Biomedical subjects

Pamela W Schaefer

Publications and source records attributed to Pamela W Schaefer.

24 records · Page 2Linked to original sources

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

'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↗

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

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↗

PubMedDate not supplied

Characterization and evolution of diffusion MR imaging abnormalities in stroke patients undergoing intra-arterial thrombolysis.

BACKGROUND AND PURPOSE: Lesions revealed by pretreatment diffusion-weighted imaging (DWI) may not progress to infarction, and apparent diffusion coefficient (ADC) or DWI thresholds for tissue viability may exist. We evaluated the evolution of abnormal DWI findings in patients with acute stroke who underwent thrombolysis. METHODS: Sixteen patients with acute occlusion of the anterior circulation underwent DWI followed by intra-arterial thrombolysis; follow-up CT or MR imaging was performed after reperfusion therapy. Lesion volumes were measured on all images. In three patients with abnormal DWI findings that appeared normal at follow-up, ADC values, ADC ratios, and DWI ratios were obtained on a section-by-section basis in the DWI-hyperintense regions that were either abnormal or normal at follow-up. RESULTS: In three patients, part of the DWI-hyperintense tissue appeared normal and part appeared abnormal at follow-up imaging. In one of these patients, the lesion decreased by -35.6%. In the other two, lesion growth appeared in regions that appeared normal at initial DWI: in one, the overall change in size was -2.4%, and in the other, the lesion increased by 89.8%. Respective mean changes at follow-up in normal-appearing and abnormal-appearing regions were: ADC, 731.7 x 10(-6) mm(2)/s and 650.4 x 10(-6) mm (2)/s; ADC ratio, 0.92 and 0.78; and DWI ratio, 1.16 and 1.32 (P <.001 for all measures). CONCLUSION: In patients with acute stroke who undergo intra-arterial thrombolysis, most abnormal, pretreatment DWI findings indicate eventual infarction. In 19% of the patients described herein, DWI-hyperintense regions appeared normal at follow-up. ADC values, ADC ratios, and DWI ratios may be useful in identifying the portion of abnormal tissue that is potentially salvageable after reperfusion therapy.

Acute Disease↗

PubMedDate not supplied

Parenchymal abnormalities associated with cerebral venous sinus thrombosis: assessment with diffusion-weighted MR imaging.

BACKGROUND AND PURPOSE: The common entity cerebral venous sinus thrombosis is associated with the poorly characterized imaging finding of parenchymal abnormalities; diffusion-weighted imaging has offered some insight into these manifestations. We assessed the relationship between the diffusion constant from apparent diffusion coefficient (ADC) maps in patients with cerebral venous thrombosis (CVT) with follow-up imaging findings and clinical outcome. METHODS: We evaluated the medical records and T2-weighted MR images of 13 patients with CVT complicated by intraparenchymal abnormality. Diffusion-weighted (DW) images and ADC maps were evaluated for increased, decreased, or unchanged signal intensity and were compared with signal intensity of contralateral, normal-appearing brain. In addition, ADCs were obtained in nine pixel regions of interest in abnormal regions in eight of the 13 patients. RESULTS: Eight patients had superficial CVT, and five had superficial and deep CVT. CVT of deep veins was associated with deep gray nucleus and deep white matter abnormalities, whereas superficial CVT was associated with cortical and subcortical abnormalities. Twenty-four nonhemorrhagic lesions were identified in 10 of 13 patients on the basis of follow-up imaging findings. Four patients without seizures had lesions with decreased diffusion that appeared hyperintense on follow-up T2-weighted images, three patients with seizures had lesions with decreased diffusion that resolved, and seven patients had lesions with increased diffusion that resolved. Three of 10 patients had more than one lesion type. No difference was noted in mean ADCs for lesions with decreased diffusion that resolved compared with lesions with decreased diffusion that persisted. CONCLUSION: DW imaging in these patients disclosed three lesion types: lesions with elevated diffusion that resolved, consistent with vasogenic edema; lesions with low diffusion that persisted, consistent with cytotoxic edema in patients without seizure activity; and lesions with low diffusion that resolved in patients with seizure activity. This information may be important in prospectively determining severity of irreversible injury and in patient treatment.

Adolescent↗