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 (Y or Ho) 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 (Tc-macroaggregated albumin, MAA) or a scout dose of Ho microspheres, imaged by SPECT/CT.

TCP post-radioembolization and TCP post-EBRT in HCC are similar and can be predicted using the in vitro radiosensitivity.

Background: Tumor equivalent uniform dose (EUD) is proposed as a predictor of patient outcome after liver radioembolization (RE) of hepatocellular carcinoma (HCC) and can be evaluated with Y-TOF-PET. The aim is to evaluate the correlation between PET-based tumors EUD and the clinical response evaluated with dual molecular tracer (C-acetate and F-FDG) PET/CT post-RE.

Methods: 34 HCC tumors in 22 patients were prospectively evaluated.

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.

Dual-layer collimator for improved spatial resolution in SPECT with CZT camera: an analytical and Monte Carlo study.

Current hole matching pixel detector (HMPD) collimators for SPECT imaging exist in two configurations: one hole per pixel (1HMPD) or four holes per pixel (4HMPD). The aim of this study was to assess the performance of a dual-layer collimator made by stacking up these two collimator types (1H/4HMDP) for low- and medium energy gamma emitters..

Antireflux catheter improves tumor targeting in liver radioembolization with resin microspheres.

Purpose: We aimed to determine whether antireflux (ARC) catheter may result in better tumor targeting in liver radioembolization using 90Y-resin microspheres.

Methods: Patients treated with resin microspheres for hepatocellular carcinoma (HCC) and secondary liver malignancies were retrospectively analyzed. All patients underwent a 99mTc-macroaggregated albumin (99mTc-MAA) single photon emission computed tomography (SPECT) following the planning arteriography with a conventional end-hole catheter.

EANM dosimetry committee series on standard operational procedures: a unified methodology for Tc-MAA pre- and Y peri-therapy dosimetry in liver radioembolization with Y microspheres.

The aim of this standard operational procedure is to standardize the methodology employed for the evaluation of pre- and post-treatment absorbed dose calculations in Y microsphere liver radioembolization. Basic assumptions include the permanent trapping of microspheres, the local energy deposition method for voxel dosimetry, and the patient-relative calibration method for activity quantification.The identity of Tc albumin macro-aggregates (MAA) and Y microsphere biodistribution is also assumed.

Yttrium-90 TOF-PET-Based EUD Predicts Response Post Liver Radioembolizations Using Recommended Manufacturer FDG Reconstruction Parameters.

Purpose: Explaining why Y TOF-PET based equivalent uniform dose (EUD) using recommended manufacturer FDG reconstruction parameters has been shown to predict response.

Methods: The hot rods insert of a Jaszczak deluxe phantom was partially filled with a 2.65 GBq Y - 300ml DTPA water solution resulting in a 100 Gy mean absorbed dose in the 6 sectors.

Accurate non-tumoral 99mTc-MAA absorbed dose prediction to plan optimized activities in liver radioembolization using resin microspheres.

Aim: The manufacturers' recommended methods to calculate delivered activities in liver radioembolization are simplistic and only slightly personalized. Activity planning could also be based on a Tc-macroaggregated albumin SPECT/CT (MAA) using the partition model but its accuracy is controversial. This study evaluates the dose parameters in the normal liver and in the tumor compartments using MAA SPECT/CT (pre-therapeutic imaging) and Y TOF-PET/CT (post-therapy imaging).

Renal and Red Marrow Dosimetry in Peptide Receptor Radionuclide Therapy: 20 Years of History and Ahead.

The development of dosimetry and studies in peptide receptor radionuclide therapy (PRRT) over the past two decades are reviewed. Differences in kidney and bone marrow toxicity reported between Y, Lu and external beam radiotherapy (EBRT) are discussed with regard to the physical properties of these beta emitter radionuclides. The impact of these properties on the response to small and large tumors is also considered.

Microspheres Used in Liver Radioembolization: From Conception to Clinical Effects.

Inert microspheres, labeled with several radionuclides, have been developed during the last two decades for the intra-arterial treatment of liver tumors, generally called Selective Intrahepatic radiotherapy (SIRT). The aim is to embolize microspheres into the hepatic capillaries, accessible through the hepatic artery, to deliver high levels of local radiation to primary (such as hepatocarcinoma, HCC) or secondary (metastases from several primary cancers, e.g.

Hepatic Arterial Buffer Response in Liver Radioembolization and Potential Use for Improved Cancer Therapy.

Liver radioembolization is a treatment option for unresectable liver cancers, performed by infusion of Y or Ho loaded spheres in the hepatic artery. As tumoral cells are mainly perfused via the liver artery unlike hepatic lobules, a twofold tumor to normal liver dose ratio is commonly obtained. To improve tumoral cell killing while preserving lobules, co-infusion of arterial vasoconstrictor has been proposed but with limited success: the hepatic arterial buffer response (HABR) and hepatic vascular escape mechanism hamper the arterioles vasoconstriction.

Prediction of tumor response and patient outcome after radioembolization of hepatocellular carcinoma using 90Y-PET-computed tomography dosimetry.

Aim: 90Y-radioembolization using glass or resin microspheres is increasingly used for the treatment of hepatocellular carcinoma (HCC). The aim of this retrospective study is to determine the prognostic relevance of dosimetric parameters defined with 90Y-PET-CT obtained immediately after radioembolization.

Methods: Forty-five HCC patients, mostly with multiple lesions, were treated by radioembolization between 2011 and 2017.

Autumn COVID-19 surge dates in Europe correlated to latitudes, not to temperature-humidity, pointing to vitamin D as contributing factor.

To determine the factor triggering the sudden surge of daily new COVID-19 cases arising in most European countries during the autumn of 2020. The dates of the surge were determined using a fitting of the two last months of reported daily new cases in 18 European countries with latitude ranging from 39° to 62°. The study proves no correlation between the country surge date and the 2 weeks preceding temperature or humidity but shows an impressive linear correlation with latitude.

Achieving sub-100 ps time-of-flight resolution in thick LSO positron emission tomography while reducing system cost: a Monte Carlo study.

Purpose: Evaluating the time-of-flight (TOF) resolution improvement that could be obtained using an easy crystal block modification which enables depth of interaction (DOI) assessment and simplifies the detector assembling process.

Method: A fast optical Monte Carlo (MC) code was developed. The code was evaluated versus measurements of the energy resolution, number of detected scintillation photons and TOF resolution (TOFr) reported for different crystal photodetector setups.

Significant artefactual noise in Y TOF-PET imaging of low specific activity phantoms arises despite increased acquisition time.

Volumes of usual PET phantoms are about four to sixfold that of a human liver. In order to avoid count rate saturation and handling of very high Y activity, reported TOF-PET phantom studies are performed using specific activities lower than those observed in liver radioembolization.However, due to the constant random coincidence rate induced by the natural crystal radioactivity, reduction of Y specific activity in TOF-PET imaging cannot be counterbalanced by increasing the acquisition time.

PET/CT Specificities in Y Imaging Post Radioembolization.

This article presents a comprehensive review of the Y PET/CT challenges in imaging post liver radioembolization. Specificities of the different PET systems are identified. Conclusions are drawn to help the design of phantom validation studies, quantification of intrahepatic activity, assessment of tumor dosimetry, and checking of extrahepatic sphere delivery in clinical routine.

The origin and reduction of spurious extrahepatic counts observed in Y non-TOF PET imaging post radioembolization.

Our literature survey revealed a physical effect unknown to the nuclear medicine community, i.e. internal bremsstrahlung emission, and also the existence of long energy resolution tails in crystal scintillation.

Update on novel trends in PET/CT technology and its clinical applications.

After a brief history of the major evolutions of positron emission tomography since its introduction in 1972, this article reviews the recent improvements and novel trends in positron emission tomography with a special focus on the time of flight that is currently the major research topic. Novel emerging acquisition modalities, such as dual tracer acquisition, inline hadron therapy dose imaging and yttrium-90 imaging are reviewed.

Biodistribution of (125)I-labeled anti-endoglin antibody using SPECT/CT imaging: Impact of in vivo deiodination on tumor accumulation in mice.

Introduction: Radiolabeled antibodies directed against endoglin (CD105) are promising tools for imaging and antiangiogenic cancer therapy. To validate iodinated antibodies as reliable tracers, we investigated the influence of the radiolabeling method (direct or indirect) on their in vivo stability.

Methods: Anti-CD105 mAbs were radioiodinated directly using chloramine-T ((125)I-anti-CD105-mAbs) or indirectly using D-KRYRR peptide as a linker ((125)I-KRYRR-anti-CD105-mAbs).

αVβ3 integrin-targeted microSPECT/CT imaging of inflamed atherosclerotic plaques in mice.

Background: αVβ3-integrin is expressed by activated endothelial cells and macrophages in atherosclerotic plaques and may represent a valuable marker of high-risk plaques. We evaluated (99m)Tc-maraciclatide, an integrin-specific tracer, for imaging vascular inflammation in atherosclerotic lesions in mice.

Methods: Apolipoprotein E-negative (ApoE(-/-)) mice on a Western diet (n = 10) and normally fed adult C57BL/6 control mice (n = 4) were injected with (99m)Tc-maraciclatide (51.

Statistical and radiobiological analysis of the so-called thyroid stunning.

Background: The origin of the reduction in thyroid uptake after a low activity iodine scan, so-called stunning effect, is still controversial. Two explanations prevail: an individual cell stunning that reduces its capability to store iodine without altering its viability, and/or a significant cell-killing fraction that reduces the number of cells in the tissue still taking up iodine. Our aim is to analyze whether this last assumption could explain the observed reduction.

MIRD Pamphlet No. 26: Joint EANM/MIRD Guidelines for Quantitative 177Lu SPECT Applied for Dosimetry of Radiopharmaceutical Therapy.

The accuracy of absorbed dose calculations in personalized internal radionuclide therapy is directly related to the accuracy of the activity (or activity concentration) estimates obtained at each of the imaging time points. MIRD Pamphlet no. 23 presented a general overview of methods that are required for quantitative SPECT imaging.