Cerebral perfusion computerized tomography: influence of reference vessels, regions of interest and interobserver variability

When a Slice Is Not Enough! Comparison of Whole-Brain versus Standard Limited-Slice Perfusion Computed Tomography in Patients with Severe Traumatic Brain Injury

Introduction: Cerebral perfusion computed tomography (PCT) provides crucial information in acute stroke and has an increasing role in traumatic brain injury (TBI) management. Most studies on TBI patients utilize 64-slice scanners, which are limited to four brain slices (limited-brain PCT, LBPCT). Newer 320-slice scanners depict the whole brain perfusion status (WBPCT). We aimed to identify the additional information gained with WBPCT when compared to LBPCT. Patients and methods: Forty-nine patients with severe TBI were investigated within 48 h from admission with WBPCT. Findings from LBPCT were compared with findings from WBPCT. Results: A perfusion abnormality was identified in 39 (80%) and 37 (76%) patients by WBPCT and LBPCT, respectively (p = 0.8). There were 90 and 68 perfusion abnormalities identified by WBPCT and LBPCT, respectively (p < 0.001). In the 39 patients with a perfusion abnormality detected by WBPCT, 15 (38%) had further perfusion abnormalities outside the LBPCT area of coverage. Thirty-six (92%) patients had a larger perfusion abnormality upon WBPCT compared with LBPCT. Additional information gained showed some statistically significant correlation with clinical outcome. Conclusions: In severe TBI patients, WBPCT provides extra information compared to LBPC. The limitations of LBPCT should be considered when evaluating studies reporting on PCT findings and their association with outcomes.

Diagnostic value of minimum apparent diffusion coefficient values in prediction of neuroepithelial tumor grading

PURPOSE

To retrospectively evaluate the diagnostic accuracy of diffusion weighted image (DWI) in the prediction of neuroepithelial tumors grading, and to appraise the apparent diffusion coefficient (ADC) value of neuroepithelial tumors with histologic findings as a reference standard.

MATERIALS AND METHODS

ADC values in 110 patients with pathologically proved neuroepithelial tumors, including 77 astrocytic tumors, 16 oligodendroglial tumors, 11 oligoastrocytic tumors, and 6 ependymal tumors, were investigated retrospectively. The minimum ADC (MinADC) value of tumors was measured postoperatively on ADC maps, avoiding cystic, necrotic, or hemorrhagic components. The Ki-67 Labeling Index (Ki-67 LI) was determined by immunohistochemistry. The patients were classified into low (WHO II) and high (WHO III or IV) grade groups. Correlation analysis, Student t-test, Welch test, receiver operating characteristic (ROC) analysis, and analysis of variance were used for statistical evaluation.

RESULTS

There was a negative correlation between MinADC value and Ki-67 LI (P < 0.001). The mean MinADC value (1.057 x 10(-3) mm(2)/s) of low grade group was higher than that (0.773 x 10(-3) mm(2)/s) of high grade group. The area under the ROC curve (AUC) was 0.809, and the cutoff MinADC value of 0.900 x 10(-3) mm(2)/s for the differentiation between high and low grade neuroepithelial tumors provided the best combination of sensitivity (85.4%) and specificity (71.0%).

CONCLUSION

MinADC value may be a simple and effective optional tool for the prediction of neuroepithelial tumor grading.

Comparison of 4 cm Z-axis and 16 cm Z-axis multidetector CT perfusion

OBJECTIVE

The aim of the study was to compare 4 cm with 16 cm Z-axis coverage in the assessment of brain CT perfusion (CTP) using. 320 slice multidetector CT METHODS: A retrospective non-randomised review of CTP performed on MD320 CT between September 2008 and January 2009 was undertaken. Two experienced readers reviewed the studies along with the 4 cm and 16 cm Z-axis CTP image data set. The outcome parameters assessed were the extent of the original finding, any additional findings and a change of diagnosis.

RESULTS

14 out of 27 patients were found to have abnormal CTP (mean age 58.1 years, 9 male). The 16 cm Z-axis increased the accuracy of the infarct core in 78% and ischaemic penumbra quantification in 100% of the cases. It also diagnosed additional infarcts in the same vascular territory in 28% of cases and in a different vascular territory in 14%.

CONCLUSIONS

The increased field of view with MD320 better defines the true extent of the infarct core and ischaemic penumbra. It also identified other areas of infarction that were not identified on the 4 cm Z-axis.

Tracer delay-insensitive algorithm can improve reliability of CT perfusion imaging for cerebrovascular steno-occlusive disease: comparison with quantitative single-photon emission CT

BACKGROUND AND PURPOSE

Reliability of CT perfusion (CTP) algorithms has not been fully validated. We investigated whether the cerebral blood flow (CBF) values obtained by using a dynamic CTP technique with a tracer delay-insensitive deconvolution algorithm are more accurate than those obtained by using CTP with delay-sensitive algorithms in unilateral cerebrovascular steno-occlusive disease, when compared with those generated by quantitative single-photon emission CT (SPECT).

MATERIALS AND METHODS

Using CTP and iodine-123-N-isopropyl-p-iodoamphetamine SPECT with an autoradiographic quantification technique, we examined 20 patients with suggested hemodynamic ischemia due to stenosis or occlusion of the unilateral internal carotid or middle cerebral artery. The algorithms used for CTP included delay-insensitive block-circulant singular value decomposition (SVD) (bSVD) and delay-sensitive standard SVD (sSVD) and box-modulation transfer function (bMTF).

RESULTS

Absolute CBF values obtained by using CTP with bSVD were significantly lower than those obtained with SPECT, but the ratios to the nonaffected side were significantly correlated to the quantitative SPECT values with significant agreements, particularly when the arterial input function was obtained from the unaffected side. Contrastingly, CBF ratios with sSVD and bMTF were significantly underestimated, and no significant agreement was determined between CTP with sSVD or bMTF and SPECT, though there were substantial correlations between them in some parameters.

CONCLUSIONS

With the CTP technique, the insensitivity of the deconvolution algorithm to the tracer-delay effect appears to be essential for estimating semiquantitative CBF values in patients with unilateral steno-occlusive lesions.

Perfusion-CT for early assessment of traumatic cerebral contusions

INTRODUCTION

To investigate the value of perfusion-CT (PCT) for assessment of traumatic cerebral contusions (TCC) and to compare the abilities of early noncontrast CT and PCT modalities to evaluate tissue viability.

METHODS

PCT studies performed in 30 patients suffering from TCC during the acute phase of their illness were retrospectively reviewed. Cerebral blood flow (CBF), volume (CBV) and mean transit time (MTT) were measured in three different areas: the hemorrhagic core of the TCC, the surrounding hypodense area and the perilesional normal-appearing parenchyma. TCC area was measured on CBF-, CBV- and MTT-derived maps and compared with the areas measured using the same slice obtained with CT scans performed on admission, at the time of PCT (follow-up CT) and at 1 week.

RESULTS

TCC were characterized by low CBF and CBV values (9.2+/-6.6 ml/100 g per min and 0.9+/-0.7 ml/100 g, respectively) and a significant prolongation of MTT (11.9+/-10.7 s) in the hemorrhagic core whereas PCT parameters were more variable in the hypodense area. The TCC whole area showed a noticeable growth of the lesions during the first week of admission. In comparison with early noncontrast CT, CBV and CBF maps proved to be more congruent with the findings of noncontrast CT scans at 1 week.

CONCLUSION

PCT confirmed the results of xenon-CT studies and was shown to allow better evaluation of tissue viability than noncontrast CT. These findings suggest that PCT could be implemented in the future for the early assessment of patients with traumatic brain injury.