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R Gilberto Gonzalez

Publications and source records attributed to R Gilberto Gonzalez.

At least 55 records · Page 3Linked to original sources
PubMed2003

Assessing tissue viability with MR diffusion and perfusion imaging.

BACKGROUND AND PURPOSE: Diffusion- (DW) and perfusion-weighted (PW) MR imaging reflect neurophysiologic changes during stroke evolution. We sought to determine parameters that distinguish regions of brain destined for infarction from those that will survive despite hypoperfusion. METHODS: DW and PW images were obtained in 30 patients at 1-12 hours after symptom onset. Relative cerebral blood volume (rCBV), flow (rCBF), mean transit time (MTT), apparent diffusion coefficient (ADC), DW image signal intensity, and fractional anisotropy (FA) lesion-contralateral normal region ratios were obtained in the following regions: 1) infarct core with hyperintensity on DW image, abnormality on rCBF and MTT images, and follow-up abnormality; 2) infarcted penumbra with normal DW image, abnormal rCBF and MTT images, and follow-up abnormality; and 3) hypoperfused tissue that remained viable, with normal DW image, abnormal rCBF and MTT images, and normal follow-up. RESULTS: rCBF ratios for regions 1, 2, and 3 were 0.32 +/- 0.11, 0.46 +/- 0.13, and 0.58 +/- 0.12, respectively, and were significantly different. DW image intensity and ADC ratios were significantly different among all regions, but were more similar than rCBF ratios. rCBV and FA ratios were not significantly different between regions 2 and 3. No MTT ratios were significantly different. No region of interest with an rCBF ratio less than 0.36, an rCBV ratio less than 0.53, an ADC ratio less than 0.85, a DW image intensity ratio greater than 1.23, or an FA ratio greater than 1.10 remained viable. No region of interest with an rCBF ratio greater than 0.79 infarcted. CONCLUSIONS: Differences among mean ratios of three regions investigated were greatest for the rCBF ratio. The rCBF ratio may be the most useful parameter in differentiating viable tissue that is likely to infarct without intervention, from tissue that will survive despite hypoperfusion. ADC, DW intensity, FA, and rCBV ratios may provide adjunctive information.

Adult↗
PubMed2002

Somatotopic activation in the human trigeminal pain pathway.

Functional magnetic resonance imaging was used to image pain-associated activity in three levels of the neuraxis: the medullary dorsal horn, thalamus, and primary somatosensory cortex. In nine subjects, noxious thermal stimuli (46 degrees C) were applied to the facial skin at sites within the three divisions of the trigeminal nerve (V1, V2, and V3) and also to the ipsilateral thumb. Anatomical and functional data were acquired to capture activation across the spinothalamocortical pathway in each individual. Significant activation was observed in the ipsilateral spinal trigeminal nucleus within the medulla and lower pons in response to at least one of the three facial stimuli in all applicable data sets. Activation from the three facial stimulation sites exhibited a somatotopic organization along the longitudinal (rostrocaudal) axis of the brain stem that was consistent with the classically described "onion skin" pattern of sensory deficits observed in patients after trigeminal tractotomy. In the thalamus, activation was observed in the contralateral side involving the ventroposteromedial and dorsomedial nuclei after stimulation of the face and in the ventroposterolateral and dorsomedial nuclei after stimulation of the thumb. Activation in the primary somatosensory cortex displayed a laminar sequence that resembled the trigeminal nucleus, with V2 more rostral, V1 caudal, and V3 medial, abutting the region of cortical activation observed for the thumb. These results represent the first simultaneous imaging of pain-associated activation at three levels of the neuraxis in individual subjects. This approach will be useful for exploring central correlates of plasticity in models of experimental and clinical pain.

Adult↗
PubMed2002

Quantification of neurons in Alzheimer and control brains with ex vivo high resolution magic angle spinning proton magnetic resonance spectroscopy and stereology.

Samples from human brains were examined with both stereologic methods for neuronal counting and high resolution magic angle spinning (HRMAS) proton magnetic resonance spectroscopy (1HMRS) for quantification of cellular metabolites. A statistically significant linear correlation between neuronal density and the concentration of N-acetylaspartate (NAA) in the superior temporal sulcus (STS) area was observed. Although NAA has been widely utilized as a neuronal marker in in vivo MRS, an emerging sub-discipline of diagnostic neuroradiology, the experimental proof of the unilateral relationship between NAA and neurons has yet to be confirmed. The observed correlation provides experimental evidence that NAA concentration is proportional to the neuronal density. Metabolite ratios measured from the STS area were compared to those from frontal association cortex for their sensitivities in differentiating Alzheimer disease brains from control brains.

Aged↗
PubMed2002

Projected digital radiologic images for teaching: balance of image quality with data size constraints.

RATIONALE AND OBJECTIVES: The authors performed this study to determine, in the context of a teaching presentation with slides, the information content needed in a digitized radiologic image for it to be equivalent in quality to an analog image. MATERIALS AND METHODS: Eleven sets of radiologic images were obtained from a teaching file collection and digitized. The images were scanned at high resolution and saved as image files. The information content of each image was then halved repeatedly with repeat sampling of the image. This procedure was repeated nine times to yield a total of 10 images with an information content that ranged from very low (32 kB) to high (12 MB). Each of these image files was made into a 35-mm slide by using a digital slide maker. The original radiographs were subsequently made into slides by using conventional photographic methods. Care was taken to make the images identical in every respect except digitization and information content. The slides were shown to radiologists, who filled out questionnaires to rate image quality. RESULTS: Digitized slides that contain an average of 416 kB of data (the equivalent of a 750 x 570-pixel matrix with 8-bit gray levels) were equivalent to analog images for 90% of viewers. At 830 kB (1,060 x 800-pixel matrix with 8-bit gray levels), 100% of viewers found no difference between digitized and analog images. CONCLUSION: Digital images become indistinguishable from analog images if a sufficient amount of information is retained in the digital image. There is a defined relationship between the perception of quality and the information content of a digital image.

Image Processing, Computer-Assisted↗
PubMed2002

CT and conventional and diffusion-weighted MR imaging in acute stroke: study in 691 patients at presentation to the emergency department.

PURPOSE: To compare the diagnostic accuracy of computed tomography (CT) and magnetic resonance (MR) imaging in a consecutive series of patients at presentation to the emergency department with symptoms of acute stroke. MATERIALS AND METHODS: Clinical data and images obtained in 691 consecutive patients with suspected acute stroke were examined. Results of first and second head CT and brain diffusion-weighted (DW) and conventional MR imaging were compared with each other and with the final neurologic discharge diagnosis. RESULTS: Five hundred seventy-three patients underwent CT at presentation, with 42% sensitivity (95% CI: 37%, 46%) and 91% specificity (95% CI: 82%, 96%). A total of 173 patients underwent a second CT examination, with 77% sensitivity (95% CI: 70%, 84%) and 79% specificity (95% CI: 49%, 95%). Of 498 MR images, 411 were DW, with 94% sensitivity (95% CI: 1%, 96%) and 97% specificity (95% CI: 88%, 100%), and 87 were conventional, with 70% sensitivity (95% CI: 58%, 81%) and 94% specificity (95% CI: 70%, 100%). By using DW MR imaging in the early period (<6 hours after presentation to emergency department), a 97% sensitivity (95% CI: 92%, 100%) and a 100% specificity (95% CI: 69%, 100%) were achieved, compared with 58% (29%-84%) and 100% (16%-100%), respectively, with conventional MR imaging, and 40% (35%-45%) and 92% (84%-97%), respectively, with CT. Negative predictive value was higher with DW MR imaging (73%) than with conventional (42%) MR imaging or CT (24%). In studies conducted within 12 hours, DW MR imaging achieved substantially superior accuracy than did CT. After 12 hours, accuracy was equivalent. CONCLUSION: In the diagnosis of stroke in the early period (<12 hours after presentation), DW MR imaging is superior to conventional MR imaging and CT.

Acute Disease↗
PubMed2002

In vivo 3-T MR spectroscopy in the distinction of recurrent glioma versus radiation effects: initial experience.

PURPOSE: To determine if 3-T magnetic resonance (MR) spectroscopy allows accurate distinction of recurrent tumor from radiation effects in patients with gliomas of grade II or higher. MATERIALS AND METHODS: This blinded prospective study included 14 patients who underwent in vivo 3-T MR spectroscopy prior to stereotactic biopsy. All patients received a previous diagnosis of glioma (grade II or higher) and high-dose radiation therapy (>54 Gy). Prior to MR spectroscopy, conventional MR imaging was performed at 1.5 T to identify a gadolinium-enhanced region within the irradiated volume. Diagnosis was assigned by means of histopathologic analysis of the biopsy samples. RESULTS: Sixteen of 17 biopsy locations could be classified as predominantly tumor or predominantly radiation effect on the basis of the ratio of choline at the biopsy site to normal creatine level by using a value greater than 1.3 as the criterion for tumor. The remaining case, classified as recurrent tumor on the basis of MR spectroscopy results, was diagnosed as predominantly radiation effect on the basis of histopathologic findings. Disease in this patient progressed to biopsy-proven recurrence within 3 months. Overall, the ratio of choline at the biopsy site to normal creatine level was significantly elevated (unpaired two-tailed Student t test, P <.002) in those biopsy samples composed predominantly of tumor (n = 9) compared with those containing predominantly radiation effects (n = 8). The ratio was not significantly different between the two histopathologic groups. CONCLUSION: In vivo 3-T MR spectroscopy has sufficient spatial resolution and chemical specificity to allow distinction of recurrent tumor from radiation effects in patients with treated gliomas.

Adult↗
PubMed2002

Dynamic single-section CT demonstrates reduced cerebral blood flow in acute intracerebral hemorrhage.

Optimum blood pressure (BP) management in acute intracerebral hemorrhage (ICH) remains controversial. BP reduction may limit hematoma expansion, but may also exacerbate ischemia. Reduced regional cerebral blood flow (rCBF) has been reported in ICH. Its extent and precise pattern, however, remain uncertain. Dynamic single-section CT perfusion (CTP) is rapid, easily performed and offers superior spatial resolution to PET, SPECT and MRI. It may be the most applicable method for assessing the effects of BP management on rCBF in ICH. We sought to assess whether CTP can identify rCBF abnormalities in acute ICH in 5 patients with ICH who underwent CTP within 24 h of symptom onset. rCBF was measured in serially expanded 2-mm rings around the hematoma and compared with rCBF in the uninvolved hemisphere. Mean time to CTP was 9 h (range 3-23). Mean ICH volume was 25 ml (range 9-64). Perihematoma perfusion was reduced in all patients compared with contralateral hemisphere rCBF. rCBF reduction was most pronounced immediately adjacent to the hematoma (p < 0.05 at 2 mm, p = 0.084 at 4 mm, p > 0.2 at 6 and 8 mm). Perihematoma rCBF increased as a function of the distance from hematoma perimeter. Rate of rCBF increase over distance correlated with time from onset (p = 0.006). We conclude that CTP identifies a rim of reduced rCBF in ICH. A gradient of hypoperfusion appears to extend at least 4 mm beyond the hematoma edge and may be time dependent. Whether reduced CBF is associated with perihematoma ischemia requires additional study.

Aged↗
PubMed2002

'Footprints' of transient ischemic attacks: a diffusion-weighted MRI study.

OBJECTIVE: Diffusion-weighted imaging (DWI) conveys temporal as well as anatomic information about brain infarction, and is therefore well suited to identify ischemic injury that has occurred simultaneously, or closely linked in time, with a transient ischemic attack (TIA). We aimed to determine the proportion and clinical characteristics of patients with TIA who harbor infarction(s) on DWI. METHODS: Using T(2)-weighted imaging (T(2)-WI), fast fluid attenuated inversion recovery (FLAIR), and DWI, we studied 57 consecutive patients presenting with acute focal neurologic symptoms lasting less than 24 h. RESULTS: A hyperintense DWI lesion was identified in a vascular territory appropriate to the symptoms in 27 patients (47%). Lesions judged to be clinically appropriate on T(2)-WI and FLAIR overlapped with a DWI lesion in 41 and 48% of patients, respectively. Independent predictors of infarction on DWI were previous nonstereotypic TIAs, presentation with motor symptoms, and identified stroke mechanism. CONCLUSION: DWI establishes that recent infarction occurs in almost half of patients with the clinical syndrome of TIA and this subgroup is more likely to harbor an underlying cardiac or cerebrovascular abnormality.

Aged↗
PubMed2002

Magnetic resonance perfusion-weighted imaging of acute cerebral infarction: effect of the calculation methods and underlying vasculopathy.

BACKGROUND AND PURPOSE: Various calculation methods are available to estimate the transit-time on MR perfusion-weighted imaging (PWI). Each method may affect the results of PWI. Steno-occlusive disease in the parent vessels is another factor that may affect the results of the PWI. The purpose of this study was to elucidate the effect of the calculation methods and underlying vasculopathy on PWI. METHODS: From a pool of 113 patients who had undergone PWI during the study period, a total of 12 patients with nonlacunar ischemic strokes who were scanned within 24 hours after onset of symptom were selected for the study. The patient population consisted of 6 patients who had extracranial internal carotid artery stenosis (>70%) and 6 individuals without stenosis. Seven different postprocessing methods were evaluated: first moment, ratio of area to peak, time to peak (TTP), relative TTP, arrival time, full-width at half-maximum, and deconvolution methods. Follow-up MR or CT images were used to determine the areas that evolved into infarcts, which served as the gold standard. Sensitivity and specificity of each transit time technique were calculated. RESULTS: Calculation methods with high sensitivity were the first moment (sensitivity, 74%), TTP (sensitivity, 77%), and deconvolution methods (sensitivity, 81% to 94%). Between the 2 groups with and without internal carotid artery stenosis, the specificity of most of the techniques was lower in the internal carotid artery stenosis group. The first moment and deconvolution methods maintained relatively high specificity even in the stenosis group. CONCLUSIONS: The calculation technique and presence of underlying vasculopathy have a direct impact on the results of PWI. The methods with high sensitivity even in the presence of steno-occlusive disease were the first moment and deconvolution methods with arterial input function derived from the peri-infarct arteries; the deconvolution method was the superior choice because of higher lesion conspicuity.

Acute Disease↗
PubMed2002

CT angiography with whole brain perfused blood volume imaging: added clinical value in the assessment of acute stroke.

BACKGROUND AND PURPOSE: In CT angiographic and perfusion imaging (CTA/CTP), rapid CT scanning is performed during the brief steady state administration of a contrast bolus, creating both vascular phase images of the major intracranial vessels and perfused blood volume-weighted parenchymal phase images of the entire brain. We assessed the added clinical value of the data provided by CTA/CTP over that of clinical examination and noncontrast CT (NCCT) alone. METHODS: NCCT and CTA/CTP imaging was performed in 40 patients presenting with an acute stroke. Short clinical vignettes were retrospectively prepared. After concurrent review of the vignettes and NCCT, a stroke neurologist rated infarct location, vascular territory, vessel(s) occluded, and Trial of Org 10172 in Acute Stroke Treatment (TOAST) and Oxfordshire Community Stroke Project classifications. The ratings were repeated after serial review of each of the CTA/CTP components: (1) axial CTA source images; (2) CTP whole brain blood volume-weighted source images; and (3) maximum-intensity projection 3-dimensional reformatted images. The sequential ratings for each case were compared with the final discharge assessment. RESULTS: Compared with the initial review after NCCT, CTA/CTP improved the overall accuracy of infarct localization (P<0.001), vascular territory determination (P=0.003), vessel occlusion identification (P<0.001), TOAST classification (P=0.039), and Oxfordshire Community Stroke Project classification (P<0.001) by 40%, 28%, 38%, 18%, and 32%, respectively. CONCLUSIONS: Admission CTA/CTP imaging significantly improves accuracy, over that of initial clinical assessment and NCCT imaging alone, in the determination of infarct localization, site of vascular occlusion, and Oxfordshire classification in acute stroke patients.

Aged↗
PubMed2002

Influence of availability of clinical history on detection of early stroke using unenhanced CT and diffusion-weighted MR imaging.

OBJECTIVE: The radiologic diagnosis of stroke requires accurate detection and appropriate interpretation of relevant imaging findings; both detection and interpretation may be influenced by knowledge of the patient's presentation. In our study, we evaluated the effect of the availability of clinical history on the sensitivity for stroke detection using unenhanced CT and diffusion-weighted MR imaging. MATERIALS AND METHODS: The records of 733 consecutive patients with a clinically based admission diagnosis of early stroke were reviewed. Among the criteria for inclusion in our study were the availability of an unenhanced CT scan (561 cases) or diffusion-weighted MR imaging examination (409 cases) obtained at admission and a discharge diagnosis indicating whether a patient had actually had a stroke. The radiology requisition forms, available at the time of image interpretation, were classified as either indicating or not indicating a clinical suspicion of early stroke. Sensitivity, specificity, and accuracy of stroke detection were computed, stratified by the presence or absence of an available history indicating suspicion of stroke. Results were compared using the Fisher's exact two-tailed test. RESULTS: Unenhanced CT sensitivity was 52% (specificity, 95%) for the suspicion-of-stroke group and 38% (specificity, 89%) for the no-suspicion-of-stroke group (p = 0.008). Diffusion-weighted MR imaging sensitivity was 95% (specificity, 94%) for the suspicion-of-stroke group and 94% (specificity, 98%) for the no-suspicion-of-stroke group (p = 0.822). CONCLUSION: Availability of a clinical history indicating that early stroke is suspected significantly improves the sensitivity for detecting strokes on unenhanced CT without reducing specificity. In contradistinction, the availability of such a history did not significantly improve the sensitivity for detecting stroke using diffusion-weighted MR imaging. Whenever possible, relevant clinical history should be made available to physicians interpreting emergency CT scans of the head.

Aged↗
PubMed2002

Biochemical characterization of pediatric brain tumors by using in vivo and ex vivo magnetic resonance spectroscopy.

OBJECT: Magnetic resonance (MR) spectroscopy provides biochemical information about tumors. The authors sought to determine the relationship between in vivo and ex vivo biochemical characterization of pediatric brain tumors by using MR spectroscopy. Their hypothesis was that ex vivo MR spectroscopy provides a link between in vivo MR spectroscopy and neuropathological analysis. METHODS: In vivo proton MR spectroscopy was performed before surgery in 11 patients with neuroepithelial tumors. During resection, a total of 40 tumor biopsy samples were obtained from within the volume of interest identified on in vivo MR spectroscopy and were frozen immediately in liquid nitrogen. High-Resolution Magic Angle Spinning (HRMAS) was used to perform ex vivo MR spectroscopy in these 40 tumor biopsy samples. Neuropathological analysis was performed using the same biopsy samples, and the tumors were classified as ependymoma, choroid plexus carcinoma, pineoblastoma (one each), and pilocytic astrocytoma, medullobastoma, low-grade glioma, and glioblastoma multiforme (two each). Ex vivo HRMAS MR spectroscopy improved line widths and line shapes in the spectra, compared with in vivo MR spectroscopy. Choline (Cho) detected in vivo corresponded to three different peaks ex vivo (glycerophosphocholine, phosphocholine [PCho], and Cho). Metabolite ratios from in vivo spectra correlated with ratios from ex vivo spectra (Pearson correlation coefficient range r = 0.72-0.91; p < or = 0.01). Metabolite ratios from ex vivo spectra, such as PCho/ total creatine (tCr) and lipid/tCr, correlated with the percentage of cancerous tissue and percentage of tumor necrosis, respectively (r = 0.84; p < 0.001). CONCLUSIONS: Agreement between in vivo and ex vivo MR spectroscopy indicates that ex vivo HRMAS MR spectroscopy can improve resolution of this modality and provide a link between in vivo MR spectroscopy and neuropathological analysis.

Adolescent↗
PubMedDate not supplied

Normal variation of vertebral artery on CT angiography and its implications for diagnosis of acquired pathology.

PURPOSE: CT angiography (CTA) is rapidly becoming a popular tool for the evaluation of cerebrovascular diseases. Noninvasive diagnosis of vertebral artery pathology using CTA relies in part on diminished vertebral artery size or eccentric position relative to the transverse foramen. However, normal variation of the vertebral artery on CT has not been systematically described. METHOD: Patients younger than 40 years who underwent CTA for reasons other than evaluation of vertebral artery disease were studied. Area measurements of the vertebral artery and the transverse foramen were performed by three radiologists. Variance component analysis was performed. RESULTS: There is marked variation in the size of the vertebral artery relative to the transverse foramen, with the vertebral artery occupying 8-85% of the foramen. In many patients, marked asymmetry in relative vertebral artery size and position was observed. This asymmetry would often vary markedly from level to level within the same patient. CONCLUSION: Vertebral artery size and position in the transverse foramina vary markedly in normal young subjects. These normal variations must be considered when evaluating vertebral artery pathology on CT angiograms.

Adult↗
PubMedDate not supplied

Diffusion-weighted imaging for the evaluation of diffuse axonal injury in closed head injury.

PURPOSE: The purpose of this work was to compare diffusion-weighted imaging (DWI) with conventional MRI in the detection of shearing injuries in acute closed head injuries. METHOD: Twenty-five patients (19 male, 6 female) were examined within 48 h of trauma. Conventional MRI included T2-weighted fast spin echo, fluid-attenuated inversion recovery (FLAIR), and T2*-weighted gradient echo sequences. Full tensor DWI with calculation of apparent diffusion coefficient (ADC) maps was also performed. Lesions were identified and compared on all sequences. RESULTS: Four hundred twenty-seven lesions were counted by the combined use of all sequences. DWI identified 70 lesions not seen on conventional MRI. DWI identified 310 shearing injuries, followed by T2/FLAIR (n = 248) and T2* (n = 202). The majority of DWI-positive lesions showed decreased diffusion (65%). CONCLUSION: DWI is valuable in closed head injury because it identifies additional shearing injuries not visible on T2/FLAIR or T2* sequences. Furthermore, DWI/ADC maps differentiate between lesions with decreased or increased diffusion. DWI is less sensitive than T2* imaging for detecting hemorrhagic lesions.

Adolescent↗
PubMedDate not supplied

US of neurovascular occlusive disease: interpretive pearls and pitfalls.

Ultrasonography (US) of the head and neck is a convenient but operator-dependent screening tool for detection and diagnosis of neurovascular occlusive disease. In US examination of the extracranial carotid arteries, stenosis is most commonly graded according to the peak systolic Doppler velocity in the region of maximal luminal narrowing rather than according to the percentage of atheromatous plaque occupying the lumen. However, the peak systolic velocity is not always reliable in estimation of the degree of stenosis. General diagnostic pitfalls include technical difficulties with scanning, failure to review the spectral waveform patterns, the presence of additional stenotic lesions, and anatomic variants. Specific examples of pitfalls include tandem lesions, differentiation of pseudo-occlusion from true total occlusion, pseudonormalization of velocities in cases of very severe stenosis, lesions of the carotid artery origin or aortic valve, progression of subclavian steal, underestimation of severe stenosis due to heavily calcified plaque, a persistent trigeminal artery, and contralateral carotid artery stenosis. Although conventional angiography remains the standard of reference for assessment of carotid artery disease, recognition of these common sources of error in US can improve the accuracy of this noninvasive test in diagnosis of carotid artery occlusion.

Arterial Occlusive Diseases↗
PubMedDate not supplied

Iron-induced susceptibility effect at the globus pallidus causes underestimation of flow and volume on dynamic susceptibility contrast-enhanced MR perfusion images.

BACKGROUND AND PURPOSE: Age-related iron accumulation in extrapyramidal nuclei causes T2 shortening, which may result in decreased signal intensity in these areas on MR images. Because the dynamic susceptibility contrast-enhanced technique uses heavily T2*- or T2-weighted images, the iron-induced susceptibility may have direct impact on perfusion imaging. The purpose of this study was to assess the effect of iron-induced susceptibility on the calculated perfusion parameters. The difference of this effect between gradient-echo and spin-echo sequences was also assessed. METHODS: Dynamic susceptibility contrast-enhanced MR perfusion imaging data of 12 patients were used for this study. Perfusion images were obtained using a single shot spin-echo echo-planar imaging sequence in seven patients and a gradient-echo echo-planar imaging sequence in five patients. Region of interest measurements of relative cerebral blood flow, relative cerebral blood volume, and mean transit time were obtained at various parts of the gray matter, including the globus pallidus, putamen, caudate nucleus, thalamus, and cerebral cortex of temporal, frontal, and occipital lobes. The baseline signal intensity on the source images and the magnitude of signal change (DeltaR2* or DeltaR2) were also assessed. RESULTS: The globus pallidus had statistically significantly lower values of relative cerebral blood flow, relative cerebral blood volume, baseline signal intensity, and magnitude of signal change compared with other parts of the gray matter for both gradient-echo and spin-echo sequences (P <.05). Underestimations of these values were more prominent for the gradient-echo than for the spin-echo sequence. Little variance in the measured mean transit time was noted. CONCLUSION: Iron-induced susceptibility effect may lead to underestimation of relative cerebral blood flow and relative cerebral blood volume in the basal ganglia.

Aged↗
PubMedDate not supplied

Predicting cerebral ischemic infarct volume with diffusion and perfusion MR imaging.

BACKGROUND AND PURPOSE: Diffusion and perfusion MR imaging have proved useful in the assessment of acute stroke. We evaluated the utility of these techniques in detecting acute ischemic infarction and in predicting final infarct size. METHODS: Diffusion and hemodynamic images were obtained in 134 patients within a mean of 12.3 hours of onset of acute ischemic stroke symptoms. We retrospectively reviewed patient radiology reports to determine the presence or absence of lesion identification on initial diffusion- (DW) and perfusion-weighted (PW) images. Radiologists were not blinded to the initial clinical assessment. For determination of sensitivity and specificity, the final discharge diagnosis was used as the criterion standard. Neurologists were not blinded to the DW or PW imaging findings. In 81 patients, acute lesions were compared with final infarct volumes. RESULTS: Sensitivities of DW imaging and cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) perfusion parameters were 94%, 74%, 84%, and 84%, respectively. Specificities of DW imaging, CBV, CBF, and MTT were 96%, 100%, 96%, and 96%, respectively. Results were similar in 93 patients imaged within 12 hours. In 81 patients with follow-up, regression analysis yielded r(2) = 0.9, slope = 1.24 for DW imaging; r(2) = 0.84, slope = 1.22 for CBV; r(2) = 0.35, slope = 0.44 for CBF; and r(2) = 0.22, slope = 0.32 for MTT, versus follow-up volume. A DW-CBV mismatch predicted additional lesion growth, whereas DW-CBF and DW-MTT mismatches did not. Results were similar in 60 patients imaged within 12 hours. CONCLUSION: Diffusion and hemodynamic images are sensitive and specific for detecting acute infarction. DW imaging and CBV best predict final infarct volume. DW-CBV mismatch predicts lesion growth into the CBV abnormality. CBF and MTT help identify additional tissue with altered perfusion but have lower correlation with final volume.

Adult↗