2-[18F]fluoro-2-deoxy-d-galactose positron emission tomography guided functional treatment planning of stereotactic body radiotherapy of liver tumours

Non-contrast based approach for liver function quantification using Bayesian-based intravoxel incoherent motion diffusion weighted imaging: A pilot study

PURPOSE

Liver cirrhosis disrupts liver function and tissue perfusion, detectable by magnetic resonance imaging (MRI). Assessing liver function at the voxel level with 13-b value intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) could aid in radiation therapy liver-sparing treatment for patients with early impairment. This study aimed to evaluate the feasibility of IVIM-DWI for liver function assessment and correlate it with other multiparametric (mp) MRI methods at the voxel level.

METHOD

This study investigates the variability of apparent diffusion coefficient (ADC) derived from 13-b value IVIM-DWI and B1-corrected dual flip angle (DFA) T1 mapping. Experiments were conducted in-vitro with QIBA and NIST phantoms and in 10 healthy volunteers for IVIM-DWI. Additionally, 12 patients underwent an mp-MRI examination. The imaging protocol included a 13-b value IVIM-DWI sequence for generating IVIM parametric maps. B1-corrected DFA T1 pulse sequence was used for generating T1 maps, and Gadoxatate low temporal resolution dynamic contrast-enhanced (LTR-DCE) MRI was used for generating the Hepatic extraction fraction (HEF) map. The Mann-Whitney U test was employed to compare IVIM-DWI parameters (Pure Diffusion, Dslow ; Pseudo diffusion, Dfast ; and Perfusion Fraction, Fp ) between the healthy volunteer and patient groups. Furthermore, in the patient group, statistical correlations were assessed at a voxel level between LTR-DCE MRI-derived HEF, T1 post-Gadoxetate administration, ΔT1%, and various IVIM parameters using Pearson correlation.

RESULTS

For-vitro measurements, the maximum coefficient of variation of the ADC and T1 parameters was 12.4% and 16.1%, respectively. The results also showed that Fp and Dfast were able to distinguish between healthy liver function and mild liver function impairment at the global level, with p = 0.002 for Fp and p < 0.001 for Dfast . Within the patient group, these parameters also exhibited a moderate correlation with HEF at the voxel level.

CONCLUSION

Overall, the study highlighted the potential of Dfast and Fp for detecting liver function impairment at both global and pixel levels.

Role of Functional MRI in Liver SBRT: Current Use and Future Directions

Stereotactic body radiation therapy (SBRT) is an emerging treatment for liver cancers whereby large doses of radiation can be delivered precisely to target lesions in 3-5 fractions. The target dose is limited by the dose that can be safely delivered to the non-tumour liver, which depends on the baseline liver functional reserve. Current liver SBRT guidelines assume uniform liver function in the non-tumour liver. However, the assumption of uniform liver function is false in liver disease due to the presence of cirrhosis, damage due to previous chemo- or ablative therapies or irradiation, and fatty liver disease. Anatomical information from magnetic resonance imaging (MRI) is increasingly being used for SBRT planning. While its current use is limited to the identification of target location and size, functional MRI techniques also offer the ability to quantify and spatially map liver tissue microstructure and function. This review summarises and discusses the advantages offered by functional MRI methods for SBRT treatment planning and the potential for adaptive SBRT workflows.

Functional Liver Imaging in Radiotherapy for Liver Cancer: A Systematic Review and Meta-Analysis

Backgrounds

Functional liver imaging can identify functional liver distribution heterogeneity and integrate it into radiotherapy planning. The feasibility and clinical benefit of functional liver-sparing radiotherapy planning are currently unknown.

Methods

A comprehensive search of several primary databases was performed to identify studies that met the inclusion criteria. The primary objective of this study was to evaluate the dosimetric and clinical benefits of functional liver-sparing planning radiotherapy. Secondary objectives were to assess the ability of functional imaging to predict the risk of radiation-induced liver toxicity (RILT), and the dose-response relationship after radiotherapy.

Results

A total of 20 publications were enrolled in descriptive tables and meta-analysis. The meta-analysis found that mean functional liver dose (f-MLD) was reduced by 1.0 Gy [95%CI: (-0.13, 2.13)], standard mean differences (SMD) of functional liver volume receiving ≥20 Gy (fV20) decreased by 0.25 [95%CI: (-0.14, 0.65)] when planning was optimized to sparing functional liver (P >0.05). Seven clinical prospective studies reported functional liver-sparing planning-guided radiotherapy leads to a low incidence of RILD, and the single rate meta-analysis showed that the RILD (defined as CTP score increase ≥2) incidence was 0.04 [95%CI: (0.00, 0.11), P <0.05]. Four studies showed that functional liver imaging had a higher value to predict RILT than conventional anatomical CT. Four studies established dose-response relationships in functional liver imaging after radiotherapy.

Conclusion

Although functional imaging modalities and definitions are heterogeneous between studies, but incorporation into radiotherapy procedures for liver cancer patients may provide clinical benefits. Further validation in randomized clinical trials will be required in the future.

Effect of stereotactic body radiotherapy on regional metabolic liver function investigated in patients by dynamic [18F]FDGal PET/CT

Purpose

Stereotactic body radiotherapy (SBRT) is increasingly used for treatment of liver tumors but the effect on metabolic liver function in surrounding tissue is largely unknown. Using 2-deoxy-2-[¹⁸F]fluoro-d-galactose ([¹⁸F]FDGal) positron emission tomography (PET)/computed tomography (CT), we aimed to determine a dose–response relationship between radiation dose and metabolic liver function as well as recovery.

Procedures.

One male subject with intrahepatic cholangiocarcinoma and five subjects (1 female, 4 male) with liver metastases from colorectal cancer (mCRC) underwent [¹⁸F]FDGal PET/CT before SBRT and after 1 and 3 months. The dose response was calculated using the data after 1 month and the relative recovery was evaluated after 3 months. All patients had normal liver function at time of inclusion.

Results

A linear dose–response relationship for the individual liver voxel dose was seen until approximately 30 Gy. By fitting a polynomial curve to data, a mean TD₅₀ of 18 Gy was determined with a 95% CI from 12 to 26 Gy. After 3 months, a substantial recovery was observed except in tissue receiving more than 25 Gy.

Conclusions

[¹⁸F]FDGal PET/CT makes it possible to determine a dose–response relationship between radiation dose and metabolic liver function, here with a TD₅₀ of 18 Gy (95% CI 12–26 Gy). Moreover, the method makes it possible to estimate metabolic recovery in liver tissue.

Inter-patient variations of radiation-induced normal-tissue changes in Gd-EOB-DTPA-enhanced hepatic MRI scans during fractionated proton therapy

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Radiation-induced effects visible in Gd-EOB-DTPA enhanced MRI during proton therapy.

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High inter-patient variation in early MRI signal change during therapy.

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Correlation of signal change with pretreatment IL-6 concentration.

Background and purpose

Previous MRI studies have shown a substantial decrease in normal-tissue uptake of a hepatobiliary-directed contrast agent 6–9 weeks after liver irradiation. In this prospective clinical study, we investigated whether this effect is detectable during the course of proton therapy.

Material and methods

Gd-EOB-DTPA enhanced MRI was performed twice during hypo-fractionated proton therapy of liver lesions in 9 patients (plus two patients with only one scan available). Dose-correlated signal changes were qualitatively scored based on difference images from the two scans. We evaluated the correlation between the MRI signal change with the planned dose map. The GTV was excluded from all analyses. In addition, were examined timing, irradiated liver volume, changes in liver function parameters as well as circulating biomarkers of inflammation.

Results

Strong, moderate or no dose-correlated signal changes were detected for 2, 3 and 5 patients, respectively. Qualitative scoring was consistent with the quantitative dose to signal change correlation. In an exploratory analysis, the strongest correlation was found between the qualitative scoring and pretreatment IL-6 concentration. For all patients, a clear dose-correlated signal decrease was seen in late follow-up scans.

Conclusion

Radiation-induced effects can be detected with Gd-EOB-DTPA enhanced MRI in a subgroup of patients within a few days after proton irradiation. The reason for the large inter-patient variations is not yet understood and will require validation in larger studies.

A phase I study on stereotactic body radiotherapy of liver metastases based on functional treatment planning using positron emission tomography with 2-[18F]fluoro-2-deoxy-d-galactose

BACKGROUND AND PURPOSE

The galactose analog 2-[¹⁸F]fluoro-2-deoxy-d-galactose (FDGal) is used for quantification of regional hepatic metabolic capacity by functional positron emission tomography computerized tomography (PET/CT). In the present study, FDGal PET/CT was used for functional treatment planning (FTP) of stereotactic body radiotherapy (SBRT) of liver metastases with the aim of minimizing radiation dose to the best functioning liver tissue.

MATERIAL AND METHODS

Fourteen patients referred for SBRT had FDGal PET/CT performed before and one month after the treatment. The planning CT and the FDGal PET/CT images were deformable co-registered.

RESULTS

A reduction in the mean dose of approximately 2 Gy to the best functioning sub-volumes was obtained. One patient developed grade 2 acute morbidity and no patients experienced grade 3 or higher acute morbidities. The regional hepatic metabolic function post-treatment was linearly correlated to the regional radiation dose and for each 10-Gy increase in dose (γ_10Gy), the metabolic function was reduced by 12%. A 50% reduction was seen at 22.9 Gy in 3 fractions (CI 95%: 16.7-30.4 Gy).

CONCLUSION

The clinical study demonstrates the feasibility for FTP in patients with liver metastases and it was possible to minimize the radiation dose to the best functioning liver tissue.

Metabolic liver function in humans measured by 2-18F-fluoro-2-deoxy-D-galactose PET/CT-reproducibility and clinical potential

Background

PET/CT with the radioactively labelled galactose analogue 2-¹⁸F-fluoro-2-deoxy-D-galactose (¹⁸F-FDGal) can be used to quantify the hepatic metabolic function and visualise regional metabolic heterogeneity. We determined the day-to-day variation in humans with and without liver disease. Furthermore, we examined whether the standardised uptake value (SUV) of ¹⁸F-FDGal from static scans can substitute the hepatic systemic clearance of ¹⁸F-FDGal (K_met, mL blood/min/mL liver tissue/) quantified from dynamic scans as measure of metabolic function.

Four patients with cirrhosis and six healthy subjects underwent two ¹⁸F-FDGal PET/CT scans within a median interval of 15 days for determination of day-to-day variation. The correlation between K_met and SUV was examined using scan data and measured arterial blood concentrations of ¹⁸F-FDGal (blood samples) from 14 subjects from previous studies. Regional and whole-liver values of K_met and SUV along with total metabolic liver volume and total metabolic liver function (total SUV, average SUV multiplied by total metabolic liver volume) were calculated.

Results

No significant day-to-day differences were found for K_met or SUV. SUV had higher intraclass correlation coefficients than K_met (0.92–0.97 vs. 0.49–0.78). The relationship between K_met and SUV was linear. Total metabolic liver volume had non-significant day-to-day variation (median difference 50 mL liver tissue; P = 0.6). Mean total SUV in healthy subjects was 23,840 (95% CI, 21,609; 26,070), significantly higher than in the patients (P < 0.001).

Conclusions

The reproducibility of ¹⁸F-FDGal PET/CT was good and SUV can substitute K_met for quantification of hepatic metabolic function. Total SUV of ¹⁸F-FDGal is a promising tool for quantification of metabolic liver function in pre-treatment evaluation of individual patients.