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ABSTRACT: INTRODUCTION: The aim of this study was to examine reliability and reproducibility of volumetric perfusion deficit assessment in patients with acute ischemic stroke who underwent recently introduced whole-brain CT perfusion (WB-CTP). METHODS: Twenty-five consecutive patients underwent 128-row WB-CTP with extended scan coverage of 100 mm in the z-axis using adaptive spiral scanning technique. Volumetric analysis of cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), time to peak (TTP), and time to drain (TTD) was performed twice by two blinded and experienced readers using OsiriX V.4.0 imaging software. Interreader agreement and intrareader agreement were assessed by intraclass correlation coefficients (ICCs) and Bland-Altman Analysis. RESULTS: Interreader agreement was highest for TTD (ICC 0.982), followed by MTT (0.976), CBF (0.955), CBV (0.933), and TTP (0.865). Intrareader agreement was also highest for TTD (ICC 0.993), followed by MTT (0.988), CBF (0.981), CBV (9.953), and TTP (0.927). The perfusion deficits showed the highest absolute volumes in the time-related parametric maps TTD (mean volume 121.4 ml), TTP (120.0 ml), and MTT (112.6 ml) and did not differ significantly within this group (each with p > 0.05). In comparison to time-related maps, the mean CBF perfusion deficit volume was significantly smaller (92.1 ml, each with p < 0.05). The mean CBV lesion size was 23.4 ml. CONCLUSIONS: Volumetric assessment in WB-CTP is reliable and reproducible. It might serve for a more accurate assessment of stroke outcome prognosis and definition of flow-volume mismatch. Time to drain showed the highest agreement and therefore might be an interesting parameter to define tissue at risk.
Neuroradiology 04/2013; · 2.82 Impact Factor
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ABSTRACT: 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 2.21mL/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.
European journal of radiology 09/2012; · 2.65 Impact Factor
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ABSTRACT: In acute stroke patients with intracranial vessel occlusion, angiographic demonstration of antegrade contrast opacification distal to the occlusion site (termed the "clot outline sign") has been associated with higher rates of vessel recanalization. We sought to determine whether antegrade flow can be demonstrated on timeresolved 4-dimensional computed tomographic angiography (4-dimensional CTA), whether it can be distinguished from retrograde collateral flow, and if it can be used to predict early recanalization.
Fiftyseven acute stroke patients with intracranial anterior circulation vessel occlusion were retrospectively identified. All patients had received a multimodal computed tomography examination including thinsection 4-dimensional CTA and subsequent digital subtraction angiography as part of an endovascular procedure. Pretreatment 4-dimensional CTA and singlephase CTA were assessed for presence of antegrade contrast opacification distal to the occlusion site. Digital subtraction angiograms were reviewed for preintervention Thrombolysis in Cerebral Infarction grade, presence of the clot outline sign, as well as postintervention Thrombolysis in Cerebral Infarction grade.
On 4-dimensional CTA, evidence of antegrade flow was present in 11 of 57 cases (19.3%). Compared with angiography, 4-dimensional CTA predicted antegrade flow with 100% sensitivity and 97.9% specificity. Singlephase CTA offered 40% sensitivity and 87.2% specificity. Early recanalization occurred in 3 patients (6.5%) after intravenous thrombolysis (n=46); all demonstrated antegrade flow on 4-dimensional CTA.
Using 4-dimensional CTA, it is possible to noninvasively distinguish antegrade flow across a cerebral artery occlusion from retrograde collateral flow. Presence of antegrade flow on 4-dimensional CTA is associated with an increased chance of early vessel recanalization.
Stroke 09/2012; 43(11):2974-9. · 5.73 Impact Factor
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ABSTRACT: Multimodal CT imaging consisting of nonenhanced CT, CT angiography (CTA), and whole-brain volume perfusion CT is increasingly used for acute stroke imaging. In these patients, presence of vessel occlusion is an important factor governing treatment decisions and possible endovascular therapy. The goal of this study was to assess the value and diagnostic accuracy of angiographic thin-slice volume perfusion CT reconstructions for the detection of intracranial large vessel occlusion in patients with stroke.
Fifty-eight patients with acute stroke received nonenhanced CT, CTA, and volume perfusion CT. All images were obtained on a 128-slice multidetector CT scanner. CT angiographic axial and coronal maximum-intensity projections of the head were reconstructed from conventional CTA and from the peak arterial scan of the volume perfusion CT data set (4-dimensional CTA). Images were assessed for the presence of intracranial vessel occlusion. The distribution of ischemic lesions was analyzed on perfusion parameter maps.
On CTA, 30 patients (52%) had a total of 33 occluded intracranial artery segments. Twenty-eight occlusions were identified on 4-dimensional CTA, resulting in an 85% sensitivity with a positive predictive value of 97%. When combined with an analysis of the perfusion parameter maps, sensitivity of 4-dimensional CTA increased to 94% with a positive predictive value of 100%.
In acute stroke, angiographic volume perfusion CT reconstructions may be a feasible option to detect intracranial arterial occlusion and evaluate patients for endovascular therapy. Sensitivity for detection of intracranial arterial occlusion can be increased by simultaneous assessment of perfusion parameter maps. Future studies should assess whether time-resolved 4-dimensional CTA may offer additional diagnostically relevant information compared with single-phase CTA.
Stroke 01/2012; 43(1):97-102. · 5.73 Impact Factor
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Fabian Bamberg,
Rabea Hinkel,
Florian Schwarz,
Torleif A Sandner,
Elisabeth Baloch,
Roy Marcus,
Alexander Becker,
Christian Kupatt,
Bernd J Wintersperger,
Thorsten R Johnson,
Daniel Theisen, Ernst Klotz,
Maximilian F Reiser,
Konstantin Nikolaou
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ABSTRACT: To determine the accuracy of computed tomography (CT) dynamic stress myocardial perfusion imaging to estimate myocardial blood flow (MBF) in a porcine animal model with variable degrees of induced coronary artery stenosis in comparison with microsphere-derived MBF.
Seven domestic pigs (36 ± 4 kg) received stents (confirmed 3.0 mm diameter) in the left anterior descending coronary artery distal to first diagonal branch. A balloon catheter was placed within the stent and inflated to various degrees to obtain a defined luminal narrowing (50% and 75% diameter stenosis) as confirmed by intra-arterial flow wire measurement. All models underwent adenosine-mediated (140 μg/kg/min) dynamic stress and rest myocardial perfusion CT imaging using a dual-source CT scanner (shuttle-mode with 100 kV/300 mAs, 20 mL iopromide) with prospective acquisitions every second heartbeat for 30 seconds. CT-estimated MBF (MBFCT) was calculated using a model-based parametric deconvolution method and correlated to that of fluorescent microspheres (MBFmic) injected at each perfusion state.
All study procedures were performed without complications, and all animals completed the study protocol. Among 448 myocardial segments, 31 (7%) were considered nonevaluable because of motion artifacts. With stress, MBFCT increased significantly (1.10 ± 0.25 vs. 0.80 ± 0.28 mL/g/min, P < 0.001; at stress and rest, respectively) in all myocardial segments and correlated with MBFmic (r = 0.67, P < 0.001). MBFCT overestimated MBFmic, independently of adenosine-stress and degree of coronary stenosis (β = 2.3, 95% confidence interval: 1.81-2.79 mL/g/min, P < 0.001). Although there were no differences in MBFCT between 50% and 75% coronary stenosis at rest (0.01 ± 0.08 mL/g/min, P = 0.86), MBFCT was significantly lower at 75% than at 50% under stress conditions (0.53 ± 0.19 vs. 0.71 ± 0.24 mL/g/min, P = 0.002).
CT-derived MBF measurements at rest and stress with varying degrees of coronary stenosis show a valid difference but an underestimated correlation with microsphere-derived MBF in a porcine animal model.
Investigative radiology 01/2012; 47(1):71-7. · 4.85 Impact Factor
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ABSTRACT: 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.
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.
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.
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.
European Radiology 05/2011; 21(9):1811-9. · 3.22 Impact Factor
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ABSTRACT: The objective of our study was to investigate the diagnostic value of the volumetric arterial enhancement fraction of the liver with color mapping for the early detection of tumor relapse after hepatic radiofrequency ablation (RFA).
Fifty-three patients (24 men, 29 women; mean age ± SD, 65 ± 10 years) with a total of 215 liver metastases treated by RFA and a mean postinterventional follow-up period of 20 ± 15 (SD) months were included in this retrospective study. Quantitative arterial enhancement fraction color maps of the whole liver were computed from triple-phase contrast-enhanced MDCT images. Follow-up examinations served as the standard of reference. The diagnostic performance of the arterial enhancement fraction color maps to predict subsequent tumor occurrence before tumor was visible on routine multiphase CT images was evaluated.
The mean arterial enhancement fraction of segments that developed metastases (62% ± 23%) was significantly higher than the mean of segments that did not develop metastases (39% ± 20%) (p < 0.0001). Receiver operating characteristic curve analysis revealed a probability of 77% for arterial enhancement fraction values to be higher in case of subsequent metastases as compared with liver parenchyma without tumor recurrence.
The arterial enhancement fraction provides incremental value in the imaging surveillance for liver metastases after RFA. Arterial enhancement fraction color maps may be suited to predict tumor recurrence earlier than routine assessment using contrast-enhanced MDCT.
American Journal of Roentgenology 05/2011; 196(5):W573-9. · 2.78 Impact Factor
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JACC. Cardiovascular imaging 11/2010; 3(11):1202. · 14.29 Impact Factor
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ABSTRACT: This study sought to describe a protocol for myocardial perfusion imaging using dipyridamole stress, with 128-slice dual-source computed tomography (CT), and to assess the ability of CT myocardial perfusion imaging (MPI) to detect abnormal flow reserve and infarction in comparison with nuclear MPI (NMPI).
CT MPI has not been previously described with the 128-slice dual-source CT scanner, or with the complete evaluation of dynamic time-attenuation curves of the myocardium.
Thirty-five patients underwent a stress CT MPI protocol. Complete time-attenuation curves of the myocardium were acquired using a novel scan mode, which acquires prospectively electrocardiogram (ECG)-triggered axial images at 2 rapidly alternating positions. Myocardial blood flow (MBF) values of fixed and reversible defects obtained were compared between rest and stress. Findings on CT MPI were correlated to NMPI. Perfusion defects detected on CT were correlated to coronary stenoses detected on CT angiography (CTA) and invasive coronary angiography (ICA).
There was a 1.5-fold difference between stress (1.21 +/- 0.31 cc/cc/min) and rest (0.82 +/- 0.22 cc/cc/min) MBF in normal tissue. In reversible defects, MBF was 0.65 +/- 0.21 cc/cc/min and 0.63 +/- 0.18 cc/cc/min at stress and rest, respectively. In fixed defects, the MBF was 0.57 +/- 0.22 cc/cc/min at stress and 0.54 +/- 0.23 cc/cc/min at rest. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of CT MPI for identifying segments with perfusion defects was 0.83, 0.78, 0.79, and 0.82, respectively. ICA results were available for 30 patients. Sensitivity, specificity, PPV, and NPV of CT MPI compared with ICA were 0.95, 0.65, 0.78, and 0.79, respectively. The radiation dose for CT MPI was 9.15 +/- 1.32 mSv for the stress scan and 9.09 +/- 1.40 mSv for the rest scan.
Vasodilator-stress CT MPI may be feasible in human subjects at a radiation dose similar to NMPI. It identifies areas of abnormal flow reserve and infarction with a high degree of correlation to NMPI as well as to stenoses detected in CTA and ICA.
JACC. Cardiovascular imaging 08/2010; 3(8):811-20. · 14.29 Impact Factor
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ABSTRACT: Perfusion computed tomography is increasingly being used in diagnostic radiology. Axial coverage of the traditional approach is limited to the width of the detector. Using continuous periodic table movement coverage can be increased beyond this limit. In this study, we compared tissue flow values determined from scans with a periodic spiral implementation with variable pitch with ones determined from standard dynamic scan modes.
A flow phantom (preserved porcine kidney) was scanned with 2 settings of a periodic spiral (Adaptive 4D Spiral) with a range of 100 and 148 mm and a temporal sampling of 1.5 seconds. Additionally, the whole phantom was scanned with the standard dynamic mode (detector width 38.4 mm, temporal sampling 1.0 seconds) at various overlapping positions as a reference. Scan parameters (80 kV, 140 mAs, 40s scan time) were selected similar to a typical brain perfusion study. All scans were repeated 5 times. Tissue flow was calculated with a dedicated deconvolution algorithm. In a center slice and 3 additional slices at various off center positions flow values were recorded in a total of 126 regions of interest (ROI). Reproducibility was determined from the variation of the repeat scans. Agreement between periodic spirals and standard mode was determined by Bland Altman plots and correlation analysis.
The reproducibility of the tissue flow determination ranged from 2.7 to 4.4 mL/100 mL/min and was similar for all scan modes. The coefficient of variation ranged from 3.9% to 6.1%. Mean tissue flow in the 126 ROIs ranged from 35 to 121 mL/100 mL/min. There was excellent correlation between both periodic spiral ranges and the standard dynamic mode with a Pearson correlation coefficient of r = 0.97. The regression slope (intercept 0) for the 100 mm range was 1.01, for the 148 mm range it was 0.97. The absolute differences per ROI varied between 1.5 and 4.1 mL/100 mL/min, the relative differences between 1.9% and 6.5%. Differences did not depend on the slice location.
Periodic spiral scan modes with variable pitch and a sampling rate of 1.5 seconds can be used for the quantitative determination of tissue flow. Their performance is equivalent to equidistant sampling with standard dynamic scan modes. The ranges of 100 and 148 mm investigated allow coverage of the whole brain or an entire organ for perfusion imaging.
Investigative radiology 07/2010; 45(7):378-86. · 4.85 Impact Factor
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Andreas Helck,
Wieland H Sommer, Ernst Klotz,
Matthias Wessely,
Steven Pieter Sourbron,
Konstantin Nikolaou,
Dirk A Clevert,
Mike Notohamiprodjo,
Wolf D Illner,
Maximilian Reiser,
Hans-Christoph Becker
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ABSTRACT: To determine the feasibility of a dynamic CT angiography-protocol in regard to simultaneous assessment of morphology and function.
Fourteen patients with renal graft dysfunction received a dynamic computed tomography angiography (CTA) using a 128-slice CT-scanner with continuous bi-directional table movement, allowing to cover a scan range of 18 cm within 1.75 seconds. Twelve scans of the entire kidney were acquired every 3.5 seconds with the aim to simultaneously obtain CTA and renal function data. The glomerular filtration rate (GFR) was calculated by a modified Patlak method and compared with creatinine-based formulas (MDRD 4 and endogenous creatinine clearance), that served as reference standard.
GFR obtained from dynamic CTA correlates well with the GFR derived by creatinine-based formulas with a correlation coefficient of r = 0.8986; P < 0.0001. The average absolute deviation was 8.1 mL/min. The mean amount of contrast medium required was 35 mL. The average effective dose was 13.8 mSv.
Dynamic CTA offers the possibility to determine the GFR and thus facilitates simultaneous assessment of morphology and function. Additionally, our dynamic CTA-protocol helps to significantly reduce the amount of contrast medium, which is beneficial for patients with impaired renal function.
Investigative radiology 07/2010; 45(7):387-92. · 4.85 Impact Factor
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ABSTRACT: To quantify differences in regional myocardial perfusion in coronary artery stenosis by the use of dual source computed tomography (DSCT) in an animal model.
In 5 pigs, an 80% stenosis of the left anterior descending artery was successfully induced by partial balloon occlusion (ischemia group). Five animals served as control group. All animals underwent contrast enhanced whole heart DSCT (Definition Flash, Siemens, Germany) perfusion imaging using a prototype electrocardiogram -triggered dynamic scan mode. Imaging was performed at rest as well as under stress conditions during continuous infusion of adenosine (240 mg/kg/min). For contrast enhancement 60 mL Iopromide 300 (Ultravist 300, Bayer-Schering Pharma, Berlin, Germany) were injected at a rate of 6 mL/s. Myocardial blood flow (MBF), first pass distribution volume, and intravascular blood volume were volumetrically quantified.
In the control group MBF increased significantly from 98.2 mL/100 mL/min to 134.0 mL/100 mL/min if adenosine was administered (P = 0.0153). There were no significant differences in the perfusion parameters comparing the control and ischemia group at rest. In the ischemia group MBF under stress was 74.0 +/- 21.9 mL/100 mL/min in the poststenotic myocardium and 117.4 +/- 18.6 mL/100 mL/min in the remaining normal myocardium (P = 0.0024).
DSCT permits quantitative whole heart perfusion imaging. As this technique is able to show the hemodynamic effect of high grade coronary artery stenosis, it exceeds the present key limitation of cardiac computed tomography, which currently only allows a morphologic assessment of coronary artery stenosis.
Investigative radiology 06/2010; 45(6):298-305. · 4.85 Impact Factor
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ABSTRACT: Perfusion computed tomography (PCT) allows to quantitatively assess haemodynamic characteristics of brain tissue. We investigated if different brain tumor types can be distinguished from each other using Patlak analysis of PCT data.
PCT data from 43 patients with brain tumours were analysed with a commercial implementation of the Patlak method. Four patients had low-grade glioma (WHO II), 31 patients had glioblastoma (WHO IV) and eight patients had intracerebral lymphoma. Tumour regions of interest (ROIs) were drawn in a morphological image and automatically transferred to maps of cerebral blood flow (CBF), cerebral blood volume (CBV) and permeability (K (Trans)). Mean values were calculated, group differences were tested using Wilcoxon and Mann Whitney U-tests.
In comparison with normal parenchyma, low-grade gliomas showed no significant difference of perfusion parameters (p > 0.05) , whereas high-grade gliomas demonstrated significantly higher values (p < 0.0001 for K (Trans), p < 0.0001 for CBV and p = 0.0002 for CBF). Lymphomas displayed significantly increased mean K(Trans) values compared with unaffected cerebral parenchyma (p = 0.0078) but no elevation of CBV. High-grade gliomas show significant higher CBV values than lymphomas (p = 0.0078).
PCT allows to reliably classify gliomas and lymphomas based on quantitative measurements of CBV and K (Trans).
European Radiology 05/2010; 20(10):2482-90. · 3.22 Impact Factor
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ABSTRACT: Multidetector row computed tomography (MDCT) has been used for cardiothoracic imaging since the advent of 4-slice computed tomography (CT) in 1999. Available since 2004, 64-slice CT systems are currently considered a prerequisite for successfully integrating cardiothoracic CT into routine clinical algorithms. Developments are ongoing that aim to solve the remaining challenges of cardiothoracic CT. In this review article, we focus on 3 aspects that have significantly influenced the design of newer CT scanners. (1) A faster scan speed enables coverage of the cardiothoracic anatomy in shorter scan times, which is beneficial for patients with limited ability to cooperate and opens new clinical possibilities. A coveted goal for cardiac CT is a "snapshot image" of the entire heart in 1 cardiac cycle, which can be obtained by using MDCT systems with area detectors or dual-source CT systems with electrocardiogram (ECG)-triggered high-pitch spiral. (2) Techniques to reduce the radiation dose to the patient, such as ECG-controlled dose modulation, ECG-triggered sequential CT, low kV scanning, and iterative reconstruction, have gained considerable attention as a consequence of the ongoing discussion of radiation exposure by CT. (3) New developments aim to establish a role for CT in the functional imaging of the lung and of the heart beyond the mere visualization of anatomy. Evaluation of the first-pass enhancement of the myocardium, with single-energy or with dual-energy data acquisition, and cardiac perfusion examinations may have the potential to enhance the application spectrum of cardiac CT by providing the means to determine the hemodynamic relevance of coronary artery stenosis.
Journal of thoracic imaging 05/2010; 25(2):100-11. · 1.42 Impact Factor
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ABSTRACT: To detail the principles of using model-based determination of regional myocardial blood flow (MBF) by computed tomography (CT) and demonstrate its in vivo applicability.
Dual-source CT was performed with a dynamic protocol comprising acquisition with alternating table positions in ECG-triggered end-systolic timing every second for 30 s. The results of two reconstructions were merged into one final image stack (coverage 73 mm), with low spatial frequency components from a 360 degrees reconstruction and high spatial frequency components from a dual-source cardiac partial image reconstruction. A parametric deconvolution technique was used to fit the time-attenuation curves (TAC), the maximum slope of which was used to derive MBF.
One study participant underwent dynamic myocardial stress perfusion imaging (9.6 mSv) followed by invasive coronary angiography and measurement of fractional flow reserve as the gold standard. MBF was 159 ml/100 ml/min in the non-ischaemic anterolateral and 86 ml/100 ml/min in the inferoseptal ischaemic wall.
This first evaluation indicates that mathematical modelling of voxel TACs can potentially be used to quantify differences in MBF in a clinical setting. If confirmed in feasibility studies, cardiac CT may allow for parallel assessment of morphology and haemodynamic relevance of coronary artery disease.
European Radiology 03/2010; 20(5):1168-73. · 3.22 Impact Factor
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ABSTRACT: In the recent years numerous studies have been undertaken to study cerebral perfusion in the surrounding of intracerebral hemorrhage, addressing the question of whether there is a secondary ischemic damage. Most of these studies found a reduced perfusion adjacent to the hematoma. However, the meaning of these findings remains controversial.
We used perfusion computed tomography in 17 patients to study time to peak, cerebral blood flow, and cerebral blood volume as markers of the perihemorrhagic perfusion within 3 hours after symptom onset to search for an early difference between the extent of edema and reduced perfusion.
All patients showed a significant reduction of all perfusion parameters in the perihemorrhagic area, while there was no difference between the latitude of the reduced perfusion and the edema.
We did not find a difference between the extension of edema and that of restricted perfusion at a very early time point and therefore could not identify any tissue at risk of ischemia. Our findings suggest reduced perfusion and edema to have a common cause rather than presupposing one another.
Journal of neuroimaging: official journal of the American Society of Neuroimaging 09/2009; 20(4):350-3. · 1.72 Impact Factor
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ABSTRACT: Perfusion computed tomography (PCT) is increasingly getting popular with the advent of computed tomography (CT) systems with adequate temporal resolution and spatial coverage. We sought to develop a biological phantom for perfusion measurements in CT to design, improve, and validate scan protocols and postprocessing algorithms in vitro.
A special technique was applied to prepare and preserve a fresh porcine kidney. The kidney was connected to an open circuit driven by a peristaltic pump with the option to inject contrast material. We evaluated repeated dynamic contrast-enhanced CT acquisitions with different input flow rates and the relation to calculated parenchymal flow results of the phantom. Flow was calculated with 2 different algorithms. Identical scans were performed with a time interval of 1 year to check long-term stability of the phantom. Different bolus geometries were designed and bolus dispersion was measured for the setup using a tubing array.
We found a linear relationship between the input flow rate of the circuit and the calculated phantom tissue flow with a correlation coefficient rr2 = 0.99 for both algorithms. Both algorithms resulted in very similar absolute values, the mean difference was 3.1 mL/100 mL/min. Perfusion measurements with contrast material injection and storage did not alter the phantom. The enhancement properties did not change over the time of 1 year. With our setup, it was possible to design typical bolus geometries as they occur in clinical practice. Bolus dispersion was small: peak enhancement and bolus width changed by about only 5% over 2-m tube length.
A phantom for parenchymal flow measurements suitable for repeated measurements over a long period of time was developed. The setup allows the design of diverse bolus geometries with negligible dispersion.
Investigative radiology 09/2009; 44(10):676-82. · 4.85 Impact Factor
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ABSTRACT: In this study the authors compared a computer simulation that models bolus dispersion during the first pass to patient PCT data acquired with three different types of injection protocols. PCT was performed in 27 patients with one of the three injection protocols: (1) Monophasic bolus injection with saline flush, (2) monophasic bolus injection without saline flush, and (3) biphasic bolus injection with saline flush. They performed computer simulation to model bolus dispersion in the three injection protocols. Finally, they compared the simulated attenuation-time curves to the measured ones. The simulated attenuation-time curves corresponded well to the measured data for protocol 1. With protocol 2 they found that simulation predicts bolus kinetics correctly but overestimates the concentration by about 31%. They attributed this to the missing saline flush. By comparing the simulated and measured data, they could show that without saline flush about 1/3 of the contrast agent does not contribute to the first pass. For the biphasic injection (protocol 3), they found that the first part of the attenuation-time curve can be modeled by simulating the bolus dispersion of only the high-flow portion of the injected bolus. Although the simulation model does only take into account of the first pass of the bolus, it is a useful tool to analyze and predict effects of modified injection protocols.
Medical Physics 08/2009; 36(8):3487-94. · 2.83 Impact Factor
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ABSTRACT: The purpose of this study was to assess virtual unenhanced brain computed tomography (CT) images obtained by dual-energy CT angiography (CTA) for the detection of intracranial bleeding. In total, 25 patients were included in the study (average age 53.2 years, range 25-75 years, 14 male, 11 female), all with intracranial bleeding on unenhanced brain CT and who underwent additional CTA performed on a dual-source CT in a dual-energy acquisition mode. The two X-ray tubes were operated at 140 and 80 kV, respectively. Data were analyzed using dual-energy evaluation software. Virtual unenhanced images were calculated by removing the relative iodine content from each voxel. The virtual unenhanced images were evaluated by a radiologist blinded to the findings of the conventional images related to the presence of intracranial bleeding. The image quality and contrast-to-noise ratio (CNR) between bleeding and brain tissue were assessed. The virtual image quality was found to be sufficient in 96%. The agreement in detection of intracranial bleeding on virtual and conventional unenhanced images reached 96% in per-lesion analysis and 100% in per-patient analysis. The averaged CNR reached 2.63 in virtual unenhanced images and 3.27 in conventional. Virtual unenhanced images are sufficient for the detection of intracranial bleeding.
European Radiology 08/2009; 19(10):2518-22. · 3.22 Impact Factor
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ABSTRACT: Computed tomography angiography (CTA) is a well-accepted imaging modality to evaluate the vessels of the head and neck. To improve the assessment of vessels at or within the skull base, different techniques to suppress bone in the final CTA image have been developed. We sought to compare the performance of fully automated bone removal based on dual energy (DE) and image registration (bone subtraction CTA [BSCTA]) for the supraaortic vasculature.
Twenty-seven patients underwent carotid CTA on a dual source CT system. Two scans were performed, one before and one after contrast agent injection in DE mode (simultaneous acquisition of 80 and 140 kV scans). For each patient, data sets were reconstructed for post processing with DE and BSCTA. Two examiners evaluated overall bone suppression and image quality regarding integrity of the vessel lumen of different vessel segments (n = 19) with a 5-point scale (1 = poor, 5 = excellent), CTA source data served as the reference. Wilcoxon signed rank test was used to determine differences between the techniques. Cohen's kappa was used to determine interobserver agreement.
Both bone suppression techniques could be applied successfully in 25 patients with high overall image quality. Two patients were excluded from the evaluation for technical reasons. Interobserver agreement was excellent (kappa = 0.85). Mean score of all vessel segments for overall bone removal was 4.45 +/- 0.76 for DE and 4.33 +/- 1.02 for BSCTA; DE performed better in the vessel segment of the neck (external carotid artery, common carotid artery, V1 to V3 segment of the vertebral artery, subclavian artery), whereas BSCTA was superior in the cranial vessels (C3-C6 segment of the internal carotid artery, ophthalmic artery). Vessel integrity was superior with BSCTA, the mean score of all vessel segments for overall vessel integrity was 3.97 +/- 1.47 for DE and 4.49 +/- 0.98 for BSCTA, the subclavian artery was most frequently truncated using DE post processing (mean score: 1.44 +/- 1.2).
Both techniques provided bone suppression in a fully automated way. DE provided more complete bone suppression in the neck, but at the cost of inferior vessel integrity, especially at the thoracic inlet. BSCTA showed excellent results for vessel integrity and was superior to DE in most of the vessels in or at the skull base.
Investigative radiology 05/2009; 44(6):322-8. · 4.85 Impact Factor
