Whole brain perfused blood volume CT: visualization of infarcted tissue compared to quantitative perfusion CT

Perfusion CT - Can it resolve the pancreatic carcinoma versus mass forming chronic pancreatitis conundrum?

OBJECTIVES

To evaluate the utility of perfusion CT (PCT) in differentiating pancreatic adenocarcinoma from mass forming chronic pancreatitis (MFCP).

METHODS

In this ethically approved study, PCT was performed in 122 patients with pancreatic masses of which 42 patients had pancreatic adenocarcinoma and 13 had MFCP on histopathology. Perfusion parameters studied included blood flow (BF), blood volume (BV), permeability surface area product (PS), time to peak (TTP), peak enhancement intensity (PEI) and mean transit time (MTT). Twenty five controls with no pancreatic pathology were also studied.

RESULTS

Amongst the perfusion parameters BF and BV were found to be the most reliable for differentiating between adenocarcinoma and mass forming pancreatitis. Although they were reduced in both pancreatic adenocarcinoma (BF- 16.6 ± 13.1 ml/100 ml/min and BV- 5 ± 3.5 ml/100 ml) and MFCP (BF- 30.4 ± 8.7 ml/100 ml/min and BV- 8.9 ± 3.1 ml/100 ml) as compared to normal controls (BF- 94.1 ± 24 ml/100 ml/min and BV- 36 ± 10.7 ml/100 ml) but the extent of reduction was greater in pancreatic adenocarcinoma than in MFCP. Based on ROC analysis cut off values of 19.1 ml/100 ml/min for BF and 5 ml/100 ml for BV yielded optimal sensitivity and specificity for differentiating pancreatic adenocarcinoma from MFCP.

CONCLUSIONS

PCT may serve as an additional paradigm for differentiating pancreatic adenocarcinoma from mass forming chronic pancreatitis and a useful tool for detecting masses which are isodense on conventional CT.

C-arm flat detector computed tomography parenchymal blood volume imaging: the nature of parenchymal blood volume parameter and the feasibility of parenchymal blood volume imaging in aneurysmal subarachnoid haemorrhage patients

INTRODUCTION

C-arm flat detector computed tomography (FDCT) parenchymal blood volume (PBV) measurements allow assessment of cerebral haemodynamics in the neurointerventional suite. This paper explores the feasibility of C-arm computed tomography (CT) PBV imaging and the relationship between the C-arm CT PBV and the MR-PWI-derived cerebral blood volume (CBV) and cerebral blood flow (CBF) parameters in aneurysmal subarachnoid haemorrhage (SAH) patients developing delayed cerebral ischemia (DCI).

METHODS

Twenty-six patients with DCI following aneurysmal SAH underwent a research C-arm CT PBV scan using a biplane angiography system and contemporaneous MR-PWI scan as part of a prospective study. Quantitative whole-brain atlas-based volume-of-interest analysis in conjunction with Pearson correlation and Bland-Altman tests was performed to explore the agreement between C-arm CT PBV and MR-derived CBV and CBF measurements.

RESULTS

All patients received medical management, while eight patients (31%) underwent selective intra-arterial chemical angioplasty. Colour-coded C-arm CT PBV maps were 91% sensitive and 100% specific in detecting the perfusion abnormalities. C-arm CT rPBV demonstrated good agreement and strong correlation with both MR-rCBV and MR-rCBF measurements; the agreement and correlation were stronger for MR-rCBF relative to MR-rCBV and improved for C-arm CT PBV versus the geometric mean of MR-rCBV and MR-rCBF. Analysis of weighted means showed that the C-arm CT PBV has a preferential blood flow weighting (≈ 60% blood flow and ≈ 40% blood volume weighting).

CONCLUSIONS

C-arm CT PBV imaging is feasible in DCI following aneurysmal SAH. PBV is a composite perfusion parameter incorporating both blood flow and blood volume weightings. That PBV has preferential (≈ 60%) blood flow weighting is an important finding, which is of clinical significance when interpreting the C-arm CT PBV maps, particularly in the setting of acute brain ischemia.

Non-invasive assessment of vasospasm following aneurysmal SAH using C-arm FDCT parenchymal blood volume measurement in the neuro-interventional suite: Technical feasibility

INTRODUCTION

Cerebral vasospasm is the leading cause of morbidity and mortality in patients with aneurysmal subarachnoid haemorrhage (SAH) surviving the initial ictus. Commonly used techniques for vasospasm assessment are digital subtraction angiography and transcranial Doppler sonography. These techniques can reliably identify only the major vessel spasm and fail to estimate its haemodynamic significance. To overcome these issues and to enable comprehensive non-invasive assessment of vasospasm inside the interventional suite, a novel protocol involving measurement of parenchymal blood volume (PBV) using C-arm flat detector computed tomography (FDCT) was implemented.

MATERIALS AND METHODS

Patients from the neuro-intensive treatment unit (ITU) with suspected vasospasm following aneurysmal SAH were scanned with a biplane C-arm angiography system using an intravenous contrast injection protocol. The PBV maps were generated using prototype software. Contemporaneous clinically indicated MR scan including the diffusion- and perfusion-weighted sequences was performed. C-arm PBV maps were compared against the MR perfusion maps.

RESULTS

Distribution of haemodynamic impairment on C-arm PBV maps closely matched the pattern of abnormality on MR perfusion maps. On visual comparison between the two techniques, the extent of abnormality indicated PBV to be both cerebral blood flow and cerebral blood volume weighted.

CONCLUSION

C-arm FDCT PBV measurements allow an objective assessment of the severity and localisation of cerebral hypoperfusion resulting from vasospasm. The technique has proved feasible and useful in very sick patients after aneurysmal SAH. The promise shown in this early study indicates that it deserves further evaluation both for post-SAH vasospasm and in other relevant clinical settings.

Intraprocedural parenchymal blood volume as a marker of reperfusion status in acute ischemic stroke intervention

Parenchymal blood volume (PBV) mapping with flat panel detectors may provide real-time estimates of tissue perfusion during endovascular ischemic stroke procedures. We present two cases of acute middle cerebral artery (MCA) occlusion to demonstrate how PBV may: (1) be used in acute stroke; (2) influence intraprocedural decision-making; and (3) potentially serve as a predicator of clinical outcome. Both cases were successfully recanalized with endovascular embolectomy. Intraprocedural PBV maps were obtained immediately before and after recanalization. Pre-intervention reductions in PBV were seen throughout the MCA territory in both cases, with significant improvement in PBV in one case with good radiographic and clinical outcome and a lack of improvement in PBV in the second case with a large infarct volume. PBV deficit normalization may occur with recanalization of the parent artery and probably represents successful reperfusion. Baseline PBV maps should therefore be interpreted with caution and not interpreted to represent irreversible core infarct.

Intraprocedural parenchymal blood volume as a marker of reperfusion status in acute ischemic stroke intervention

Parenchymal blood volume (PBV) mapping with flat panel detectors may provide real-time estimates of tissue perfusion during endovascular ischemic stroke procedures. We present two cases of acute middle cerebral artery (MCA) occlusion to demonstrate how PBV may: (1) be used in acute stroke; (2) influence intraprocedural decision-making; and (3) potentially serve as a predicator of clinical outcome. Both cases were successfully recanalized with endovascular embolectomy. Intraprocedural PBV maps were obtained immediately before and after recanalization. Pre-intervention reductions in PBV were seen throughout the MCA territory in both cases, with significant improvement in PBV in one case with good radiographic and clinical outcome and a lack of improvement in PBV in the second case with a large infarct volume. PBV deficit normalization may occur with recanalization of the parent artery and probably represents successful reperfusion. Baseline PBV maps should therefore be interpreted with caution and not interpreted to represent irreversible core infarct.

Diagnostic performance of whole brain volume perfusion CT in intra-axial brain tumors: preoperative classification accuracy and histopathologic correlation

BACKGROUND

To evaluate the preoperative diagnostic power and classification accuracy of perfusion parameters derived from whole brain volume perfusion CT (VPCT) in patients with cerebral tumors.

METHODS

Sixty-three patients (31 male, 32 female; mean age 55.6 ± 13.9 years), with MRI findings suspected of cerebral lesions, underwent VPCT. Two readers independently evaluated VPCT data. Volumes of interest (VOIs) were marked circumscript around the tumor according to maximum intensity projection volumes, and then mapped automatically onto the cerebral blood volume (CBV), flow (CBF) and permeability Ktrans perfusion datasets. A second VOI was placed in the contra lateral cortex, as control. Correlations among perfusion values, tumor grade, cerebral hemisphere and VOIs were evaluated. Moreover, the diagnostic power of VPCT parameters, by means of positive and negative predictive value, was analyzed.

RESULTS

Our cohort included 32 high-grade gliomas WHO III/IV, 18 low-grade I/II, 6 primary cerebral lymphomas, 4 metastases and 3 tumor-like lesions. Ktrans demonstrated the highest sensitivity, specificity and positive predictive value, with a cut-off point of 2.21 mL/100mL/min, for both the comparisons between high-grade versus low-grade and low-grade versus primary cerebral lymphomas. However, for the differentiation between high-grade and primary cerebral lymphomas, CBF and CBV proved to have 100% specificity and 100% positive predictive value, identifying preoperatively all the histopathologically proven high-grade gliomas.

CONCLUSION

Volumetric perfusion data enable the hemodynamic assessment of the entire tumor extent and provide a method of preoperative differentiation among intra-axial cerebral tumors with promising diagnostic accuracy.

Acute ischemic stroke: infarct core estimation on CT angiography source images depends on CT angiography protocol

PURPOSE

To test whether the relationship between acute ischemic infarct size on concurrent computed tomographic (CT) angiography source images and diffusion-weighted (DW) magnetic resonance images is dependent on the parameters of CT angiography acquisition protocols.

MATERIALS AND METHODS

This retrospective study had institutional review board approval, and all records were HIPAA compliant. Data in 100 patients with anterior-circulation acute ischemic stroke and large vessel occlusion who underwent concurrent CT angiography and DW imaging within 9 hours of symptom onset were analyzed. Measured areas of hyperintensity at acute DW imaging were used as the standard of reference for infarct size. Information regarding lesion volumes and CT angiography protocol parameters was collected for each patient. For analysis, patients were divided into two groups on the basis of CT angiography protocol differences (patients in group 1 were imaged with the older, slower protocol). Intermethod agreement for infarct size was evaluated by using the Wilcoxon signed rank test, as well as by using Spearman correlation and Bland-Altman analysis. Multivariate analysis was performed to identify predictors of marked (≥20%) overestimation of infarct size on CT angiography source images.

RESULTS

In group 1 (n=35), median hypoattenuation volumes on CT angiography source images were slightly underestimated compared with DW imaging hyperintensity volumes (33.0 vs 41.6 mL, P=.01; ratio=0.83), with high correlation (ρ=0.91). In group 2 (n=65), median volume on CT angiography source images was much larger than that on DW images (94.8 vs 17.8 mL, P<.0001; ratio=3.5), with poor correlation (ρ=0.49). This overestimation on CT angiography source images would have inappropriately excluded from reperfusion therapy 44.4% or 90.3% of patients eligible according to DW imaging criteria on the basis of a 100-mL absolute threshold or a 20% or greater mismatch threshold, respectively. Atrial fibrillation and shorter time from contrast material injection to image acquisition were independent predictors of marked (≥20%) infarct size overestimation on CT angiography source images.

CONCLUSION

CT angiography protocol changes designed to speed imaging and optimize arterial opacification are associated with significant overestimation of infarct size on CT angiography source images.

Brain volume perfusion CT performed with 128-detector row CT system in patients with cerebral gliomas: a feasibility study

OBJECTIVES

Validation of the feasibility and efficacy of volume perfusion computed tomography (VPCT) in the preoperative assessment of cerebral gliomas by applying a 128-slice CT covering the entire tumour.

METHODS

Forty-six patients (25 men, 21 women; mean age 52.8 years) with cerebral gliomas were evaluated with VPCT. Two readers independently evaluated VPCT data, drawing volumes of interest (VOIs) around the tumour according to maximum intensity projection volumes, which were mapped automatically onto the cerebral blood volume (CBV), flow (CBF) and permeability (Ktrans) perfusion datasets. As control, a second VOI was placed in the contralateral healthy cortex. Correlation among perfusion parameters, tumour grade, hemisphere and VOIs was assessed. The diagnostic power of perfusion parameters was analysed by receiver operating characteristics curve analyses.

RESULTS

VPCT was feasible in the assessment of the entire tumour extent. Mean values of Ktrans, CBV, CBF in high-grade gliomas were significantly higher compared with low-grade (p < 0.01). Ktrans demonstrated the highest diagnostic (97% sensitivity), positive (100%) and negative (94%) prognostic values.

CONCLUSIONS

VPCT was feasible in all subjects. All areas of different perfusion characteristics are depicted and quantified in colour-coded 3D maps. The derived parameters correlate well with tumour histopathology, differentiating low- from high-grade gliomas.

Perfusion-weighted map and perfused blood volume in comparison with CT angiography source imaging in acute ischemic stroke different sides of the same coin?

RATIONALE AND OBJECTIVES

Computed tomography angiography source imaging (CTA-SI) in acute ischemic stroke improves detection rate and estimation of extent of cerebral infarction. This study compared the new components color-coded perfusion weighted map (PWM) and color-coded perfused blood volume (PBV) derived from CTA data with CTA-SI for the visualization of cerebral infarction.

MATERIALS AND METHODS

Fifty patients (women = 30; mean age = 74.9 ± 13.3 years) underwent nonenhanced computed tomography and CTA for suspected acute ischemic stroke. PWM, PBV, and CTA-SI were reconstructed with identical slice thickness of 1.0 mm with commercial software. Extent of infarction was measured using the Alberta Stroke Program Early Computed Tomography Score (ASPECTS). For statistical analysis, Spearman's R correlation and paired-samples t-test was used. P < .05 was considered significant.

RESULTS

PBV had superior sensitivity for detection of cerebral infarction with 0.88 compared to PWM and CTA-SI with 0.79 and 0.76, respectively. The accuracy of correct diagnosis was superior for PBV with 0.82 compared to PWM and CTA-SI with 0.76, respectively. ASPECTS of PWM and PBV showed strong correlation with CTA-SI with r = 0.903 (P < .001) and r = 0.866 (P < .001), respectively. Mean ASPECTS of CTA-SI (6.24 ± 3.62) revealed no significant difference with PWM (6.26 ± 3.45), but a significant difference with PBV (5.62 ± 3.41; P < .02).

CONCLUSIONS

PWM was equal to CTA-SI in detection of cerebral infarction and estimation of extent of cerebral ischemia. Although PBV was superior to CTA-SI in detection of cerebral infarction, PBV seems to overestimate the extent of critical cerebral ischemia. Therefore, CTA-SI information is not identical to PBV and further clinical evaluation is mandatory.

64-slice CT perfusion imaging of pancreatic adenocarcinoma and mass-forming chronic pancreatitis

RATIONALE AND OBJECTIVES

To investigate 64 computed tomography (CT) perfusion imaging features of patients with pancreatic cancer and mass-forming chronic pancreatitis.

MATERIALS AND METHODS

Between January 2003 and April 2010, 234 patients with pancreatic mass underwent 64-CT perfusion imaging. Among them, the histopathological results of 64 patients were proven to be pancreatic adenocarcinoma and 15 patients were proven to be mass-forming chronic pancreatitis. Additionally, CT perfusion imaging was performed in 33 healthy volunteers served as controls. The slice data were processed using CT perfusion software. Perfusion parameters including time density curve, blood flow, blood volume, permeability, peak enhancement, and time to peak were recorded.

RESULTS

Blood flow was 77% lower in patients with pancreatic adenocarcinoma than in controls, 48% lower in patients with mass-forming chronic pancreatitis than in controls, and 56% lower in patients with pancreatic adenocarcinoma than with mass-forming chronic pancreatitis (P < .016). Blood volume was 65% lower in pancreatic adenocarcinoma than in controls, 27% lower in mass-forming chronic pancreatitis than in controls, and 53% lower in cancer than mass-forming chronic pancreatitis (P < .016). Permeability was 559% higher in pancreatic adenocarcinoma than in controls, 821% higher in mass-forming chronic pancreatitis than in controls, and 28% lower in cancer than mass-forming chronic pancreatitis (P < .016). Peak enhancement was 27% lower and time to peak 23% longer in pancreatic adenocarcinoma than mass-forming chronic pancreatitis (P < .016). Time-density curve showed the peak of mass-forming chronic pancreatitis is earlier and higher than that of pancreatic adenocarcinoma, and the peak of mass-forming chronic pancreatitis is later and lower than that of controls.

CONCLUSION

CT perfusion imaging can provide additional quantitative hemodynamic information of pancreatic adenocarcinoma and mass-forming chronic pancreatitis.