Quantitative liver tumor blood volume measurements by a C-arm CT post-processing software before and after hepatic arterial embolization therapy: comparison with MDCT perfusion

Model-based perfusion reconstruction with time separation technique in cone-beam CT dynamic liver perfusion imaging

BACKGROUND

The success of embolization, a minimally invasive treatment of liver cancer, could be evaluated in the operational room with cone-beam CT by acquiring a dynamic perfusion scan to inspect the contrast agent flow.

PURPOSE

The reconstruction algorithm must address the issues of low temporal sampling and higher noise levels inherent in cone-beam CT systems, compared to conventional CT.

METHODS

Therefore, a model-based perfusion reconstruction based on the time separation technique (TST) was applied. TST uses basis functions to model time attenuation curves. These functions are either analytical or based on prior knowledge (PK), extracted using singular value decomposition of the classical CT perfusion data of animal subjects. To explore how well the PK can model perfusion dynamics and what the potential limitations are, the dynamic cone-beam CT (CBCT) perfusion scan was simulated from a dynamic CT perfusion scan under different noise levels. The TST method was compared to static reconstruction.

RESULTS

It was demonstrated on this simulated dynamic CBCT perfusion scan that a set consisting of only four basis functions results in perfusion maps that preserve relevant information, denoise the data, and outperform static reconstruction under higher noise levels. TST with PK would not only outperform static reconstruction but also the TST with analytical basis functions. Furthermore, it has been shown that only eight CBCT rotations, unlike previously assumed ten, are sufficient to obtain the perfusion maps comparable to the reference CT perfusion maps. This contributes to saving dose and reconstruction time. The real dynamic CBCT perfusion scan, reconstructed under the same conditions as the simulated scan, shows potential for maintaining the accuracy of the perfusion maps. By visual inspection, the embolized region was matching to that in corresponding CT perfusion maps.

CONCLUSIONS

CBCT reconstruction of perfusion scan data using the TST method has shown promising potential, outperforming static reconstructions and potentially saving dose by reducing the necessary number of acquisition sweeps. Further analysis of a larger cohort of patient data is needed to draw final conclusions regarding the expected advantages of the TST.

Renal perfusion improvement in the perioperative period after unilateral endovascular revascularization in patients with atherosclerotic renal artery stenosis

Background

The clinical benefits of endovascular treatment in renal artery stenosis (RAS) remain controversial. This study used an intraoperative renal perfusion imaging technique, called flat-panel detector parenchymal blood volume imaging (FD-PBV), to observe the change in renal perfusion after endovascular treatment in RAS.

Materials and methods

In a prospective, single-center study, we assigned 30 patients with atherosclerotic RAS who underwent endovascular treatment between March 2016 and March 2021. The preoperative and postoperative results of renal perfusion, blood pressure, and renal function, were compared.

Results

Both median kidney volume (p < 0.001) and median preoperative mean density of contrast medium (MDCM) (p = 0.028) increased significantly after endovascular treatment. The ratio of postoperative and preoperative MDCM differed greatly among the patients. For patients with preoperative MDCM <304.0 HU (Subgroup A, 15 cases), MDCM significantly increased after treatment (p = 0.001) and 12 (80.0%) patients had more than 10% increase in renal perfusion. For patients who had relatively high preoperative renal perfusion (MDCM ≥304.0 HU, Subgroup B, 15 cases), preoperative and postoperative MDCM were similar (p = 0.776). On the other hand, the serum creatinine levels significantly decreased in Subgroup A (p = 0.033) and fewer antihypertensive drugs were used after endovascular revascularization (p = 0.041). The preoperative and postoperative creatinine levels and number of antihypertensive drugs were similar in Subgroup B.

Conclusions

During the perioperative period, RAS patients with relatively low preoperative renal perfusion levels had greater improvement in renal perfusion, renal function, and blood pressure control after endovascular treatment. The improvement of renal function needs to be confirmed by long-term follow-up.

Clinical Applications of Quantitative Perfusion Imaging with a C-Arm Flat-Panel Detector-A Systematic Review

C-arm systems with digital flat-panel detectors are used in interventional radiology and hybrid operating rooms for visualizing and performing interventions on three-dimensional structures. Advances in C-arm technology have enabled intraoperative quantitative perfusion imaging with these scanners. This systematic review provides an overview of flat-panel detector C-arm techniques for quantifying perfusion, their clinical applications, and their validation. A systematic search was performed for articles published between January 2000 and October 2022 in which a flat-panel detector C-arm technique for quantifying perfusion was compared with a reference technique. Nine articles were retrieved describing two techniques: two-dimensional perfusion angiography (n = 5) and dual-phase cone beam computed tomography perfusion (n = 4). A quality assessment revealed no concerns about the applicability of the studies. The risk of bias was relatively high for the index and reference tests. Both techniques demonstrated potential for clinical application; however, weak-to-moderate correlations were reported between them and the reference techniques. In conclusion, both techniques could add new possibilities to treatment planning and follow-up; however, the available literature is relatively scarce and heterogeneous. Larger-scale randomized prospective studies focusing on clinical outcomes and standardization are required for the full understanding and clinical implementation of these techniques.

Angiosome-directed endovascular intervention and infrapopliteal disease: Intraoperative evaluation of distal hemodynamic changes and foot blood volume of lower extremity

Objectives

To evaluate foot blood volume and hemodynamics and explore whether quantitative techniques can guide revascularization.

Materials and methods

A prospective single-center cohort study included thirty-three patients with infrapopliteal artery occlusion who underwent percutaneous transluminal angioplasty (PTA) between November 2016 and May 2020. The time-to-peak (TTP) from color-coded quantitative digital subtraction angiography (CCQ-DSA) and parenchymal blood volume (PBV) were used to evaluate the blood volume and hemodynamic changes in different regions of the foot before and after the operation.

Results

After the intervention procedure, the overall blood volume significantly increased from 25.15 ± 21.1 ml/1,000 ml to 72.33 ± 29.3 ml/1,000 ml (p &lt; 0.001, with an average increase of 47.18 ml/1,000 ml. The overall TTP decrease rate, postoperative blood flow time significantly faster than those preoperatively, from 22.93 ± 7.83 to 14.85 ± 5.9 s (p &lt; 0.001, with an average decrease of 8.08 s). Direct revascularization (DR) resulted in significant blood volume improvement than compared with indirect revascularization (IR) [188% (28, 320) vs.51% (10, 110), p = 0.029]. Patients with DR had a significantly faster blood flow time than those with IR [80% (12, 180) vs. 26% (5, 80), p = 0.032]. The ankle-brachial index (ABI) of the affected extremity also showed an significant change from 0.49 ± 0.3 to 0.63 ± 0.24 (p &lt; 0.001) after the intervention. The relative values of ΔTTP and ΔABI showed a weak correlation (r = −0.330).

Conclusions

The quantitative measurement results based on PBV and CCQ-DSA techniques showed that the overall blood volume increased significantly and that the foot distal hemodynamics were significantly improved after endovascular treatment. DR in the ischemic area could r improve foot perfusion.

Correlation of C-arm CT acquired parenchymal blood volume (PBV) with 99mTc-macroaggregated albumin (MAA) SPECT/CT for radioembolization work-up

OBJECTIVE

SPECT/CT with 99mTc-macroaggregated albumin (MAA) is generally used for diagnostic work-up prior to transarterial radioembolization (TARE) to exclude shunts and to provide additional information for treatment stratification and dose calculation. C-arm CT is used for determination of lobular vascular supply and assessment of parenchymal blood volume (PBV). Aim of this study was to correlate MAA-uptake and PBV-maps in hepatocellular carcinoma (HCC) and hepatic metastases of the colorectal carcinoma (CRC).

MATERIALS AND METHODS

34 patients underwent a PBV C-arm CT immediately followed by 99mTc-MAA injection and a SPECT/CT acquisition after 1 h uptake. MAA-uptake and PBV-maps were visually assessed and semi-quantitatively analyzed (MAA-tumor/liver-parenchyma = MAA-TBR or PBV in ml/100ml). In case of a poor match, tumors were additionally correlated with post-TARE 90Y-Bremsstrahlung-SPECT/CT as a reference.

RESULTS

102 HCC or CRC metastases were analyzed. HCC presented with significantly higher MAA-TBR (7.6 vs. 3.9, p<0.05) compared to CRC. Tumors showed strong intra- and inter-individual dissimilarities between TBR and PBV with a weak correlations for capsular HCCs (r = 0.45, p<0.05) and no correlation for CRC. The demarcation of lesions was slightly better for both HCC and CRC in PBV-maps compared to MAA-SPECT/CT (exact match: 52%/50%; same intensity/homogeneity: 38%/39%; insufficient 10%/11%). MAA-SPECT/CT revealed a better visual correlation with post-therapeutic 90Y-Bremsstrahlung-SPECT/CT.

CONCLUSION

The acquisition of PBV can improve the detectability of small intrahepatic tumors and correlates with the MAA-Uptake in HCC. The results indicate that 99mTc-MAA-SPECT/CT remains to be the superior method for the prediction of post-therapeutic 90Y-particle distribution, especially in CRC. However, intra-procedural PBV acquisition has the potential to become an additional factor for TARE planning, in addition to improving the determination of segment and tumor blood supply, which has been demonstrated previously.

Infrapopliteal endovascular intervention and the angiosome concept: intraoperative real-time assessment of foot regions' blood volume guides and improves direct revascularization

OBJECTIVE

There is no consensus for determining which vessel should be revascularized in patients with multiple diseased infrapopliteal arteries. The angiosome concept may guide a more efficient targeted direct revascularization. Therefore, we conducted a study to assess whether the regional evaluation of foot blood volume may guide direct revascularization (DR) and if it will lead to better perfusion improvement than indirect revascularization (IR).

METHODS

We performed a prospective single-center observational cohort study in patients treated in the Department of Vascular Surgery of Peking Union Medical College Hospital from November 2016 to April 2019. Twenty-seven patients treated with endovascular intervention were included. The intraoperative parenchymal blood volume of different foot regions was obtained for each patient using C-arm CT before and after intervention.

RESULTS

The intervention procedure significantly increased the overall blood volume (48.95 versus 81.97 ml/1000 ml, p = 0.002). Patients with direct revascularization had a 197% blood volume increase while patients with indirect revascularization had a 39% increase (p = 0.028). The preoperative blood volume was higher in patients with mild symptoms than in patients with severe symptoms (58.20 versus 30.45 ml/1000 ml, p = 0.039). However, in regard to postoperative blood volume, no significant difference was discovered between these two groups (75.05 versus 95.01 ml/1000 ml, p = 0.275).

CONCLUSION

Based on quantitative measurements, we conclude that overall blood volume can rise significantly after the intervention. Revascularizing the supplying vessel of the ischemic area directly will result in better perfusion improvement than restoring blood supply through the collateral circulation. Preoperative blood volume is associated with preoperative symptoms.

KEY POINTS

• Flat panel detector CT can obtain intraoperative perfusion status and guide treatment in endovascular intervention. • Revascularizing the supplying vessel of the ischemic area directly will result in better perfusion improvement than restoring the blood supply through the collateral circulation. • Patients with severer clinical manifestations have lower blood volumes.

Utility of 'dual phase' cone beam computed tomography during radioembolisation in patients with hepatocellular carcinoma: what is really changing in flow dynamics before and after 90Y delivery?

Purpose

The aims of the study were: 1) to compare two phases of dual-phase cone beam computed tomography (DP-CBCT) achieved before and after Yttrium-90 (⁹⁰Y) administration and to evaluate additional benefits during radioembolisation (RE) procedures; and 2) to compare DP-CBCT with pre-procedure contrast enhanced cross-sectional images in terms of tumour detection.

Material and methods

Twenty-three hepatocellular carcinoma patients undergoing RE treatment were scanned with DP-CBCT consisting of early arterial (EA) and late arterial (LA) phases before and after ⁹⁰Y administration. The CT-like datasets were compared according to embolisation effect, enhancement patterns, lesion detectability, image quality, and artifacts by two interventional radiologists blinded to each other. The compatibility of the two radiologists was evaluated with kappa statistical analysis, and the difference between EA and LA phases was evaluated with marginal homogeneity test. Also, DP-CBCT images were compared with preprocedural cross-sectional images (CT/MRI).

Results

For 23 patients 92 data were acquired. Thirteen patients showed a decrease on post-embolisation images both visually and on Hounsfield unit (HU) measurements. No statistical difference was found for tumour detection between EA and LA phases (p = 1.0). Tumour enhancement was visually superior at LA phases whereas EA phases were better for arterial mapping for selective catheterisation. DP-CBCT images were not inferior to preprocedural cross-sectional imaging findings.

Conclusions

DP-CBCT is a promising tool for predicting tumour response to therapy and is not inferior to preprocedural cross-sectional imaging in terms of tumour detection. It allows better assessment during RE procedures because early phases provide good mapping for superselective catheterisation whereas late phases are better for visualisation of tumour enhancement.

C-arm cone-beam CT parenchymal blood volume imaging for transarterial chemoembolization of hepatocellular carcinoma: implications for treatment planning and response

We report on the feasibility of C-arm cone-beam computed tomography (CBCT) parenchymal blood volume imaging (PBVI) performed immediately following transarterial chemoembolization (TACE) of hepatocellular carcinoma (HCC) to assess the need for repeat treatment. Eighteen TACE procedures were included. A retrospective assessment was made for the presence or absence of residual disease requiring treatment on immediate post-TACE PBVI and on interval follow-up multidetector computed tomography (MDCT) or magnetic resonance imaging (MRI). In 9/18 cases, both PBVI and MDCT/MRI showed that no further treatment was required. In 6/18 cases, further treatment was required on both PBVI and MDCT/MRI. In three cases, PBVI showed that further treatment was not required but MDCT/MRI showed residual disease requiring repeat treatment. There were no cases with PBVI showing residual disease not detected on follow-up MDCT/MRI. The PBVI sensitivity for detecting disease requiring repeat TACE was 67% (95% confidence interval [CI] 30-93%), and specificity was 100% (95% CI 66-100%). The use of C-arm CBCT PBVI for the detection of residual viable tumor within a treated lesion immediately after TACE is feasible. It may allow repeat TACE to be planned without performing interval imaging with MDCT or MRI.

Image quality of arterial phase and parenchymal blood volume (PBV) maps derived from C-arm computed tomography in the evaluation of transarterial chemoembolization

Background

To evaluate the benefits of arterial phase imaging and parenchymal blood volume (PBV) maps acquired by C-arm computed tomography during TACE procedure in comparison to cross-sectional imaging (CSI) using CT or MRI.

Methods

From January 2014 to December 2016, a total of 29 patients with HCC stage A or B (mean age 65 years; range 47 to 81 years, 86% male) were included in this study. These patients were referred to our department for TACE treatment and received peri-interventional C-arm CT. Dual phase findings of each lesion in terms of overall image quality, conspicuity, tumor size and feeding arteries were compared between arterial phase imaging and PBV using 5-point semi-quantitative Likert-scale, whereby pre-interventional CSI served as reference standard.

Results

A significantly higher overall image quality of the PBV maps compared to arterial phase C-arm CT acquisitions (4.34 (±0.55) vs. 3.93 (±0.59), p = 0.0032) as well as a higher conspicuity of HCC lesions (4.27 ± 0.74 vs. 3.83 ± 1.08, p < 0.0001) was observed. Arterial phase imaging led to an overestimation of tumor size (mean size, 26.5 ± 15.9 mm) compared to PBV (24.9 ± 15.2 mm, p = 0.0004) as well as CSI (25.2 ± 15.1 mm), p = 0.021). Regarding detectability of tumor feeding arterial vessels, significantly more feeding vessels were detected in arterial phase C-arm CT (n = 1.67 ± 0.92 vessels) compared to PBV maps (n = 1.27 ± 0.63 vessels) (p = 0.0001). One lesion was missed in pre-interventional CT imaging, but detected by C-arm CT.

Conclusion

The combination of PBV maps and arterial phase images acquired by C-arm CT during TACE procedure enables precise detection of the majority of HCC lesions and tumor feeding arteries and has therefore the potential to improve patient outcome.

Intraprocedural 3D perfusion measurement during chemoembolisation with doxorubicin-eluting beads in liver metastases of malignant melanoma

OBJECTIVES

To study feasibility and validity of a new software application for intraprocedural assessment of perfusion during chemoembolisation of melanoma metastases.

METHODOLOGY

In a prospective phase-II trial, ten melanoma patients with liver-only metastases underwent chemoembolisation with doxorubicin-eluting beads (DEBDOX-TACE). Tumour perfusion was evaluated immediately before and after treatment at cone beam computer tomography (CBCT) using a new software application. For control and comparison, patients underwent perfusion measurement via contrast-enhanced multidetector CT (MDCT) before and after treatment.

RESULTS

CBCT showed 94.7 % reduction in perfusion in metastases after DEBDOX-TACE, whereas MDCT showed 96.8 %. Reduction in perfusion after treatment was statistically significant (p < 0.01) for both methods. The additional time needed for data acquisition during treatment was 5 min per case or less; the post-processing data analysis was 10 min or less. Perfusion imaging was associated with additional contrast agent and patient exposure to radiation (dose-length product [DLP]): 18 ml and 394 mGy*cm in CBCT and 100 ml and 446 mGy*cm in MDCT, respectively.

CONCLUSIONS

Reduction in perfusion of melanoma metastases after DEBDOX-TACE can be reliably assessed during the intervention via perfusion software at CBCT. Data acquisition and analysis require additional time but can be easily performed during the treatment.

KEY POINTS

• Tumour perfusion of melanoma metastases can be assessed at cone beam CT. • The software shows a significant decrease of tumour perfusion after DEBDOX-TACE. • Data acquisition and analysis require an acceptable additional time during the procedure. • CBCT requires less radiation exposure and contrast for perfusion study than MSCT. • This software can monitor the course of DEBDOX-TACE in melanoma metastases.

Dynamic Measurement of Arterial Liver Perfusion With an Interventional C-Arm System

PURPOSE

Objective intraprocedural measurement of hepatic blood flow could provide a quantitative treatment end point for locoregional liver procedures. This study aims to validate the accuracy and reproducibility of cone-beam computed tomography perfusion (CBCTp) measurements of arterial liver perfusion (ALP) against clinically available computed tomography perfusion (CTp) measurements in a swine embolization model.

METHODS

Triplicate CBCTp measurements using a selective arterial contrast injection were performed before and after complete embolization of the left lobe of the liver in 5 swine. Two CBCTp protocols were evaluated that differed in sweep duration (3.3 vs 4.5 seconds) and the number of acquired projection images (166 vs 248). The mean ALP was measured within identical volumes of interest selected in the embolized and nonembolized regions of the perfusion map generated from each scan. Postembolization CBCTp values were also compared with CTp measurements.

RESULTS

The 2 CBCTp protocols demonstrated high concordance correlation (0.90, P < 0.001). Both CBCTp protocols showed higher reproducibility than CTp in the nontarget lobe, with an intraclass correlation of 0.90 or greater for CBCTp and 0.83 for CTp (P < 0.001 for all correlations). The ALP in the embolized lobe was nearly zero and hence excluded for reproducibility. High concordance correlation was observed between the CTp and each CBCTp protocol, with the shorter CBCTp protocol reaching a concordance correlation of 0.75 and the longer achieving 0.87 (P < 0.001 for both correlations).

CONCLUSIONS

Dynamic blood flow measurement using an angiographic C-arm system is feasible and produces quantitative results comparable to CTp.

Reproducibility of Parenchymal Blood Volume Measurements Using an Angiographic C-arm CT System

RATIONALE AND OBJECTIVES

Intra-procedural measurement of hepatic perfusion following liver embolization continues to be a challenge. Blood volume imaging before and after interventional procedures would allow identifying the treatment end point or even allow predicting treatment outcome. Recent liver oncology studies showed the feasibility of parenchymal blood volume (PBV) imaging using an angiographic C-arm system. This study was done to evaluate the reproducibility of PBV measurements using cone beam computed tomography (CBCT) before and after embolization of the liver in a swine model.

MATERIALS AND METHODS

CBCT imaging was performed before and after partial bland embolization of the left lobe of the liver in five adult pigs. Intra-arterial injection of iodinated contrast with a 6-second x-ray delay was used with a two-sweep 8-second rotation imaging protocol. Three acquisitions, each separated by 10 minutes to allow for contrast clearance, were obtained before and after embolization in each animal. Post-processing was carried out using dedicated software to generate three-dimensional (3D) PBV maps. Two region-of-interest measurements were placed on two views within the right and left lobe on each CBCT 3D PBV map. Variation in PBV for scans acquired within each animal was determined by the coefficient of variation and intraclass correlation. A Wilcoxon signed-rank test was used to test post-procedure reduction in PBV.

RESULTS

The CBCT PBV maps showed mean coefficients of variation of 7% (range: 2%-16%) and 25% (range:  13%-34%) for baseline and embolized PBV maps, respectively. The intraclass correlation for PBV measurements was 0.89, demonstrating high reproducibility, with measurable reduction in PBV displayed after embolization (P = 0.007).

CONCLUSIONS

Intra-procedural acquisition of 3D PBV maps before and after liver embolization using CBCT is highly reproducible and shows promising application for obtaining intra-procedural PBV maps during locoregional therapy.

Parenchymal Blood Volume Assessed by C-Arm-Based Computed Tomography in Immediate Posttreatment Evaluation of Drug-Eluting Bead Transarterial Chemoembolization in Hepatocellular Carcinoma

OBJECTIVES

The aim of this study was to assess clinical utility of the quantitative perfusion parameter called parenchymal blood volume (PBV), as derived from C-arm-based computed tomography (CT), for immediate posttreatment assessment of drug-eluting bead (DEB) transarterial chemoembolization (TACE) in hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Twenty-four patients with early- or intermediate-stage HCC received DEB-TACE. A total of 52 HCC lesions were treated and assessed by C-arm CT before and after intervention. C-arm CT consisted of nonenhanced and contrast-enhanced acquisitions; from these, PBV maps were reconstructed. Lesion diameter, maximum PBV, and unenhanced parenchyma density were assessed before and after treatment. Diameter of visible contrast media deposits as well as residual vascularization was assessed after delivery of DEB. All patients underwent follow-up using cross-sectional imaging. All assessed lesions were evaluated concerning modified Response Evaluation Criteria in Solid Tumors for HCC.

RESULTS

All treated lesions showed significant decrease in PBV after DEB-TACE (mean difference, -15.61 mL/100 mL, P < 0.0001). Eleven lesions showed residual tumoral perfusion in PBV maps associated with an unfavorable outcome compared with completely treated lesions in terms of a lower tumor shrinkage over time (-0.02 ± 0.49 vs -0.76 ± 0.38; P < 0.0001). A contrast media deposit was seen in 78% of treated HCC lesions with a tendency toward better visibility in encapsulated lesions. Nonenhanced parenchyma density was significantly higher in all treated segments (149.69 ± 58.6 vs 68.42 ± 18.04, P < 0.0001).

CONCLUSIONS

Parenchymal blood volume values as derived from C-arm CT acquisitions in combination with nonenhanced and contrast-enhanced C-arm CT images are useful in posttreatment assessment of DEB-TACE in HCC. Residual tumor perfusion in PBV maps have predictive potential for mid-term tumor response in HCC and could allow a more individualized treatment schedule for DEB-TACE in HCC patients.

C-arm computed tomography and volume perfusion computed tomography (VPCT)-based assessment of blood volume changes in hepatocellular carcinoma in prediction of midterm tumor response to transarterial chemoembolization: a single center retrospective trial

Background

This study aims to evaluate immediate changes in perfusion parameters in hepatocellular carcinoma (HCC) to transarterial chemoembolization (TACE) in C-arm computed tomography (CT) and volume perfusion CT (VPCT) and prediction of midterm tumor response.

Methods

Twenty-five patients (median age 66, range 61 to 75 years) with 62 HCC lesions undergoing TACE received immediate pre- and post-interventional assessment by C-arm CT and VPCT. Cross-sectional imaging was analyzed at baseline and approximately 12 weeks after TACE according to modified RECIST criteria. Outcome was defined as objective response (OR, > 30 % reduction of viable tumor) or non-OR. Perfusion parameters were evaluated in C-arm CT [parenchymal blood volume (PBV)] and VPCT [blood volume (BV) and blood flow (BF)]. Ratios of perfusion parameters before and after TACE within the tumor and the non-affected liver parenchyma were calculated.

Results

Correlation between tumor PBV and BV revealed a moderate correlation (rho = 0.45, p = 0.005). In non-affected liver parenchyma, a significant decrease in PBV was seen, compared to a significant increase in BF and BV. Perfusion ratios in HCC lesions were significantly (p < 0.05) increased in OR group compared to non-OR patients in C-arm CT and VPCT: PBV ratio (0.95 (0.06) to 0.67 (0.38), BV ratio 0.63 (0.34) to 0.15 (0.6), and BF ratio 0.6 (0.32) to 0.22 (0.51). Logistic regression including PBV and BF allowed prediction of OR (sensitivity 88 %/specificity of 83 %).

Conclusions

Perfusion parameters acquired by C-arm CT and VPCT cannot simply be substituted by each other, but show similar capability in prediction of midterm tumor response.

Assessment of the parenchymal blood volume by C-arm computed tomography for radioembolization dosimetry

PURPOSE

Aim of the study was to evaluate the impact of parenchymal blood volume (PBV) C-arm CT in transarterial radioembolization (TARE) planning procedure regarding the appropriateness of segmental blood supply from selective catheter positions defined by angiographic images compared to PBV mapsto determine the influence of changed target volumes on dose calculation.

MATERIAL AND METHODS

A total of 22 consecutive patients (median age, 62 years) underwent a TARE planning procedure were included in this retrospective study. Selective angiograms and selective PBV C-arm CT (right and left liver lobe) were evaluated in a blinded fashion, regarding segmental hepatic artery variants. Volumetry of target volume and dosimetry of glass and resin microspheres were performed.

RESULTS

Classification of segment IV and segment I to the corresponding target vascular bed supply was correct in 91.0% (20/22) and 86.4% (19/22) for angiography and C-arm CT, respectively. Except one case, all other liver segments were classified properly to the left and right hepatic arterial supply. Based on the mismatch of the angiographic and the C-arm CT approach, changes of target volume were evident in 27.3% of patients, resulting in a mean mismatch volume of 90±54ml (range, 51-198ml) and a percentage of dose differences of 14.2±11.8% and 12.6±10.6% for the right and 12.5±8.5% and 11.1±7.8% for the left liver lobe in glass and resin microspheres, respectively.

CONCLUSION

The C-arm CT approach is superior to the angiographic determination of vascular supply of specific liver segments for dosimetry before radioembolization. Especially for unexperienced interventional radiologists or for a complex anatomy, C-arm CT improves individualized dosimetry concepts.

Advanced imaging techniques in the therapeutic response of transarterial chemoembolization for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the major causes of morbidity and mortality in patients with chronic liver disease. Transarterial chemoembolization (TACE) can significantly improve the survival rate of patients with HCC and is the first treatment choice for patients who are not suitable for surgical resections. The evaluation of the response to TACE treatment affects not only the assessment of the therapy efficacy but also the development of the next step in the treatment plan. The use of imaging to examine changes in tumor volume to assess the response of solid tumors to treatment has been controversial. In recent years, the emergence of new imaging technology has made it possible to observe the response of tumors to treatment prior to any morphological changes. In this article, the advances in studies reporting the use of computed tomography perfusion imaging, diffusion-weighted magnetic resonance imaging (MRI), intravoxel incoherent motion, diffusion kurtosis imaging, magnetic resonance spectroscopy, magnetic resonance perfusion-weighted imaging, blood oxygen level-dependent MRI, positron emission tomography (PET)/computed tomography and PET/MRI to assess the TACE treatment response are reviewed.

C-arm computed tomography parenchymal blood volume measurement in evaluation of hepatocellular carcinoma before transarterial chemoembolization with drug eluting beads

BACKGROUND

C-arm computed tomography (CT) guided intervention is an increasingly applied technique in transarterial chemoembolization (TACE) of hepatocellular carcinoma (HCC). The aim of this study was to analyse the value of parenchymal blood volume (PBV) maps acquired during C-arm CT acquisition, for pre-treatment evaluation and planning of TACE in HCC patients.

METHODS

A total of 64 HCC lesions in 29 patients (median age, 73 years, range, 62-77 years) were included in this retrospective study. All patients received cross-sectional imaging (MRI or CT) prior to TACE and C-arm CT PBV measurement acquisition before performing TACE. Results of cross-sectional imaging regarding the number of HCC lesions and maximum diameter were compared to PBV-maps. Number of lesions and tumour feeding vessels detected in PBV-maps were compared to conventional angiography. Results of PBV were analysed concerning different tumour morphologies (pre-treated, encapsulated and diffuse).

RESULTS

Pre-interventional cross-sectional imaging and PBV maps showed an excellent agreement in lesion diameter (p = 0.88, MD = -0.28 mm) and number of detected lesions (κ = 1.0). Compared to conventional angiography, PBV maps showed an increased number of detected lesions (κ = 0.77, p = 0.001) and tumour feeding vessels (κ = 0.71, p < 0.0001). Diffuse HCC lesion revealed a significantly lower PBV compared to encapsulated lesions (p = 0.0001).

CONCLUSIONS

C-arm CT acquired PBV measurements detect HCC tumours with a lesion detectability comparable to pre-interventional cross-sectional imaging. Furthermore, this technique facilitates TACE, allowing a more precise localization of HCC lesions and tumour feeding vessels compared to conventional angiography. Additionally, calculated PBV values enable a real time quantitative assessment of tumour perfusion.

Imaging of HCC-Current State of the Art

Early diagnosis of hepatocellular carcinoma (HCC) is crucial for optimizing treatment outcome. Ongoing advances are being made in imaging of HCC regarding detection, grading, staging, and also treatment monitoring. This review gives an overview of the current international guidelines for diagnosing HCC and their discrepancies as well as critically summarizes the role of magnetic resonance imaging (MRI) and computed tomography (CT) techniques for imaging in HCC. The diagnostic performance of MRI with nonspecific and hepatobililiary contrast agents and the role of functional imaging with diffusion-weighted imaging will be discussed. On the other hand, CT as a fast, cheap and easily accessible imaging modality plays a major role in the clinical routine work-up of HCC. Technical advances in CT, such as dual energy CT and volume perfusion CT, are currently being explored for improving detection, characterization and staging of HCC with promising results. Cone beam CT can provide a three-dimensional analysis of the liver with tumor and vessel characterization comparable to cross-sectional imaging so that this technique is gaining an increasing role in the peri-procedural imaging of HCC treated with interventional techniques.

Microvascular Perfusion Changes following Transarterial Hepatic Tumor Embolization

PURPOSE

To quantify changes in tumor microvascular (< 1 mm) perfusion relative to commonly used angiographic endpoints.

MATERIALS AND METHODS

Rabbit Vx2 liver tumors were embolized with 100-300-μm LC Bead particles to endpoints of substasis or complete stasis (controls were not embolized). Microvascular perfusion was evaluated by delivering two different fluorophore-conjugated perfusion markers (ie, lectins) through the catheter before embolization and 5 min after reaching the desired angiographic endpoint. Tumor microvasculature was labeled with an anti-CD31 antibody and analyzed with fluorescence microscopy for perfusion marker overlap/mismatch. Data were analyzed by analysis of variance and post hoc test (n = 3-5 per group; 18 total).

RESULTS

Mean microvascular density was 70 vessels/mm(2) ± 17 (standard error of the mean), and 81% ± 1 of microvasculature (ie, CD31(+) structures) was functionally perfused within viable Vx2 tumor regions. Embolization to the extent of substasis eliminated perfusion in 37% ± 9 of perfused microvessels (P > .05 vs baseline), whereas embolization to the extent of angiographic stasis eliminated perfusion in 56% ± 8 of perfused microvessels. Persistent microvascular perfusion following embolization was predominantly found in the tumor periphery, adjacent to normal tissue. Newly perfused microvasculature was evident following embolization to substasis but not when embolization was performed to complete angiographic stasis.

CONCLUSIONS

Nearly half of tumor microvasculature remained patent despite embolization to complete angiographic stasis. The observed preservation of tumor microvasculature perfusion with angiographic endpoints of substasis and stasis may have implications for tumor response to embolotherapy.