DynaCT during EVAR--a comparison with multidetector CT

Intraoperative CBCT imaging in endovascular abdomen aneurysm repair - Optimization of exposure parameters using a stent phantom

Cone beam computed tomography (CBCT) may provide essential additional image guidance to endovascular abdominal aneurysm repair (EVAR) operations but also significant radiation exposure to patients if scans are not carefully optimized. The purpose of our study was to define the image quality requirements for intraoperative EVAR CBCT imaging and to optimize the CBCT exposure parameters accordingly. A Multi-Energy CT phantom simulating a large patient was used by replacing the central phantom cylinder with a custom water-filled insert including an EVAR stent. Different exposure parameters covering a range of radiation qualities and dose levels were used to define the optimal image quality level regarding stent graft evaluation (compressed, bent, or collapsed). The radiation dose was measured with a calibrated air kerma-area product (KAP) meter and organ doses were calculated based on Monte Carlo simulations and a mathematical patient model. Based on the results, updated exposure parameters with the highest mean energy and lowest dose level available were recommended. With the updated protocol, the radiation exposure could be significantly decreased. The KAP value decreased from 9720 μGy·m2 to 440 μGy·m2 and reference point air kerma from 351 mGy to 16 mGy (a reduction of 96%) and organ doses of the organs in the irradiated region decreased on an average 91%. The new protocol resulted in acceptable clinical image quality based on testing with clinical cases.

High-Dose Fluoroscopically Guided Procedures in Patients: Radiation Management Recommendations for Interventionalists

The article is part of the series of articles on radiation protection. You can find further articles in the special section of the CVIR issue. In addition to the risks from fluoroscopic-guided interventional procedures of tissue injuries, recent studies have drawn attention to the risk of stochastic effects. Guidelines exist for preprocedural planning and radiation management during the procedure. The concept of a substantial radiation dose level (SRDL) is helpful for patient follow-up for tissue injury. The uncommon nature of tissue injuries requires the interventionalist to be responsible for follow-up of patients who receive substantial radiation doses. Dose management systems for recognizing and avoiding higher patient exposures have been introduced. The European Directive provides a legal framework and requirements for equipment, training, dose monitoring, recording and optimization that are helpful in radiation risk management.

Comparison of pulmonary artery dimensions in swine obtained from catheter angiography, multi-slice computed tomography, 3D-rotational angiography and phase-contrast magnetic resonance angiography

Accurate pulmonary artery (PA) imaging is necessary for management of patients with complex congenital heart disease (CHD). The ability of newer imaging modalities such as 3D rotational angiography (3DRA) or phase-contrast magnetic resonance angiography (PC-MRA) to measure PA diameters has not been compared to established angiography techniques. Measurements of PA diameters (including PA stenosis and PA stents) from 3DRA and non-contrast-enhanced PC-MRA were compared to 2D catheter angiography (CA) and multi-slice computed tomography (MSCT) in a swine CHD model (n = 18). For all PA segments 3DRA had excellent agreement with CA and MSCT (ICC = 0.94[0.91-0.95] and 0.92[0.89-0.94]). 3DRA PA stenosis measures were similar to CA and MSCT and 3DRA was on average within 5% of 10.8 ± 1.3 mm PA stent diameters from CA and MSCT. For compliant PA segments, 3DRA was on average 3-12% less than CA (p < 0.05) and MSCT (p < 0.01) for 6-14 mm vessels. PC-MRA could not reliably visualize stents and distal PA vessels and only identified 34% of all assigned measurement sites. For measured PA segments, PC-MRA had good agreement to CA and MSCT (ICC = 0.87[0.77-0.92] and 0.83[0.72-0.90]) but PC-MRA overestimated stenosis diameters and underestimated compliant PA diameters. Excellent CA-MSCT PA diameter agreement (ICC = 0.95[0.93-0.96]) confirmed previous data in CHD patients. There was little bias in PA measurements between 3DRA, CA and MSCT in stenotic and stented PAs but 3DRA underestimates measurements of compliant PA regions. Accurate PC-MRA imaging was limited to unstented proximal PA anatomy.

Comparison of Radiation Exposure Associated With Intraoperative Cone-Beam Computed Tomography and Follow-up Multidetector Computed Tomography Angiography for Evaluating Endovascular Aneurysm Repairs

Purpose: To compare the radiation exposure associated with intraoperative contrast-enhanced cone-beam computed tomography (ceCBCT) acquisitions to standard 3-phase multidetector computed tomography (MDCT) angiography used for assessing technical success after endovascular aortic repair (EVAR). Methods: Effective doses (EDs) were calculated for 66 EVAR patients (mean age 71 years; 61 men) with a mean 27.7-kg/m2 body mass index (range 17–49) who had both intraoperative ceCBCT and postoperative 3-phase MDCT angiography between November 2012 and April 2015. In addition, EDs were directly determined using thermoluminescent dosimeters (TLDs) embedded in anthropomorphic phantoms with body mass indexes of 22 and 30 kg/m2. Effective doses were calculated by summing doses recorded by all TLDs corresponding to a specific tissue type before applying the International Commission on Radiological Protection (ICRP) 60 and 103 weighting factors. EDs were compared with each other for both imaging modalities as well as to TLD measurements. Results: Average EDs of the patient collective were 4.9±1.1 mSv for ceCBCT, 2.6±1.2 mSv for single-phase MDCT (46% decrease, covering solely the area of the implanted endograft), and 13.6±5.5 mSv for comprehensive 3-phase MDCT examinations (178% increase, anatomical coverage from the aortic arch to femoral artery bifurcation). EDs determined in phantom measurements ranged from 3.1 to 4.5 mSv for ceCBCT, amounting to 2.6 mSv for a single MDCT phase (15% to 40% decrease) using ICRP 60 conversion factors. Applying ICRP 103 factors resulted in higher values for ceCBCT and slightly lower ones for MDCT. Conclusion: ceCBCT offers the chance for immediate intraoperative revisions of endograft-related problems. Requiring only a single-phase acquisition, ceCBCT is associated with a considerable reduction in ED (50%–75%) compared to standard 3-phase MDCT angiography after EVAR. On the other hand, MDCT has a larger field of view and is associated with less radiation exposure for a single phase (reduction of 20%–60%) if only the stented region is covered; however, MDCT angiography also uses larger amounts of contrast.

Accurate and rapid identification of feeding arteries with multidetector-row angiography-assisted computed tomography for transarterial chemoembolization for hepatocellular carcinoma

BACKGROUND

Transarterial chemoembolization (TACE) is an important treatment modality for hepatocellular carcinoma (HCC). Accurate identification of feeding arteries and catheterization are necessary for achieving treatment efficacy, especially with selective TACE. However, this often requires multiple imaging studies. We evaluated the utility of a newly developed apparatus that combines multidetector-row computed tomography (MDCT) and angiography (angio-MDCT) to facilitate TACE for treatment of HCC.

METHODS

A total of 73 patients who underwent selective TACE with angio-MDCT were compared with 57 patients who had undergone selective TACE with single-row computed tomography assisted by angiography (angio-CT) in terms of the number of imaging studies needed to complete TACE.

RESULTS

The mean number of digital subtraction arteriography (DSA) and CT studies required for characterization of feeding arteries before embolization was 3.53 (range 1-8) and 5.16 (range 2-11), respectively, with single-row angio-CT, and 1.67 (range 1-5) and 2.90 (range 1-5), respectively, with angio-MDCT. Fewer studies were needed in patients who underwent TACE with angio-MDCT (p < 0.0001 for both DSA and CT). Whereas single-row angio-CT failed to identify extrahepatic feeders in three patients (37.5%), all extrahepatic feeders could be identified with angio-MDCT.

CONCLUSIONS

Angio-MDCT facilitates rapid and accurate identification of feeding arteries in patients undergoing TACE through the three-dimensional image analyses by the reconstruction with the workstation.

A comparison study of radiation exposure to patients during EVAR and Dyna CT in an angiosuite vs. an operating theatre

The aim of this study was to assess the patient dosimetric impact of endovascular abdominal aortic aneurysm repair (EVAR), both in an operating theatre (OR) and in an angiosuite (AS), with the facility of Dynamic CT (Dyna CT, Siemens AG, Berlin, Germany). One hundred and forty-six consecutive EVAR procedures dating from May 2011 to March 2013 were analysed. These were performed either in an OR (n = 97) using a mobile C-arm or in an AS (n = 49) equipped with a ceiling-mounted angiography system. Air kerma area product (P(KA)) and total air kerma at reference point (K(a,r)) values were reported for all procedures and Dyna CT. Radiation exposure during EVAR was quite low in the majority of patients but nearly 50 % higher if performed in AS vs. OR. Median Dyna CT K(a,r) was the same as an entire EVAR procedure in OR. The higher patient's radiation exposure recorded in the AS should be balanced with the technical advantages given to the EVAR procedure.

Liver deformation in an animal model due to pneumoperitoneum assessed by a vessel-based deformable registration

PURPOSE

Surgical navigation based on preoperative images partly overcomes some of the drawbacks of minimally invasive interventions - reduction of free sight, lack of dexterity and tactile feedback. The usefulness of preoperative images is limited in laparoscopic liver surgery, as the liver shifts due to respiration, induction of pneumoperitoneum and surgical manipulation. In this study, we evaluated the shift and deformation in an animal liver caused by respiration and pneumopertioneum using intraoperative cone beam CT.

MATERIAL AND METHODS

3D cone beam CT scans were acquired with arterial contrast. The centerlines of the segmented vessels were extracted from the images taken at different respiration and pressure settings. A non-rigid registration method was used to measure the shift and deformation. The mean Euclidean distance between the annotated landmarks was used for evaluation.

RESULTS

A shift and deformation of 44.6 mm on average was introduced due to the combined effect of respiration and pneumoperitoneum. On average 91% of the deformations caused by the respiration and pneumoperitoneum were recovered.

CONCLUSION

The results can contribute to the use of intraoperative imaging to correct for anatomic shift so that preoperative data can be used with greater confidence and accuracy during guidance of laparoscopic liver procedures.

Transcatheter aortic valve implantation

With the improvement in the overall life expectancy, the incidence of aortic stenosis has been increasing. Although aortic valve replacement is a standard therapy, many patients do not undergo surgery for various reasons, including advanced age or the presence of multiple comorbidities. Transcatheter aortic valve implantation (TAVI) has been proposed as a less invasive and equally effective treatment for inoperable or high-risk symptomatic aortic stenosis. Numerous rigorous global clinical trials, as well as a pivotal clinical trial in Japan, have been conducted. In this review, we provide data on the development of TAVI worldwide and discuss the prospects for TAVI in Japan.

Radiation exposure of abdominal cone beam computed tomography

PURPOSE

To evaluate patients radiation exposure of abdominal C-arm cone beam computed tomography (CBCT).

METHODS

This prospective study was approved by the institutional review board; written, informed consent was waived. Radiation exposure of abdominal CBCT was evaluated in 40 patients who underwent CBCT during endovascular interventions. Dose area product (DAP) of CBCT was documented and effective dose (ED) was estimated based on organ doses using dedicated Monte Carlo simulation software with consideration of X-ray field location and patients' individual body weight and height. Weight-dependent ED per DAP conversion factors were calculated. CBCT radiation dose was compared to radiation dose of procedural fluoroscopy. CBCT dose-related risk for cancer was assessed.

RESULTS

Mean ED of abdominal CBCT was 4.3 mSv (95 % confidence interval [CI] 3.9; 4.8 mSv, range 1.1-7.4 mSv). ED was significantly higher in the upper than in the lower abdomen (p = 0.003) and increased with patients' weight (r = 0.55, slope = 0.045 mSv/kg, p < 0.001). Radiation exposure of CBCT corresponded to the radiation exposure of on average 7.2 fluoroscopy minutes (95 % CI 5.5; 8.8 min) in the same region of interest. Lifetime risk of exposure related cancer death was 0.033 % or less depending on age and weight.

CONCLUSIONS

Mean ED of abdominal CBCT was 4.3 mSv depending on X-ray field location and body weight.

Comparison of air kerma between C-arm CT and 64-multidetector-row CT using a phantom

PURPOSE

To compare air kerma after scanning a phantom with C-arm CT and with 64-multidetector row CT (64MDCT).

MATERIALS AND METHODS

A phantom was scanned using parameters based on data of ten patients with hepatocellular carcinoma who had C-arm CT during hepatic arteriography and 64MDCT during arterial portography. Radiation monitors were used to measure air kerma ten times at each of five points: the center (A), top (B), left side (C), bottom (D), and right side (E).

RESULTS

For C-arm CT vs. 64MDCT, air kerma after scanning was 10.5 ± 0.2 vs. 6.4 ± 0.0 for A, 1.5 ± 0.0 vs. 11.6 ± 0.2 for B, 37.1 ± 0.2 vs. 11.1 ± 0.1 for C, 55.6 ± 1.0 vs. 10.6 ± 0.1 for D, and 40.5 ± 0.5 vs. 11.7 ± 0.1 for E, respectively. Air kerma for A, B, C, D, and E was 1.64, 0.13, 3.34, 5.24, and 3.46 times greater for C-arm CT than for 64MDCT, respectively.

CONCLUSION

Using the same scanning parameters as for clinical cases, air kerma values were greater with C-arm CT than with 64MDCT; at the dorsal side of the phantom, they were 5.24 times greater with C-arm CT compared with 64MDCT.

Current and emerging robot-assisted endovascular catheterization technologies: a review

Endovascular techniques have been embraced as a minimally-invasive treatment approach within different disciplines of interventional radiology and cardiology. The current practice of endovascular procedures, however, is limited by a number of factors including exposure to high doses of X-ray radiation, limited 3D imaging, and lack of contact force sensing from the endovascular tools and the vascular anatomy. More recently, advances in steerable catheters and development of master/slave robots have aimed to improve these practices by removing the operator from the radiation source and increasing the precision and stability of catheter motion with added degrees-of-freedom. Despite their increased application and a growing research interest in this area, many such systems have been designed without considering the natural manipulation skills and ergonomic preferences of the operators. Existing studies on tool interactions and natural manipulation skills of the operators are limited. In this manuscript, new technical developments in different aspects of robotic endovascular intervention including catheter instrumentation, intra-operative imaging and navigation techniques, as well as master/slave based robotic catheterization platforms are reviewed. We further address emerging trends and new research opportunities towards more widespread clinical acceptance of robotically assisted endovascular technologies.

Hepatoma feeding arteriogram created by CT during aortography using IVR 64-multidetector-row CT for catheterization in transcatheter arterial chemoembolization for hepatocellular carcinoma

CT during aortography (CTAo) using IVR 64-multidetector-row CT (IVR-64MDCT) enables the rapid and simultaneous depiction of both the hepatic and extrahepatic feeding arteries in hepatocellular carcinoma (HCC), and can be achieved using a reasonable volume of contrast medium. The scan time is approximately 6 s from the diaphragm to the kidney using CTAo with 64MDCT with a slice thickness and slice interval of 0.5 mm. The hepatoma feeding arteriogram appears in the angiographic monitor after CTAo, and can then be used to guide catheterization. We introduce the process for creating a hepatoma feeding arteriogram, synthesized from the following three volume-rendered images: background bone, aorta to hepatic-branch artery, and hepatoma to feeding artery. Uniquely, the hepatoma feeding arteriogram enables investigation of the feeding artery from the tumor side, rather than from the aorta side, and appears superior to selective arteriography in terms of detecting small HCC and its accompanying fine feeding arteries. Identification of these arteries by CT angiography with intravenous contrast medium injection is difficult because of the similarity in CT values between the feeding artery and the surrounding liver, thereby preventing the creation of a hepatoma feeding arteriogram. CTAo accelerates the process of deciding upon the catheter treatment strategy, shifting the decision to the point at which the feeding artery is investigated, because the hepatoma feeding arteriogram enables instant identification of the feeding artery and its connection to the hepatic branch artery. CTAo with IVR-64MDCT can potentially contribute to remarkable advances in IVR, especially transcatheter arterial chemoembolization for HCC.

High-resolution CT vascular imaging using blood pool contrast agents

While the evolution of computed tomography imaging in the last 2 decades has been driven almost exclusively by improvements in the instrumentation and processing algorithms, there have been comparatively modest advances in contrast agent technology.A notable change in the last decade has been the development of blood pool contrast agents based on nanoparticle technology.While not yet ready for clinical use, the stable and uniform opacification provided by these agents in normal vasculature and controlled extravasation in compromised vasculature enables novel techniques for imaging and diagnosis of pathologies. This manuscript presents preclinical examples demonstrating cardiovascular pathologies and tumor characterization by high-resolution computed tomography imaging.

Three-dimensional electromagnetic navigation vs. fluoroscopy for endovascular aneurysm repair: a prospective feasibility study in patients

PURPOSE

To evaluate the in vivo feasibility of a 3-dimensional (3D) electromagnetic (EM) navigation system with electromagnetically-tracked catheters in endovascular aneurysm repair (EVAR).

METHODS

The pilot study included 17 patients undergoing EVAR with a bifurcated stent-graft. Ten patients were assigned to the control group, in which a standard EVAR procedure was used. The remaining 7 patients (intervention group) underwent an EVAR procedure during which a cone-beam computed tomography image was acquired after implantation of the main stent-graft. The 3D image was presented on the navigation screen. From the contralateral side, the tip of an electromagnetically-tracked catheter was visualized in the 3D image and positioned in front of the contralateral cuff in the main stent-graft. A guidewire was inserted through the catheter and blindly placed into the stent-graft. The placement of the guidewire was verified by fluoroscopy before the catheter was pushed over the guidewire. If the guidewire was incorrectly placed outside the stent-graft, the procedure was repeated. Successful placement of the guidewire had to be achieved within a 15-minute time limit.

RESULTS

Within 15 minutes, the guidewire was placed correctly inside the stent-graft in 6 of 7 patients in the intervention group and in 8 of 10 patients in the control group. In the intervention group, fewer attempts were needed to insert the guidewire correctly.

CONCLUSION

A 3D EM navigation system, used in conjunction with fluoroscopy and angiography, has the potential to provide more spatial information and reduce the use of radiation and contrast during endovascular interventions. This pilot study showed that 3D EM navigation is feasible in patients undergoing EVAR. However, a larger study must be performed to determine if 3D EM navigation is better than the existing practice for these patients.

Prediction of optimal deployment projection for transcatheter aortic valve replacement: angiographic 3-dimensional reconstruction of the aortic root versus multidetector computed tomography

BACKGROUND

Identifying the optimal fluoroscopic projection of the aortic valve is important for successful transcatheter aortic valve replacement (TAVR). Various imaging modalities, including multidetector computed tomography (MDCT), have been proposed for prediction of the optimal deployment projection. We evaluated a method that provides 3-dimensional angiographic reconstructions (3DA) of the aortic root for prediction of the optimal deployment angle and compared it with MDCT.

METHODS AND RESULTS

Forty patients undergoing transfemoral TAVR at St Paul's Hospital, Vancouver, Canada, were evaluated. All underwent preimplant 3DA and 68% underwent preimplant MDCT. Three-dimensional angiographic reconstructions were generated from images of a C-arm rotational aortic root angiogram during breath-hold, rapid ventricular pacing, and injection of 32 mL contrast medium at 8 mL/s. Two independent operators prospectively predicted perpendicular valve projections. The implant angle was chosen at the discretion of the physician performing TAVR. The angles from 3DA, from MDCT, the implant angle, and the postdeployment perpendicular prosthesis view were compared. The shortest distance from the postdeployment perpendicular prosthesis projection to the regression line of predicted perpendicular projections was calculated. All but 1 patient had adequate image quality for reproducible angle predictions. There was a significant correlation between 3DA and MDCT for prediction of perpendicular valve projections (r=0.682, P<0.001). Deviation from the regression line of predicted angles to the postdeployment prosthesis view was 5.1±4.6° for 3DA and 7.9±4.9° for MDCT (P=0.01).

CONCLUSIONS

Three-dimensional angiographic reconstructions and MDCT are safe, practical, and accurate imaging modalities for identifying the optimal perpendicular valve deployment projection during TAVR.

The comparison of radiation dose between C-arm flat-detector CT (DynaCT) and multi-slice CT (MSCT): a phantom study

PURPOSE

To assess and compare the radiation dose of DynaCT in phantoms to that of MSCT.

METHODS AND MATERIALS

A male Anderson Radiation Therapy 200 phantom with embedded thermoluminescence dosimeters (TLDs) was scanned with DynaCT (Axiom Artis dTA, Siemens Healthcare, Forchheim, Germany) and MSCTs (MSCT1: Lightspeed VCT, GE, Milwaukee, USA; MSCT2: Sensation Cardiac 64, Siemens Healthcare, Erlangen, Germany), respectively. For DynaCT, radiation exposure data with automatic exposure control were obtained from scanning of head, chest and abdomen. For MSCT, scanning protocols for head, chest, and abdomen were examined under conventional exposure conditions. Effective doses were calculated from LiF-TLD measurements according to ICRP103. A Catphan phantom (Phantom Lab, USA) was used to evaluate the spatial resolution and low contrast detectability of DynaCT and MSCT.

RESULTS

The effective doses for DynaCT from head, chest and abdomen scanning were 1.18, 7.32, 7.48 mSv (20 s scan) and 0.85, 6.01, 7.04 mSv (8 s scan); the effective doses for MSCT from head, chest and abdomen scanning were 3.33, 7.62 and 8.42 mSv (MSCT1), and 1.89, 7.52, 8.23 mSv (MSCT2). Significant difference between the organ doses from DynaCT and from MSCT (p<.05) was shown. The spatial resolution of 12 lp/cm was achieved and it was able to recognize a 3mm low contrast object at 0.5% contrast level in DynaCT, which was on the same level as in the MSCT images.

CONCLUSION

The phantom study indicates that DynaCT applies significantly less dose to patient and achieves similar spatial resolution and low contrast detectability to standard diagnostic MSCT.

Use of angiographic CT imaging in the cardiac catheterization laboratory for congenital heart disease

OBJECTIVES

This study sought to retrospectively evaluate our initial experience using angiographic computed tomography (ACT) in a pediatric cardiac catheterization laboratory.

BACKGROUND

ACT provides cross-sectional CT images from a rotational angiography run using a C-arm mounted flat-panel detector in the interventional suite. A 3-dimensional (3D) angiographic image can be created from the CT volume set and used in real time during the procedure. To our knowledge, its use has never previously been described for congenital heart disease.

METHODS

3D reconstructions were created and we retrospectively reviewed cases during our first year of ACT use. Images obtained were independently evaluated to determine their diagnostic utility. Radiation dose reduction protocols were defined using phantom testing and radiation dose calculation.

RESULTS

ACT was used during 41 cardiac catheterizations in patients at a median age of 5.1 years (range: 0.4 to 58.8 years) for evaluation of: right ventricular outflow tract (RVOT)/central pulmonary arteries (PAs) in 20; cavopulmonary connection (CPC) in 11; pulmonary veins in 5; distal PAs in 4; and other locations in 5. Four subjects had 2 anatomic areas studied by ACT. The mean contrast volume for ACT was 1.2 ± 0.4 ml/kg. Diagnostic-quality imaging was obtained in 71% of cases: 13/20 RVOT/central PAs; 9/11 CPC; 4/5 pulmonary veins; 2/4 distal PAs; and 4/5 others. In 12 cases, ACT contributed to clinical outcomes beyond standard angiography. Radiation dose reduction protocols allowed ACT to be comparable in exposure to a standard biplane cineangiogram.

CONCLUSIONS

Diagnostic-quality imaging can be obtained using ACT in 71% of cases without a significant increase in contrast or radiation exposure. In certain cases, ACT provides additional anatomic detail and may aid complex catheter manipulations. Future work is needed to continue to define applications of this new technology.

Development of a multimodal tumor model for porcine liver

In our efforts to develop a guidance system for laparoscopic liver surgery, we are working towards a live animal tumor model. The objective of this study was to establish the tumor model for live porcine liver, visible on both computed tomography (CT) and ultrasound images. The tumor model was created by injecting a mixture of agarose, sephadex, and glycerol. Together with water, the mixture was heated to bring its components into solution. Once heating was complete, methylthionine chloride and CT contrast were added. Using laparoscopic ultrasound guidance, the tumor model mixture was injected into in vivo porcine liver. The resulting model tumors were radiolucent, visible on both CT and conventional X-ray. They appeared as hyperechoic lesions on ultrasound images. Compared to the CT images, the model tumors in the ultrasound images showed good correspondence in size. We conclude that our tumor model, due to its clearly identifiable nature on multiple imaging modalities, is a valuable tool for further studies on laparoscopic ultrasound (2D and 3D) and navigated ultrasound in laparoscopic surgery of the liver and other organs in a pre-clinical set-up.

Intra-arterial brachytherapy of hepatic malignancies: watch the flow

Although the liver possesses a dual blood supply, arterial vessels deliver only a small proportion of blood to normal parenchyma, but they deliver the vast majority of blood to primary and secondary cancers of the liver. This anatomical discrepancy is the basis for intra-arterial brachytherapy of liver cancers using radioactive microspheres, termed radio-embolization (RE). Radioactive microspheres implant preferentially in the terminal arterioles of tumors. Although biological models of the flow dynamics and distribution of microspheres are currently in development, there is a need to improve the imaging biomarkers of flow dynamics used to plan RE. Since a direct consequence of RE is vascular disruption and necrosis, we suggest that imaging protocols sensitive to changes in vasculature are highly likely to represent useful early biomarkers for treatment efficacy. We propose dynamic contrast-enhanced CT as the most appropriate imaging modality for studying vascular parameters in clinical trials of RE treatment.