Reevaluating the imaging definition of tumor progression: perfusion MRI quantifies recurrent glioblastoma tumor fraction, pseudoprogression, and radiation necrosis to predict survival

INTRODUCTION: Contrast-enhanced MRI (CE-MRI) represents the current mainstay for monitoring treatment response in glioblastoma multiforme (GBM), based on the premise that enlarging lesions reflect increasing tumor burden, treatment failure, and poor prognosis. Unfortunately, irradiating such tumors can induce changes in CE-MRI that mimic tumor recurrence, so called post treatment radiation effect (PTRE), and in fact, both PTRE and tumor re-growth can occur together. Because PTRE represents treatment success, the relative histologic fraction of tumor growth versus PTRE affects survival. Studies suggest that Perfusion MRI (pMRI)–based measures of relative cerebral blood volume (rCBV) can noninvasively estimate histologic tumor fraction to predict clinical outcome. There are several proposed pMRI-based analytic methods, although none have been correlated with overall survival (OS). This study compares how well histologic tumor fraction and OS correlate with several pMRI-based metrics. METHODS: We recruited previously treated patients with GBM undergoing surgical re-resection for suspected tumor recurrence and calculated preoperative pMRI-based metrics within CE-MRI enhancing lesions: rCBV mean, mode, maximum, width, and a new thresholding metric called pMRI–fractional tumor burden (pMRI-FTB). We correlated all pMRI-based metrics with histologic tumor fraction and OS. RESULTS: Among 25 recurrent patients with GBM, histologic tumor fraction correlated most strongly with pMRI-FTB (r = 0.82; P < .0001), which was the only imaging metric that correlated with OS (P<.02). CONCLUSION: The pMRI-FTB metric reliably estimates histologic tumor fraction (i.e., tumor burden) and correlates with OS in the context of recurrent GBM. This technique may offer a promising biomarker of tumor progression and clinical outcome for future clinical trials

Effect of voxel position on single-voxel MR spectroscopy findings.

BACKGROUND AND PURPOSE: Single-voxel MR spectroscopy is a widely used tool for evaluating brain tumors. Although extensive data are available on the MR spectral appearance of tumors, less is known about the effect of voxel position on the accuracy of single-voxel MR spectroscopy findings. The purpose of this study was to test the hypothesis that the accuracy of single-voxel MR spectroscopy in the categorization of lesions as either tumor or not tumor is dependent on voxel position. METHODS: Fifty single-voxel MR spectra acquired with a fully automated stimulated-echo spectroscopy sequence were reviewed retrospectively in 43 patients with new or previously treated intra-axial brain tumors. Spectra were analyzed for the presence of choline, creatine, N-acetylaspartate (NAA), and lipid/lactate. Choline/creatine and NAA/creatine peak area ratios were assessed qualitatively. Lesions were grouped into one of three categories on the basis of spectral pattern: tumor, not tumor, or indeterminate. Results of MR spectroscopy were compared with the final histopathologic diagnosis. RESULTS: Histologic confirmation was obtained in 19 patients; MR spectra were interpretable in 17 of those. MR spectra correctly categorized nine of 17 lesions (six tumor, three nontumor). All eight misdiagnosed lesions were tumors. When the MR spectroscopy voxel included the enhancing edge of the lesion, the spectra correctly categorized seven of eight lesions (four of five tumors and all three cases of radiation necrosis). When the MR spectroscopy voxel was positioned centrally within the lesion, the spectra correctly reflected histologic outcome in two of nine lesions (all tumors). CONCLUSION: The reliability of single-voxel MR spectroscopy findings is dependent on voxel position. Spectra obtained from voxels at the enhancing edge of a tumor more accurately reflect lesion histopathology than do spectra obtained from the lesion center, even if the centrally placed voxels contain solidly enhancing tissue

Titanium aneurysm clips: Part III--Clinical application in 16 patients with subarachnoid hemorrhage

This report describes the first clinical use of newly developed titanium clips in the treatment of 16 patients with subarachnoid hemorrhage. There were no immediate or delayed complications related to the titanium clips. Thirteen patients had good outcomes, and one patient had moderate disabilities (mean follow-up, 5.4 mo). Two patients with Hunt and Hess Grade IV hemorrhages died postoperatively. The average cross-sectional areas of clip artifact on postoperative magnetic resonance imaging studies was 0.96, 1.36, and 1.05 cm2 on T1-, T2-, and intermediate-weighted images, respectively. In comparison, a matched control group with cobalt alloy clips had average cross-sectional areas of 3.13, 3.70, and 2.81 cm2 on T1-, T2-, and intermediate-weighted images, respectively. The average artifact volumes on gradient echo magnetic resonance images for titanium and cobalt alloy clips were 1.8 and 10.1 cm3, respectively. In addition, the gap on magnetic resonance imaging angiograms from clip artifacts was 0.9 cm with titanium and 2.6 cm with cobalt alloy clips. In conclusion, titanium aneurysm clips seem to be safe and effective and seem to reduce clip artifacts on magnetic resonance imaging threefold, compared with commercially available cobalt alloy clips. Because of this important advantage over conventional clips, titanium clips should be considered for routine use in aneurysm surgery

Surgical management of spinal epidural hematoma: Relationship between surgical timing and neurological outcome

Thirty patients were treated surgically for spinal epidural hematoma (SEH). Twelve of these cases resulted from spinal surgery, seven from epidural catheters, four from vascular lesions, three from anticoagulation medications, two from trauma, and two from spontaneous causes. Pain was the predominant initial symptom, and all patients developed neurological deficits. Eight patients had complete motor and sensory loss (Frankel Grade A); six had complete motor loss but some sensation preserved (Frankel Grade B); and 16 had incomplete loss of motor function (10 patients Frankel Grade C and six patients Frankel Grade D). The average interval from onset of initial symptom to maximum neurological deficit was 13 hours, and the average interval from onset of symptom to surgery was 23 hours. Surgical evacuation of the hematoma was performed in all patients; 26 of these improved; four remained unchanged, and no patients worsened (mean follow up 11 months). Complete recovery (Frankel Grade E) was observed in 43% of the patients and functional recovery (Frankel Grades D or E) was observed in 87%. One postoperative death occurred from a pulmonary embolus (surgical mortality 3%). Preoperative neurological status correlated with outcome; 83% of Frankel Grade D patients recovered completely compared to 25% of Frankel Grade A patients. The rapidity of surgical intervention also correlated with outcome; greater neurological recovery occurred as the interval from symptom onset to surgery decreased. Patients taken to surgery within 12 hours had better neurological outcomes than patients with identical preoperative Frankel grades whose surgery was delayed beyond 12 hours. This large series of SEH demonstrates that rapid diagnosis and emergency surgical treatment maximize neurological recovery. However, patients with complete neurological lesions or long-standing compression can improve substantially with surgery

Assessment of Silent Embolism From Carotid Endarterectomy by Use of Diffusion-Weighted Imaging: Work in Progress

BACKGROUND AND PURPOSE: Transcranial Doppler studies have suggested that microemboli are released into the arterial circulation during the majority of carotid endarterectomy (CEA) procedures. This, together with the observation that neuropsychological performance may decline postoperatively, has led to concern that cerebral infarction may occur unrecognized during CEA. Our objective was to examine this risk with diffusion-weighted imaging, a technique that is highly sensitive to acute cerebral infarction. METHODS: Eighteen participants (median age, 68 years; age range, 56-87 years) were assessed with diffusion-weighted imaging and the National Institutes of Health Stroke Scale before and after CEA. Imaging was performed using single-shot echo-planar imaging with a maximum diffusion sensitivity of b = 1000 s/mm2 applied to three orthogonal planes. Preoperative imaging was performed a median of 2.5 hours before surgery (range, 0.5-12.5 hours) and 15 hours after surgery (range, 1.5-58.5 hours). Two neuroradiologists independently interpreted the diffusion-weighted images, blinded to operative status and clinical findings. RESULTS: There was no diffusion-weighted imaging evidence of silent embolism in this series of 18 participants (95% confidence interval limits, 0 to 10%). Clinical complications were confined to one case of confusion occurring after CEA; the diffusion-weighted imaging results were normal in this case. CONCLUSION: There is no evidence from our series that silent cerebral infarction is a common occurrence during CEA. These data provide further support for the safety of CEA

Anatomical and biomechanical analyses of the unique and consistent locations of sacral insufficiency fractures

STUDY DESIGN.: Correlation of locations of sacral insufficiency fractures is made to regions of stress depicted by finite element analysis derived from biomechanical models of patient activities. OBJECTIVE.: Sacral insufficiency fractures occur at consistent locations. It was postulated that sacral anatomy and sites of stress within the sacrum with routine activities in the setting of osteoporosis are foundations for determining patterns for the majority of sacral insufficiency fractures. SUMMARY OF BACKGROUND DATA.: The predominant vertical components of sacral insufficiency fractures most frequently occur bilaterally through the alar regions of the sacrum, which are the thickest and most robust appearing portions of the sacrum instead of subjacent to the central sacrum, which bears the downward force of the spine. METHODS.: First, the exact locations of 108 cases of sacral insufficiency fractures were catalogued and compared to sacral anatomy. Second, different routine activities were simulated by pelvic models from CT scans of the pelvis and finite element analysis. Analyses were done to correlate sites of stress with activities within the sacrum and pelvis compared to patterns of sacral insufficiency fractures from 108 cases. RESULTS.: The sites of stress depicted by the finite element analysis walking model strongly correlated with identical locations for most sacral and pelvic insufficiency fractures. Consistent patterns of sacral insufficiency fractures emerged from the 108 cases and a biomechanical classification system is introduced. Additionally, alteration of walking mechanics and asymmetric sacral stress may alter the pattern of sacral insufficiency fractures noted with hip pathology (P = 0.002). CONCLUSION.: Locations of sacral insufficiency fractures are nearly congruous with stress depicted by walking biomechanical models. Knowledge of stress locations with activities, cortical bone transmission of stress, usual fracture patterns, intensity of sacral stress with different activities, and modifiers of walking mechanics may aid medical management, interventional, or surgical efforts. © 2009, Lippincott Williams & Wilkins