Quantitative 4D transcatheter intraarterial perfusion MRI for monitoring chemoembolization of hepatocellular carcinoma

Purpose:

To develop a fully quantitative 4D transcatheter intraarterial perfusion (TRIP) magnetic resonance imaging (MRI) technique and prospectively test the hypothesis that quantitative 4D TRIP‐MRI can be used clinically to monitor intraprocedural liver tumor perfusion reductions during transcatheter arterial chemoembolization (TACE).

Materials and Methods:

TACE was performed within an x‐ray digital subtraction angiography (DSA)‐MRI procedure suite in 16 patients with hepatocellular carcinoma. Quantitative 4D TRIP‐MRI with targeted radiofrequency field mapping and dynamic longitudinal relaxation rate mapping was used to monitor changes in tumor perfusion during TACE. First‐pass perfusion analysis was performed to produce intraprocedural blood flow (Fρ) maps. Mean liver tumor perfusions before and after TACE were compared with a paired t‐test (α = 0.05).

Results:

Perfusion reductions were successfully measured with quantitative 4D TRIP‐MRI in 22 separate tumors during 18 treatment sessions. Mean tumor perfusion Fρ decreased from 16.3 (95% confidence interval [CI]: 10.7–21.9) before TACE to 5.0 (95% CI: 3.5–6.5) (mL/min/100 mL) after TACE. Tumor perfusion reductions were statistically significant (P < 0.0005), with a mean absolute perfusion change of 11.4 (95% CI: 5.6–17.1) (mL/min/100 mL) and a mean percentage reduction of 61.0% (95% CI: 48.3%–73.6%).

Conclusion:

Quantitative 4D TRIP‐MRI can be successfully performed within clinical interventional settings to monitor intraprocedural changes in liver tumor perfusion during TACE. J. Magn. Reson. Imaging 2010;31:1106–1116. © 2010 Wiley‐Liss, Inc.     

Four‐dimensional transcatheter intraarterial perfusion (TRIP)‐MRI for monitoring liver tumor embolization in VX2 rabbits

Transcatheter intraarterial perfusion (TRIP)‐MRI is an intraprocedural technique to iteratively monitor liver tumor perfusion changes during transcatheter arterial embolization (TAE) and chemoembolization (TACE). However, previous TRIP‐MRI approaches using two‐dimensional (2D) T₁‐weighted saturation‐recovery gradient‐recalled echo (GRE) sequences provided only limited spatial coverage and limited capacity for accurate perfusion quantification. In this preclinical study, a quantitative 4D TRIP‐MRI technique (serial iterative 3D volumetric perfusion imaging) with rigorous radiofrequency (RF) B₁ field calibration and dynamic tissue longitudinal relaxation rate R₁ measurement is presented for monitoring intraprocedural liver tumor perfusion during TAE. 4D TRIP‐MRI and TAE were performed in five rabbits with eight VX2 liver tumors (N = 8). After B₁ calibrated baseline and dynamic R₁ quantification, subsequent tissue contrast agent concentration time curves were derived. A single‐input flow‐limited pharmacokinetic model and peak gradient method were applied for perfusion analysis. The perfusion Fρ reduced significantly from pre‐TAE 0.477 (95% confidence interval [CI]: 0.384–0.570) to post‐TAE 0.131 (95% CI: 0.080–0.183 ml/min/ml, P < 0.001). Magn Reson Med 60:970–975, 2008. © 2008 Wiley‐Liss, Inc.     

Four‐dimensional transcatheter intra‐arterial perfusion MR imaging before and after uterine artery embolization in the rabbit VX2 tumor model

Purpose:

To test the hypothesis that four‐dimensional (4D) transcatheter intra‐arterial perfusion (TRIP) MR imaging can measure uterine fibroid perfusion changes immediately before and after uterine artery embolization (UAE) in the rabbit VX2 tumor model.

Materials and Methods:

Eight VX2 uterine tumors were grown in six rabbits. After positioning a catheter within the uterine artery, we performed 4D TRIP‐MRI measurements with 3‐mL injections of 2.5% gadopentetate dimeglumine. We used a dynamic 3D spoiled‐gradient echo sequence with in vivo B₁‐field correction for improved accuracy during perfusion quantification. We performed UAE using 1 mL of gelatin microspheres (2 × 10⁶ particles; diameter 40–120 μm). Two regions‐of‐interest were drawn within each tumor upon perfusion maps. Functional embolic endpoints were reported as the mean percent reduction in fibroid tumor perfusion. Measurements before and after UAE were compared using paired t‐tests (α = 0.05).

Results:

VX2 uterine tumor perfusion decreased significantly from 27.1 at baseline to 7.09 after UAE (mL/min/100 mL of tissue, P < 0.0001). Overall perfusion reduction was 76.3% (95% confidence interval: 66.3–86.3%).

Conclusion:

Four‐dimensional TRIP MRI can objectively quantify uterine fibroid perfusion reductions during UAE in VX2 rabbits. This technique could be used clinically to potentially determine an optimal embolic endpoint with the long‐term goals of improving UAE success rates and minimizing procedure‐related ischemic pain. J. Magn. Reson. Imaging 2010;31:1137–1143. © 2010 Wiley‐Liss, Inc.     

Comparison of transcatheter intraarterial perfusion MR imaging and fluorescent microsphere perfusion measurements during transcatheter arterial embolization of rabbit liver tumors

PURPOSE: Transcatheter intraarterial perfusion (TRIP) magnetic resonance (MR) imaging is clinically used in the interventional MR imaging setting to verify distribution of injected embolic or chemoembolic material during liver-directed transcatheter therapies and to monitor reductions in perfusion. The accuracy of this technique remains unknown. In the present study, rabbit VX2 liver tumors were used to test the hypothesis that TRIP MR imaging accurately measures changes in tumor perfusion during transcatheter arterial embolization (TAE), with injection of fluorescent microspheres used as the gold-standard technique. MATERIALS AND METHODS: Five New Zealand White rabbits were used for this study (two donor rabbits and three with VX2 liver tumors). In three rabbits with implanted VX2 liver tumors, catheters were superselectively placed under digital subtraction angiographic guidance into the left hepatic artery supplying the targeted tumor. Fluorescent microspheres were injected into each rabbit's left ventricle before and after TAE. TRIP MR images were obtained at baseline and after embolizations for all rabbits with intraarterial injections of 2.5% gadopentetate dimeglumine solution. Linear regression was used to compare relative reductions in tumor perfusion between TRIP MR imaging and fluorescent microspheres. Results were considered statistically significant at a P value less than .05. RESULTS: There was good correlation between TRIP MR imaging and fluorescent microsphere measurements of reduction in tumor perfusion (r = 0.722, P < .012). CONCLUSIONS: TRIP MR imaging provides accurate semiquantitative measurement of perfusion reduction during TAE in rabbit liver tumors.     

Liver tumors: monitoring embolization in rabbits with VX2 tumors--transcatheter intraarterial first-pass perfusion MR imaging

PURPOSE: To prospectively test the hypothesis that transcatheter intraarterial first-pass perfusion (TRIP) magnetic resonance (MR) imaging can depict serial reductions in rabbit liver tumor perfusion during transcatheter arterial embolization (TAE). MATERIALS AND METHODS: All experiments had institutional animal care and use committee approval. In four rabbits implanted with eight VX2 liver tumors, catheters were positioned in the hepatic arteries with conventional angiographic guidance. After transfer to the MR imaging suite, serial TAE was performed, with approximately 0.5 million 40-120-microm embolic particles injected at each embolic stage. TRIP MR imaging was performed at baseline and after each subsequent embolic stage (10 minutes between stages). Serial TAE and TRIP MR imaging were repeated until stasis. The first-pass time course of signal enhancement was measured in both tumors and hepatic arteries. Tumor area under the curve (AUC) and maximum upslope (MUS) values, each normalized by arterial input, were measured to assess iterative perfusion reduction. Perfusion measurements across TAE stages were compared with paired t tests and linear regression. RESULTS: AUC decreased from a pre-TAE baseline of 0.408 (95% confidence interval [CI]: 0.330, 0.486) to 0.065 (95% CI: 0.046, 0.085) (P<.001) after TAE. MUS decreased from a pre-TAE baseline of 0.151 (95% CI: 0.121, 0.181) to 0.027 (95% CI: 0.022, 0.031) (P<.001) after TAE. Reductions to AUC and MUS after each embolic stage were statistically significant (P<.006 for each group of paired comparisons). AUC strongly correlated with MUS (r=0.966, P<.001). CONCLUSION: TRIP MR imaging can depict serial reductions in liver tumor perfusion during TAE. TRIP MR imaging offers the potential to target functional embolic end points during TAE.     

Percutaneous Microwave versus Radiofrequency Ablation of Colorectal Liver Metastases: Ablation with Clear Margins (A0) Provides the Best Local Tumor Control

Purpose

To identify and compare predictors of local tumor progression (LTP)-free survival (LTPFS) after radiofrequency (RF) ablation and microwave (MW) ablation of colorectal liver metastases (CLMs).

MRI assessment of percutaneous ablation of liver tumors: Value of subtraction images

Purpose:

To evaluate the value of subtraction images when using MRI to assess liver tumors treated with percutaneous ablation.

Materials and Methods:

Following percutaneous ablation of 35 liver tumors, two abdominal radiologists, blinded to outcomes, independently reviewed follow‐up MRI examinations for tumoral enhancement suggestive of residual/recurrent tumor and rated their confidence level. After one year, the readers reviewed the same examinations with added subtraction images. Accuracy of the detection of residual/recurrent tumor and contrast‐to‐noise ratios (CNR; for tumoral enhancement‐to‐liver, tumoral enhancement‐to‐ablation zone, and ablation zone‐to‐liver) were calculated with and without subtraction images and compared using Wilcoxon signed rank test. Interobserver variability was computed using Kappa (κ) statistics.

Results:

Residual/recurrent tumor was present in 8 (23.5%) of 34 tumors. Accuracy of detecting residual/recurrent tumor with subtraction images and interobserver agreement (κ = 0.72, good) were better than accuracy of detecting residual/recurrent tumor and interobserver agreement (κ = 0.57, moderate) of enhanced MR images without subtraction. Mean CNR of subtraction images was significantly higher than that of enhanced MR images for tumoral enhancement‐to‐liver (0.2 ± 5 versus 11.6 ± 14.4, P = 0.03), tumoral enhancement‐to‐ablation zone (10.1 ± 12.5 versus 34.4 ± 29.4, P = 0.02), and ablation zone‐to‐liver (11.8 ± 13.3 versus 102.5 ± 238.4, P = 0.03).

Conclusion:

When using MRI, subtraction images help both detect and exclude residual/recurrent tumor following percutaneous liver ablations. J. Magn. Reson. Imaging 2013;37:407–413. © 2012 Wiley Periodicals, Inc.     

Effects of Arsenic Trioxide on Radiofrequency Ablation of VX2 Liver Tumor: Intraarterial versus Intravenous Administration

Objective

Arsenic trioxide (As₂O₃) can be used as a possible pharmaceutical alternative that augments radiofrequency (RF) ablation by reducing tumor blood flow. The aim of this study was to assess the effect of intraarterial and intravenous administration of As₂O₃ on RF-induced ablation in an experimentally induced liver tumor.

Materials and Methods

VX2 carcinoma was grown in the livers of 30 rabbits. As₂O₃ (1 mg/kg) was administered through the hepatic artery (n = 10, group A) or ear vein (n = 10, group B), 30 minutes before RF ablation (125 mA ± 35; 90 ± 5℃). As a control group, 10 rabbits were treated with RF ablation alone (group C). RF was intentionally applied to the peripheral margin of the tumor so that ablation can cover the tumor and adjacent hepatic parenchyma. Ablation areas of the tumor and adjacent parenchymal changes among three groups were compared by the Kruskal-Wallis and Mann-Whitney U test.

Results

The overall ablation areas were 156 ± 28.9 mm² (group A), 119 ± 31.7 (group B), and 92 ± 17.4 (group C, p < 0.04). The ablation area of the tumor was significantly larger in group A (73 ± 19.7 mm²) than both group B (50 ± 19.4, p = 0.02) and group C (28 ± 2.2, p < 0.01). The ratios of the tumoral ablation area to the overall ablation area were larger in group A (47 ± 10.5%) than that of the other groups (42 ± 7.3% in group B and 32 ± 5.6% in group C) (p < 0.03).

Conclusion

Radiofrequency-induced ablation area can be increased with intraarterial or intravenous administration of As₂O₃. The intraarterial administration of As₂O₃ seems to be helpful for the selective ablation of the tumor.     

Percutaneous radiofrequency (RF) thermal ablation of rabbit tumors embedded in fat: a model for RF ablation of breast tumors

RATIONALE AND OBJECTIVES: To develop an experimental tumor model for RF ablation of breast tumors surrounded by fat and to investigate the minimally invasive treatment of such tumors by saline-enhanced RF ablation monitored by ultrasound (US). METHODS: Twenty-eight VX2 tumors were implanted into the retroperitoneum of 14 rabbits and monitored by B-mode US at regular intervals of 2 to 3 days. Saline-enhanced RF ablation (25-mm tip length) was performed 16 days after tumor implantation (10-minute treatment time, 28 W, 15 mL/h infusion of 0.9% NaCl, which was increased to 30 mL/h in cases of an impedance increase). Thermal lesion growth was monitored by B-mode US. Treatment was considered complete if no relapse was detectable histopathologically after a follow-up period of up to 3 weeks. RESULTS: All tumor implantations were successful, reaching sizes from 5 to 38 mm 16 days after implantation. Tumors >20 mm showed central necrosis on US. Smaller tumors without signs of necrosis required greater needle perfusion to maintain constant needle-to-tissue impedance. Local relapses occurred in 14 of 27 tumors (51.8%), all with tumors >20 mm. In 12 cases, they were already detected sonographically. In 2 cases, "islands" of vital tumor were detected only during histopathological assessment. CONCLUSIONS: VX2 tumors are implantable into hypovascular adipose tissue with a high success rate and may be used as a model for RF ablation of breast tumors. B-mode US is not suitable for guiding RF ablation of tumors embedded in fat. The method appears to be more successful with smaller tumors.     

Image-Guided Percutaneous Radiofrequency Ablation of Central Renal Cell Carcinoma: Assessment of Clinical Efficacy and Safety in 31 Tumors

Purpose

To assess clinical efficacy and safety of image-guided percutaneous radiofrequency (RF) ablation of central renal cell carcinoma with adjunctive pyeloperfusion.

Open radio-frequency thermal ablation of renal VX2 tumors in a rabbit model using a cooled-tip electrode: feasibility,safety, and effectiveness

The purpose of this study was to evaluate the feasibility, safety, and effectiveness of radio-frequency (RF) ablation using an internally cooled-tip electrode on renal VX2 tumors implanted in rabbits. Thirty-three rabbits with implanted renal VX2 tumors were divided into two groups: an RF ablation (RFA) group (n=27) and a control group (n=6). In the RFA group, RFA was performed on 27 implanted VX2 tumors using a cooled RF electrode and they were divided into three subgroups according to the follow-up period: acute (1–3 days, n=12); subacute (1–4 weeks, n=9); and chronic (2–7 months, n=6). Contrast-enhanced spiral CT was performed before the RFA and at the day, day 3, weeks 1, 2, 4, and months 2 and 7, after the RFA. The therapeutic efficacy was evaluated by the survival rate, CT, and pathologic findings. The RFA of renal tumors was technically successful in each instance. Complete tumor ablation was achieved in 22 of the 27 rabbits (81.5%) in the RFA group: 5 rabbits survived longer than 8 weeks without any evidence of viable tumor (18.5%) and 17 rabbits were found free of viable tumors when killed (63.0%). Five rabbits showed local tumor relapse and/or hematogenous lung metastasis after ablation (a recurrence rate of 18.5%). There were 11 (40.7%) complications related to the procedure. This experimental study demonstrates the feasibility of RFA therapy to treat renal VX2 tumors in rabbits, although RFA for central tumors carries some major potential complications, including renal arterial injury. Electronic Publication     

FDG-PET for Evaluating the Antitumor Effect of Intraarterial 3-Bromopyruvate Administration in a Rabbit VX2 Liver Tumor Model

Objective

We wanted to investigate the feasibility of using FDG-PET for evaluating the antitumor effect of intraarterial administration of a hexokinase II inhibitor, 3-bromopyruvate (3-BrPA), in a rabbit VX2 liver tumor model.

Materials and Methods

VX2 carcinoma was grown in the livers of ten rabbits. Two weeks later, liver CT was performed to confirm appropriate tumor growth for the experiment. After tumor volume-matched grouping of the rabbits, transcatheter intraarterial administration of 3-BrPA was performed (1 mM and 5 mM in five animals each, respectively). FDG-PET scan was performed the day before, immediately after and a week after 3-BrPA administration. FDG uptake was semiquantified by measuring the standardized uptake value (SUV). A week after treatment, the experimental animals were sacrificed and the necrosis rates of the tumors were calculated based on the histopathology.

Results

The SUV of the VX2 tumors before treatment (3.87 ±1.51 [mean ±SD]) was significantly higher than that of nontumorous liver parenchyma (1.72 ±0.34) (p < 0.0001, Mann-Whitney U test). The SUV was significantly decreased immediately after 3-BrPA administration (2.05 ±1.21) (p = 0.002, Wilcoxon signed rank test). On the one-week follow up PET scan, the FDG uptake remained significantly lower (SUV 1.41 ±0.73) than that before treatment (p = 0.002), although three out of ten animals showed a slightly increasing tendency for the FDG uptake. The tumor necrosis rate ranged from 50.00% to 99.90% (85.48% ±15.87). There was no significant correlation between the SUV or the SUV decrease rate and the tumor necrosis rate in that range.

Conclusion

Even though FDG-PET cannot exactly reflect the tumor necrosis rate, FDG-PET is a useful modality for the early assessment of the antitumor effect of intraarterial administration of 3-BrPA in VX2 liver tumor.     

Gadoxetic acid‐enhanced MRI versus multiphase multidetector row computed tomography for evaluating the viable tumor of hepatocellular carcinomas treated with image‐guided tumor therapy

Purpose:

To compare the diagnostic performance of gadoxetic acid‐enhanced MRI with that of multi‐phase 40‐ or 64‐multidetector row computed tomography (MDCT) to evaluate viable tumors of hepatocellular carcinomas (HCCs) treated with image‐guided tumor therapy.

Materials and Methods:

A total of 108 patients with 162 HCCs (56 lesions with viable tumor and 106 without viable tumor) treated by means of transcatheter arterial chemoembolization or radiofrequency ablation were retrospectively included in this study. All patients underwent multi‐phase CT at 40‐ or 64‐MDCT and gadoxetic acid‐enhanced MRI using 3.0 Tesla (T). Two observers independently and randomly reviewed the CT and MR images of the treated lesions. The diagnostic performance of two techniques for the evaluation of the viable tumors in the treated lesions was assessed with a receiver operating characteristic (ROC) analysis.

Results:

For each observer, the areas under the ROC curve were 0.953 and 0.969 for MRI, and 0.870 and 0.888 for MDCT (P < 0.05). The diagnostic accuracies (96.3% for each observer) and sensitivities (92.9% and 96.4%) of MRI in two observers were significantly higher than those (82.7% and 80.9%, 53.6% for each observer, respectively) of MDCT (P < 0.001). The negative predictive values (96.3% and 98.1%) of MRI in two observers were significantly higher than those (80.0% and 79.5%) of MDCT (P < 0.001). For each observer, specificities and positive predictive values did not differ significantly between the two techniques (P > 0.05).

Conclusion:

Gadoxetic acid‐enhanced MRI shows better diagnostic performance than that of MDCT for evaluating the viable tumors of HCCs treated with image‐guided tumor therapy. J. Magn. Reson. Imaging 2010;32:629–638. © 2010 Wiley‐Liss, Inc.     

Radio-frequency ablation of VX2 rabbit tumors: assessment of completeness of treatment by using contrast-enhanced harmonic power Doppler US

PURPOSE: To assess contrast material-enhanced harmonic power Doppler and fundamental color Doppler ultrasonography (US) in the detection of residual viable tumor tissue after radio-frequency (RF) ablation in tumors embedded in fat. MATERIALS AND METHODS: Twenty-eight VX2 tumors were implanted into the retroperitoneum of 14 rabbits. Tumors were examined with contrast-enhanced fundamental color Doppler US and harmonic power Doppler US before and 10 minutes after RF ablation. Saline-enhanced RF ablation (30 mL/h) was performed over 10 minutes with 28-W RF power. Follow-up included repeat US examinations. Necropsies and histopathologic assessment were performed after detection of residual untreated tumor at US or 3 weeks after ablation. RESULTS: VX2 tumors reached a mean size of 21 mm +/- 9 (SD) (size range, 6-43 mm) 25 days after implantation. All tumors larger than 31 mm showed signs of central necrosis at US. Before ablation, intense vascularity was detected in all tumors with both contrast-enhanced US modes. Histopathologic assessment at the end of the follow-up period revealed local relapses due to incomplete ablation in 14 (50%) of 28 cases. Detection of residual tumor was missed in all cases with contrast-enhanced color Doppler US. Contrast-enhanced harmonic power Doppler US depicted residual flow in 12 of the 14 cases (sensitivity, 86%) in which local relapses occurred. There was a significant (P <.005, McNemar test) improvement in detection of residual tumor when the harmonic power Doppler mode was used. CONCLUSION: Contrast-enhanced harmonic power Doppler US has greater sensitivity than contrast-enhanced color Doppler US for detecting residual VX2 tumor following ablation. Therefore, contrast-enhanced harmonic power Doppler US may be a useful additional method for the detection of residual tumors after RF ablation.     

Intraprocedural diffusion‐weighted PROPELLER MRI to guide percutaneous biopsy needle placement within rabbit VX2 liver tumors

Purpose

To test the hypothesis that diffusion‐weighted (DW)‐PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) magnetic resonance imaging (MRI) can be used to guide biopsy needle placement during percutaneous interventional procedures to selectively target viable and necrotic tissues within VX2 rabbit liver tumors.

Materials and Methods

Our institutional Animal Care and Use Committee approved all experiments. In six rabbits implanted with 15 VX2 liver tumors, baseline DW‐PROPELLER images acquired prior to the interventional procedure were used for apparent diffusion coefficient (ADC) measurements. Next, intraprocedural DW‐PROPELLER scans were performed with needle position iteratively adjusted to target viable, necrotic, or intermediate border tissue regions. DW‐PROPELLER ADC measurements at the selected needle tip locations were compared with the percentage of tumor necrosis qualitatively assessed at histopathology.

Results

DW‐PROPELLER images demonstrated intratumoral tissue heterogeneity and clearly depicted the needle tip position within viable and necrotic tumor tissues. Mean ADC measurements within the region‐of‐interest encompassing the needle tip were highly correlated with histopathologic tumor necrotic tissue assessments.

Conclusion

DW‐PROPELLER is an effective method to selectively position the biopsy needle tip within viable and necrotic tumor tissues. The DW‐PROPELLER method may offer an important complementary tool for functional guidance during MR‐guided percutaneous procedures. J. Magn. Reson. Imaging 2009;30:366–373. © 2009 Wiley‐Liss, Inc.     

In vitro blood-perfused bovine liver model: a physiologic model for evaluation of the performance of radiofrequency ablation devices

Purpose

To describe an in vitro blood-perfused bovine liver model for the testing of radiofrequency (RF) ablation devices and compare the performance of a specific RF ablation device in the model relative to three other biologic models.

Materials and Methods

Fresh bovine livers were used to create three in vitro models: blood-perfused, Krebs–Henseleit (KH) solution–perfused, and nonperfused. The perfused models were connected to a heart–lung machine via the portal vein and perfused with heparinized autologous blood or KH solution under physiologic conditions. Six swine were used as in vivo liver models. A cluster electrode and RF ablation system was operated in impedance mode for 12 minutes in all models. Ablated livers were sectioned, with long- and short-axis measurements of the ablations obtained, and statistical analysis was performed.

Results

A total of 39, 23, 17, and 12 ablations were performed in 14, 6, 5, and 6 blood-perfused bovine livers, KH solution–perfused bovine livers, nonperfused bovine livers, and in vivo porcine livers, respectively. On cut specimens, the average diameters of ablation zones were 4.00 cm (95% CI, 3.88–4.13) in blood-perfused livers, 4.34 cm (95% CI, 4.14–4.50) in KH solution–perfused livers, 4.67 cm (95% CI, 4.50–4.83) in nonperfused livers, and 3.56 cm (95% CI, 3.26–3.83) in in vivo porcine livers. In all models, the ablation zone diameters were normally distributed.

Conclusions

In the in vitro blood-perfused bovine liver model, the size of ablations produced by an RF ablation device are closer in size to those seen in porcine liver in vivo compared with the lesions produced in KH solution–perfused or nonperfused bovine liver.     

Temporal sampling requirements for reference region modeling of DCE‐MRI data in human breast cancer

Purpose

To assess the temporal sampling requirements needed for quantitative analysis of dynamic contrast‐enhanced MRI (DCE‐MRI) data with a reference region (RR) model in human breast cancer.

Materials and Methods

Simulations were used to study errors in pharmacokinetic parameters (K^trans and v_e) estimated by the RR model using six DCE‐MRI acquisitions over a range of pharmacokinetic parameter values, arterial input functions, and temporal samplings. DCE‐MRI data were acquired on 12 breast cancer patients and parameters were estimated using the native resolution data (16.4 seconds) and compared to downsampled 32.8‐second and 65.6‐second data.

Results

Simulations show that, in the majority of parameter combinations, the RR model results in an error less than 20% in the extracted parameters with temporal sampling as poor as 35.6 seconds. The experimental results show a high correlation between K^trans and v_e estimates from data acquired at 16.4‐second temporal resolution compared to the downsampled 32.8‐second data: the slope of the regression line was 1.025 (95% confidence interval [CI]: 1.021, 1.029), Pearson's correlation r = 0.943 (95% CI: 0.940, 0.945) for K^trans, and 1.023 (95% CI: 1.021. 1.025), r = 0.979 (95% CI: 0.978, 0.980) for v_e. For the 64‐second temporal resolution data the results were: 0.890 (95% CI: 0.894, 0.905), r = 0.8645, (95% CI: 0.858, 0.871) for K^trans, and 1.041 (95% CI: 1.039, 1.043), r = 0.970 (95% CI: 0.968, 0.971) for v_e.

Conclusion

RR analysis allows for a significant reduction in temporal sampling requirements and this lends itself to analyze DCE‐MRI data acquired in practical situations. J. Magn. Reson. Imaging 2009;30:121–134. © 2009 Wiley‐Liss, Inc.     

Value of diffusion‐weighted magnetic resonance images for discrimination of focal benign and malignant hepatic lesions: A meta‐analysis

Purpose:

To evaluate the ability of DW‐MRI in differentiating malignant hepatic tumors from benign lesions.

Materials and Methods:

Meta‐analysis of 14 diagnostic studies was used. A systematic search in Medline, Embase, Web of Science (from January, 1966, to October, 2009), and Cochrane Controlled Clinical Trials Register Database (through third Quarter 2009) was used with screening of the literature.

Results:

A meta‐analysis of all 95 published studies was performed. Fourteen studies fulfilled the inclusion criteria (804 patients with 1665 hepatic lesions). The global sensitivity was 0.91 (95% confidence interval [CI], 0.86–0.94), the specificity was 0.93 (95% CI, 0.86–0.97), the positive likelihood ratio (PLR) was 13.10 (95% CI, 6.30–27.26), the negative likelihood ratio (NLR) was 0.10 (95% CI, 0.06–0.15), and the diagnostic odds ratio (DOR) was 133.76 (95% CI, 49.77–359.45). The area under the curve of the summary receiver operator characteristic (SROC) was 0.96 (95% CI 0.94–0.98).

Conclusion:

Diffusion‐weighted magnetic resonance imaging is potential technically feasible to differentiate malignant from benign focal liver lesions. Apparent diffusion coefficient measurements can be useful in providing rapid quantifiable information. J. Magn. Reson. Imaging 2010;32:130–137. © 2010 Wiley‐Liss, Inc.     

Value of 18F-FDG PET/MR Imaging in the Early Evaluation of Treatment Response following Radiofrequency Ablation of Liver Cancer in a Rabbit Model

PurposeTo test the hypothesis that ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) and magnetic resonance (MR) imaging can detect early residual tumor following radiofrequency (RF) ablation of liver cancer using a VX2 tumor model.Materials and MethodsTwenty-four rabbits with VX2 liver tumors were randomly divided into 3 groups (n = 8/group): Group 1 without RF ablation treatment, Group 2 with complete ablation, and Group 3 with partial ablation. An ¹⁸F-FDG PET/MR imaging scan was obtained within 2 hours after RF ablation. The maximum standardized uptake values (SUV) of the nontreated liver tumor, benign periablational enhancement (BPE), residual tumor, ablated tumor, and adjacent liver parenchyma and mean SUV of the normal liver were measured. The ratios of maximum SUV for these targets to the mean SUV of the normal liver (TNR) were calculated and compared.ResultsThe mean TNR of the nontreated liver tumors in Group 1 was significantly greater than that of the adjacent liver parenchyma (8.68 ± 0.71 vs 1.89 ± 0.26, P < .001). In Group 2, the mean TNR of BPE was significantly greater than that of the adjacent liver parenchyma (2.85 ± 0.20 vs 1.86 ± 0.25, P < .001). In Group 3, the mean TNR of the residual tumor was significantly greater than that of BPE (8.64 ± 0.59 vs 2.78 ± 0.23, P < .001), which was significantly greater than that of completely ablated tumor (2.78 ± 0.23 vs 0.50 ± 0.06, P < .001).Conclusions¹⁸F-FDG PET/MR imaging may serve as a promising imaging tool for the early detection of viable residual tumors due to incomplete tumor ablation.     

Radiofrequency Ablation of Liver Tumors in Combination with Local OK-432 Injection Prolongs Survival and Suppresses Distant Tumor Growth in the Rabbit Model with Intra- and Extrahepatic VX2 Tumors

Purpose

To evaluate survival and distant tumor growth after radiofrequency ablation (RFA) and local OK-432 injection at a single tumor site in a rabbit model with intra- and extrahepatic VX2 tumors and to examine the effect of this combination therapy, which we termed immuno-radiofrequency ablation (immunoRFA), on systemic antitumor immunity in a rechallenge test.

Methods

Our institutional animal care committee approved all experiments. VX2 tumors were implanted to three sites: two in the liver and one in the left ear. Rabbits were randomized into four groups of seven to receive control, RFA alone, OK-432 alone, and immunoRFA treatments at a single liver tumor at 1 week after implantation. Untreated liver and ear tumor volumes were measured after the treatment. As the rechallenge test, tumors were reimplanted into the right ear of rabbits, which survived the 35 weeks and were followed up without additional treatment. Statistical significance was examined by log-rank test for survival and Student’s t test for tumor volume.

Results

Survival was significantly prolonged in the immunoRFA group compared to the other three groups (P < 0.05). Untreated liver and ear tumor sizes became significantly smaller after immunoRFA compared to controls (P < 0.05). In the rechallenge test, the reimplanted tumors regressed without further therapy compared to the ear tumors of the control group (P < 0.05).

Conclusion

ImmunoRFA led to improved survival and suppression of distant untreated tumor growth. Decreases in size of the distant untreated tumors and reimplanted tumors suggested that systemic antitumor immunity was enhanced by immunoRFA.