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Biomedical subjects

J E Heiserman

Publications and source records attributed to J E Heiserman.

At least 19 recordsLinked to original sources
PubMed2003

Diffusion-weighted imaging provides support for secondary neuronal damage from intraparenchymal hematoma.

It is controversial whether an intracerebral hematoma (ICH) causes ischemia of surrounding brain. By virtue of its high sensitivity to acute cerebral infarction, diffusion-weighted imaging (DWI) helps answer this question. We used this technique to assess the parenchyma surrounding ICH for restricted diffusion. Echoplanar DWI (b 1000 s/mm(2)) and conventional MRI sequences were performed in 30 subjects (symptom duration 7-75 h) with primary ICH, mean volume: 13+/-15 cm(3). We calculated mean apparent diffusion coefficients (ADC) within high signal regions around the hematoma on DWI or T2-weighted images and within the ICH itself, comparing them to the contralateral brain. We used the Student's t -test to examine for differences between these regions and linear regression to relate changes to the age of the ICH. A thin rim of high signal on DWI and a wider rim on T2-weighted images surrounded all hematomas. The ADC within the rim on DWI showed a maximum reduction of 40%, in two patients imaged within 10 h of symptom onset. They rose during the first day (r(2)=0.84; P <0.03) and then showed a mild decrease, becoming the same as ADC in other areas of the brain (r(2)=0.5; P <0.03). The rim on T2-weighting showed a mean increase of 50% and ADC within the ICH were reduced by a mean of 38%; these variations showed no relationship with ICH age and no group showed any relationship with ICH size. The ADC within the three regions was significantly different from each other. The presence of restricted diffusion in the parenchyma surrounding ICH provides support for secondary neuronal damage.

Aged↗
PubMed2001

PROPELLER MRI: clinical testing of a novel technique for quantification and compensation of head motion.

While head motion is considered a significant problem in magnetic resonance imaging (MRI), there is no data to quantify its extent, severity, or effect on image quality. PROPELLER (Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction) MRI offers a novel means of quantifying and compensating for head motion. We performed axial T2-weighted PROPELLER (motion corrected: P-CR; uncorrected: P-UNCR) and conventional MRI (CONV), with equal scan times, in five normal volunteers and 35 clinical subjects. Volunteers were examined lying still and performing two separate head movements (shake "no" and nod "yes") to assess detection and compensation of in-plane motion by PROPELLER MRI. Images were examined by three radiologists for motion artifact and for overall image quality. Head rotation and translation was detected in all subjects during each slice acquisition, with expected changes occurring with volunteer head motion. Motion artifact was less commonly seen on PROPELLER than CONV MR (chi(2) test P < 0.001). PROPELLER was preferred over CONV in all subjects (P < 0.05) and P-CR was judged superior to P-UNCR (P = 0.02). Intracranial pathology was equally or better demonstrated with PROPELLER. PROPELLER MRI offers a means of quantifying head motion, reducing motion artifact, and improving image quality.

Brain↗
PubMed2001

Magnetic resonance angiography and evaluation of cervical arteries.

Multiple clinical trials have demonstrated the efficacy of endarterectomy in selected groups of patients based primarily on percent diameter stenosis. Although measurement of stenosis in the clinical trials was established by conventional angiography, there is considerable interest in noninvasive alternatives. Magnetic resonance angiography, performed using time-of-flight methods or with contrast enhancement, is one of several alternatives for noninvasive carotid evaluation. Screening examinations are routinely performed for carotid stenosis. Preoperative evaluations based on one or a combination of noninvasive tests have been proposed, although these proposals are the subject of ongoing controversy. Evaluation of the vertebral arteries is more difficult and less well studied: however, the increasing availability of therapies for posterior circulation atherosclerotic narrowing is resulting in increased interest in this problem.

Arterial Occlusive Diseases↗
PubMed2001

Evidence for cytotoxic edema in the pathogenesis of cerebral venous infarction.

BACKGROUND AND PURPOSE: The pathogenesis of cerebral venous infarction (CVI) remains controversial, with uncertainty over whether cytotoxic edema plays a role. Recent animal studies have shown that cytotoxic edema reliably occurs in acute CVI and precedes the onset of vasogenic edema. Our hypothesis was that cytotoxic edema would also occur in acute human CVI and would be detectable as an area of restricted diffusion on diffusion-weighted images. METHODS: Twelve subjects with acute cerebral venous thrombosis confirmed by MR venography underwent both conventional MR and echo-planar diffusion-weighted imaging (maximum diffusion sensitivity [b=1000 s/mm(2)]). Images were examined for areas of CVI that were identified as T2 hyperintensity, diffusion hyperintensity, or hemorrhage. The percent change in apparent diffusion coefficient (ADC) and T2 signal as well as the T2/diffusion volume were calculated within areas of edematous CVI. Regression techniques were used to examine the relationship of these variables to symptom duration. RESULTS: Ten regions of CVI were detected in seven subjects, all showing T2 hyperintensity. Two of these regions were predominantly hemorrhagic and did not display diffusion hyperintensity. The remaining eight regions displayed diffusion hyperintensity that was associated with a decreased ADC. ADC values increased with symptom duration (r(2) = 0.96; P <.006). Both T2 hyperintensity and T2/diffusion volume peaked approximately 2 days after symptom onset. CONCLUSION: Restricted water diffusion suggesting cytotoxic edema is commonly found in subjects with acute CVI and decreases over time. This supports an important etiologic role for cytotoxic edema in the pathogenesis of CVI.

Adolescent↗
PubMed2001

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/mm(2) 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.

Aged↗
PubMed2000

Incidence of postangiographic abnormalities revealed by diffusion-weighted MR imaging.

BACKGROUND AND PURPOSE: Occasionally we have observed anecdotal cases of asymptomatic hyperintensities on diffusion-weighted MR (DW-MR) examinations of the brain of patients who previously underwent routine cerebral angiography. These observations, as well as MR imaging and transcranial Doppler data in the literature suggesting a high rate of procedure-associated emboli, raise concern regarding the underdiagnosis of asymptomatic focal infarction associated with cerebral angiography. In order to determine whether asymptomatic diffusion abnormalities are frequently associated with procedures, we prospectively obtained DW-MR images before and after routine cerebral angiography. METHODS: Twenty consecutive patients, who met protocol criteria and received a routine three- or four-vessel diagnostic cerebral angiogram at our institution, were evaluated. Using a Bayesian estimate to establish an upper bound for the incidence of an event with zero occurrences in a study sample, the study group size was selected to exclude a 10% incidence of abnormalities revealed by DW-MR imaging of patients who underwent previous cerebral angiography. Two neuroradiologists evaluated imaging studies. RESULTS: Neither clinical signs nor abnormalities on DW-MR images were found, which suggested no infarction after angiography in our patient sample. Based on this data, an upper bound of 9% (95% confidence) is predicted for the appearance of abnormalities revealed by DW-MR imaging after cerebral angiography. CONCLUSION: Cerebral angiography is associated with an incidence of asymptomatic cerebral infarction of no more than 9%. It well may be substantially lower than this estimate; a more accurate evaluation of the true incidence would require a significantly larger study population. This test provides a convenient noninvasive means of assessing procedure-related cerebral infarction, such as that which occurs after carotid endarterectomy or vascular angioplasty and stenting.

Adult↗
PubMed2000

Cerebral MR venography: normal anatomy and potential diagnostic pitfalls.

BACKGROUND AND PURPOSE: MR venography is often used to examine the intracranial venous system, particularly in the evaluation of dural sinus thrombosis. The purpose of this study was to evaluate the use of MR venography in the depiction of the normal intracranial venous anatomy and its variants, to assess its potential pitfalls in the diagnosis of dural venous sinus thrombosis, and to compare the findings with those of conventional catheter angiography. METHODS: Cerebral MR venograms obtained in 100 persons with normal MR imaging studies were reviewed to determine the presence or absence of the dural sinuses and major intracranial veins. RESULTS: Systematic review of the 100 cases revealed transverse sinus flow gaps in 31% of the cases, with 90% of these occurring in the nondominant transverse sinus and 10% in the codominant transverse sinuses. No flow gaps occurred in the dominant transverse sinuses. The superior sagittal and straight sinuses were seen in every venogram; the occipital sinus was seen in only 10%. The vein of Galen and internal cerebral veins were also seen in every case; the basal veins of Rosenthal were present in 91%. CONCLUSIONS: Transverse sinus flow gaps can be observed in as many as 31% of patients with normal MR imaging findings; these gaps should not be mistaken for dural sinus thrombosis.

Adolescent↗
PubMed2000

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.

Aspartic Acid↗
PubMed1999

MR angiography. Toward faster and more accurate methods.

MR angiography is a class of methods developed to noninvasively evaluate vascular structures. After first reviewing the different approaches and comparing strengths and weaknesses, new methods to improve the quality or speed of acquisition of these important sequences are examined.

Artifacts↗
PubMed1998

The radiographic and imaging characteristics of porous tantalum implants within the human cervical spine.

STUDY DESIGN: Seven cadaveric cervical spines were implanted with a porous tantalum spacer and a titanium alloy spacer, and their radiographic and imaging characteristics were evaluated. OBJECTIVE: To determine the radiographic characteristics of porous tantalum and titanium implants used as spacers in the cervical spine. SUMMARY OF BACKGROUND DATA: Anterior decompressive surgery of the disc space or the vertebral body creates a defect that frequently is repaired with autologous bone grafts to promote spinal fusion. Donor site morbidity, insufficient donor material, and additional surgical time have spurred the development of biomaterials to replace or supplement existing spinal reconstruction techniques. Although the promotion of a solid bony fusion is critical, the implanted biomaterial should be compatible with modern imaging techniques, should allow visualization of the spinal canal and neural foramina, and should permit radiographic assessment of bony ingrowth. METHODS: Cadaveric spines containing the implants were imaged with plain radiography, computerized tomography, and magnetic resonance imaging. The image distortion produced by the implants was determined qualitatively and quantitatively. RESULTS: The tantalum and titanium spacers were opaque on plain radiographic films. On computed tomographic scans, more streak artifact was associated with the tantalum implants than with the titanium. On magnetic resonance imaging, the porous tantalum implant demonstrated less artifact than did the titanium spacer on T1- and T2-weighted spin echo and on T2*-weighted gradient-echo magnetic resonance images. Overall, the tantalum implant produced less artifact on magnetic resonance imaging than did the titanium spacer and therefore allowed for better visualization of the surrounding bony and neural structures. CONCLUSION: The material properties of titanium and porous tantalum cervical interbody implants contribute to their differential appearance in different imaging methods. The titanium implant appears to image best with computed tomography, whereas the porous tantalum implant produces less artifact than does the titanium implant on several magnetic resonance imaging sequences.

Artifacts↗
PubMed1998

Differentiating recurrent tumor from radiation necrosis: time for re-evaluation of positron emission tomography?

UNLABELLED: Our purpose was to evaluate the ability of FDG PET to differentiate recurrent tumor from posttherapy radiation necrosis. METHODS: MR images, PET scans, and medical records of 84 consecutive patients with a history of a treated intracranial neoplasm were evaluated retrospectively. In all patients, recurrent tumor or radiation necrosis was suggested by clinical or MR findings. Metabolic activity of the PET abnormality was compared qualitatively with normal contralateral gray and white matter. RESULTS: PET findings were confirmed histologically in 31 patients. With contralateral white matter as the standard of comparison, the PET scan sensitivity and specificity were found to be 86% and 22%, respectively. With contralateral gray matter as the reference standard, the sensitivity and specificity became 73% and 56%, respectively. Overall, nearly one third of the patients would have been treated inappropriately in either scheme had the PET scan been the sole determinant of therapy. CONCLUSION: Our data suggest that the ability of FDG PET to differentiate recurrent tumor from radiation necrosis is limited. Both false-positive and false-negative PET scan results contributed to unacceptably low sensitivity and specificity values.

Diagnosis, Differential↗
PubMed1997

Absence of pontine lesions in narcolepsy.

A recent study reporting pontine lesions on magnetic resonance imaging in three patients with idiopathic narcolepsy postulated that the lesions represented tissue change secondary to long duration of disease. We studied twelve narcoleptic patients with MRI to validate these findings. The diagnosis of narcolepsy was established with both clinical and electrophysiological criteria in all twelve patients. Pontine lesions were present in two patients, both of whom were hypertensive. The lesions were associated with similar lesions in the hemispheres and were indistinguishable from ischemic change. No lesions were evident in the other ten patients, eight of whom were normotensive, and six of whom had narcolepsy for more than 37 years. We were unable to confirm the presence of pontine lesions specific to narcolepsy.

Adult↗
PubMed1997

Juvenile active ossifying fibroma. Report of four cases.

Juvenile active ossifying fibroma is a rare lesion seldom seen by neurosurgeons. It originates in the paranasal sinuses during childhood, grows slowly, and encroaches on adjacent orbital and cranial compartments. In the past 3 years, four patients with this lesion were seen (three men and one woman; mean age 28 years). The clinical presentations were different with each patient: sinusitis, meningitis, periorbital pain, and a unique case of a juvenile active ossifying fibroma presenting with high-grade internal carotid artery stenosis and ischemic symptoms. Three patients were treated by transfacial approaches: two with a transfrontal-nasal approach and one with a transfrontal-nasoorbital approach. Two open resections resulted in gross-total excision and no recurrence as of the 2-year follow-up review. In the third patient, the tumor-encased carotid artery was preserved at the expense of a complete resection; that patient underwent superficial temporal artery-middle cerebral artery bypass and remains without ischemic symptoms or tumor recurrence at 2 years. The fourth patient underwent three subtotal endoscopic resections and is also without symptomatic recurrence at 2 years. Three points must be made concerning these lesions. First, the clinical and radiographic characteristics of juvenile active ossifying fibroma may not be easily recognized by neurosurgeons, which could lead to misdiagnosis and mismanagement of these lesions. Second, this tumor can encase the carotid artery and cause severe stenosis or occlusion. Third, complete resection of the tumor is required to effect a cure, and transfacial approaches, which give wide exposure of the sinuses, appear to yield better, more radical resections than endoscopic procedures.

Adult↗
PubMed1996

An alternative to GRASE: toward spin-echo-like contrast with independent reconstruction of gradient-echo images.

Multiple gradient echoes are generated for each RF echo of a Carr-Purcell-Meiboom-Gill (CPMG) train. Independently, phase-encoded fast spin-echo images are obtained from the different gradient echoes. Presently, three images are formed from three gradient-echoes from each of four RF echoes. The two peripheral gradient echo images are encoded for a late effective TE, then summed after reconstruction: this image has decreased fat intensity and increased susceptibility contrast compared with fast spin echo. The central gradient echoes yielded another image of intermediate contrast useful for neuroimaging. Raw data from the variously timed gradient echoes are not combined as they are in GRASE.

Brain↗
PubMed1996

Comparison of centralized versus "site-based" measurement of angiographic stenosis for eligibility in the asymptomatic carotid atherosclerosis study.

RATIONALE AND OBJECTIVES: The authors determine the reliability of centralized versus noncentralized (site-based) measurement of angiographic stenosis of patients enrolled into the multicenter, prospective, Asymptomatic Carotid Atherosclerosis Study by angiographic studies. METHODS: Percent agreements and correlations of 244 masked and prospectively interpreted angiograms were calculated for comparison of centralized and noncentralized readers measuring the percent carotid stenosis from the same angiographic studies. Univariate summary statistics for differences in percent stenoses were calculated for these readings. RESULTS: Agreement between readings were 88.5% and 91.8% with kappa statistics of 0.77 and 0.73 for > or = 60% and > or = 80% stenosis, respectively, for comparison of 33 centers to the designated central reader. Comparison between the designated central reader and a second central reader derived percent agreements of 85.0% and 86.5% with kappa statistics of 0.69 and 0.41 for > or = 60% and > or = 80% stenoses, respectively, for arteries selected from the original group. Hence, agreement was slightly better between the enrolling centers and the designated central reader than between the two central readers. CONCLUSIONS: Both centralized and noncentralized (site-based) methods of angiographic measurement of stenosis are equally reliable for large, prospective, masked, multicenter trials when quality control measures are instituted to ensure uniform application of eligibility criteria.

Angiography↗
PubMed1996

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.

Adult↗