Large mismatch profile predicts rapidly progressing brain edema in acute anterior circulation large vessel occlusion patients undergoing endovascular thrombectomy

Background

Brain edema is a severe complication in patients with large vessel occlusion (LVO) that can reduce the effectiveness of endovascular therapy (EVT). This study aimed to investigate the association of the perfusion profile at baseline computed tomography (CT) perfusion with rapidly progressing brain edema (RPBE) after EVT in patients with acute anterior LVO.

Methods

We retrospectively reviewed consecutive data collected from 149 patients with anterior LVO who underwent EVT at our center. Brain edema was measured by the swelling score (0-6 score), and RPBE was defined as the swelling score increased by more than 2 scores within 24 h after EVT. We investigated the effect of RPBE on poor outcomes [National Institute of Health Stroke Scale (NIHSS) score and modified Rankin scale (mRS) score at discharge, the occurrence of hemorrhagic transformation, and mortality rate in the hospital] using the Mann-Whitney U-test and chi-square test. A multivariate logistic regression model was used to assess the relationship between perfusion imaging parameters and RPBE occurrence.

Results

Overall, 39 patients (26.2%) experienced RPBE after EVT. At discharge, RPBE was associated with higher NIHSS scores (Z = 3.52, 95% CI 2.0-12.0, P < 0.001) and higher mRS scores (Z = 3.67, 95% CI 0.0-1.0, P < 0.001) including the more frequent occurrence of hemorrhagic transformation (χ² = 22.17, 95% CI 0.29-0.59, P < 0.001) and higher mortality rates in hospital (χ² = 9.54, 95% CI 0.06-0.36, P = 0.002). Univariate analysis showed that intravenous thrombolysis, baseline ischemic core volume, and baseline mismatch ratio correlated with RPBE (all P < 0.05). After dividing the mismatch ratio into quartiles and performing a chi-square test between quartiles, we found that the occurrence of RPBE in Q4 (mismatch ratio > 11.3) was significantly lower than that in Q1 (mismatch ratio ≤ 3.0) (P < 0.05). The result of multivariate logistic regression analysis showed that compared with baseline mismatch ratio <5.1, baseline mismatch ratio between 5.1 and 11.3 (OR:3.85, 95% CI 1.06-14.29, P = 0.040), and mismatch ratio >11.3 (OR:5.26, 95% CI 1.28-20.00, P = 0.021) were independent protective factors for RPBE.

Conclusion

In patients with anterior circulation LVO stroke undergoing successful EVT, a large mismatch ratio at baseline is a protective factor for RPBE, which is associated with poor outcomes.

[Orbital venous varices: modern diagnostic methods and differential diagnosis]

OBJECTIVE

To study the possibility of the modern CT and MRI methods in diagnostics of the orbital venous varices (OVV), discover the special characteristics of these lesions concerning their hemodynamic and differential diagnosis with other orbital lesions.

MATERIAL AND METHODS

In the period from 2012 to 2019 ten patients with OVV were evaluated. Four of them were men, three - women and three - children (boys aged 7, 10, and 12 years). Age of the patients varied from 7 to 75 years old (mediana - 34).

CT was performed on 9 patients using low dose protocol with injecting the contrast in standard position (supine) and in the prone position. CT-angiography was performed on 3 patients and CT-perfusion - 5 patients which allowed the assessment of the blood supply and quantitative lesions hemodynamic by calculating blood flow (BF_OVV), blood volume (BV_OVV) and mean transit time (MTT_OVV).

MRI with contrast injection and Fat Sat technology was performed on 9 patients, 3 of them were both in the supine and prone positions. 4 patients were evaluated by bolus MR-angiography (TRICKS).

RESULTS

The majority of the OVV was localized in the medial compartments and apex of the orbit. Left sided lesions were found in 6 cases, right - 3. One patient had both sided OVV. In one of the cases in 10-year-old child, we revealed malformation of the Galen vein associated with bilateral varicose enlargement of the intraorbital veins (secondary OVV).

In CT studies all of the lesions enhanced after the contrast injection. When the patients were study in the prone position, all lesions were enlarging; which lead to the diagnosis of OVV. CT-angiography (venous blood flow) proved vascular nature of the lesions. While studying the quantitative lesion hemodynamic by the CT perfusion technology, it was discovered, that OVV tend to have high blood volume (BV_OVV=19.61±3.23(ml/100g) and high blood flow (BF_OVV= 60.87±8.11) and the prolongation of mean transit time (MTT_OVV=19.23±3.07). Normal parameters measured in white matter were CBV_N=1.37±0.69(ml/100g), CBF_N=38.4±4.31(ml/100g/min), MTT_N=2.89±0.44s.

In MRI studies all the lesions had iso-hypointense MR-signal on T1- and hyperintense on T2-images. The pattern of contrast enhancement was inhomogeneous, however reaching homogeneity after some time. TRICKS MR-angiography was more sensitive than CT-angiography (venous phase). Moreover, the absence of radiation exposition was an additional advantage of the MR-venography.

CONCLUSION

Diagnosis of orbital vascular pathology requires an understanding of the classification of vascular lesions, the integration of the patient's medical history with epidemiological data, as well as a through analysis of the results of instrumental diagnostic methods. CT or MRI, including scanning in the prone position, as well as minimally invasive CT- and MR-TRICKS-angiography and ophthalmological studies of the patient, determine a comprehensive approach to the diagnosis and selection of adequate treatment for orbital venous varices.

In the differential diagnosis of OVV with other neoplasms of the orbit, we recommend CT-perfusion study with determine the quantitative characteristics of its hemodynamics.

A prospective feasibility study evaluating the role of multimodality imaging and liquid biopsy for response assessment in locally advanced rectal carcinoma

PURPOSE

Colorectal cancer is a commonly encountered disease that poses several diagnostic and therapeutic challenges. The inherent heterogeneity of tumor biology and propensity to relapse despite "curative" resection pose significant challenges with regard to response assessment. Although MR imaging already plays a key role in primary staging of patients with rectal carcinoma, its reliability in restaging after neoadjuvant therapy is debatable (Van der broek et al. in Dis Colon Rectum 60(3):274-283, 2017). Therefore, there is significant interest in developing additional methods which may improve diagnostic accuracy. This study aims to evaluate the role of multimodality imaging and liquid biopsy in therapeutic response assessment.

METHODS

Seventeen patients were enrolled into the study over a span of 24 months. All underwent hybrid PET-MRI and CT-perfusion (CT-P), prior to and following neoadjuvant therapy for locally advanced rectal carcinoma. Twelve of the 17 patients also underwent liquid biopsy, which consisted of blood sampling and analysis of circulating tumor cells (CTCs) and extracellular vesicles (EVs), including cell fragments and microparticles (MPs), using the Cell Search System (Menarini Silicon Biosystems). SUV, DWI, and ADC were calculated during PET-MRI, and several parameters were evaluated during CT-perfusion, including average perfusion, blood flow (BF), blood volume (BV), mean transit time (MTT), permeability-surface area product (PS), contrast extraction efficiency (E), and K-trans (K). Changes observed pre- and post-neoadjuvant therapy in each modality were compared to tumor response at histopathology using a modified Ryan tumor regression grading system.

RESULTS

Of the 17 patients included in the study, 14 were classified as non-responders, and 3 were classified as responders as determined by the modified Ryan Tumor Regression Grade (TRG) scoring system (Van der broek et al. in Dis Colon Rectum 60(3):274-283, 2017). When combined, blood markers and CT-P parameters (mean transit time (MTT), K-trans, and permeability-surface area product (PS)) produced the strongest models (p < 0.01). PET (SUV measurement) combined with CT-P-derived K-trans produced a marginally significant (p = 0.057) model for predicting response. MRI-derived ADC value did not provide a significant model for response prediction.

CONCLUSION

A model of CT-P parameters plus liquid biopsy more accurately predicts tumor response than PET-MRI, CT-P alone, or liquid biopsy alone. These results suggest that in the evaluation of treatment response, liquid biopsy could provide additional information to functional imaging modalities such as CT-P and should therefore be explored further in a trial with larger sample size.

[Significance of CT perfusion examination of cerebral blood flow for assessing the risk of brain ischemia in patients with intracranial arterial aneurysm ruptures]

Prognosing the outcome of cerebral ischemia in the acute SAH phase still remains the topical issue for clinical practice because this largely affects the choice of an optimal timing of aneurysm clipping. The traditional criteria are often not effective enough to predict changes in cerebral ischemia, especially in patients in a compensated or subcompensated state who often develop delayed ischemia, which may lead to serious complications. The introduction of a CT perfusion technique for evaluating the volumetric cerebral blood flow stimulated the development of a new stage in investigation of cerebral ischemia in non-traumatic SAH.

PURPOSE

The study purpose was to evaluate the significance of cerebral blood flow indicators obtained by CT perfusion for prediction of delayed cerebral ischemia and postoperative ischemic complications to optimize treatment of patients with ruptures of intracranial arterial aneurysms.

MATERIAL AND METHODS

The study included 70 patients who underwent aneurysm clipping and 42 non-operated patients. The inclusion criteria were as follows: WFNS grade I-III condition, vasospasm according to transcranial Doppler sonography, and availability of CT scans, including CT perfusion data. The vasospasm severity and perfusion indicators _(rCBV and MTT) were evaluated. The severity of subarachnoid and ventricular hemorrhage was evaluated according to the A. Hijdra method. The final results were evaluated using a clinical-statistical method, including ROC analysis.

RESULTS

An analysis of the obtained data revealed that the risk of delayed cerebral ischemia and postoperative ischemia increases significantly if the baseline hemispheric CBF value is below a threshold of 40 ml/100 g/min, and the baseline MMT indicator is above a threshold of 5 s. There was asymmetry of these CT perfusion indicators due to a larger deviation from the threshold values in the homolateral hemisphere compared to the opposite side. The ROC analysis results demonstrated diagnostic sensitivity and diagnostic specificity of the CT perfusion technique.

CONCLUSION

The CT perfusion data together with the SAH severity and localization indicators may be used as predictors for the cerebral ischemia outcome in choosing the optimal timing of aneurysm clipping during the acute SAH period in patients in a WFNS grade I-III condition and with signs of mild or moderate vasospasm.

[Orbital hemangiomas: capabilities of modern neuroradiological diagnostics]

MATERIAL AND METHODS

In the period from 2010 to 2016. 14 patients with cavernous hemangioma (CH) and 2 patients with capillary hemangioma (CapH) of the orbit were examined. The age of CH patients varied from 17 to 67 years (median, 53 years); 8 females and 6 males. The age of CapH patients was 35 and 54 years. All patients underwent surgery with subsequent histological verification. CT-perfusion was performed in 10 CH patients and 2 CapH patients according to a developed low-dose protocol (80 kV, 200 mAs, t_scan=40 s) with allowance for a target localizer (80 kV, 120 mAs) and at a maximum radiation dose of not more than 4.0 mZv. Neoplasm microcirculation was quantitatively assessed by calculating hemodynamic parameters: blood flow velocity (BFV), blood volume (BV), and mean transit time (MTT). MRI without and with contrast enhancement was performed in 11 CH patients and 2 CapH patients according to the ophthalmologic protocol (Signa GE, 3.0 T) accepted at the Institute: without contrast enhancement - T1, T2, and T2-FLAIR modes, T1 and T2 with a Fat Sat technique at a scan thickness of 3 mm, and DWI MRI; contrast enhancement - T1 (three projections) mode, including the Fat Sat technique. SWAN (n=2) and non-contrast MR perfusion ASL (n=3) were also used. Diffusion-weighted images (DWI) were processed with calculation of the apparent diffusion coefficient (ACD).

RESULTS

In all CH patients, CT-perfusion revealed low perfusion parameters of blood flow: BV_CH=0.86±0.37 mL/100 g, BFV_CH= 4.89±2.01 mL/100 g/min with a high mean transit time MTT_CH=10.13±3.05 s compared to the same parameters of blood flow in the normal white matter: CBV_NormWM=1.63±2.22 mL/100 g, CBFV_NormWM=9.72±3.13 mL/100 g/min, and MTT_NormWM=6.76±2.78 s. In CapH cases, significantly increased blood flow velocity and volume values and a low MTT value in the tumor were observed: BV_CapH=10.30±4.10 mL/100 g, BFV_CapH=119.72±53.13 mL/100 g/min, and MTT_CapH=4.35±1.79 s. In the case of orbital hemangiomas, optimal MRI modes were T1 and T2 with the Fat Sat technique, a scan thickness of 3 mm, and intravenous contrast enhancement. The revealed pattern of contrast agent accumulation by CH, initially in the central part and then in the periphery, may be a useful radiographic sign in the differential diagnosis with other orbital tumors.

CONCLUSION

Modern CT- and MRI-based diagnostics of orbital hemangiomas provides not only the exact location, size, and spread of the lesion but also reveals the characteristic structural features of these tumors, and the use of perfusion techniques visualizes hemodynamics of the tumors. CT-perfusion-based hemodynamic parameters of cavernous hemangiomas typical of this type of hemangiomas may be used in the differential diagnosis with other tumors of this location. The use of contrast enhancement and the Fat Sat technique with a scan thickness of not more than 3 mm is optimal for MRI diagnostics of orbital hemangiomas.

[Brain atrophy and perfusion changes in patients with remitting and secondary progressive multiple sclerosis]

AIM

To study the relationship of brain atrophy and changes in perfusion with an increase in the level of disability in patients with multiple sclerosis (MS).

MATERIAL AND METHODS

Twenty patients with remitting MS, 20 patients with secondary progressive multiple sclerosis (SPMS) and 20 healthy people were studied. The level of neurological deficit was assessed with EDSS and cognitive status with PASAT. MRI of the brain (standard impulse sequences and 3D-T1-MPR for voxel MRI-morphometry) and perfusion computed tomography with the assessment of visually intact white matter (VIWM) and thalamus were performed.

RESULTS

Compared to the control group, patients with MS had a significant atrophy of subcortical gray matter. Patients with SPMS in addition had an atrophy of some cortical areas which was correlated with EDSS scores (p<0.05). The correlation between cognitive impairment and the volume of the left inferior parietal lobule (r=0.677; p=0.011) and worsening of perfusion of VIWM of frontal and parietal lobes, thalamus on both sides was observed in patients with SPMS compared to those with remitting MS. That was correlated with cognitive performance assessed by PASAT.

CONCLUSION

Patterns of atrophy distribution in different types of MS were determined. The level of disability is correlated with the severity of brain atrophy. Hypoperfusion of VIWM that was correlated with cognitive impairment was found in patients with SPMS.

Computational Fluid Dynamics as an Engineering Tool for the Reconstruction of Hemodynamics after Carotid Artery Stenosis Operation: A Case Study

Background and objectives: Brain ischemic stroke is caused by impaired or absolutely blocked blood flow into the brain regions. Despite the large number of possible origins, there is no general strategy for preventive treatment. In this paper, we aimed to predict the hemodynamics in a patient who experienced a critical stenosis operation in the carotid artery. This is a unique study where we used medical data together with the computational fluid (CFD) technique not to plan the surgery, but to predict its outcome. Materials and Methods: AngioCT data and blood perfusion of brain tissue (CT-perfusion) together with CFD technique were applied for stroke formation reconstruction in different clinical conditions. With the use of self-made semiautomatic algorithm for image processing and 3DDoctror software, 3D-vascular geometries before and after surgical intervention were reconstructed. As the paper is focused on the analysis of stroke appearance, apparent stroke was simulated as higher and lower pressure values in the cranial part due to different outcomes of the surgical intervention. This allowed to investigate the influence of spatial configuration and pressure values on blood perfusion in the analyzed circulatory system. Results: Application of CFD simulations for blood flow reconstruction for clinical conditions in the circulatory system accomplished on average 98.5% and 98.7% accuracy for CFD results compared to US-Doppler before and after surgical intervention, respectively. Meanwhile, CFD results compared to CT-perfusion indicated an average 89.7% and 92.8% accuracy before and after surgical intervention, respectively. Thus, the CFD is a reliable approach for predicting the patient hemodynamics, as it was confirmed by postoperative data. Conclusions: Our study indicated that the application of CFD simulations for blood flow reconstruction for clinical conditions in circulatory system reached 98% and 90% accuracy for US-Doppler and CT-perfusion, respectively. Therefore, the proposed method might be used as a tool for reconstruction of specific patients' hemodynamics after operation of critical stenosis in the carotid artery. However, further studies are necessary to confirm its usefulness in clinical practice.

Perfusion CT and PET with 18F-FDG and 18F-FCh in the complex diagnosis of hepatocellular carcinoma

Background

The purpose of the study to evaluate possibilities of CT-perfusion and PET methods with 18F-FDG and 18F-fluorocholine in the complex diagnosis of hepatocellular carcinoma. The study included the results of PET/CT with 18F-FDG, 18F-FCh and CT-perfusion of the liver in 18 patients with histologically confirmed diagnosis of hepatocellular carcinoma (HCC). Depending on the degree of tumor differentiation, all patients were divided into 3 groups - patients with highly differentiated (6 patients), moderately differentiated (4 patients), and low-differentiated HCC (8 patients).

Results

Average values of maxSUV in the group of patients with highly differentiated HCC in PET/CT with 18F-FDG and 18F- fluorocholine in a solid component of tumor reached 3.51 and 18.24, respectively; in patients with moderately differentiated HCC - 3.91 and 12.32, respectively; in patients with low-differentiated HCC - 9.58 and 9.70, respectively. Average values of CT perfusion imaging in a solid component of the tumor in the group of patients with highly differentiated HCC were the following: BF - 55,33 ml/100 ml/min, BV - 13,71 ml/100 ml, ALP - 52,41 ml/100 ml/min, PVP - 10.81 ml/100 ml/min (p ≤ 0,05), in the group of patients with moderately differentiated HCC: BF - 52,78 ml/100 m /min, BV - 12,23 ml/100 ml, ALP - 47,26 ml/100 ml/min, PVP - 9,10 ml/100 ml/min (p ≤ 0.05), in the solid component of low-differentiated HCC: BF - 46,96 ml/100 ml/min, BV - 9,49 ml/100 ml, ALP - 40.54 ml/100 ml/min, PVP - 7,66 ml/100 ml/min (p ≤ 0,05).

Conclusions

The diagnostic capabilities of the complex of PET/CT techniques with 18F-FDG and 18F-FCh and CT perfusion in a single-scan mode for hepatocellular carcinoma were evaluated for the first time. The obtained data allow to assume that the integrated use of PET with 18F-FDG and 18F-FCh and CT perfusion in a single scan improves the differential diagnostic possibilities of PET/CT diagnostics, which can find application in planning and prognosis of the disease. Due to the small number of patients further study of the problem is required.

CT perfusion imaging of the liver and the spleen in patients with cirrhosis: Is there a correlation between perfusion and portal venous hypertension?

OBJECTIVES

To correlate hepatic and splenic CT perfusion parameters with hepatic venous pressure gradient (HVPG) measurements in patients with cirrhosis.

METHODS

Twenty-one patients with cirrhosis (males, 17; females, 4; mean ± SD age, 57 ± 7 years) underwent hepatic and splenic perfusion CT on a 320-detector row volume scanner as well as invasive measurement of HVPG. Different CT perfusion algorithms (maximum slope analysis and Patlak plot) were used to measure hepatic arterial flow (HAF), portal venous flow (PVF), hepatic perfusion index (HPI), splenic arterial flow (SAF), splenic blood volume (SBV) and splenic clearance (SCL). Hepatic and splenic perfusion parameters were correlated with HVPG, and sensitivity and specificity for detection of severe portal hypertension (≥12 mmHg) were calculated.

RESULTS

The Spearman correlation coefficient was -0.53 (p < 0.05) between SAF and HVPG, and -0.68 (p < 0.01) between HVPG and SCL. Using a cut-off value of 125 ml/min/100 ml for SCL, sensitivity for detection of a HVPG of ≥12 mmHg was 94%, and specificity 100%. There was no significant correlation between hepatic perfusion parameters and HVPG.

CONCLUSION

CT perfusion in patients with cirrhosis showed a strong correlation between SCL and HVPG and may be used for detection of severe portal hypertension.

KEY POINTS

• SAF and SCL are statistically significantly correlated with HVPG • SCL showed stronger correlation with HVPG than SAF • 125 ml/min/100 ml SCL-cut-off yielded 94 % sensitivity, 100 % specificity for severe PH • HAF, PVF and HPI showed no statistically significant correlation with HVPG.

Myocardial ischemia detection with single-phase CT perfusion in symptomatic patients using high-pitch helical image acquisition technique

Coronary CT angiography (CCTA) suffers from a reduced diagnostic accuracy in patients with heavily calcified coronary arteries or prior myocardial revascularisation due to artefacts caused by calcifications and stent material. CT myocardial perfusion imaging (CTMPI) yields high potential for the detection of myocardial ischemia and might help to overcome the above mentioned limitations. We analysed CT single-phase perfusion using high-pitch helical image acquisition technique in patients with prior myocardial revascularisation. Thirty-six patients with an indication for invasive coronary angiography (28 with coronary stents, 2 with coronary artery bypass grafts and 6 with both) were included in this prospective study at two study sites. All patients were examined on a 2nd generation dual-source CT system. Stress CT images were obtained using a prospectively ECG-triggered single-phase high-pitch helical image acquisition technique. During stress the tracer for myocardial perfusion (MP) SPECT imaging was administered. Rest CT images were acquired using prospectively ECG-triggered sequential CT. MP-SPECT imaging and invasive coronary angiography served as standard of reference. In this heavily diseased patient cohort CCTA alone showed a low overall diagnostic accuracy for detection of hemodynamically relevant coronary artery stenosis of only 31% on a per-patient base and 60% on a per-vessel base. Combining CCTA and CTMPI allowed for a significantly higher overall diagnostic accuracy of 78% on a per-patient base and 92% on a per-vessel base (p < 0.001). Mean radiation dose for stress CT scans was 0.9 mSv, mean radiation dose for rest CT scans was 5.0 mSv. In symptomatic patients with known coronary artery disease and prior myocardial revascularization combining CCTA and CTMPI showed significantly higher diagnostic accuracy in detection of hemodynamically significant coronary artery stenosis when compared to CCTA alone.

Pre-and postoperative cerebral blood flow changes in patients with idiopathic normal pressure hydrocephalus measured by computed tomography (CT)-perfusion

In idiopathic normal pressure hydrocephalus (iNPH), the cerebral blood flow (CBF) is of pathophysiological interest and a potential biomarker. Computed tomography perfusion (CTP), an established technique with high spatial resolution and quantitative measurements, has not yet been used in the iNPH context. If CTP were sensitive to the CBF levels and changes in iNPH, this technique might provide diagnostic and prognostic absolute perfusion thresholds. The aim of this work was to determine the applicability of CTP to iNPH. CBF measurements of 18 patients pre- and 17 three months postoperatively, and six healthy individuals (HI) were evaluated in 12 cortical and subcortical regions of interest. Correlations between CBF and symptomatology were analyzed in shunt-responders. Compared to HI, the preoperative CBF in iNPH was significantly reduced in normal appearing and periventricular white matter (PVWM), the lentiform nucleus and the global parenchyma. No CBF differences were shown between responders and non-responders. In responders, the CBF recovered postoperatively by 2.5-32% to approximately the level of HI, but remained significantly decreased in the PVWM of non-responders. The pre- and postoperative CBF of cortical and subcortical regions correlated with the intensity of symptoms. In spite of limited spatial coverage, CTP can measure CBF changes in iNPH.

Computed Tomography Perfusion, Magnetic Resonance Imaging, and Histopathological Findings After Laparoscopic Renal Cryoablation: An In Vivo Pig Model

The present study investigates how computed tomography perfusion scans and magnetic resonance imaging correlates with the histopathological alterations in renal tissue after cryoablation. A total of 15 pigs were subjected to laparoscopic-assisted cryoablation on both kidneys. After intervention, each animal was randomized to a postoperative follow-up period of 1, 2, or 4 weeks, after which computed tomography perfusion and magnetic resonance imaging scans were performed. Immediately after imaging, open bilateral nephrectomy was performed allowing for histopathological examination of the cryolesions. On computed tomography perfusion and magnetic resonance imaging examinations, rim enhancement was observed in the transition zone of the cryolesion 1week after laparoscopic-assisted cryoablation. This rim enhancement was found to subside after 2 and 4 weeks of follow-up, which was consistent with the microscopic examinations revealing of fibrotic scar tissue formation in the peripheral zone of the cryolesion. On T2 magnetic resonance imaging sequences, a thin hypointense rim surrounded the cryolesion, separating it from the adjacent renal parenchyma. Microscopic examinations revealed hemorrhage and later hemosiderin located in the peripheral zone. No nodular or diffuse contrast enhancement was found in the central zone of the cryolesions at any follow-up stage on neither computed tomography perfusion nor magnetic resonance imaging. On microscopic examinations, the central zone was found to consist of coagulative necrosis 1 week after laparoscopic-assisted cryoablation, which was partially replaced by fibrotic scar tissue 4 weeks following laparoscopic-assisted cryoablation. Both computed tomography perfusion and magnetic resonance imaging found the renal collecting system to be involved at all 3 stages of follow-up, but on microscopic examination, the urothelium was found to be intact in all cases. In conclusion, cryoablation effectively destroyed renal parenchyma, leaving the urothelium intact. Both computed tomography perfusion and magnetic resonance imaging reflect the microscopic findings but with some differences, especially regarding the peripheral zone. Magnetic resonance imaging seems an attractive modality for early postoperative follow-up.

Functional and anatomical measures for outflow boundary conditions in atherosclerotic coronary bifurcations

The aim of this research was finding the influence of anatomy-based and functional-based outflow boundary conditions for computational fluid dynamics (CFD) on fractional flow reserve (FFR) and wall shear stress (WSS) in mildly diseased coronary bifurcations. For 10 patient-specific bifurcations three simulations were set up with different outflow conditions, while the inflow was kept constant. First, the outflow conditions were based on the diameter of the outlets. Second, they were based on the volume estimates of the myocardium that depended on the outlets. Third, they were based on a myocardial flow measure derived from computed tomography perfusion imaging (CTP). The difference in outflow ratio between the perfusion-based and the diameter-based approach was -7 p.p. [-14 p.p.:7 p.p.] (median percentage point and interquartiles), and between the perfusion-based and volume-based this was -2 p.p. [-2 p.p.:1 p.p.]. Despite of these differences the computed FFRs matched very well. A quantitative analysis of the WSS results showed very high correlations between the methods with an r(2) ranging from 0.90 to 1.00. But despite the high correlations the diameter-based and volume-based approach generally underestimated the WSS compared to the perfusion-based approach. These differences disappeared after normalization. We demonstrated the potential of CTP for setting patient-specific boundary conditions for atherosclerotic coronary bifurcations. FFR and normalized WSS were unaffected by the variations in outflow ratios. In order to compute absolute WSS a functional measure to set the outflow ratio might be of added value in this type of vessels.

Tumour-related neoangiogenesis: functional dynamic perfusion computed tomography for diagnosis and treatment efficacy assessment in hepatocellular carcinoma

BACKGROUND

Aim of the study was to determine the value of perfusion computed tomography in the quantitative assessment of tumour-related neoangiogenesis for the diagnosis and treatment of hepatocellular carcinoma lesions.

METHODS

Overall, 47 consecutive patients with cirrhotic liver disease, with a high risk of hepatocellular carcinoma, and undergoing standard surveillance (six-month intervals) were eligible for inclusion in this prospective study; based on Barcelona Clinic Liver Cancer guidelines, 27 patients were enrolled. Perfusion computed tomography was performed in 29 biopsy-proven hepatocellular carcinoma lesions before and after treatment with transarterial chemoembolization or radiofrequency ablation. The dynamic study was performed with a 256-slice multidetector-computed tomography scanner; the following parameters were measured: hepatic perfusion, arterial perfusion, blood volume, hepatic perfusion index, and time-to-peak in all patients.

RESULTS

Hepatocellular carcinoma lesions had the following median perfusion values: perfusion 46.3mL/min/100g; blood volume 20.4mL/100mg; arterial perfusion 42.9mL/min; hepatic perfusion index 92.5%; time to peak 18.7s. Significantly lower perfusion values were obtained in correctly treated lesions or surrounding parenchyma than in viable hepatocellular carcinoma tissue.

CONCLUSIONS

In hepatocellular carcinoma, perfusion computed tomography could contribute to a non-invasive quantification of tumour blood supply related to the formation of new arterial structures, and enable the assessment of therapeutic response.