Y-loaded Microspheres Research Articles

Occupational radiation exposure of medical staff performing ⁹⁰Y-loaded microsphere radioembolization.

Radioembolization of liver cancer with (90)Y-loaded microspheres is increasingly used but data regarding hospital staff exposure are scarce. We evaluated the radiation exposure of medical staff while preparing and injecting (90)Y-loaded glass and resin microspheres especially in view of the increasing use of these products. Exposure of the chest and finger of the radiopharmacist, nuclear medicine physician and interventional radiologist during preparation and injection of 78 glass microsphere preparations and 16 resin microsphere preparations was monitored. Electronic dosimeters were used to measure chest exposure and ring dosimeters were used to measure finger exposure. Chest exposure was very low for both products used (<10 μSv from preparation and injection). In our experience, finger exposure was significantly lower than the annual limit of 500 mSv for both products. With glass microspheres, the mean finger exposure was 13.7 ± 5.2 μSv/GBq for the radiopharmacist, and initially 17.9 ± 5.4 μSv/GBq for the nuclear medicine physician reducing to 13.97 ± 7.9 μSv/GBq with increasing experience. With resin microspheres, finger exposure was more significant: mean finger exposure for the radiopharmacist was 295.1 ± 271.9 μSv/GBq but with a reduction with increasing experience to 97.5 ± 35.2 μSv/GBq for the six most recent dose preparations. For administration of resin microspheres, the greatest mean finger exposure for the nuclear medicine physician (the most exposed operator) was 235.5 ± 156 μSv/GBq. Medical staff performing (90)Y-loaded microsphere radioembolization procedures are exposed to safe levels of radiation. Exposure is lower than that from treatments using (131)I-lipiodol. The lowest finger exposure is from glass microspheres. With resin microspheres finger exposure is acceptable but could be optimized in accordance with the ALARA principle, and especially in view of the increasing use of radioembolization.

Clinical impact of (99m)Tc-MAA SPECT/CT-based dosimetry in the radioembolization of liver malignancies with (90)Y-loaded microspheres.

Radioembolization with 90Y-loaded microspheres is increasingly used in the treatment of primary and secondary liver cancer. Technetium-99 m macroaggregated albumin (MAA) scintigraphy is used as a surrogate of microsphere distribution to assess lung or digestive shunting prior to therapy, based on tumoral targeting and dosimetry. To date, this has been the sole pre-therapeutic tool available for such evaluation. Several dosimetric approaches have been described using both glass and resin microspheres in hepatocellular carcinoma (HCC) and liver metastasis. Given that each product offers different specific activities and numbers of spheres injected, their radiobiological properties are believed to lightly differ. This paper summarizes and discusses the available studies focused on MAA-based dosimetry, particularly concentrating on potential confounding factors like clinical context, tumor size, cirrhosis, previous or concomitant therapy, and product used. In terms of the impact of tumoral dose in HCC, the results were concordant and a response relationship and tumoral threshold dose was clearly identified, especially in studies using glass microspheres. Tumoral dose has also been found to influence survival. The concept of treatment intensification has recently been introduced, yet despite several studies publishing interesting findings on the tumor dose-metastasis relationship, no consensus has been reached, and further clarification is thus required. Nor has the maximal tolerated dose to the liver been well documented, requiring more accurate evaluation. Lung dose was well described, despite recently identified factors influencing its evaluation, requiring further assessment. Conclusion: MAA SPECT/CT dosimetry is accurate in HCC and can now be used in order to achieve a fully customized approach, including treatment intensification. Yet further studies are warranted for the metastasis setting and evaluating the maximal tolerated liver dose.

Radiation lobectomy: Time-dependent analysis of future liver remnant volume in unresectable liver cancer as a bridge to resection

Portal vein embolization (PVE) is a standard technique for patients not amenable to liver resection due to small future liver remnant ratio (FLR). Radiation lobectomy (RL) with (90)Y-loaded microspheres (Y90) is hypothesized to induce comparable volumetric changes in liver lobes, while potentially controlling the liver tumor and limiting tumor progression in the untreated lobe. We aimed at testing this concept by performing a comprehensive time-dependent analysis of liver volumes following radioembolization. 83 patients with right unilobar disease with hepatocellular carcinoma (HCC; N=67), cholangiocarcinoma (CC; N=8) or colorectal cancer (CRC; N=8) were treated by Y90 RL. The total liver volume, lobar (parenchymal) and tumor volumes, FLR and percentage of FLR hypertrophy from baseline (%FLR hypertrophy) were assessed on pre- and post-Y90 CT/MRI scans in a dynamic fashion. Right lobe atrophy (p=0.003), left lobe hypertrophy (p<0.001), and FLR hypertrophy (p<0.001) were observed 1 month after Y90 and this was consistent at all follow-up time points. Median %FLR hypertrophy reached 45% (5-186) after 9 months (p<0.001). The median maximal %FLR hypertrophy was 26% (-14 → 86). Portal vein thrombosis was correlated to %FLR hypertrophy (p=0.02). Median Child-Pugh score worsening (6 → 7) was seen at 1 to 3 months (p=0.03) and 3 to 6 months (p=0.05) after treatment. Five patients underwent successful right lobectomy (HCC N=3, CRC N=1, CC N=1) and 6 HCCs were transplanted. Radiation lobectomy by Y90 is a safe and effective technique to hypertrophy the FLR. Volumetric changes are comparable (albeit slightly slower) to PVE while the right lobe tumor is treated synchronously. This novel technique is of particular interest in the bridge-to-resection setting.

From the Angio Suite to the γ-Camera: Vascular Mapping and 99mTc-MAA Hepatic Perfusion Imaging Before Liver Radioembolization—A Comprehensive Pictorial Review

Endovascular mapping and conjoint (99m)Tc-macroaggregated albumin ((99m)Tc-MAA) hepatic perfusion imaging provide essential information before liver radioembolization with (90)Y-loaded microspheres in patients with primary and secondary hepatic malignancies. The aims of this integrated procedure are to determine whether there is a risk for excessive shunting of (90)Y-microspheres to the lungs; to detect extrahepatic perfusion emerging from the injected vascular territory, which might lead to nontargeted radioembolization; to reveal incomplete coverage of the liver parenchyma involved by the tumor, which may be related to anatomic or acquired variants of the arterial vasculature; and to aid in calculation of the (90)Y-microsphere dose to be delivered to the liver. This pictorial essay presents an integrated comprehensive review of the anatomic, angiographic, and nuclear imaging aspects of planned liver radioembolization. The relevant anatomy of the liver, including the standard and the variant arterial vasculature, will be shown using digital subtraction angiography, SPECT/CT, contrast-enhanced CT, and anatomic illustrations. Technical details that will optimize the imaging protocols and important imaging findings will be discussed. From the angio suite to the γ-camera-the goal of this review is to help the reader better understand how the technical details of the angiographic procedure are reflected in the imaging findings of the (99m)Tc-MAA hepatic perfusion study. In addition, the reader should learn to better recognize the pertinent findings and their clinical implications. This knowledge will enable the reader to provide a more useful interpretation of this complex multidisciplinary procedure.

Dosimetry Based on 99mTc-Macroaggregated Albumin SPECT/CT Accurately Predicts Tumor Response and Survival in Hepatocellular Carcinoma Patients Treated with 90Y-Loaded Glass Microspheres: Preliminary Results

Radioembolization of liver cancers using (90)Y-loaded microspheres is experiencing more widespread use. However, few data are available concerning the doses delivered to the tumors and the healthy liver. This retrospective study was conducted to calculate the tumor dosimetry (planned tumor dose [T(plan) D]) and nontumor dosimetry in patients treated by (90)Y-loaded glass microspheres and determine whether tumor dosimetry could predict response and survival. Thirty-six patients with hepatocellular carcinoma (HCC), including 16 with portal vein thrombosis (PVT), were treated with (90)Y-loaded glass microspheres. The T(plan) D and the dose delivered to the injected healthy liver were calculated using a quantitative analysis of the (99m)Tc-macroaggregated albumin ((99m)Tc-MAA) SPECT/CT exam. Responses were assessed after 3 mo, using the criteria of the European Association for the Study of the Liver. Progression-free survival (PFS) and overall survival (OS) were evaluated using Kaplan-Meier tests. The response rate was 69% for the overall population and 75% for the PVT patients. The dose delivered to the tumor was the only parameter associated with response with multivariate analysis (P = 0.019). A threshold T(plan) D value of 205 Gy was predictive of response, with a sensitivity of 100% and an accuracy of 91%. Quantitative (99m)Tc-MAA SPECT/CT allowed us to increase the injected activity for 4 patients with large lesions. PFS was only 5.2 mo and OS 9 mo when using a T(plan) D of less than 205 Gy versus 14 mo (P = 0.0003) and 18 mo (P = 0.0322), respectively, with a T(plan) D of 205 Gy or more. Quantitative (99m)Tc-MAA SPECT/CT is predictive of response, PFS, and OS. Dosimetry based on (99m)Tc-MAA SPECT/CT can be used for the selection of patients and for an adaptation of treatment planning, especially in selected patients (particularly in the case of large tumors). These results also confirm the efficacy and safety of (90)Y-loaded microspheres in treating HCC, even in the presence of PVT (and especially when (99m)Tc-MAA uptake is seen inside the PVT).