Impact of intraoperative imaging on decision-making during spine surgery: a survey among spine surgeons using simulated intraoperative images.

PURPOSE: To assess whether the intention to intraoperatively reposition pedicle screws differs when spine surgeons evaluate the same screws with 2D imaging or 3D imaging. METHODS: In this online survey study, 21 spine surgeons evaluated eight pedicle screws from patients who had undergone posterior spinal fixation. In a simulated intraoperative setting, surgeons had to decide if they would reposition a marked pedicle screw based on its position in the provided radiologic imaging. The eight assessed pedicle screws varied in radiologic position, including two screws positioned within the pedicle, two breaching the pedicle cortex < 2 mm, two breaching the pedicle cortex 2-4 mm, and two positioned completely outside the pedicle. Surgeons assessed each pedicle screw twice without knowing and in random order: once with a scrollable three-dimensional (3D) image and once with two oblique fluoroscopic two-dimensional (2D) images. RESULTS: Almost all surgeons (19/21) intended to reposition more pedicle screws based on 3D imaging than on 2D imaging, with a mean number of pedicle screws to be repositioned of, respectively, 4.1 (± 1.3) and 2.0 (± 1.3; p < 0.001). Surgeons intended to reposition two screws placed completely outside the pedicle, one breaching 2-4mm, and one breaching < 2 mm more often based on 3D imaging. CONCLUSION: When provided with 3D imaging, spine surgeons not only intend to intraoperatively reposition pedicle screws at risk of causing postoperative complications more often but also screws with acceptable positions. This study highlights the potential of intraoperative 3D imaging as well as the need for consensus on how to act on intraoperative 3D information.

CT-based study of vertebral and intravertebral rotation in right thoracic adolescent idiopathic scoliosis.

PURPOSE: To define the longitudinal rotation axis around which individual vertebrae rotate, and to establish the various extra- and intravertebral rotation patterns in thoracic adolescent idiopathic scoliosis (AIS) patients, for better understanding of the 3D development of the rotational deformity. METHODS: Seventy high-resolution CT scans from an existing database of thoracic AIS patients (Cobb angle: 46°-109°) were included to determine the vertebral axial rotation, rotation radius, intravertebral axial rotation, and local mechanical torsion for each spinal level, using previously validated image processing techniques. RESULTS: For all levels, the longitudinal rotation axis, from which the vertebrae rotate away from the midline, was localized posterior to the spine. The axis became closer to the spine at the apex: apex, r = 11.5 ± 5.1 cm versus two levels above (radius = 15.8 ± 8.5 cm; p < 0.001) and beneath (radius = 14.2 ± 8.2 cm; p < 0.001). The vertebral axial rotation, intravertebral axial rotation, and local mechanical torsion of the vertebral bodies were largest at the apex (21.9° ± 7.4°, 8.7° ± 13.5° and 3.0° ± 2.5°) and decreased toward the neutral, junctional zones (p < 0.001). CONCLUSION: In AIS, the vertebrae rotate away around an axis that is localized posterior to the spine. The distance between this axis and the spine is minimal at the apex and increases gradually to the neutral zones. The vertebral axial rotation is accompanied by smaller amounts of intravertebral rotation and local mechanical torsion, which increases toward the apical region. The altered morphology and alignment are important for a better understanding of the 3D pathoanatomical development of AIS and better therapeutic planning for bracing and surgical intervention. These slides can be retrieved under Electronic Supplementary Material.

Volumetric image interpretation in radiology: scroll behavior and cognitive processes.

The interpretation of medical images is a primary task for radiologists. Besides two-dimensional (2D) images, current imaging technologies allow for volumetric display of medical images. Whereas current radiology practice increasingly uses volumetric images, the majority of studies on medical image interpretation is conducted on 2D images. The current study aimed to gain deeper insight into the volumetric image interpretation process by examining this process in twenty radiology trainees who all completed four volumetric image cases. Two types of data were obtained concerning scroll behaviors and think-aloud data. Types of scroll behavior concerned oscillations, half runs, full runs, image manipulations, and interruptions. Think-aloud data were coded by a framework of knowledge and skills in radiology including three cognitive processes: perception, analysis, and synthesis. Relating scroll behavior to cognitive processes showed that oscillations and half runs coincided more often with analysis and synthesis than full runs, whereas full runs coincided more often with perception than oscillations and half runs. Interruptions were characterized by synthesis and image manipulations by perception. In addition, we investigated relations between cognitive processes and found an overall bottom-up way of reasoning with dynamic interactions between cognitive processes, especially between perception and analysis. In sum, our results highlight the dynamic interactions between these processes and the grounding of cognitive processes in scroll behavior. It suggests, that the types of scroll behavior are relevant to describe how radiologists interact with and manipulate volumetric images.

The virtual dissecting room: Creating highly detailed anatomy models for educational purposes.

INTRODUCTION: Virtual 3D models are powerful tools for teaching anatomy. At the present day, there are a lot of different digital anatomy models, most of these commercial applications are based on a 3D model of a human body reconstructed from images with a 1mm intervals. The use of even smaller intervals may result in more details and more realistic appearances of 3D anatomy models. The aim of this study was to create a realistic and highly detailed 3D model of the hand and wrist based on small interval cross-sectional images, suitable for undergraduate and postgraduate teaching purposes with the possibility to perform a virtual dissection in an educational application. METHODS: In 115 transverse cross-sections from a human hand and wrist, segmentation was done by manually delineating 90 different structures. With the use of Amira the segments were imported and a surface model/polygon model was created, followed by smoothening of the surfaces in Mudbox. In 3D Coat software the smoothed polygon models were automatically retopologied into a quadrilaterals formation and a UV map was added. In Mudbox, the textures from 90 structures were depicted in a realistic way by using photos from real tissue and afterwards height maps, gloss and specular maps were created to add more level of detail and realistic lightning on every structure. Unity was used to build a new software program that would support all the extra map features together with a preferred user interface. CONCLUSION: A 3D hand model has been created, containing 100 structures (90 at start and 10 extra structures added along the way). The model can be used interactively by changing the transparency, manipulating single or grouped structures and thereby simulating a virtual dissection. This model can be used for a variety of teaching purposes, ranging from undergraduate medical students to residents of hand surgery. Studying the hand and wrist anatomy using this model is cost-effective and not hampered by the limited access to real dissecting facilities.

Quantification of deep medullary veins at 7 T brain MRI.

OBJECTIVES: Deep medullary veins support the venous drainage of the brain and may display abnormalities in the context of different cerebrovascular diseases. We present and evaluate a method to automatically detect and quantify deep medullary veins at 7 T. METHODS: Five participants were scanned twice, to assess the robustness and reproducibility of manual and automated vein detection. Additionally, the method was evaluated on 24 participants to demonstrate its application. Deep medullary veins were assessed within an automatically created region-of-interest around the lateral ventricles, defined such that all veins must intersect it. A combination of vesselness, tubular tracking, and hysteresis thresholding located individual veins, which were quantified by counting and computing (3-D) density maps. RESULTS: Visual assessment was time-consuming (2 h/scan), with an intra-/inter-observer agreement on absolute vein count of ICC = 0.76 and 0.60, respectively. The automated vein detection showed excellent inter-scan reproducibility before (ICC = 0.79) and after (ICC = 0.88) visually censoring false positives. It had a positive predictive value of 71.6 %. CONCLUSION: Imaging at 7 T allows visualization and quantification of deep medullary veins. The presented method offers fast and reliable automated assessment of deep medullary veins. KEY POINTS: • Deep medullary veins support the venous drainage of the brain • Abnormalities of these veins may indicate cerebrovascular disease and quantification is needed • Automated methods can achieve this and support human observers • The presented method provides robust and reproducible detection of veins • Intuitive quantification is provided via count and venous density maps.

Automated joint space width quantification of hand and wrist joints: a proof of concept study.

OBJECTIVES: To compare as proof of concept the sensitivity to change of automated quantification of radiographic wrist and hand joint space width (JSW) with scoring JSW according to the Sharp/van der Heijde scoring method (SHS) in two strategy groups of a treat-to-target and tight-control early rheumatoid arthritis (RA) study. METHODS: Digital radiographs were assessed for JSW changes of 134 patients of the 236 patients participating in the second Computer Assisted Management in Early Rheumatoid Arthritis trial, of whom both baseline and year 2 radiographs were available (year 1 radiographs n=125). Of those 134 patients, 70 started with methotrexate and prednisone (MTX+Pred) and 64 with MTX and placebo (MTX+Plac). JSW change over 1 and 2 years of the hands and wrists was assessed, applying both the joint space narrowing (JSN) subscore of the SHS by 2 readers and the automated assessment with the JSW quantification software 'JSQ'. For both methods, progression of JSW change of the hand and wrist was analysed using linear mixed modelling (dependent variable 'JSW', factor 'strategy group', covariate 'follow-up time in years', interaction term 'strategy group*follow-up time'; radiographs of baseline, year 1 and year 2 were used). For each method the standardised mean difference (SMD) for the change in JSW from baseline to year 2 between the treatment strategies was obtained using a non-parametric method. RESULTS: Patient characteristics of the current subpopulation were similar to those of the whole study population. JSN of the hand and wrist according to SHS at 2 years was present in 16 vs. 23% in the MTX+Pred group vs. the MTX+Plac group. The mean yearly progression rates of JSW change of the hands and wrists using JSQ were -0.00mm (95% confidence interval (CI) -0.01; 0.01) for MTX+Pred vs. -0.02mm (95%CI -0.03; -0.01) for MTX+Plac, p=0.045, and using SHS JSN they were 0.19 units (95%CI 0.09; 0.30) vs. 0.30 units (95%CI 0.14; 0.45) for MTX+Pred vs. MTX+Plac, p=0.271. The SMD for the change from baseline to year 2 between the treatment strategies was 0.37 for JSQ and 0.13 for SHS JSN. CONCLUSIONS: In this proof of concept study the yearly progression rate of JSW change of hand and wrist joints, according to the automated JSW quantification software package 'JSQ', was higher in the group initiating MTX+Plac than in the group initiating MTX+Pred. A similar trend was seen with the JSN assessment according to the SHS method of the hand and wrist. However, JSN of the hand and wrist according to SHS, the current gold standard to assess radiographic progression, was seen in only about 20%. Therefore, further studies are needed to conclude firmly that JSQ should be incorporated into quantitative scoring of radiographs in RA.

Longitudinal relationship between cerebral small-vessel disease and cerebral blood flow: the second manifestations of arterial disease-magnetic resonance study.

BACKGROUND AND PURPOSE: Cerebral small-vessel disease and cerebral blood flow (CBF) are interrelated. However, the direction of the relationship is unknown, and longitudinal studies are scarce. We investigated the longitudinal relationship between CBF and white matter hyperintensities (WMHs) and lacunes, as representatives of cerebral small-vessel disease, in patients with manifest arterial disease. METHODS: Within the Second Manifestations of Arterial Disease-Magnetic Resonance (SMART-MR) study, 1.5T brain magnetic resonance imaging, including an MR angiography, was obtained at baseline and after on ≈3.9 years of follow-up in 575 patients with manifest arterial disease (mean age, 57±10 years). Longitudinal associations of WMHs and lacunes with parenchymal CBF (pCBF; per 100-mL brain volume) were estimated using regression analyses, adjusted for age, sex, follow-up time, and baseline brain measures. RESULTS: Baseline pCBF was not associated with progression of WMHs and lacunes over time. However, periventricular and deep WMHs at baseline were associated with decline in pCBF; mean (95% confidence interval) decline in pCBF per % intracranial volume increase in periventricular and deep WMH volume was -0.70 (-1.40 to -0.00) and -1.01 (-1.64 to -0.38) mL/min per 100-mL brain volume, respectively. These associations were partly explained by cardiovascular risk factors but remained significant for deep WMHs (mean decline [95% confidence interval] in pCBF per % intracranial volume increase in deep WMH volume was -0.92 [-1.56 to -0.28] mL/min per 100-mL brain volume). Lacunes were not associated with change in pCBF. CONCLUSIONS: In patients with manifest arterial disease, baseline periventricular and deep WMH volumes were associated with decline in pCBF over time, but baseline pCBF was not associated with progression of WMHs and lacunes over time.

Microstructural brain abnormalities in Huntington's disease: A two-year follow-up.

OBJECTIVES: To investigate both cross-sectional and time-related changes of striatal and whole-brain microstructural properties in different stages of Huntington's disease (HD) using diffusion tensor imaging. EXPERIMENTAL DESIGN: From the TRACK-HD study, premanifest gene carriers (preHD), early manifest HD and controls were scanned at baseline and 2-year follow-up. Stratification of the preHD group into a far (preHD-A) and near (preHD-B) to predicted disease onset was performed. Age-corrected histograms of whole-brain white matter (WM), gray matter (GM) and striatal diffusion measures were computed and normalised by the number of voxels in each subject's data set. PRINCIPLE OBSERVATIONS: Higher cross-sectional mean, axial and radial diffusivities were found in both WM (P ≤ 0.001) and GM (P ≤ 0.001) of the manifest HD compared to the preHD and control groups. In preHD, only WM axial diffusivity (AD) was higher than in controls (P ≤ 0.01). This finding remained valid only in preHD-B (P ≤ 0.001). AD was also higher in the striatum of preHD-B compared to controls and preHD-A (P ≤ 0.01). Fractional anisotropy (FA) lacked sensitivity in differentiating between the groups. Histogram peak heights were generally lower in manifest HD compared to the preHD and control groups. No longitudinal differences were found in the degree of diffusivity change between the groups in the two year follow-up. There was a significant relationship between diffusivity and neurocognitive measures. CONCLUSIONS: Alterations in cross-sectional diffusion profiles between manifest HD subjects and controls were evident, both in whole-brain and striatum. In the preHD stage, only AD alterations were found, a finding suggesting that this metric is a sensitive marker for early change in HD prior to disease manifestation. The individual diffusivities were superior to FA in revealing pathologic microstructural brain alterations. Diffusion measures were well related to clinical functioning and disease stage.

Natural sagittal spino-pelvic alignment in boys and girls before, at and after the adolescent growth spurt.

PURPOSE: Adolescent idiopathic scoliosis occurs far more often in girls than in boys, and its initiation and progression normally takes place around the adolescent growth spurt. Despite extensive research into the topic, no solid explanation for both well-known phenomena has been offered. The sagittal profile of the growing spine has been demonstrated previously to play an important role in the spine's rotational stiffness. Changes in this sagittal alignment around the growth spurt can be inferred to play an important role in the spine's propensity to develop a rotatory deformity, i.e. scoliosis. The aim of this study was to quantify sagittal spino-pelvic alignment and orientation in space of each individual vertebra in normal boys and girls in the beginning, at the peak and at the end of pubertal growth. METHODS: Standardized lateral radiographs of the spine of boys (n = 57) and girls (n = 99) between the age of seven and eighteen who underwent screening for scoliosis, but had a normal spine were enrolled in this study. Children with spino-pelvic pathology at initial screening or during follow-up were excluded. According to Dimeglio's data, subjects were classified into three groups: before, at and after the peak growth spurt. Seven regional sagittal spino-pelvic parameters, as well as the inclination angles of each individual vertebra between C7 and L5 compared to the gravity line, were measured semi-automatically using in-house developed software. RESULTS: In all subjects, the posteriorly tilted segment was longer, vertebrae T1-T8 were more posteriorly inclined and thoracic kyphosis, pelvic incidence and pelvic tilt were lower before as well as during the peak of the growth spurt, when compared to after the growth spurt (P ≤ 0.023). Furthermore, in girls, thoracic kyphosis was smaller (P = 0.023), the posteriorly inclined segment was longer (P < 0.001) and T1 as well as levels T3-T11 were more posteriorly inclined (P < 0.05) compared to boys at all stages of development. At the peak of the growth spurt, girls had more posterior inclination of upper thoracic vertebrae and lower values for thoracic kyphosis than boys (P = 0.005). CONCLUSIONS: These results imply that the spines of girls during the growth spurt are more posteriorly inclined, and thus rotationally less stable, compared to boys at the same stage of development, as well as compared to girls after the growth spurt. This may explain why initiation and progression of adolescent idiopathic scoliosis are more prevalent in girls around puberty.

Diffusion-weighted magnetic resonance imaging using different b-value combinations for the evaluation of treatment results after volumetric MR-guided high-intensity focused ultrasound ablation of uterine fibroids.

OBJECTIVES: To assess the value of diffusion-weighted magnetic resonance imaging (DWI) and apparent diffusion coefficient (ADC) mapping using different b-value combinations for treatment evaluation after magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) of uterine fibroids. METHODS: Fifty-six patients with 67 uterine fibroids were treated with volumetric MR-HIFU. Pre-treatment and post-treatment images were obtained using contrast-enhanced T1-weighted MRI (CE-T1WI) and DWI using b = 0, 200, 400, 600, 800 s/mm(2). ADC maps were generated using subsets of b-values to investigate the effects of tissue ablation on water diffusion and perfusion in fibroids treated with MR-HIFU. Four combinations of b-values were used: (1) all b-values; (2) b = 0, 200 s/mm(2); (3) b = 400, 600, 800 s/mm(2); and (4) b = 0, 800 s/mm(2). RESULTS: Using the lowest b-values (0 and 200 s/mm(2)), the mean ADC value in the ablated tissue reduced significantly (p < 0.001) compared with baseline. Calculating the ADC value with the highest b-values (400, 600, 800 s/mm(2)), the ADC increased significantly (p < 0.001) post-treatment. ADC maps calculated with the lowest b-values resulted in the best visual agreement of non-perfused fibroid tissue detected on CE images. Other b-value combinations and normal myometrium showed no difference in ADC after MR-HIFU treatment. CONCLUSIONS: A decrease in contrast agent uptake within the ablated region on CE-T1WI was correlated to a significantly decreased ADC when b = 0 and 200 s/mm(2) were used. KEY POINTS: DWI could be useful for treatment evaluation after MR-HIFU of uterine fibroids. The ADC in fibroid tissue is influenced by the choice of b- values. Low b-values seem the best choice to emphasise perfusion effects after MR-HIFU.

Evolution of the ischio-iliac lordosis during natural growth and its relation with the pelvic incidence.

PURPOSE: Human fully upright ambulation, with fully extended hips and knees, and the body's center of gravity directly above the hips, is unique in nature, and distinguishes humans from all other mammalians. This bipedalism is made possible by the development of a lordosis between the ischium and ilium; it allows to ambulate in this unique bipedal manner, without sacrificing forceful extension of the legs. This configuration in space introduces unique biomechanical forces with relevance for a number of spinal conditions. The aim of this study was to quantify the development of this lordosis between ischium and ilium in the normal growing and adult spine and to evaluate its correlation with the well-known clinical parameter, pelvic incidence. METHODS: Consecutive series of three-dimensional computed tomography scans of the abdomen of 189 children and 310 adults without spino-pelvic pathologies were used. Scan indications were trauma screening or acute abdominal pathology. Using previously validated image processing techniques, femoral heads, center of the sacral endplate and the axes of the ischial bones were semi-automatically identified. A true sagittal view of the pelvis was automatically reconstructed, on which ischio-iliac angulation and pelvic incidence were calculated. The ischio-iliac angle was defined as the angle between the axes of the ischial bones and the line from the midpoint of the sacral endplate to the center of the femoral heads. RESULTS: A wide natural variation of the ischio-iliac angle (3°-46°) and pelvic incidence (14°-77°) was observed. Pearson's analysis demonstrated a significant correlation between the ischio-iliac angle and pelvic incidence (r = 0.558, P < 0.001). Linear regression analysis revealed that ischio-iliac angle, as well as pelvic incidence, increases during childhood (+7° and +10°, respectively) and becomes constant after adolescence. CONCLUSIONS: The development of the ischio-iliac lordosis is unique in nature, is in harmonious continuity with the highly individual lumbar lordosis and defines the way the human spine is biomechanically loaded. The practical parameter that reflects this is the pelvic incidence; both values increase during growth and remain stable in adulthood.

Quantification of cerebral volumes on MRI 6 months after aneurysmal subarachnoid hemorrhage.

BACKGROUND AND PURPOSE: MRI can be used to assess structural damage to the brain after aneurysmal subarachnoid hemorrhage. We tuned, validated, and applied k-Nearest Neighbor-based segmentation to quantify cerebral volumes on MRI 6 months after aneurysmal subarachnoid hemorrhage. METHODS: After tuning, the accuracy of k-Nearest Neighbor-based segmentation was assessed with manual segmentations. Next, supratentorial cerebral parenchymal, peripheral cerebrospinal fluid, and lateral ventricular volumes of 55 patients were compared with those of 25 age- and sex-matched control subjects and related to clinical outcome (modified Rankin Scale). RESULTS: k-Nearest Neighbor-based segmentation showed good agreement with manual segmentations. Compared with control subjects, patients had a larger lateral ventricular volume (difference: log-transformed values 0.54; 95% CI,0.33-0.75), smaller peripheral cerebrospinal fluid volume (-26 mL; 95% CI, -40 to -11), and similar cerebral parenchymal volume (2 mL; 95% CI, -10 to 15). In patients, parenchymal (median split; OR, 38.8; 95% CI, 4.6-329.0) and ventricular volumes (7.4; 95% CI, 1.6-33.5) correlated with functional outcome. CONCLUSIONS: k-Nearest Neighbor-based segmentation provides accurate cerebral volume measurements after aneurysmal subarachnoid hemorrhage. In this proof-of-principle study of this volumetric technique, we demonstrated volume changes relative to controls, which correlated with functional outcome.

Efficient detection of cerebral microbleeds on 7.0 T MR images using the radial symmetry transform.

Cerebral microbleeds (CMBs) are commonly detected on MRI and have recently received an increased interest, because they are associated with vascular disease and dementia. Identification and rating of CMBs on MRI images may be facilitated by semi-automatic detection, particularly on high-resolution images acquired at high field strength. For these images, visual rating is time-consuming and has limited reproducibility. We present the radial symmetry transform (RST) as an efficient method for semi-automated CMB detection on 7.0 T MR images, with a high sensitivity and a low number of false positives that have to be censored manually. The RST was computed on both echoes of a dual-echo T2*-weighted gradient echo 7.0 T MR sequence in 18 participants from the Second Manifestations of ARTerial disease (SMART) study. Potential CMBs were identified by combining the output of the transform on both echoes. Each potential CMB identified through the RST was visually checked by two raters to identify probable CMBs. The scoring time needed to manually reject false positives was recorded. The sensitivity of 71.2% is higher than that of individual human raters on 7.0 T scans and the required human rater time is reduced from 30 to 2 minutes per scan on average. The RST outperforms published semi-automated methods in terms of either a higher sensitivity or less false positives, and requires much less human rater time.

Mood problems increase the risk of mortality in patients with lacunar infarcts: the SMART-MR study.

OBJECTIVE: A relationship between depression and mortality has been well established, but underlying mechanisms remain unclear. We investigated the influence of cerebral small vessel disease (CSVD), characterized by white matter lesions (WMLs) and lacunar infarcts, on the relationship between mood mortality during 6 years follow-up. METHODS: Mood problems were assessed with the mental component summary of the 36-item Short-Form Medical Outcomes Study in 1110 patients with symptomatic atherosclerotic disease (mean age 59 years). Volumetric WML estimates were obtained with 1.5-T magnetic resonance imaging; lacunar infarcts were scored visually. Cox regression models were adjusted for age, sex, vascular risk, physical functioning, antidepressants and infarcts. We adjusted for CSVD to examine whether it may be an intermediate or confounding factor. Second, we added interaction terms to investigate whether associations differed between patients with CSVD (absent/present). RESULTS: Patients in the lowest quartile of mental functioning, representing most severe mood problems, were at higher, although not significant, risk of death (hazard ratio [HR] = 1.47, 95% confidence interval [CI] = 0.94-2.30) compared with patients in higher quartiles. Adjustment for CSVD did not change this association. Lacunar infarcts, not WML, modified the association of mood problems with mortality (p value for interaction = .01); mood problems strongly increased the risk of mortality in patients with lacunar infarcts (HR = 2.75, 95% CI = 1.41-5.38) but not in those without it (HR = 0.78, 95% CI = 0.39-1.57). CONCLUSIONS: Patients with lacunar infarcts may be especially vulnerable for the effect of mood problems on mortality.

Cerebral small vessel disease and risk of death, ischemic stroke, and cardiac complications in patients with atherosclerotic disease: the Second Manifestations of ARTerial disease-Magnetic Resonance (SMART-MR) study.

BACKGROUND AND PURPOSE: Cerebral small vessel disease may be related to vascular and nonvascular pathology. We assessed whether lacunar infarcts and white matter lesions on MRI increased the risk of vascular and nonvascular death and future vascular events in patients with atherosclerotic disease. METHODS: Brain MRI was performed in 1309 patients with atherosclerotic disease from the Second Manifestations of ARTerial disease-Magnetic Resonance (SMART-MR) study. Infarcts were scored visually and volumetric assessment of white matter lesion was performed. Patients were followed for a median of 4.5 years (range, 0.2 to 7.1 years) for death, ischemic stroke, and ischemic cardiac complications. RESULTS: Cox regression models showed that presence of lacunar infarcts (n=229) increased the risk of vascular (hazard ratio, 2.6; 95% CI, 1.4 to 4.9) and nonvascular death (hazard ratio, 2.7; 95% CI, 1.3 to 5.3), adjusted for age, sex, vascular risk factors, nonlacunar infarcts, and white matter lesion. These risks were similar for patients with silent lacunar infarcts. White matter lesion volume (relative to total intracranial volume) increased the risk of vascular death (hazard ratio per milliliter increase, 1.03; 95% CI, 1.01 to 1.05) and white matter lesions in the upper quintile compared with lower quintiles increased risk of ischemic stroke (hazard ratio, 2.6; 95% CI, 1.3 to 4.9). CONCLUSIONS: Cerebral small vessel disease, with or without a history of cerebrovascular disease, is associated with increased risk of death and ischemic stroke in patients with atherosclerotic disease.

Use of multispectral MRI to monitor aneurysm sac contents after endovascular abdominal aortic aneurysm repair.

PURPOSE: To validate a newly developed semi-automatic multispectral magnetic resonance imaging (MRI) tool for quantitatively monitoring aneurysm sac contents in patients after endovascular aneurysm repair (EVAR). METHODS: MRI studies from 24 EVAR patients were retrospectively analyzed. The precontrast T1-weighted and T2-weighted and the postcontrast T1-weighted images were displayed simultaneously. Two independent observers classified the aneurysm sac voxels into categories for endoleak, unorganized thrombus, or organized thrombus by interactively thresholding the multispectral images relative to the signal intensity of fat. Voxel classification was visualized as a color overlay on the MR images; when the observer changed the thresholds, the color overlay was updated immediately. The volumes of the voxels in each category were calculated and expressed in milliliters. The intra- and interobserver variability for measuring the volumes of endoleak and unorganized and organized thrombus were calculated; a Bland and Altman analysis was applied to determine the mean differences and the repeatability coefficient (RC). RESULTS: Mean aneurysm sac volume was 78 ± 42 mL. The intraobserver mean difference for the endoleak volume was 0.5 ± 1.9 mL with an RC of 3.7 mL; the interobserver mean difference was -0.8 ± 3.6 mL (RC 7.1 mL). The intraobserver mean difference for unorganized thrombus volume was -1.2 ± 4.4 mL (RC 8.6 mL); the interobserver mean difference was 0.3 ± 6.3 mL with an RC of 12.3 mL. The intraobserver mean difference for organized thrombus volume was 0.8 ± 5.0 mL (RC 9.7 mL); the interobserver mean difference was 0.4 ± 6.3 mL (RC 12.4 mL). CONCLUSION: Reproducible monitoring of aneurysm sac contents in EVAR patients is feasible with multispectral MRI in combination with our semi-automatic post-processing tool.

Quantitative diffusion weighted imaging for differentiation of benign and malignant breast lesions: the influence of the choice of b-values.

PURPOSE: To evaluate the influence of the choice of different combinations of b-values on the ADC and on the diagnostic performance of quantitative diffusion weighted imaging (DWI) in breast lesions. MATERIALS AND METHODS: Seventy-three patients (90 lesions) underwent 3 Tesla (T) breast MRI including a DWI-scan using b-values 0, 150, 499, and 1500 s/mm(2) and histological analysis. Five combinations of b-values were used to calculate the ADC, each with different sensitivities to perfusion and diffusion effects. The median ADC of benign lesions, noninvasive carcinomas and invasive carcinomas and the diagnostic performance of the five methods were compared. RESULTS: Eighty-eight lesions were analyzed (37 benign, 13 noninvasive carcinomas, 38 invasive carcinomas). The median ADC was highest in benign lesions, intermediate in noninvasive carcinomas and lowest in invasive carcinomas for all methods. Calculating the ADC with the lowest 2 b-values yielded the highest ADC for all lesions types; the highest 2 b-values yielded the lowest ADC. The area under the receiver operating characteristic curve was approximately equal for all methods. CONCLUSION: The ADC of breast lesions varied substantially with the choice of different b-values, indicating that absolute ADC threshold values to differentiate benign and malignant lesions should be interpreted with caution. However, the diagnostic performance of quantitative DWI was not affected by the choice of different b-values.

White matter lesions and lacunar infarcts are independently and differently associated with brain atrophy: the SMART-MR study.

OBJECTIVE: To investigate the independent association of white matter lesions (WML) and lacunar infarcts (LI) with measures of global brain atrophy on MRI. METHODS: Within the SMART-MR study, a cohort study among patients with manifest arterial disease, cross-sectional analyses were performed in 840 patients (mean age 58 +/- 10 years, 80% male) without cortical, large subcortical or infratentorial infarcts. Brain segmentation was used to quantify volumes of brain tissue, cerebrospinal fluid and WML. Total brain volume, ventricular volume and cortical gray matter volume were divided by intracranial volume to obtain brain parenchymal fraction (BPF), ventricular fraction (VF) and cortical gray matter fraction (GMF). Location and number of infarcts were rated visually. RESULTS: Mean +/- SD BPF was 79.3 +/- 2.8%, mean +/- SD VF was 2.01 +/- 0.95%, and mean +/- SD GMF was 36.6 +/- 3.3%. Linear regression analyses, adjusted for age, sex, vascular risk factors, intima media thickness and LI showed that in patients with moderate to severe WML (upper quartile) BPF was lower (-0.51%; 95% CI -0.93 to -0.08%), VF was higher (0.48%; 95% CI 0.31-0.65%) and GMF was lower (-1.48%; 95% CI -2.07 to -0.88%) than in patients with few WML (lower quartile). Presence of LI was associated with lower BPF (-0.52%; 95% CI -0.96 to -0.07%) and higher VF (0.25%; 95% CI 0.07-0.42%), but not with GMF, independent of WML and other potential confounders. CONCLUSION: WML are associated with total, subcortical and cortical brain atrophy, whereas LI are associated with total and subcortical atrophy, but not with cortical atrophy, suggesting an independent role for WML and LI in the pathogenesis of brain atrophy.

Pre-existent vertebral rotation in the human spine is influenced by body position.

Both the humans as well as the quadrupedal spine have been shown to exhibit a pattern of pre-existent rotation that is similar in direction to what is found in the most common types of idiopathic scoliosis. It has been postulated that human bipedalism introduces forces to the spine that increase a tendency of the vertebrae to rotate. The objective of this study was to examine the effect of body position on vertebral rotation in vivo. Thirty asymptomatic volunteers underwent magnetic resonance imaging scanning of the spine (T2-L5) in three different body positions; upright, quadrupedal-like (on hands-and-knees) and supine. Vertebral rotation in the local transverse plane was measured according to a pre-established method and compared at different spinal levels between the three body positions. It was shown that in all three positions the mid- and lower thoracic vertebrae were predominantly rotated to the right. However, vertebral rotation was significantly less in the quadrupedal position than in both the standing upright and supine positions.

Pre-existent vertebral rotation in the human spine is influenced by body position.

Human bipedalism appears to be a prerequisite for the development of idiopathic scoliosis. The objective of this study was to examine the effect of different positions of the human spine on vertebral rotation in vivo. Thirty asymptomatic volunteers underwent MRI scanning of the spine in three different body positions; upright, quadrupedal-like and supine. Vertebral rotation in the local transverse plane was measured and compared at different spinal levels between the three body positions. It was shown that in all three positions the mid and lower thoracic vertebrae were predominantly rotated to the right. However, rotation was significantly less in certain areas of the spine in the quadrupedal-like position than in both the standing upright and supine positions. We hypothesize that the erect position of the human spine, but also the supine position, increases dorsally directed shear loads that may increase the tendency of certain spinal segments to rotate.