Effects of non-linear flow and spatial orientation on technetium-99m hexamethylpropylene amine oxime single-photon emission tomography

Neurobiological status at initial presentation predicts neuropsychological functioning in early onset anorexia nervosa at four-year follow up

This study explores whether neurobiological status (indexed by regional cerebral blood flow) at initial presentation predicts neuropsychological status at four-year follow up in a sample of children with early onset anorexia nervosa. Neuropsychological assessment was conducted on 15 females four years after their initial treatment, and matched controls. At follow up there were significant differences between subgroups (based on neurobiological status at initial presentation) and matched controls in long-term visual memory and cognitive inhibition. This study offers preliminary evidence that neurobiological abnormalities at initial presentation predict neuropsychological status at follow up, suggesting a distinct neurodevelopmental subtype of early onset anorexia nervosa.

A survey of medical image registration

The purpose of this paper is to present a survey of recent (published in 1993 or later) publications concerning medical image registration techniques. These publications will be classified according to a model based on nine salient criteria, the main dichotomy of which is extrinsic versus intrinsic methods. The statistics of the classification show definite trends in the evolving registration techniques, which will be discussed. At this moment, the bulk of interesting intrinsic methods is based on either segmented points or surfaces, or on techniques endeavouring to use the full information content of the images involved.

Brain single-photon emission CT with HMPAO and safety of thrombolytic therapy in acute ischemic stroke. Proceedings of the meeting of the SPECT Safe Thrombolysis Study Collaborators and the members of the Brain Imaging Council of the Society of Nuclear Medicine

BACKGROUND

To reliably identify patients at risk for symptomatic hemorrhagic transformation (SHT), future trials of thrombolysis for acute ischemic stroke might use a vascular imaging protocol applicable to a multicenter setting. The goal of this commentary is to address the safety of intravenous thrombolysis with the recombinant tissue plasminogen activator (rTPA) and potential solutions offered by single-photon emission CT (SPECT) as a noninvasive brain perfusion imaging modality.

SUMMARY OF REVIEW

Even if patients with severe stroke, extensive ischemic changes on CT scan, advanced age, and high blood pressure are excluded from thrombolytic therapy, this cannot completely guarantee the safety of using rTPA. Brain SPECT scanning with hexamethylpropyleneamine-oxime (HMPAO) may help to screen out patients at risk if performed in addition to clinical and CT tests. The knowledge of pretreatment severity, extent, and location of ischemia might identify good versus poor responders to rTPA therapy. HMPAO-SPECT is widely available and feasible to perform without delaying rTPA therapy. Rigorous quality control and use of reproducible visual and semiquantitative methods of interpreting SPECT are necessary for implementation of SPECT technology in multicenter clinical trials.

CONCLUSIONS

The major obstacle to general acceptance of thrombolytic therapies and rTPA in particular is the fear of symptomatic hemorrhagic transformation, and because HMPAO-SPECT might reliably identify patients at high risk of symptomatic hemorrhagic transformation, the clinical value of HMPAO-SPECT in patient selection for thrombolysis during the first hours of acute ischemic stroke should be determined through a prospective clinical trial.

Predictors of hemorrhagic transformation occurring spontaneously and on anticoagulants in patients with acute ischemic stroke

BACKGROUND AND PURPOSE

Hemorrhagic transformation (HT) is a common evolution of large-volume ischemic lesions, particularly of cardioembolic origin. We used transcranial Doppler ultrasound (TCD), single-photon emission computed tomography (SPECT) with 99mTc-hexamethylpropyleneamine oxime (HMPAO), and the Toronto Embolic Scale (TES) to decide (1) whether TCD, HMPAO-SPECT, and TES can improve on clinical and CT tests to predict spontaneous HT and (2) whether SPECT can help to predict the outcome of symptomatic HT.

METHODS

Prognostic criteria included Canadian Neurological Scale (CNS) scores < or = 50 on admission, early ischemic changes on CT, M1 middle cerebral artery occlusion on TCD, the focal absence of brain perfusion on SPECT, and a high risk of cardiogenic embolism on TES.

RESULTS

In part 1, 85 consecutive patients admitted within the first 6 hours were studied. No patient received thrombolysis. HT was found in 11 patients (13%) at 3 to 5 days. Admission CNS and CT were not predictive of HT: odds ratios (95% confidence intervals) were 0.49 (0.18 to 1.23) (P = .1) and 0.88 (0.23 to 3.45) (P = .8), respectively, TCD, SPECT, and TES were significant predictors of HT (P < .05), as follows: TCD, 8.67 (1.42 to 70.59); SPECT, 17.40 (2.69 to 170.89); and TES, 18.13 (2.6 to 406.86). In part 2, 490 consecutive patients were studied and 21 (4%) had symptomatic HT, of which 12 had focal hypoperfusion on SPECT at 4 days after stroke onset and 9 had focal hyperperfusion. Patients with hypoperfusion had larger CT lesions (115 +/- 97 versus 42 +/- 29 cm3; P = .04) and poorer outcome at 2 weeks (CNS, 38 +/- 45 versus 96 +/- 10; P = .001), including death (6/12 versus 0/9; P = .04); compared with those with hyperperfusion on SPECT.

CONCLUSIONS

High risk of cardioembolism, M1 middle cerebral artery occlusion, and absence of collateral flow evaluated by TES, TCD, and SPECT help to identify patients at risk for spontaneous HT. Although TES was the most powerful predictor of HT, SPECT is the best single adjunct to the triage of clinical and CT tests. Patients with brain hyperperfusion on HMPAO-SPECT after symptomatic HT have better chances for recovery.

Feasibility of SPECT for studies of brain perfusion during cardiopulmonary bypass

Single-photon emission computed tomography (SPECT) and transcranial Doppler (TCD) ultrasonography were used to assess brain perfusion during cardiopulmonary bypass. Intravenous injections of technetium 99 m-hexamethylpropyleneamineoxime (99mTc-HMPAO) were administered before surgery and intraoperatively after the first 2 minutes in the first patient and at the end (42 minutes) of cardiopulmonary bypass in the second patient. The total middle cerebral artery territory counts were calculated using the region-of-interest method and compared to cerebellar regional counts. 99mTc-HMPAO uptake on SPECT scans was increased at the beginning and at the end of cardiopulmonary bypass, compared to baseline preoperative values (11-17%) in the presence of multiple microembolic signals on TCD (n1 = 35 and n2 = 42 for unilateral middle cerebral artery monitoring). These results indicate the feasibility of using HMPAO-SPECT to study brain perfusion changes during cardiac surgery. A combination of SPECT and TCD ultrasonography may be used to study the impact of microembolism during cardiac surgery with cardiopulmonary bypass.

Simple visual analysis of brain perfusion on HMPAO SPECT predicts early outcome in acute stroke

BACKGROUND AND PURPOSE

Single-photon emission computed tomography (SPECT) is used in patients with acute stroke but as yet is of controversial value. We investigated an association of brain perfusion changes in stroke patients with stroke severity, volume of brain damage, and recovery.

METHODS

Consecutive patients with hemispheric stroke were studied prospectively with serial neurological examinations using the Canadian Neurological Scale (CNS), CT. and 99mTc-hexamethylpropyleneamine oxime (HMPAO) SPECT. Visual SPECT patterns of brain perfusion (normal, high, mixed, low, and absent) were correlated with the severity of stroke, lesion volume, and short-term outcome.

RESULTS

SPECT studies were performed in a total of 458 consecutive acute stroke patients within 2 weeks after the onset (mean time, 5 days; range, 1 to 12 days). SPECT perfusion patterns correlated with stroke severity (CNS score) during the first 2 weeks (P < .001). Focal absence of brain perfusion on SPECT was associated with the largest volume of brain damage: 104 +/- 84 mL (P < .0001). SPECT perfusion patterns predicted the shortterm outcome: 97% of patients with normal and increased HMPAO uptake made good recovery, 52% of those with decreased perfusion had moderate stroke, and 62% of patients with absent patterns fared badly. In a multiple logistic regression model, admission CNS scores had the strongest predictive value (P = .0001). SPECT had its own prognostic value independent of clinical judgment (P = .03). SPECT statistically improved predictive power of the CNS score (+1% receiver operating characteristic curve area, [X2]2 = 20, P < .001) because of distinction between focal decrease or absence of brain perfusion in patients studied within the first 72 hours of stroke.

CONCLUSIONS

Visual brain perfusion patterns correlate with the extent, severity, and short-term outcome of hemispheric stroke. HMPAO SPECT may improve the prognostic value of clinical examination if performed during the first 72 hours of stroke.

Clinical significance of increased uptake of HMPAO on brain SPECT scans in acute stroke

Single-photon emission computed tomography (SPECT) with 99mtechnetium-hexamethylpropylamineoxime (HMPAO) noninvasively shows brain perfusion in patients after acute stroke. However, the clinical significance of the increased HMPAO uptake remains unclear. In this study, consecutive patients with hemispheric hemorrhagic and ischemic stroke admitted to the hospital were evaluated prospectively. The increased uptake of HMPAO was determined by visual analysis of SPECT images. The pathogenic mechanism of ischemic stroke was determined using the clinical and computed tomography (CT) criteria including the Toronto Embolic Scale. Of the 500 consecutive patients with acute hemispheric stroke, SPECT was performed in 458 at a mean time 5 +/- 7 days after the onset of symptoms. A strong association was found between SPECT perfusion patterns and pathogenic subtypes of stroke (p < 0.0001). Thus, in 95% of patients with intracerebral hemorrhage the focal absence of perfusion was found, and 26% of lacunar infarctions presented with a normal SPECT appearance. The mean volume of lacunar lesions that did not produce significant abnormalities on SPECT was 2.5 +/- 1.2 ml. Increased HMPAO uptake was associated with a cardioembolic mechanism of stroke: High and mixed perfusion patterns were present subacutely in 29% of patients with cardioembolic stroke, compared to 15% of patients with other types of ischemic stroke (p < or = 0.0006). The increased uptake of HMPAO on SPECT as determined by visual analysis is associated with a cardioembolic mechanism of cerebral ischemia, which could be explained by glutathione-mediated trapping of the tracer during reperfusion and later in newly developed granulation tissue. HMPAO-SPECT may help in early management decisions since it indicates stroke pathogenesis and evolution.