR imaging-based measurements demonstrated excellent consistency with FEM-anticipated ablation zones (r > 0.90 and P < .001 for both T1- and T2-weighted images). MR imaging measurements were also highly correlated with histologically confirmed ablation zone measurements (rho > 0.90 and P < .001 for both T1- and T2-weighted images). CONCLUSION: MR imaging permits immediate depiction of ablated tissue zones for monitoring of IRE ablation procedures. These measurements could potentially be used during treatment to elicit repeat application of IRE pulses or adjustments to electrode positions to ensure complete treatment of targeted lesions.

Accelerated two- and three-dimensional cine MR imaging of the heart by using a 32-channel coil.

PURPOSE: To compare accelerated real-time two-dimensional (2D) and segmented three-dimensional (3D) cine steady-state free precession magnetic resonance (MR) imaging techniques by using a 32-channel coil with a conventional 2D cine imaging approach for imaging the heart and to evaluate any difference caused by free breathing and breath holding for real-time imaging. MATERIALS AND METHODS: In this institutional review board-approved HIPAA-compliant study, 10 healthy volunteers and 22 consecutive patients who were suspected of having or were known to have heart disease underwent cardiac MR imaging by using a 32-channel coil. A conventional multisection 2D real-time cine sequence was used as the reference standard, and three additional accelerated cine sequences were implemented. Volumetric parameters, including ejection fraction (EF), end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume(SV), and myocardial mass, were derived. Wall motion and image quality were assessed by two radiologists. In addition, image time was registered. An additional set of images was acquired by using real-time sequences with free breathing, and quantitative measurements were compared with measurements on images obtained with breath holding. For quantitative analysis, repeated-measures analysis of variance, paired t test, and Bland-Altman analysis were used; for qualitative analysis, nonparametric Wilcoxon signed-rank test was used. RESULTS: All volumetric measurements were significantly correlated with those of the standard sequence (r > 0.80, P < .01). No significant difference among protocols was observed in terms of mean levels for EF or ESV (P > .05). However, a significant difference was indicated for EDV and SV (P < .01).The accelerated protocols had significantly shorter image times (P < .001). Wall motion scores were concordant with the standard sequence in 43-44 (93%-96%) segments for the accelerated protocols, with a strong interreader agreement (intraclass correlation coefficient, > or =0.93). No significant difference was identified between real-time protocols with free breathing and those with breath holding for measurement of volumetric parameters. CONCLUSION: Accelerated real-time 2D and segmented 3D cine techniques are comparable to the standard clinical protocol in assessment of left ventricular global and regional parameters in substantially shorter image times.

Sub-millimeter isotropic MRI for segmentation of subcortical brain regions and brain visualization.

PURPOSE: To evaluate a rapid sub-millimeter isotropic spoiled gradient-echo (nonselective SPGR) to facilitate the brain subcortical segmentation and the visualization of brain volume compared with the commonly accepted inversion recovery-prepared SPGR (SPGR-IR) technique. MATERIALS AND METHODS: The feasibility of the nonselective SPGR was evaluated for two segmentation algorithms. FAST was used to segment the brain into constituent tissue classes (white matter, gray matter, cerebrospinal fluid) and FreeSurfer was used to segment specific subcortical structures (hippocampus, caudate, putamen, and thalamus). Localized apparent signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) values for nonselective SPGR and the SPGR-IR were compared for the studied subcortical regions. The three-dimensional volume rendering was generated to evaluate the nonselective SPGR and the SPGR-IR for brain visualization. RESULTS: In basal ganglia regions, nonselective SPGR allows for consistent segmentation results for both FAST and FreeSurfer. This sequence also better differentiated gray/white matter compared with SPGR-IR. An approximate two-fold improvement of image quality in apparent SNR and CNR was indicated for subcortical brain anatomical structures with nonselective SPGR versus SPGR-IR. The nonselective SPGR improved clarity and yielded a more realistic depiction of the brain surface for visualization compared with SPGR-IR. CONCLUSION: Compared with SPGR-IR, nonselective SPGR allows for consistent segmentation results for basal ganglia regions and improved clarity for visualization of the brain.

Serum matrix metalloproteinase levels correlate with brain injury in human immunodeficiency virus infection.

Circulating levels of specific matrix metalloproteinases (MMPs; 1 and 7) were evaluated as correlates of brain injury in eight individuals in advanced human immunodeficiency virus (HIV) infection. Neurological status was quantified in vivo with automated segmentation algorithms and with diffusion tensor imaging. Both metalloproteinases correlated with microstructural brain alterations and the degree of atrophy. MMPs may influence neurological outcome through involvement in neuroimmune response, blood-brain barrier permeability, leukocyte migration, and MMP-mediated neurotoxicity.