Time-density Curves Research Articles

Transluminal attenuation-gradient coronary CT angiography on a 320-MDCT volume scanner: Effect of scan timing, coronary artery stenosis, and cardiac output using a contrast medium flow phantom

PurposeTransluminal-attenuation-gradient (TAG) may reflect patient characteristics and physiological parameters. Furthermore, TAG may be affected by factors such as the CT scanner speed, scanning method, scan timing after contrast-medium (CM) injection, and the injection methods. The purpose of our study was to investigate quantitative TAG at different scan timing points after CM injection for coronary CT angiography. Materials and methodsUsing a CM flow phantom and two types of connecting tube mimicking 0% and 70% coronary artery stenosis, we performed 320-detector volume scanning. The heart rate was set at 60bpm and cardiac-output (CO) at 2.0 and 4.0 l/min, respectively. The acquisition time repeated at 0.5-s intervals for 40 and 25s at a CO of 2.0- and 4.0 l/min. We measured the CT number on the same slice level, calculated the time-density-curve (TDC) and the TAG at each time point. ResultsAt COs of 2.0 and 4.0 l/min at 0% stenosis, TAG exhibited smaller variations (−3.02 to +0.55HU/cm at 2.0 l/min, −2.63 to +0.43HU/cm at 4.0 l/min) than at 70% stenosis at each time point along the TDC. Compared with a CO at 2.0 l/min with 70% stenosis, the TAG curve for a CO at 4.0 l/min gradually changed with time (−6.64 to +1.18HU/cm at 2.0 l/min vs. −3.46 to +2.75HU/cm at 4.0 l/min). ConclusionThe TAG value was affected by scan timing after CM injection and by CO although the size of the connecting tube with and without stenosis was identical.

Quantifying the Cerebral Hemodynamics of Dural Arteriovenous Fistula in Transverse Sigmoid Sinus Complicated by Sinus Stenosis: A Retrospective Cohort Study.

Sinus stenosis occasionally occurs in dural arteriovenous fistulas. Sinus stenosis impedes venous outflow and aggravates intracranial hypertension by reversing cortical venous drainage. This study aimed to analyze the likelihood of sinus stenosis and its impact on cerebral hemodynamics of various types of dural arteriovenous fistulas. Forty-three cases of dural arteriovenous fistula in the transverse-sigmoid sinus were reviewed and divided into 3 groups: Cognard type I, type IIa, and types with cortical venous drainage. Sinus stenosis and the double peak sign (occurrence of 2 peaks in the time-density curve of the ipsilateral drainage of the internal jugular vein) in dural arteriovenous fistula were evaluated. "TTP" was defined as the time at which a selected angiographic point reached maximum concentration. TTP of the vein of Labbé, TTP of the ipsilateral normal transverse sinus, trans-fistula time, and trans-stenotic time were compared across the 3 groups. Thirty-six percent of type I, 100% of type IIa, and 84% of types with cortical venous drainage had sinus stenosis. All sinus stenosis cases demonstrated loss of the double peak sign that occurs in dural arteriovenous fistula. Trans-fistula time (2.09 seconds) and trans-stenotic time (0.67 seconds) in types with cortical venous drainage were the most prolonged, followed by those in type IIa and type I. TTP of the vein of Labbé was significantly shorter in types with cortical venous drainage. Six patients with types with cortical venous drainage underwent venoplasty and stent placement, and 4 were downgraded to type IIa. Sinus stenosis indicated dysfunction of venous drainage and is more often encountered in dural arteriovenous fistula with more aggressive types. Venoplasty ameliorates cortical venous drainage in dural arteriovenous fistulas and serves as a bridge treatment to stereotactic radiosurgery in most cases.

SU-G-IeP2-12: The Effect of Iterative Reconstruction and CT Tube Voltage On Hounsfield Unit Values of Iodinated Contrast

Purpose: To investigate the effects of changing iterative reconstruction strength and tube voltage on Hounsfield Unit (HU) values of varying concentrations of Iodinated contrast medium in a phantom. Method: Iodinated contrast (Omnipaque 300, GE Healthcare, Princeton NJ) was diluted with distilled water to concentrations of 0.6, 0.9, 1.8, 3.6, 7.2, and 10.8 mg/mL of Iodine. The solutions were scanned in a patient equivalent water phantom on two MDCT scanners: VCT 64 slice (GE Medical Systems, Waukesha, WI) and an Aquilion One 320 slice scanner (Toshiba America Medical Systems, Tustin CA). The phantom was scanned at 80, 100, 120, 140 kV using 400, 255, 180, and 130 mAs, respectively, for the VCT scanner, and 80, 100, 120, and 135 kV using 400, 250, 200, and 150 mAs, respectively, on the Aquilion One. Images were reconstructed at 2.5 mm (VCT) and 0.5 mm (Aquilion One). The VCT images were reconstructed using Advanced Statistical Iterative Reconstruction (ASIR) at 6 different strengths: 0%, 20%, 40%, 60%, 80%, and 100%. Aquilion One images were reconstructed using Adaptive Iterative Dose Reduction (AIDR) at 4 strengths: no AIDR, Weak AIDR, Standard AIDR, and Strong AIDR. Regions of interest (ROIs) were drawn on the images to measure the HU values and standard deviations of the diluted contrast. Second order polynomials were used to fit the HU values as a function of Iodine concentration. Results: For both scanners, there was no significant effect of changing the iterative reconstruction strength. The polynomial fits yielded goodness-of-fit (R2) values averaging 0.997. Conclusion: Changing the strength of the iterative reconstruction has no significant effect on the HU values of Iodinated contrast in a tissue-equivalent phantom. Fit values of HU vs Iodine concentration are useful in quantitative imaging protocols such as the determination of cardiac output from time-density curves in the main pulmonary artery.

Characterization of a murine xenograft model for contrast agent development in breast lesion malignancy assessment.

BackgroundThe aim of the study was to develop a nude mouse xenograft model implanted with both benign and malignant xenografts as the preliminary candidate screening tool for contrast agent development in lesion malignancy indication.ResultsA malignant xenograft (either MCF-7 cell/matrigel™ or MDA-MB 231 cell/matrigel) and a benign xenograft (culture medium/matrigel) with cleft and slit-like features of intracanaliculer fibroadenoma were implanted subcutaneously into flanks of individual nu/nu nude mouse with >90 % successful inoculation rate. Both malignant and benign xenografts with volume up to 4 cm3 and (size up to 2 cm) after 5th week were characterized in vivo by sonogram (exhibiting endogenous morphological contrast features between benign and malignant xenografts), dynamic contrast enhanced multi-detector computed tomography (presenting non-targeting exogenous morphological and dynamic contrast features between benign and malignant xenografts), and then were harvested for histological and immunohistochemistry (revealing example of targeting/molecular contrast features, such as expression of cancer vascular markers of malignant xenografts). Malignant xenografts appeared morphologically taller than wide (axis parallel to skin) with angular/ill-defined margin under sonogram observations, revealed more evident rim enhancement, angular margin and washout pattern in the time-density curve from dynamic contrast enhance multi-detector computed tomography images, and had more visible cancer vascular markers (CD31 and VEGF) expression. With limited number of subjects (5–27 for each group of a specific imaging contrast feature), those imaging contrast features of the xenograft model had larger than 85 % sensitivity, specificity, accuracy, positive and negative prediction values in indicating xenograft malignancy except for results from color Doppler detections.ConclusionsThe murine xenograft model might provide an earlier efficacy evaluation of new contrast agent candidate for lesion malignancy interrogation with qualitative and quantitative indication before a human study to reduce the risk and conserve the resources (time, finance and manpower).

Differential diagnostic value of computed tomography perfusion combined with vascular endothelial growth factor expression in head and neck lesions.

There are numerous types of head and neck lesions (HNLs), and conventional computed tomography (CT) has low specificity and sensitivity in the definitive and differential diagnosis of HNLs. The aim of the present study was to evaluate the value of perfusion CT (CTP) combined with vascular endothelial growth factor (VEGF) expression in the differentiation between malignant and benign HNLs. In total, 41 HNLs, which were pathologically confirmed, underwent CTP and VEGF expression analysis. All lesions were divided into three groups: Group A, benign hypovascular lesions; Group B, benign hypervascular lesions; and Group C, malignant lesions. Time density curve (TDC) and CTP parameters [maximum intensity projection (MIP), blood volume (BV), blood flow (BF), mean transit time and capillary permeability] were analyzed. The association between perfusion measurements and VEGF was assessed using Pearson's correlation. TDCs were classified into three types, and type I was more frequently identified in benign tumors (Groups A and B) compared with malignant tumors (Group C) (P=0.003). Malignant tumors primarily had a TDC of type II and III. MIP, BF and BV were all significantly higher in Groups B and C compared to Group A (P<0.01). VEGF expression of malignant tumors was significantly higher than benign tumors (P=0.007). No correlation was identified between VEGF and any CTP parameter. The present findings suggest that CTP combined with VEGF may differentiate between malignant and benign HNLs, and between benign hypovascular and hypervascular lesions.

Sensitivity evaluation of DSA-based parametric imaging using Doppler ultrasound in neurovascular phantoms.

An evaluation of the relation between parametric imaging results obtained from Digital Subtraction Angiography (DSA) images and blood-flow velocity measured using Doppler ultrasound in patient-specific neurovascular phantoms is provided. A silicone neurovascular phantom containing internal carotid artery, middle cerebral artery and anterior communicating artery was embedded in a tissue equivalent gel. The gel prevented movement of the vessels when blood mimicking fluid was pumped through it to obtain Colour Doppler images. The phantom was connected to a peristaltic pump, simulating physiological flow conditions. To obtain the parametric images, water was pumped through the phantom at various flow rates (100, 120 and 160 ml/min) and 10 ml contrast boluses were injected. DSA images were obtained at 10 frames/sec from the Toshiba C-arm and DSA image sequences were input into LabVIEW software to get parametric maps from time-density curves. The parametric maps were compared with velocities determined by Doppler ultrasound at the internal carotid artery. The velocities measured by the Doppler ultrasound were 38, 48 and 65 cm/s for flow rates of 100, 120 and 160 ml/min, respectively. For the 20% increase in flow rate, the percentage change of blood velocity measured by Doppler ultrasound was 26.3%. Correspondingly, there was a 20% decrease of Bolus Arrival Time (BAT) and 14.3% decrease of Mean Transit Time (MTT), showing strong inverse correlation with Doppler measured velocity. The parametric imaging parameters are quite sensitive to velocity changes and are well correlated to the velocities measured by Doppler ultrasound.

Quantification of coronary flow using dynamic angiography with 320-detector row CT and motion coherence image processing: Detection of ischemia for intermediate coronary stenosis

ObjectivesAnatomical coronary stenosis is not always indicative of functional stenosis, particularly for intermediate coronary lesions. The purpose of this study is to propose a new method for quantifying coronary flow using dynamic CT angiography for the whole heart (heart-DCT) and investigate its ability for detecting ischemia from intermediate coronary stenosis. MethodsParticipants comprised 36 patients with coronary artery disease who underwent heart-DCT using 320-detector CT with tube voltage of 80kV and myocardial perfusion scintigraphy (MPS). Heart-DCT was continuously performed at mid-diastole throughout 15–25 cardiac cycles with prospective ECG-gating after bolus injection of contrast media (12–24ml). Dynamic datasets were computed into 90–100 data sets by motion coherence image processing (MCIP). Next, time-density curves (TDCs) for coronary arteries with a diameter >3mm were automatically calculated for all phases using MCIP. On the basis of the maximum slope method, coronary flow index (CFI) was defined as the ratio of the maximum upslope of coronary artery attenuation to the upslope of ascending aorta attenuation on the TDC, and was used to quantify coronary flow. CFIs for the proximal and distal sites of coronary arteries with mild-to-moderate stenosis were calculated. Coronary territories were categorized as non-ischemic or ischemic by MPS. Receiver-operating-characteristic (ROC) analysis was performed to determine the optimal cutoff for CFI to detect ischemia. ResultsDistal CFI was significantly lower for ischemia (0.26±0.08) than for non-ischemia (0.50±0.17, p<0.0001). No significant difference in proximal CFI was seen between ischemia (0.55±0.23) and non-ischemia (0.62±0.24). ROC analysis revealed 0.39 as the optimal cutoff for distal CFI to detect ischemia, with C-statistics of 0.91, 100% sensitivity, and 75% specificity. ConclusionsThis novel imaging technique allows coronary flow quantification using heart-DCT. Distal CFI can detect myocardial ischemia derived from intermediate coronary stenosis.

Tumoral angiogenesis in both adrenal adenomas and nonadenomas: a promising computed tomography biomarker for diagnosis.

To explore the correlation between the typical findings of dynamic contrast-enhanced computed tomography (DCE-CT) and tumoral angiogenesis (microvessel density [MVD] and vascular endothelial growth factor [VEGF]) in adenomas and nonadenomas such that the enhancement mechanism of DCE-CT in adrenal masses can be explained more precisely. Forty-two patients with 46 adrenal masses confirmed by surgery and pathology were included in the study; these masses included 23 adenomas, 18 nonadenomas, and 5 hyperplastic nodules. The findings of DCE-CT and angiogenesis in adrenal masses were studied. The features of DCE-CT in adenomas and nonadenomas were evaluated to determine whether the characteristics of DCE-CT in adrenal masses were closely correlated with tumoral angiogenesis. Adrenal adenomas were significantly different from nonadenomas in the time density curve and the mean percentage of enhancement washout at the 7-minute delay time in DCE-CT. The mean MVD and VEGF expression exhibited significant differences between the rapid washout group (types A and C) and the slow washout group (types B, D, and E) and between the relative washout (Washr) ≥34% and the absolute washout (Washa) ≥43% on the 7-minute enhanced CT scans (P=0.000). Adenomas were suggested when adrenal masses presented as types A and C, and/or the Washr ≥34%, and/or the Washa ≥43%, and the opposite was suggested for nonadenomas. These results showed a close correlation between the characteristics of DCE-CT and both MVD and VEGF expression in adrenal masses. There was also a significant difference in MVD and VEGF expression between adenomas and nonadenomas. In conclusion, MVD and VEGF expression are two important pathological factors that play important roles in the characterization of DCE-CT in adrenal masses because they cause different time density curve types, the Washr and the Washa for adrenal adenomas and nonadenomas.

Arterial input function placement effect on computed tomography lung perfusion maps.

A critical source of variability in dynamic perfusion computed tomography (DPCT) is the arterial input function (AIF). However, the impact of the AIF location in lung DPCT has not been investigated yet. The purpose of this study is to determine whether the location of the AIF within the central pulmonary arteries influences the accuracy of lung DPCT maps. A total of 54 lung DPCT scans were performed in three pigs using different rates and volumes of iodinated contrast media. Pulmonary blood flow (PBF) perfusion maps were generated using first-pass kinetics in three different AIF locations: the main pulmonary trunk (PT), the right main (RM) and the left main (LM) pulmonary arteries. A total of 162 time density curves (TDCs) and corresponding PBF perfusion maps were generated. Linear regression and Spearman's rank correlation coefficient were used to compare the TDCs. PBF perfusion maps were compared quantitatively by taking twenty six regions of interest throughout the lung parenchyma. Analysis of variance (ANOVA) was used to compare the mean PBF values among the three AIF locations. Two chest radiologists performed qualitative assessment of the perfusion maps using a 3-point scale to determine regions of perfusion mismatch. The linear regression of the TDCs from the RM and LM compared to the PT had a median (range) of 1.01 (0.98-1.03). The Spearman rank correlation between the TDCs was 0.88 (P<0.05). ANOVA analysis of the perfusion maps demonstrated no statistical difference (P>0.05). Qualitative comparison of the perfusion maps resulted in scores of 1 and 2, demonstrating either identical or comparable maps with no significant difference in perfusion defects between the different AIF locations. Accurate PBF perfusion maps can be generated with the AIF located either at the PT, RM or LM pulmonary arteries.

Time density curve analysis for C-arm FDCT PBV imaging.

Parenchymal blood volume (PBV) estimation using C-arm flat detector computed tomography (FDCT) assumes a steady-state contrast concentration in cerebral vasculature for the scan duration. Using time density curve (TDC) analysis, we explored if the steady-state assumption is met for C-arm CT PBV scans, and how consistent the contrast-material dynamics in cerebral vasculature are across patients. Thirty C-arm FDCT datasets of 26 patients with aneurysmal-SAH, acquired as part of a prospective study comparing C-arm CT PBV with MR-PWI, were analysed. TDCs were extracted from the 2D rotational projections. Goodness-of-fit of TDCs to a steady-state horizontal-line-model and the statistical similarity among the individual TDCs were tested. Influence of the differences in TDC characteristics on the agreement of resulting PBV measurements with MR-CBV was calculated. Despite identical scan parameters and contrast-injection-protocol, the individual TDCs were statistically non-identical (p < 0.01). Using Dunn's multiple comparisons test, of the total 435 individual comparisons among the 30 TDCs, 330 comparisons (62%) reached statistical significance for difference. All TDCs deviated significantly (p < 0.01) from the steady-state horizontal-line-model. PBV values of those datasets for which the TDCs showed largest deviations from the steady-state model demonstrated poor agreement and correlation with MR-CBV, compared with the PBV values of those datasets for which the TDCs were closer to steady-state. For clinical C-arm CT PBV examinations, the administered contrast material does not reach the assumed 'ideal steady-state' for the duration of scan. Using a prolonged injection protocol, the degree to which the TDCs approximate the ideal steady-state influences the agreement of resulting PBV measurements with MR-CBV.

Pleomorphic Adenoma Versus Warthin Tumor of the Parotid Gland: Diagnostic Value of CT Perfusion Imaging and Its Pathologic Explanation

AIM: To investigate the value of CT perfusion (CTP) imaging in the differentiation of pleomorphic adenoma and warthin tumor deriving singly from the parotid gland, and to explain its pathological basis. Methods: CTP was successfully performed in 29 patients with parotid tumors whose diagnoses were confirmed by surgery or biopsy. Data were postprocessed by using the Philips EBW workstation and analyzed using a dynamic analysis module. Postprocessing-generated a tissue time-density curve (TDC) and maps showed blood flow (BF), blood volume (BV), time-to-peak (TTP) and peak enhancement index (PEI). Independent-sample test and receiver operating characteristic (ROC) curves were used to analyze the difference and diagnostic efficacies of all perfusion data between the tumors. HE dyeing pathological section of all tumors was obtained after operation. Results: Perfusion maps of all tumors were successfully obtained. TDC of pleomorphic adenomas mainly showed a gradually ascension, and warthin tumours showed a fast ascent followed by a fast descent. The BF, BV, PEI and TTP values were statistically significant different between the pleomorphic adenomas and warthin tumors (p < 0. 01). ROC demonstrated that BF, BV and PEI, except for TTP, had actual significant differences between these two tumor types. Warthin tumors contains rich capillary network, and with a high cellularity-stromal grade. With regard to pleomorphic adenomas, it had less angiogenesis, but abundant muciform and chondroid tissue. Conclusions: CTP could provide TDC and perfusion data, which is feasible to differentiate pleomorphic adenomas from Warthin tumors, and could reflect tumors histopathological feature.

Perfusion Angiography in Acute Ischemic Stroke.

Visualization and quantification of blood flow are essential for the diagnosis and treatment evaluation of cerebrovascular diseases. For rapid imaging of the cerebrovasculature, digital subtraction angiography (DSA) remains the gold standard as it offers high spatial resolution. This paper lays out a methodological framework, named perfusion angiography, for the quantitative analysis and visualization of blood flow parameters from DSA images. The parameters, including cerebral blood flow (CBF) and cerebral blood volume (CBV), mean transit time (MTT), time-to-peak (TTP), and T max, are computed using a bolus tracking method based on the deconvolution of the time-density curve on a pixel-by-pixel basis. The method is tested on 66 acute ischemic stroke patients treated with thrombectomy and/or tissue plasminogen activator (tPA) and also evaluated on an estimation task with known ground truth. This novel imaging tool provides unique insights into flow mechanisms that cannot be observed directly in DSA sequences and might be used to evaluate the impact of endovascular interventions more precisely.

Two-Dimensional Perfusion Angiography of the Foot

Purpose: To report the feasibility, technical considerations, and initial results of 2-dimensional (2D) perfusion angiography of the foot before and after endovascular interventions. Methods: A retrospective single-center study involved 21 patients (mean age 73.4±10.5 years; 14 men) with severe peripheral vascular disease [Fontaine stage III (n=10) or IV (n=14)] who underwent lower limb digital subtraction angiography (DSA) prior to and following endovascular treatment of above- and/or below-knee lesions. A standardized contrast administration protocol (15 mL iodixanol 320 mg I/mL at 3 mL/s via a 5/6-F antegrade sheath) was applied during DSA using a 2D perfusion–enabled image intensifier. Representative hindfoot and forefoot regions of interest were analyzed, and representative numeric density values [time to peak (TTP), peak density value (PDV), and area under the (time-density) curve (AUC)] were calculated using 2D perfusion–enabled angiographic software to assess foot perfusion. Values were compared before and after angioplasty and by level of treatment (above or below knee). The parameters were correlated with disease severity (stenosis vs occlusion) and symptom level (Fontaine stage). Results: A clinically significant improvement (29.4%) in the AUC was noted following angioplasty, reaching statistical significance within the hindfoot (p=0.03). No significant change in TTP or PDV was detected following angioplasty. Foot movement remained problematic when measuring time-density values. No statistical difference in perfusion values was appreciable between above- and below-knee angioplasty. Conclusion: Two-dimensional perfusion angiography of the foot allows quantitative evaluation using various density values with potential benefit for treatment planning and technical outcome analysis. Methodical restrictions currently remain, mainly regarding patient movement.

Evaluation of the blood flow in common hepatic tumors by multi-slice spiral CT whole-liver perfusion imaging

To study the characteristics of blood flow in common hepatic tumors by 256-slice spiral CT whole-liver perfusion imaging. Seventy-one patients with hepatic tumors were examined retrospectively by 256-slice spiral CT whole-liver perfusion. Among them, twenty-seven cases were of primary hepatic cancer, twenty-four cases of hepatic hemangioma, and twenty cases of hepatic metastases.Regions of interest (ROIs) were placed in the tumor parenchyma (Area A), peritumoral hepatic parenchyma (Area B), and normal hepatic parenchyma (Area C), respectively. The time density curves (TDC) were drawn, and perfusion parameters including hepatic arterial perfusion(HAP), portal venous perfusion(PVP), total liver perfusion(TLP) and hepatic erfusion index(HPI) were obtained. The values of ROIs were measured, and the perfusion parameters in the areas A, B, C of different hepatic tumors were statistically analyzed. The values of HAP, PVP, HPI in the tumor parenchyma of primary hepatic carcinoma were (20.00 ± 11.41)ml · min(-1) · 100 ml(-1,) (32.31 ± 21.06)ml · min(-1) · 100 ml(-1,) (52.31 ± 30.55)ml · min(-1) · 100 ml(-1,) and (39.67 ± 11.19)%, showing significant difference as compared with those in peritumoral hepatic parenchyma and in normal hepatic parenchyma(P<0.05). The values of HAP, TLP, and HPI in the tumor parenchyma of hepatic hemangioma were (40.39 ± 29.23)ml · min(-1) · 100 ml(-1,) (132.72 ± 132.65) ml · min(-1) · 100 ml(-1,) and (35.51 ± 15.12)%, were significantly different as compared with those in the peritumoral hepatic parenchyma and in normal hepatic parenchyma(P<0.05). The values of HAP, PVP, HPI in the tumor parenchyma of hepatic metastases were (17.43 ± 12.27)ml · min(-1) · 100 ml(-1,) (36.19 ± 34.99) ml · min(-1) · 100 ml(-1,) and (37.86 ± 14.49)%, significantly different as compared normal hepatic parenchyma (P<0.05). The HAP, PVP, and TLP of tumor tissue and the PVP and HPI of peritumoral tissue in different hepatic tumors were statistically significantly different (P<0.05). The multi-slice spiral CT whole-liver perfusion has certain value in the diagnosis of common hepatic tumors. Perfusion parameters in different areas of common hepatic tumors have their own hemodynamic characteristics.

Flow-diverting stents allow efficient treatment of unruptured, intradural dissecting aneurysms of the vertebral artery: An explanatory approach using in vivo flow analysis

Our study aimed to evaluate the efficiency of flow-diverting stents (FDS) in treating unruptured, intradural dissecting aneurysms of the vertebral artery (VADAs). Additionally, the effect of FDS on the aneurysmal flow pattern was investigated by performing invivo flow analysis using parametric color coding (PCC). We evaluated 11 patients with unruptured, intradural VADAs, treated with FDS. Pre- and postinterventional DSA-series were postprocessed by PCC, and time-density curves were calculated. The parameters aneurysmal inflow-velocity, outflow-velocity and relative time-to-peak (rTTP) were calculated. Pre- and postinterventional values were compared and correlated with the occlusion rate after six months. Follow-up DSA detected 10 aneurysms occluded, meaning an occlusion rate of 91%. No procedure-related morbidity and mortality was found. Flow analyses revealed a significant reduction of aneurysmal inflow- velocity and prolongation of rTTP after FDS deployment. Concerning aneurysm occlusion, the postinterventional outflow-velocity turned out to be a marginally statistically significant predictor. A definite threshold value (-0.7 density change/s) could be determined for the outflow-velocity that allows prediction of complete aneurysm occlusion with high sensitivity and specificity (100%). Using FDS can be considered an efficient and safe therapy option in treating unruptured, intradural VADA. From invivo flow analyses the postinterventional aneurysmal outflow-velocity turned out to be a potential predictor for later complete aneurysm occlusion. Here, it might be possible to determine a threshold value that allows prediction of aneurysm occlusion with high specificity and sensitivity. As fast, applicable and easy-to-handle tool, PCC could be used for procedural monitoring and might contribute to further treatment optimization.

Investigations on the Flat-Detector Computed Tomography−Based CBV Map Acquisition Using a Left Ventricle Contrast Media Injection Protocol

Cerebral blood volume (CBV) acquired with the use of flat-detector computed tomography with contrast media (CM) injected at the ascending aorta provides real-time brain functional information with minimized CM usage; however, unexpected asymmetric perfusion is observed for certain patients without cerebral circulatory disorders. This work tested the feasibility of left ventricle (LV) CM injection to achieve symmetric perfusion. CBV maps were acquired for 10 patients without perfusion-related cerebral abnormities. Perfusion symmetry was predicted with the use of color-coded quantitative digital subtracted angiography with CM injected at ascending aorta. Time density curves were extracted at bilateral common carotid arteries with area under curves calculated. Planes were selected on CBV maps with regions of interest defined covering characteristic regions, where asymmetric perfusion most likely to appear. No adverse physiological changes were detected for any patient. Non-uniform CM distributions were detected for 4 patients with relative area under curves 0.66 ± 0.03, indicating asymmetric perfusion using ascending aorta injection. With LV injection, all the patients demonstrated good perfusion symmetry with relative CBV 1.03 ± 0.07. CBV maps acquisition with LV injection offered an approach to acquire immediate brain functional information for patients who are limited by asymmetric perfusion using ascending aorta injection and are sensitive to CM dose.

Enhancement Characteristics of the Computed Tomography Pulmonary Angiography Test Bolus Curve and Its Use in Predicting Right Ventricular Dysfunction and Mortality in Patients With Acute Pulmonary Embolism.

The purpose of the study was to evaluate the relationship between computed tomography pulmonary angiography (CTPA) test bolus curve data and mortality in patients with pulmonary embolism (PE) in comparison with conventional methods of right ventricular (RV) dysfunction. The study was approved by our institutional review board and is HIPAA-compliant. We retrospectively evaluated consecutive CTPA studies performed with a test bolus technique in a 2-year period. A time-density curve was derived from each test bolus. For comparison, left ventricular (LV) and RV dimensions (area, diameter) and PE load score (Qanadli method) were measured using CT data. A cardiologist blinded to the clinical and other imaging data reviewed a subset of the corresponding echocardiographic images to assess for RV dysfunction. Demographic data, mode of treatment, and patient outcome information were gathered using electronic medical records. Test bolus and anatomic data were correlated with PE-related mortality. A total of 71 patients (34 men and 37 women, average age 54.4 y) who had a CTPA performed using a test bolus technique were diagnosed with acute PE. Factors that significantly correlated with PE-related mortality on univariate analysis were: age above 60 years (odds ratio 19.1, P = 0.05), RV/LV diameter >1.5 (odds ratio 48.8, P < 0.001), RV/LV area >1 (odds ratio 8.6, P = 0.06), bolus curve upslope time >6 seconds (odds ratio 23.3, P = 0.04), 50% downslope time >6 seconds (odds ratio 20, P = 0.01), and embolus load score >15 (odds ratio 25, P = 0.03). The predictive value of upslope time (Exp(B) 1.65, P = 0.05), RV/LV diameter (Exp(B) 43.8, P = 0.01), and RV/LV area (Exp(B) 16.7, P = 0.01) were confirmed to be statistically significant in multivariate analyses. Data from the CTPA timing bolus curve provide prognostic value similar to the best conventional methods for predicting PE-related mortality.

TU‐F‐CAMPUS‐I‐02: Contrast Enhanced Cone Beam CT Imaging with Dual‐ Gantry Image Acquisition and Constrained Iterative Reconstruction‐a Simulation Study for Liver Imaging Application

Purpose:Contrast time‐density curves may help differentiate malignant tumors from normal tissues or benign tumors. Repetitive scans using conventional CT or cone beam CT techniques, which Result in unacceptably high dose, may not achieve the desired temporal resolution. In this study we describe and demonstrate a 4D imaging technique for imaging and quantifying contrast flows requiring only one or two 360° scans.Methods:A dual‐gantry system is used to simultaneously acquire two projection images at orthogonal orientations. Following the scan, each or both of the two 360° projection sets are used to reconstruct an average contrast enhanced image set which is then segmented to form a 3D contrast map. Alternatively, a pre‐injection scan may be made and used to reconstruct a pre‐injection image set which is subtracted from the post‐injection image set to form the 3D contrast map. Each of the two 360° projection sets is divided into 12 subsets, thus creating 12 pairs of 30° limited angle projection sets, each corresponding to a time spanning over 1/12 of the scanning time. Each pair of the projection sets are reconstructed as a time specific 3D image set with the maximum likelihood estimation iterative algorithm using the contrast map as the constraint. As a demonstration, a 4D abdominal phantom was constructed from clinical CT images with blood flow through the normal tissue and a tumor modeled and imaging process simulated.Results:We have successfully generated a 4D image phantom, and calculated the projection images. The time density curves derived from the reconstructed image set matched well with the flow model used to generate the phantom.Conclusion:Dual‐gantry image acquisition and constrained iterative reconstruction algorithm may help to obtain time‐density curves of contrast agents in blood flows, which may help differentiate malignant tumors from normal tissues or benign tumors.

CT perfusion cerebral blood volume does not always predict infarct core in acute ischemic stroke.

We investigated the practical clinical utility of the CT perfusion (CTP) cerebral blood volume (CBV) parameter for differentiating salvageable from non-salvageable tissue in acute ischemic stroke (AIS). Fifty-five patients with AIS were imaged within 6 h from onset using CTP. Admission CBV defect (CBVD) volume was outlined using previously established gray and white matter CBV thresholds for infarct core. Admission cerebral blood flow (CBF) hypoperfusion and CBF/CBV mismatch were visually evaluated. Truncation of the ischemic time-density curve (ITDC) and hypervolemia status at admission, recanalization at 24-h CT angiography, hemorrhagic transformation (HT) at 24 h and/or 7-day non-contrast CT (NCCT), final infarct volume as indicated by 3-month NCCT defect (NCCTD) and 3-month modified Rankin Score were determined. Patients with recanalization and no truncation had the highest correlation (R = 0.81) and regression slope (0.80) between CBVD and NCCTD. Regression slopes were close to zero for patients with admission hypervolemia with/without recanalization. Hypervolemia underestimated (p = 0.02), while recanalization and ITDC truncation overestimated (p = 0.03) the NCCTD. Among patients with confirmed recanalization at 24 h, 38 % patients had an admission CBF/CBV mismatch within normal appearing areas on respective NCCT. 83 % of these patients developed infarction in admission hypervolemic CBF/CBV mismatch tissue. A reduction in CBV is a valuable predictor of infarct core when the acquisition of ITDC data is complete and hypervolemia is absent within the tissue destined to infarct. Raised or normal CBV is not always indicative of salvageable tissue, contrary to the current definition of penumbra.

X-ray Angiography Perfusion Analysis for the Balloon Occlusion Test of the Internal Carotid Artery

A perfusion study should be performed during the balloon occlusion test (BOT) to prevent ischemic events after therapeutic carotid occlusion. We evaluated the efficacy of X-ray angiography perfusion analysis during the BOT. Twenty-one consecutive patients who underwent the BOT of the internal carotid artery were included. Patients who had a venous phase delay of less than .5 seconds and a mean stump pressure of more than 50 mm Hg without any neurologic symptoms were considered tolerant, and other patients were considered intolerant. A time-density curve was constructed for each hemisphere using X-ray angiography perfusion software (2D-Perfusion). The mean transit time and area under the curve, which correspond to cerebral blood volume, were calculated from the curve. Differences in these parameters between the occluded and nonoccluded hemispheres and the perfusion index were compared between the tolerant and intolerant groups. In the intolerant group, the mean transit time was significantly longer (1.31 ± .72 seconds versus .44 ± .21 seconds, P = .001) and the perfusion index was significantly lower (.72 ± .16 versus .94 ± .08, P = .001) compared with those in the tolerant group. The area under the curve was not different between the groups. Parameters obtained by X-ray angiography perfusion analysis were significantly different between the tolerant and intolerant groups. The X-ray angiography perfusion analysis could be a safe and effective method for assessing ischemic tolerance before therapeutic carotid occlusion.