Diagnostic and prognostic value of 99mTc-MAA SPECT/CT for treatment planning of 90Y-resin microsphere radioembolization for hepatocellular carcinoma: comparison with planar image

Use of dose-volume histograms for metabolic response prediction in hepatocellular carcinoma patients undergoing transarterial radioembolization with Y-90 resin microspheres

INTRODUCTION

Voxel-based dosimetry offers improved outcomes in the treatment of hepatocellular carcinoma (HCC) with transarterial radioembolization (TARE) using glass microspheres. However, the adaptation of voxel-based dosimetry to resin-based microspheres has been poorly studied, and the prognostic relevance of heterogeneous dose distribution remains unclear. This study aims to explore the use of dose-volume histograms for resin microspheres and to determine thresholds for objective metabolic response in HCC patients treated with resin-based TARE.

METHODS

We retrospectively reviewed HCC patients who underwent TARE with Y-90-loaded resin microspheres in our institution between January 2021 and December 2022. Voxel-based dosimetry was performed on post-treatment Y-90 PET/CT images to extract parameters including mean dose absorbed by the tumor (mTD), the percentage of the targeted tumor volume (pTV), and the minimum doses absorbed by consecutive percentages within the tumor volume (D10, D25, D50, D75, D90). Assessment of metabolic response was done according to PERCIST criteria with F-18 FDG PET/CT imaging at 8-12 weeks after the treatment.

RESULTS

This study included 35 lesions targeted with 22 TARE sessions in 19 patients (15 males, 4 females, mean age 60 ± 13 years). Objective metabolic response was achieved in 43% of the lesions (n = 15). Responsive lesions had significantly higher mTD, pTV, and D25-D90 values (all p < 0.05). Optimal cut-off values for mTD, pTV, and D50 were 94.6 Gy (sensitivity 73%, specificity 70%, AUC 0.72), 94% (sensitivity 73%, specificity 55%, AUC 0.64), and 91 Gy (sensitivity 80%, specificity 80%, AUC 0.80), respectively.

CONCLUSION

Parameters derived from dose-volume histograms could offer valuable insights for predicting objective metabolic response in HCC patients treated with resin-based TARE. If verified with larger prospective cohorts, these parameters could enhance the precision of dose distribution and potentially optimize treatment outcomes.

Voxel-based tumor dose correlates to complete pathologic necrosis after transarterial radioembolization for hepatocellular carcinoma

PURPOSE

The transarterial radioembolization (TARE) dose is traditionally calculated using the single-compartment Medical Internal Radiation Dose (MIRD) formula. This study utilized voxel-based dosimetry to correlate tumor dose with explant pathology in order to identify dose thresholds that predicted response.

METHODS

All patients with HCC treated with TARE using yttrium-90 [90Y] glass microspheres at a single institution between January 2015 - June 2023 who underwent liver transplantation were eligible. The [90Y] distribution and dose-volume histograms were determined using Simplicity90 (Mirada Medical, Oxford UK) with a Bremsstrahlung SPECT/CT. A complete response was assigned if explant pathology showed complete necrosis and the patient had not undergone additional treatments to the same tumor after TARE. Logistic regression and receiver operator characteristic (ROC) curves were constructed to evaluate dose thresholds correlated with response.

RESULTS

Forty-one patients were included. Twenty-six (63%) met criteria for complete response. Dose to 95% (D95), 70% (D70), and 50% (D50) of the tumor volume were associated with likelihood of complete response by logistic regression (all p < 0.05). For lesions with complete response versus without, the median D95 was 813 versus 232 Gy, D70 was 1052 versus 315 Gy, and D50 was 1181 versus 369 Gy (all p < 0.01). A D95 > 719 Gy had the highest accuracy at 68% (58% sensitivity, 87% specificity) for predicting complete response. Median percent of tumor volume receiving at least 100 Gy (V100), 200 Gy (V200), 300 Gy (V300), and 400 Gy (V400) also differed by pathologic response: the median V100, V200, V300, and V400 was 100% versus 99%, 100% versus 97%, 100% versus 74%, and 100% versus 43% in the complete response versus non-complete response groups, respectively (all p < 0.05).

CONCLUSION

Voxel-based dosimetry was well-correlated with explant pathology. The D95 threshold had the highest accuracy, suggesting the D95 may be a relevant target for multi-compartment dosimetry.

Efficacy of Yttrium-90 Transarterial Radioembolisation in Advanced Hepatocellular Carcinoma: An Experience With Hybrid Angio-Computed Tomography and Glass Microspheres

Background

Hepatocellular carcinoma is one of the most common malignancies worldwide. Transarterial radioembolisation (TARE) involves selective intra-arterial administration of microspheres loaded with a radioactive compound like Yttrium-90 (Y-90). Conventionally, C-arm-based cone-beam computed tomography has been extensively used during TARE. However, angio-computed tomography (CT) is a relatively new modality which combines the advantages of both fluoroscopy and fCT. There is scarce literature detailing the use of angio-CT in Y90 TARE.

Methods

This was a retrospective study of primary liver cancer cases in which the TARE procedure was done from November 2017 to December 2021. Glass-based Y-90 microspheres were used in all these cases. All the cases were performed in the hybrid angio-CT suite. A single photon emission computed tomography-computed comography (SPECT-CT) done postplanning session determined the lung shunt fraction and confirmed the accurate targeting of the lesion. Postdrug delivery, positron emission tomography-computed tomography (PET-CT) was obtained to confirm the distribution of the Y-90 particles. The technical success, median follow-up, objective response rate (ORR), progression-free survival (PFS), and overall survival (OS) were recorded.

Results

A total of 56 hepatocellular carcinoma patients underwent TARE during this period, out of which 36 patients (30 males and 6 females) underwent Y90 TARE. The aetiology of cirrhosis included non-alcoholic steatohepatitis (NASH) (11), hepatitis C (HCV) (11), hepatitis B (HBV) (9), metabolic dysfunction and alcohol-associated liver disease (MetALD) (2), alcoholic liver disease (ALD) (1), cryptogenic (1), and autoimmune hepatitis (AIH) (1). The technical success was 100 % and the median follow-up was 7 months (range: 1-32 months). The median OS was 15 months (range 10.73-19.27 months; 95 % CI) and the median local PFS was 4 months (range 3.03-4.97 months; 95 % CI). The ORR (best response, CR + PR) was 58 %. No major complications were seen in this study.

Conclusion

TARE is a viable option for liver cancer in all stages, but more so in the advanced stages. The use of angio-CT in TARE aids in the precise delivery of the particles to the tumour and avoids non-target embolisation.

Hepatopulmonary Shunt Ratio Verification Model for Transarterial Radioembolization

INTRODUCTION

The most important toxicity of transarterial radioembolization therapy applied in liver malignancies is radiation pneumonitis and fibrosis due to hepatopulmonary shunt of Yttrium-90 (90Y) microspheres. Currently, Technetium-99m macroaggregated albumin (99mTc-MAA) scintigraphic images are used to estimate lung shunt fraction (LSF) before treatment. The aim of this study was to create a phantom to calculate exact LFS rates according to 99mTc activities in the phantom and to compare these rates with LSF values calculated from scintigraphic images.

MATERIALS AND METHODS

A 3D-printed lung and liver phantom containing two liver tumors was developed from Polylactic Acid (PLA) material, which is similar to the normal-sized human body in terms of texture and density. Actual %LSFs were calculated by filling phantoms and tumors with 99mTc radionuclide. After the phantoms were placed in the water tank made of plexiglass material, planar, SPECT, and SPECT/CT images were obtained. The actual LSF ratio calculated from the activity amounts filled into the phantom was used for the verification of the quantification of scintigraphic images and the results obtained by the Simplicity90YTM method.

RESULTS

In our experimental model, LSFs calculated from 99mTc activities filled into the lungs, normal liver, small tumor, and large tumor were found to be 0%, 6.2%, 10.8%, and 16.9%. According to these actual LSF values, LSF values were calculated from planar, SPECT/CT (without attenuation correction), and SPECT/CT (with both attenuation and scatter correction) scintigraphic images of the phantom. In each scintigraphy, doses were calculated for lung, small tumor, large tumor, normal liver, and Simplicity90YTM. The doses calculated from planar and SPECT/CT (NoAC+NoSC) images were found to be higher than the actual doses. The doses calculated from SPECT/CT (with AC+with SC) images and Simplicity90YTM were found to be closer to the real dose values.

CONCLUSION

LSF is critical in dosimetry calculations of 90Y microsphere therapy. The newly introduced hepatopulmonary shunt phantom in this study is suitable for LSF verification for all models/brands of SPECT and SPECT/CT devices.

Quantification of liver-Lung shunt fraction on 3D SPECT/CT images for selective internal radiation therapy of liver cancer using CNN-based segmentations and non-rigid registration

PURPOSE

Selective internal radiation therapy (SIRT) has been proven to be an effective treatment for hepatocellular carcinoma (HCC) patients. In clinical practice, the treatment planning for SIRT using ⁹⁰Y microspheres requires estimation of the liver-lung shunt fraction (LSF) to avoid radiation pneumonitis. Currently, the manual segmentation method to draw a region of interest (ROI) of the liver and lung in 2D planar imaging of ^99mTc-MAA and 3D SPECT/CT images is inconvenient, time-consuming and observer-dependent. In this study, we propose and evaluate a nearly automatic method for LSF quantification using 3D SPECT/CT images, offering improved performance compared with the current manual segmentation method.

METHODS

We retrospectively acquired 3D SPECT with non-contrast-enhanced CT images (nCECT) of 60 HCC patients from a SPECT/CT scanning machine, along with the corresponding diagnostic contrast-enhanced CT images (CECT). Our approach for LSF quantification is to use CNN-based methods for liver and lung segmentations in the nCECT image. We first apply 3D ResUnet to coarsely segment the liver. If the liver segmentation contains a large error, we dilate the coarse liver segmentation into the liver mask as a ROI in the nCECT image. Subsequently, non-rigid registration is applied to deform the liver in the CECT image to fit that obtained in the nCECT image. The final liver segmentation is obtained by segmenting the liver in the deformed CECT image using nnU-Net. In addition, the lung segmentations are obtained using 2D ResUnet. Finally, LSF quantitation is performed based on the number of counts in the SPECT image inside the segmentations. Evaluations and Results: To evaluate the liver segmentation accuracy, we used Dice similarity coefficient (DSC), asymmetric surface distance (ASSD), and max surface distance (MSD) and compared the proposed method to five well-known CNN-based methods for liver segmentation. Furthermore, the LSF error obtained by the proposed method was compared to a state-of-the-art method, modified Deepmedic, and the LSF quantifications obtained by manual segmentation. The results show that the proposed method achieved a DSC score for the liver segmentation that is comparable to other state-of-the-art methods, with an average of 0.93, and the highest consistency in segmentation accuracy, yielding a standard deviation of the DSC score of 0.01. The proposed method also obtains the lowest ASSD and MSD scores on average (2.6 mm and 31.5 mm, respectively). Moreover, for the proposed method, a median LSF error of 0.14% is obtained, which is a statically significant improvement to the state-of-the-art-method (p=0.004), and is much smaller than the median error in LSF manual determination by the medical experts using 2D planar image (1.74% and p<0.001).

CONCLUSIONS

A method for LSF quantification using 3D SPECT/CT images based on CNNs and non-rigid registration was proposed, evaluated and compared to state-of-the-art techniques. The proposed method can quantitatively determine the LSF with high accuracy and has the potential to be applied in clinical practice.

A Theranostic Approach in SIRT: Value of Pre-Therapy Imaging in Treatment Planning

Selective internal radiation therapy (SIRT) is one of the treatment options for liver tumors. Microspheres labelled with a therapeutic radionuclide (⁹⁰Y or ¹⁶⁶Ho) are injected into the liver artery feeding the tumor(s), usually achieving a high tumor absorbed dose and a high tumor control rate. This treatment adopts a theranostic approach with a mandatory simulation phase, using a surrogate to radioactive microspheres (^99mTc-macroaggregated albumin, MAA) or a scout dose of ¹⁶⁶Ho microspheres, imaged by SPECT/CT. This pre-therapy imaging aims to evaluate the tumor targeting and detect potential contraindications to SIRT, i.e., digestive extrahepatic uptake or excessive lung shunt. Moreover, the absorbed doses to the tumor(s) and the healthy liver can be estimated and used for planning the therapeutic activity for SIRT optimization. The aim of this review is to evaluate the accuracy of this theranostic approach using pre-therapy imaging for simulating the biodistribution of the microspheres. This review synthesizes the recent publications demonstrating the advantages and limitations of pre-therapy imaging in SIRT, particularly for activity planning.

Radiochemical Feasibility of Mixing of 99mTc-MAA and 90Y-Microspheres with Omnipaque Contrast

Yttrium-90 (90Y) microspheres are widely used for the treatment of liver-dominant malignant tumors. They are infused via catheter into the hepatic artery branches supplying the tumor under fluoroscopic guidance based on pre-therapy angiography and Technetium-99m macroaggregated albumin (99mTc-MAA) planning. However, at present, these microspheres are suspended in radiolucent media such as dextrose 5% (D5) solution. In order to monitor the real-time implantation of the microspheres into the tumor, the 90Y microspheres could be suspended in omnipaque contrast for allowing visualization of the correct distribution of the microspheres into the tumor. The radiochemical purity of mixing 90Y-microspheres in various concentrations of omnipaque was investigated. The radiochemical purity and feasibility of mixing 99mTc-MAA with various concentrations of a standard contrast agent were also investigated. Results showed the radiochemical feasibility of mixing 90Y-microspheres with omnipaque is radiochemically acceptable for allowing real-time visualization of radioembolization under fluoroscopy.

Optimization of the Clinical Effectiveness of Radioembolization in Hepatocellular Carcinoma with Dosimetry and Patient-Selection Criteria

Selective internal radiation therapy (SIRT) is part of the treatment strategy for hepatocellular carcinoma (HCC). Strong clinical data demonstrated the effectiveness of this therapy in HCC with a significant improvement in patient outcomes. Recent studies demonstrated a strong correlation between the tumor response and the patient outcome when the tumor-absorbed dose was assessed by nuclear medicine imaging. Dosimetry plays a key role in predicting the clinical response and can be optimized using a personalized method of activity planning (multi-compartmental dosimetry). This paper reviews the main clinical results of SIRT in HCC and emphasizes the central role of dosimetry for improving it effectiveness. Moreover, some patient and tumor characteristics predict a worse outcome, and toxicity related to SIRT treatment of advanced HCC patient selection based on the performance status, liver function, tumor characteristics, and tumor targeting using technetium-99m macro-aggregated albumin scintigraphy can significantly improve the clinical performance of SIRT.

Automatic scan range for dose-reduced multiphase CT imaging of the liver utilizing CNNs and Gaussian models

Multiphase CT scanning of the liver is performed for several clinical applications; however, radiation exposure from CT scanning poses a nontrivial cancer risk to the patients. The radiation dose may be reduced by determining the scan range of the subsequent scans by the location of the target of interest in the first scan phase. The purpose of this study is to present and assess an automatic method for determining the scan range for multiphase CT scans. Our strategy is to first apply a CNN-based method for detecting the liver in 2D slices, and to use a liver range search algorithm for detecting the liver range in the scout volume. The target liver scan range for subsequent scans can be obtained by adding safety margins achieved from Gaussian liver motion models to the scan range determined from the scout. Experiments were performed on 657 multiphase CT volumes obtained from multiple hospitals. The experiment shows that the proposed liver detection method can detect the liver in 223 out of a total of 224 3D volumes on average within one second, with mean intersection of union, wall distance and centroid distance of 85.5%, 5.7 mm and 9.7 mm, respectively. In addition, the performance of the proposed liver detection method is comparable to the best of the state-of-the-art 3D liver detectors in the liver detection accuracy while it requires less processing time. Furthermore, we apply the liver scan range generation method on the liver CT images acquired from radiofrequency ablation and Y-90 transarterial radioembolization (selective internal radiation therapy) interventions of 46 patients from two hospitals. The result shows that the automatic scan range generation can significantly reduce the effective radiation dose by an average of 14.5% (2.56 mSv) compared to manual performance by the radiographer from Y-90 transarterial radioembolization, while no statistically significant difference in performance was found with the CT images from intra RFA intervention (p = 0.81). Finally, three radiologists assess both the original and the range-reduced images for evaluating the effect of the range reduction method on their clinical decisions. We conclude that the automatic liver scan range generation method is able to reduce excess radiation compared to the manual performance with a high accuracy and without penalizing the clinical decision.

Dosimetry in Clinical Radiopharmaceutical Therapy of Cancer: Practicality Versus Perfection in Current Practice

The use of radiopharmaceutical therapies (RPTs) in the treatment of cancers is growing rapidly, with more agents becoming available for clinical use in last few years and many new RPTs being in development. Dosimetry assessment is critical for personalized RPT, insofar as administered activity should be assessed and optimized in order to maximize tumor-absorbed dose while keeping normal organs within defined safe dosages. However, many current clinical RPTs do not require patient-specific dosimetry based on current Food and Drug Administration-labeled approvals, and overall, dosimetry for RPT in clinical practice and trials is highly varied and underutilized. Several factors impede rigorous use of dosimetry, as compared with the more convenient and less resource-intensive practice of empiric dosing. We review various approaches to applying dosimetry for the assessment of activity in RPT and key clinical trials, the extent of dosimetry use, the relative pros and cons of dosimetry-based versus fixed activity, and practical limiting factors pertaining to current clinical practice.

Treatment response assessment following transarterial radioembolization for hepatocellular carcinoma

Transarterial radioembolization with yttrium-90 microspheres is an established therapy for hepatocellular carcinoma. Post-procedural imaging is important for the assessment of both treatment response and procedural complications. A variety of challenging treatment-specific imaging phenomena complicate imaging assessment, such as changes in tumoral size, tumoral and peritumoral enhancement, and extrahepatic complications. A review of the procedural steps, emerging variations, and timelines for post-treatment tumoral and extra-tumoral imaging changes are presented, which may aid the reporting radiologist in the interpretation of post-procedural imaging. Furthermore, a description of post-procedural complications and their significance is provided.