Mathematic Modeling of Tumor Growth During [Lu]Lu-PSMA Therapy: Insights into Treatment Optimization.

The treatment regimen for [Lu]Lu-prostate-specific membrane antigen (PSMA) 617 therapy follows that of chemotherapy: 6 administrations of a fixed activity, each separated by 6 wk. Mathematic modeling can be used to test the hypothesis that the current treatment regimen for a radiopharmaceutical modality is suboptimal. A mathematic model was developed to describe tumor growth during [Lu]Lu-PSMA therapy.

Intraprocedural C-arm dual-phase cone-beam enhancement patterns correlate with tumor absorbed dose after radioembolization.

Background: Recent studies have shown a clear relationship between absorbed dose and tumor response to treatment after hepatic radioembolization. These findings help to create more personalized treatment planning and dosimetry. However, crucial to this goal is the ability to predict the dose distribution prior to treatment.

Bone Marrow Relative Biological Effectiveness for a Pb-labeled Anti-HER2/neu Antibody.

Purpose: We have determined the in vivo relative biological effectiveness (RBE) of an alpha-particle-emitting radiopharmaceutical therapeutic agent (Pb-labeled anti-HER2/neu antibody) for the bone marrow, a potentially dose-limiting normal tissue.

Methods And Materials: The RBE was measured in mice using femur marrow cellularity as the biological endpoint. External beam radiation therapy (EBRT), delivered by a small-animal radiation research platform was used as the reference radiation.

Pb-conjugated anti-rat HER2/ antibody against a -N derived murine mammary carcinoma cell line: cell kill and RBE in vitro.

Purpose: In the current work, the RBE of a Pb-conjugated anti-HER2/ antibody construct has been evaluated, in vitro, by colony formation assay. The RBE was estimated by comparing two absorbed dose-survival curves: the first obtained from the conjugated Pb experiments (test radiation), the second obtained by parallel experiments of single bolus irradiation of external beam (reference radiation).

Materials And Methods: Mammary carcinoma NT2.

Minimizing the need for coil attenuation correction in integrated PET/MRI at 1.5 T using low-density MR-linac receive arrays.

The simultaneous use of positron emission tomography (PET) and magnetic resonance imaging (MRI) requires attenuation correction (AC) of photon-attenuating objects, such as MRI receive arrays. However, AC of flexible, on-body arrays is complex and therefore often omitted. This can lead to significant, spatially varying PET signal losses when conventional MRI receive arrays are used.

Current Status and Future Direction of Hepatic Radioembolisation.

Radioembolisation is a locoregional treatment modality for hepatic malignancies. It consists of several stages that are vital to its success, which include a pre-treatment angiographic simulation followed by nuclear medicine imaging, treatment activity choice, treatment procedure and post-treatment imaging. All these stages have seen much advancement over the past decade.

Use of an anti-reflux catheter to improve tumor targeting for holmium-166 radioembolization-a prospective, within-patient randomized study.

Purpose: The objective of this study was to investigate whether the use of an anti-reflux catheter improves tumor targeting for colorectal cancer patients with unresectable, chemorefractory liver metastases (mCRC) treated with holmium-166 (Ho)-radioembolization.

Materials And Methods: In this perspective, within-patient randomized study, left and right hepatic perfusion territories were randomized between infusion with a Surefire® anti-reflux catheter or a standard microcatheter. The primary outcome was the difference in tumor to non-tumor (T/N) activity distribution.

Dose-Effect Relationships of Ho Radioembolization in Colorectal Cancer.

Radioembolization is a treatment option for colorectal cancer (CRC) patients with inoperable, chemorefractory hepatic metastases. Personalized treatment requires established dose thresholds. Hence, the aim of this study was to explore the relationship between dose and effect (i.

Feasibility of CT quantification of intratumoural Ho-microspheres.

Background: Microspheres loaded with radioactive Ho (Ho-MS) are novel particles for radioembolisation and intratumoural treatment. Because of the limited penetration of β radiation, quantitative imaging of microsphere distribution is crucial for optimal intratumoural treatment. Computed tomography (CT) may provide high-resolution and fast imaging of the distribution of these microspheres, with lower costs and widespread availability in comparison with current standard single-photon emission tomography (SPECT) and magnetic resonance imaging.

Fast and accurate quantitative determination of the lung shunt fraction in hepatic radioembolization.

Radioembolization treatment is preceded by a Tc-MAA safety procedure, which is used to estimate the lung shunt fraction (LSF). Normally, the LSF is estimated by using the geometric mean of planar scintigraphy (PS-GM). However, concern has been raised about the potential overestimation of the LSF by PS-GM.

First Evidence for a Dose-Response Relationship in Patients Treated with Ho Radioembolization: A Prospective Study.

Ho-microspheres have recently been approved for clinical use for hepatic radioembolization in the European Union. The aim of this study was to investigate the absorbed dose-response relationship and its association with overall survival for Ho radioembolization in patients with liver metastases. Patients treated in the HEPAR I and II studies who underwent an F-FDG PET/CT scan at baseline, a posttreatment Ho SPECT/CT scan, and another F-FDG PET/CT scan at the 3-mo follow-up were included for analysis.

The Unique Role of Fluorodeoxyglucose-PET in Radioembolization.

Recent research into the efficacy of radioembolization has brought this field to an interesting position, in which fluorodeoxyglucose (FDG)-PET/CT is being used extensively for prognosis and response assessment, as well as a tool to define viable tumor volumes for the use in dosimetry. As such, there is an overlap with existing techniques used in radiotherapy; however, many are very specific to the radioembolization paradigm. This article describes the current state-of-the-art of the use of FDG-PET/CT for patient selection, prognosis, treatment evaluation, and as a research tool into absorbed dose-response relationships in radioembolization.

Respiratory motion compensation in interventional liver SPECT using simultaneous fluoroscopic and nuclear imaging.

Purpose: Quantitative accuracy of the single photon emission computed tomography (SPECT) reconstruction of the pretreatment procedure of liver radioembolization is crucial for dosimetry; visual quality is important for detecting doses deposited outside the planned treatment volume. Quantitative accuracy is limited by respiratory motion. Conventional gating eliminates motion by count rejection but increases noise, which degrades the visual reconstruction quality.

The physics of radioembolization.

Radioembolization is an established treatment for chemoresistant and unresectable liver cancers. Currently, treatment planning is often based on semi-empirical methods, which yield acceptable toxicity profiles and have enabled the large-scale application in a palliative setting. However, recently, five large randomized controlled trials using resin microspheres failed to demonstrate a significant improvement in either progression-free survival or overall survival in both hepatocellular carcinoma and metastatic colorectal cancer.

Radioembolization lung shunt estimation based on a Y pretreatment procedure: A phantom study.

Purpose: Prior to Y radioembolization, a pretreatment procedure is performed, in which Tc-macroaggerated albumin ( Tc-MAA) is administered to estimate the amount of activity shunting to the lungs. A high lung shunt fraction (LSF) may impose lower prescribed treatment activity or even impede treatment. Accurate LSF measurement is therefore important, but is hampered by the use of MAA particles, which differ from Y microspheres.

Intratumoral injection of radioactive holmium-166 microspheres in recurrent head and neck squamous cell carcinoma: preliminary results of first use.

Background: Limited treatment options exist for patients with locoregional recurrences of head and neck squamous cell carcinoma (HNSCC). In the palliative setting, a single session, minimally invasive, and relatively safe therapy is desirable. This case series illustrates the feasibility of a direct intratumoral injection of radioactive holmium-166 microspheres (HoMS) in patients as a palliative treatment for recurrent HNSCC.

Estimation of lung shunt fraction from simultaneous fluoroscopic and nuclear images.

Unlabelled: Radioembolisation with yttrium-90 (Y) is increasingly used as a treatment of unresectable liver malignancies. For safety, a scout dose of technetium-99m macroaggregated albumin (Tc-MAA) is used prior to the delivery of the therapeutic activity to mimic the deposition of Y. One-day procedures are currently limited by the lack of nuclear images in the intervention room.

Impact of respiratory motion and acquisition settings on SPECT liver dosimetry for radioembolization.

Purpose: Respiratory motion may impose significant inaccuracies on emission activity estimation in quantitative SPECT. This effect may be a major issue in dosimetry as used in the management of liver radioembolization. The purpose of this study was to investigate the impact of respiratory motion on radioembolization liver dosimetry for different SPECT acquisition settings.