Internal Radionuclide Therapy Research Articles

Safety and Efficacy of Selective Internal Radionuclide Therapy with 90Y Glass Microspheres in Patients with Progressive Hepatocellular Carcinoma after the Failure of Repeated Transarterial Chemoembolization.

Transarterial chemoembolization (TACE) is currently the standard of care in patients with unresectable hepatocellular carcinoma (HCC), and selective internal radionuclide therapy (SIRT) with 90Y microspheres is mainly used as an alternative modality in patients considered poor candidates for TACE. Treatment with sorafenib is the recommended option for patients with progressive disease after TACE. This study aims to evaluate the safety and efficacy of SIRT with glass microspheres in patients with progressive HCC after repeated TACE who are not eligible for treatment with sorafenib. Forty-seven patients with progressive HCC after a median of three TACE sessions (range 2-14) underwent SIRT (3.5 ± 1.5 GBq; liver target dose 110-120 Gy). Toxicity was recorded 4 and 12 weeks after treatment and reported according to the Common Terminology Criteria for Adverse Events Version 5.0. Treatment response was assessed three months after SIRT using multiphase computed tomography and modified criteria in solid tumors (mRECIST). Survival analyses were performed using Kaplan-Meier curves and a Cox proportional hazards model for uni- and multivariate analyses. Significant but reversible hepatotoxicity (≥grade 3) occurred in five patients (11%). No radioembolization-induced liver disease (REILD) was observed. The number of previous TACE sessions and cumulative administered activity did not predict the incidence of post-SIRT significant hepatotoxicity. Treatment responses consisted of partial responses in 26 (55%), stable disease in 12 (26%), and progressive disease in 9 (19%) patients. The median overall survival (OS) was 11 months (95% confidence interval (CI), 9-13), and objective responses to SIRT were associated with a longer OS (p = 0.008). Significant hepatotoxicity (≥grade 3) after SIRT was a contributor to impaired survival (median OS 6 months (95% CI, 4-8) vs. 12 months (95% CI, 10-14), p < 0.001). SIRT with glass microspheres is a safe and effective salvage treatment for patients with progressive HCC refractory to TACE who are considered poor candidates for sorafenib treatment.

Size-dependent therapeutic efficiency of 223Ra-labeled calcium carbonate carriers for internal radionuclide therapy of breast cancer.

The size of drug carriers strongly affects their biodistribution, tissue penetration, and cellular uptake in vivo. As a result, when such carriers are loaded with therapeutic compounds, their size can influence the treatment outcomes. For internal α-radionuclide therapy, the carrier size is particularly important, because short-range α-emitters should be delivered to tumor volumes at a high dose rate without any side effects, i.e. off-target irradiation and toxicity. In this work, we aim to evaluate and compare the therapeutic efficiency of calcium carbonate (CaCO3) microparticles (MPs, >2 μm) and nanoparticles (NPs, <100 nm) labeled with radium-223 (223Ra) for internal α-radionuclide therapy against 4T1 breast cancer. To do this, we comprehensively study the internalization and penetration efficiency of these MPs and NPs, using 2D and 3D cell cultures. For further therapeutic tests, we develop and modify a chelator-free method for radiolabeling of CaCO3 MPs and NPs with 223Ra, improving their radiolabeling efficiency (>97%) and radiochemical stability (>97%). After intratumoral injection of 223Ra-labeled MPs and NPs, we demonstrate their different therapeutic efficiencies against a 4T1 tumor. In particular, 223Ra-labeled NPs show a tumor inhibition of approximately 85%, which is higher compared to 60% for 223Ra-labeled MPs. As a result, we can conclude that 223Ra-labeled NPs have a more suitable biodistribution within 4T1 tumors compared to 223Ra-labeled MPs. Thus, our study reveals that 223Ra-labeled CaCO3 NPs are highly promising for internal α-radionuclide therapy.

The Accuracy of TIAC Calculated Using SPECT/CT Imaging Data at 36- and 100-Hours Post Injection and Prior Information in 177Lu-DOTATATE

In internal radionuclide therapy, there is a growing demand for streamlined methods that alleviate the measurement burden on patients and reduce the associated costs of individual dosimetry. This study assessed the precision of the Two Time Point Dosimetry (2TPD) model, a data-efficient approach, compared to the well-established All Time Point Dosimetry (ATPD) model. The investigation involved the analysis of time-activity data collected from the kidneys of seven patients who were administered 177Lu-DOTATATE and underwent SPECT/CT imaging (PMID 3344306). Data points were specifically gathered at the 36-hour and 100-hour post-injection marks. Employing prior information, a monoexponential function was applied to fit the biokinetic data. Consequently, two crucial metrics, TIAC ATPD and TIAC 2TPD, were computed for ATPD and 2TPD, respectively. To provide a benchmark, the TIAC determined via the Hänscheid method was also incorporated for comparison. The comparative analysis revealed that the percentage error between the population ATPD model and the 2TPD model was (3.97 ± 7.85)%, and for the Hänscheid model, it was (1.8 ± 7.9)%. These findings affirm that the accuracy of TIAC values derived from the 2TPD approach, leveraging prior-information fitting, is reasonably satisfactory.

Improving 90Y PET Scan Image Quality Through Optimized Reconstruction Algorithms.

This study aimed to improve the quality of 90Y PET imaging by optimizing the reconstruction algorithm. Methods: We recruited 10 patients with neuroendocrine tumor metastatic to the liver or primary hepatocellular carcinoma who were qualified for 90Y-labeled selective internal radiation therapy or peptide receptor radionuclide therapy. They underwent posttherapeutic PET/CT imaging using 3 different reconstruction parameters: VUE Point HD with a 6.4-mm filter cutoff, 24 subsets, and 2 iterations (algorithm A); VUE Point FX with a 6.0-mm filter cutoff, 18 subsets, and 3 iterations using time of flight (algorithm B); and VUE Point HD (LKYG) with a 5-mm filter cutoff, 32 subsets, and 1 iteration (algorithm C). The reconstructed PET/CT images were assessed by 10 nuclear medicine physicians using 4-point semiqualitative scoring criteria. A P value of less than 0.05 was considered significant. Results: The median quality assessment scores for algorithm C were consistently scored the highest, with algorithms A, B, and C, scoring 3, 2, and 4, respectively. The 90Y PET scans using algorithm C were deemed diagnostic 91% of the time. There was a statistically significant difference in quality assessment scores among the algorithms by the Kruskal-Wallis rank sum test ([Formula: see text] = 86.5, P < 0.001), with a mean rank quality score of 130.03 for algorithm A, 109.76 for algorithm B, and 211.71 for algorithm C. Subgroup analysis for quality assessment scoring of post-peptide receptor radionuclide therapy imaging alone showed a statistically significant difference between different scanning algorithms ([Formula: see text] = 35.35, P < 0.001), with mean rank quality scores of 45.85 for algorithm A, 50.05 for algorithm B, and 85.6 for algorithm C. Similar results were observed for quality assessment scoring of imaging after selective internal radiation therapy ([Formula: see text] = 79.90, P < 0.001), with mean ranks of 82.33 for algorithm A, 55.79 for algorithm B, and 133.38 for algorithm C. Conclusion: The new LKYG algorithm that was featured by decreasing the number of iterations, decreasing the cutoff of the filter thickness, and increasing the number of subsets successfully improved image quality.

Recent Advances in Hepatocellular Carcinoma Treatment with Radionuclides.

As the third leading cause of cancer death worldwide, hepatocellular carcinoma (HCC) is characterized by late detection, difficult diagnosis and treatment, rapid progression, and poor prognosis. Current treatments for liver cancer include surgical resection, radiofrequency ablation, liver transplantation, chemotherapy, external radiation therapy, and internal radionuclide therapy. Radionuclide therapy is the use of high-energy radiation emitted by radionuclides to eradicate tumor cells, thus achieving the therapeutic effect. Recently, with the continuous development of biomedical technology, the application of radionuclides in treatment of HCC has progressed steadily. This review focuses on three types of radionuclide-based treatment regimens, including transarterial radioembolization (TARE), radioactive seed implantation, and radioimmunotherapy. Their research progress and clinical applications are summarized. The advantages, limitations, and clinical potential of radionuclide treatment of HCC are discussed.

Y90 selective internal radiation therapy and peptide receptor radionuclide therapy for the treatment of metastatic neuroendocrine tumors: combination or not?

Peptide receptor radionuclide therapy and selective internal radiation therapy are effective radionuclide therapy modalities for unresectable metastatic neuroendocrine tumor patients that cannot be controlled with somatostatin analogs. The present study is intended to evaluate the therapeutic efficacy and toxicity of the combined therapy of selective internal radiation therapy and peptide receptor radionuclide therapy and stand-alone selective internal radiation therapy in patients with neuroendocrine tumor, a liver-dominant disease. This cohort consists of 27 patients with metastatic neuroendocrine tumor and liver-dominant disease. They were grouped as the patients who were treated with selective internal radiation therapy for unresectable liver metastasis (n = 15) and the patients who received a combination of selective internal radiation therapy and peptide receptor radionuclide therapy (n = 12) for hepatic and extrahepatic metastasis. Treatment efficacy and treatment-associated toxicity were retrospectively assessed in both groups. The objective treatment response and stable disease were found in 13 patients (86.6%) in the selective internal radiation therapy group and eight patients (66.6%) in the selective internal radiation therapy + peptide receptor radionuclide therapy group. The median overall survival rate was found to be 34.9 months, in the selective internal radiation therapy group and 67.5 months in the selective internal radiation therapy + peptide receptor radionuclide therapy group (P = 0.217). The median progression-free survival data was not reached, and the mean values of progression-free survival were 53.1 ± 9.9 months in the selective internal radiation therapy group, and 27.2 ± 5.9 months in the selective internal radiation therapy + peptide receptor radionuclide therapy group (P = 0.561). Temporary lymphopenia was the most common side effect. Grade 1-2 hepatotoxicity was observed to be 6.6% in the selective internal radiation therapy group, while it was not observed in selective internal radiation therapy + peptide receptor radionuclide therapy group. In the neuroendocrine tumors with liver-dominant metastatic disease, personalized selective internal radiation therapy and peptide receptor radionuclide therapy and their combinations result in increased survival rates. Selective internal radiation therapy alone could be an effective treatment in patients with liver-limited and -dominant disease.

Clustering effects in nanoparticle-enhanced β− emitting internal radionuclide therapy: a Monte Carlo study

We investigate the effects of an increase in the production of secondary electrons when a β− source commonly used in internal radionuclide therapy, 67Cu, is radiolabelled to a super-paramagnetic iron oxide nanoparticle (SPION), with specific emphasis on the role of SPION cluster size and geometry. A positive relationship is found between the degree to which the nanoparticles are clustered and the associated radio-enhancement effects, with cluster population size playing a major role, as well as SPION separation within a cluster and the distance between clusters. Our simulation results indicate that SPIONs labelled with 67Cu can induce a nonlinear amplification in the number of secondary electrons produced of up to 4% in bulk, with localised regions of nearer inter-SPION separation producing an increase of over 400% for a 20 nm average SPION separation. Such variation in enhancement due to local concentration effects may help identify clinical strategies that enhance efficacy for a given radiation dosage, or achieve equal efficacy with reduced radiation dosage.

48 Medical physicist responsibilities in internal radionuclide therapy

Introduction. The internal radionuclide therapy brings together therapy techniques using radiophamaceuticals and radioactive implants. Mostly used in oncology, two kinds of therapy techniques can be distinguished: selective and systemic methods.

Preparation and characterization of inorganic radioactive holmium-166 microspheres for internal radionuclide therapy.

Microspheres with high specific activities of radionuclides are very interesting for internal radiotherapy treatments. This work focuses on the formulation and characterization of inorganic microspheres with a high content of holmium and therefore a high specific radioactivity of holmium-166. Two novel formulations of inorganic microspheres were obtained by dispersing solid holmium acetylacetonate microspheres (Ho2(AcAc)3-ms) in NaH2PO4 or NaOH solutions followed by 2 h incubation at room temperature. By exchange of acetylacetonate with phosphate or hydroxyl ions, holmium phosphate microspheres (HoPO4-ms) and holmium hydroxide microspheres (Ho(OH)3-ms) were formed respectively. The inorganic microspheres had a significantly smaller diameter (28.5 ± 4.4 μm (HoPO4-ms) and 25.1 ± 3.5 μm (Ho(OH)3-ms)) than those of Ho2(AcAc)3-ms (32.6 ± 5.2 μm). The weight percentage of holmium-165 in the microspheres increased significantly from 47% (Ho2(AcAc)3-ms) to 55% (HoPO4-ms) and 73% (Ho(OH)3-ms). After preparation of both HoPO4-ms and Ho(OH)3-ms, the stable holmium-165 isotope was partly converted by neutron activation into radioactive holmium-166 to yield radioactive microspheres. High specific activities were achieved ranging from 21.7 to 59.9 MBq/mg (166HoPO4-ms) and from 28.8 to 79.9 MBq/mg (166Ho(OH)3-ms) depending on the neutron activation time. The structure of both microspheres was preserved up to neutron activations of 6 h in a thermal neutron flux of 4.72 × 1016 n m-2 s-1. After activation, both microspheres revealed excellent stability in administration fluids (saline and phosphate buffer) having less than 0.05% of holmium released after 72 h incubation. Finally, the hemocompatibility of these inorganic microspheres was evaluated and it was shown that the microspheres did cause neither hemolysis nor depletion or inhibition of the coagulation factors of the intrinsic blood coagulation pathway meaning that the microspheres have a good hemocompatibility. Overall, this work shows that radioactive inorganic microspheres with high specific activities of holmium-166 can be prepared which potentially can be used for internal radionuclide therapy.

Radio-enhancement effects by radiolabeled nanoparticles

In cancer radiation therapy, dose enhancement by nanoparticles has to date been investigated only for external beam radiotherapy (EBRT). Here, we report on an in silico study of nanoparticle-enhanced radiation damage in the context of internal radionuclide therapy. We demonstrate the proof-of-principle that clinically relevant radiotherapeutic isotopes (i.e. 213Bi, 223Ra, 90Y, 177Lu, 67Cu, 64Cu and 89Zr) labeled to clinically relevant superparamagnetic iron oxide nanoparticles results in enhanced radiation damage effects localized to sub-micron scales. We find that radiation dose can be enhanced by up to 20%, vastly outperforming nanoparticle dose enhancement in conventional EBRT. Our results demonstrate that in addition to the favorable spectral characteristics of the isotopes and their proximity to the nanoparticles, clustering of the nanoparticles results in a nonlinear collective effect that amplifies nanoscale radiation damage effects by electron-mediated inter-nanoparticle interactions. In this way, optimal radio-enhancement is achieved when the inter-nanoparticle distance is less than the mean range of the secondary electrons. For the radioisotopes studied here, this corresponds to inter-nanoparticle distances <50 nm, with the strongest effects within 20 nm. The results of this study suggest that radiolabeled nanoparticles offer a novel and potentially highly effective platform for developing next-generation theranostic strategies for cancer medicine.

Eighty per cent more patients in 10 years of UK molecular radiotherapy: Internal Dosimetry Users Group survey results from 2007 to 2017.

The Internal Dosimetry Users Group has surveyed UK molecular radiotherapy (MRT) activity for cancer treatment in the UK. Data are presented here spanning 10 years of MRT activity across 31 UK centres, one from Northern Ireland, one from Wales, two from Scotland and 27 from England. Results were compiled from a survey of 2007 activity by the British Institute of Radiology Molecular Radiotherapy Working Party 1, subsequent matched surveys by Internal Dosimetry Users Group of data from 2011, 2012, 2013, 2014 and 2015 which have previously been presented 2,3 and new data from 2016 and 2017. The 2011 and 2012 surveys were carried out online using a dedicated webpage and subsequent surveys were distributed by email, all being publicized widely within the nuclear medicine and medical physics communities. Centres were asked a range of questions about MRT but presented here are data on the number of patients and treatments for each therapy type, activity regimens and trial participation. Treatments identified were Na131I radioiodine (RAI) for thyroid cancer, 131I-metaiodobenzylguanidine (131I-mIBG) and peptide receptor radionuclide therapy (PRRT) for neuroendocrine tumours (NETs), 89Sr-chloride, 153Sm-EDTMP and 223Ra-chloride (Xofigo; Bayer, Leverkusen, Germany) for bone metastases, MRT for haematological malignancies and selective internal radionuclide therapy (SIRT) for liver metastases.

Transarterial Radioembolization (TARE) Agents beyond 90Y-Microspheres.

Liver malignancies, either primary tumours (mainly hepatocellular carcinoma and cholangiocarcinoma) or secondary hepatic metastases, are a major cause of death, with an increasing incidence. Among them, hepatocellular carcinoma (HCC) presents with a dark prognosis because of underlying liver diseases and an often late diagnosis. A curative surgical treatment can therefore only be proposed in 20 to 30% of the patients. However, new treatment options for intermediate to advanced stages, such as internal radionuclide therapy, seem particularly attractive. Transarterial radioembolization (TARE), which consists in the use of intra-arterial injection of a radiolabelled embolising agent, has led to very promising results. TARE with 90Y-loaded microspheres is now becoming an established procedure to treat liver tumours, with two commercially available products (namely, SIR-Sphere® and TheraSphere®). However, this technology remains expensive and is thus not available everywhere. The aim of this review is to describe TARE alternative technologies currently developed and investigated in clinical trials, with special emphasis on HCC.

Single Low-Dose Injection of Evans Blue Modified PSMA-617 Radioligand Therapy Eliminates Prostate-Specific Membrane Antigen Positive Tumors.

Prostate cancer is the most frequently diagnosed malignant tumor in men worldwide. Prostate-specific membrane antigen (PSMA) is a surface molecule specifically expressed by prostate tumors that has been shown to be a valid target for internal radionuclide therapy in both preclinical and clinical settings. The most common radiotherapeutic agent is the small molecule 177Lu-PSMA-617, which is under clinical evaluation in multiple countries. Nevertheless, its efficacy in causing tumor regression is still suboptimal, even when administered in several cycles per patient, perhaps due to poor pharmacokinetics (PK), which limits uptake by the tumor cells. We postulated that the addition of the Evans blue (EB) moiety to PSMA-617 would improve the PK by extending circulation half-life, which would increase tumor uptake and improve radiotherapeutic efficacy. PSMA-617 was modified by conjugation of a 2-thiol acetate group onto the primary amine and thereafter reacted with a maleimide functional group of an EB derivative, to give EB-PSMA-617. The PK and radiotherapeutic efficacy of 90Y- or 177Lu-EB-PSMA-617 was compared to the clinically used radiopharmaceutical 90Y- or 177Lu- PSMA-617 in PC3-PIP tumor-bearing mice. EB-PSMA-617 retained binding to serum albumin as well as a high internalization rate by tumor cells. Upon injection, metal-labeled EB-PSMA-617 demonstrated an extended blood half-life compared to PSMA-617 and, thereby, prolonged the time window for binding to PSMA. The improved PK of EB-PSMA-617 resulted in significantly higher accumulation in PSMA+ tumors and highly effective radiotherapeutic efficacy. Remarkably, a single dose of 1.85 MBq of 90Y- or 177Lu-EB-PSMA-617 was sufficient to eradicate established PMSA+ tumors in mice. No significant body weight loss was observed, suggesting little to no gross toxicity. The construct described here, EB-PSMA-617, may improve the radiotherapeutic efficacy for patients with PSMA-positive tumors by reducing both the amount of activity needed for therapy as well as the frequency of administration, as compared to PSMA-617.

135La as an Auger-electron emitter for targeted internal radiotherapy

135La has favorable nuclear and chemical properties for Auger-based targeted internal radiotherapy. Here we present detailed investigations of the production, emissions, and dosimetry related to 135La therapy. 135La was produced by 16.5 MeV proton irradiation of metallic natBa on a medical cyclotron, and was isolated and purified by trap-and-release on weak cation-exchange resin. The average production rate was 407 ± 19 MBq µA−1 (saturation activity), and the radionuclidic purity was 98% at 20 h post irradiation. Chemical separation recovered > 98 % of the 135La with an effective molar activity of 70 ± 20 GBq µmol−1. To better assess cellular and organ dosimetry of this nuclide, we have calculated the x-ray and Auger emission spectra using a Monte Carlo model accounting for effects of multiple vacancies during the Auger cascade. The generated Auger spectrum was used to calculate cellular S-factors. 135La was produced with high specific activity, reactivity, radionuclidic purity, and yield. The emission spectrum and the dosimetry are favorable for internal radionuclide therapy.

Toward Personalized Dosimetry with 32P Microparticle Therapy for Advanced Pancreatic Cancer

To develop a Monte Carlo model for patient-specific dosimetry of 32P microparticle localized internal radionuclide therapy for advanced pancreatic cancer. Spherical tumor geometries and a pancreatic phantom were modeled, as well as different 3-dimensional non-uniform clinical pancreatic geometries based on patient-specific ultrasound images. The dosimetry simulations modeled the dose distribution due to the energy spectrum of emitted beta particles. The average dose for small (3-cm diameter) and large (6-cm diameter) spherical tumors was 111Gy (for 7.6 MBq administered activity) and 128Gy (for 58 MBq), respectively. For the clinical 3-dimensional geometries, on the basis of patient data, the mean doses delivered to the tumor were calculated to be in the range 102 to 113Gy, with negligible dose to the pancreas for the smallest tumor volumes. The calculated dose distributions are highly non-uniform. For the largest tumor studied, the pancreas received approximately 6% of the tumor dose (5.7Gy). Importantly, we found that because the smallest tumor studied exhibited the most dynamic changes in volume in response to the treatment, the dose to tumor and pancreas is significantly underestimated if a static tumor volume is assumed. These results demonstrate the dosimetry of 32P microparticle localized internal radionuclide therapy for pancreatic cancer and the possibility of developing personalized treatment strategies. The results also highlight the importance of considering the effects of non-uniform dose distributions and dynamic change of tumor mass during treatment on the dosimetry of the tumor and critical organs.

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. The present document is next in a series of isotope-specific guidelines and recommendations that follow the general information that was provided in MIRD 23. This paper focuses on (177)Lu (lutetium) and its application in radiopharmaceutical therapy.

(90)Y -PET imaging: Exploring limitations and accuracy under conditions of low counts and high random fraction.

(90)Y -positron emission tomography (PET) imaging is becoming a recognized modality for postinfusion quantitative assessment following radioembolization therapy. However, the extremely low counts and high random fraction associated with (90)Y -PET may significantly impair both qualitative and quantitative results. The aim of this work was to study image quality and noise level in relation to the quantification and bias performance of two types of Siemens PET scanners when imaging (90)Y and to compare experimental results with clinical data from two types of commercially available (90)Y microspheres. Data were acquired on both Siemens Biograph TruePoint [non-time-of-flight (TOF)] and Biograph microcomputed tomography (mCT) (TOF) PET/CT scanners. The study was conducted in three phases. The first aimed to assess quantification and bias for different reconstruction methods according to random fraction and number of true counts in the scan. The NEMA 1994 PET phantom was filled with water with one cylindrical insert left empty (air) and the other filled with a solution of (90)Y . The phantom was scanned for 60 min in the PET/CT scanner every one or two days. The second phase used the NEMA 2001 PET phantom to derive noise and image quality metrics. The spheres and the background were filled with a (90)Y solution in an 8:1 contrast ratio and four 30 min acquisitions were performed over a one week period. Finally, 32 patient data (8 treated with Therasphere(®) and 24 with SIR-Spheres(®)) were retrospectively reconstructed and activity in the whole field of view and the liver was compared to theoretical injected activity. The contribution of both bremsstrahlung and LSO trues was found to be negligible, allowing data to be decay corrected to obtain correct quantification. In general, the recovered activity for all reconstruction methods was stable over the range studied, with a small bias appearing at extremely high random fraction and low counts for iterative algorithms. Point spread function (PSF) correction and TOF reconstruction in general reduce background variability and noise and increase recovered concentration. Results for patient data indicated a good correlation between the expected and PET reconstructed activities. A linear relationship between the expected and the measured activities in the organ of interest was observed for all reconstruction method used: a linearity coefficient of 0.89 ± 0.05 for the Biograph mCT and 0.81 ± 0.05 for the Biograph TruePoint. Due to the low counts and high random fraction, accurate image quantification of (90)Y during selective internal radionuclide therapy is affected by random coincidence estimation, scatter correction, and any positivity constraint of the algorithm. Nevertheless, phantom and patient studies showed that the impact of number of true and random coincidences on quantitative results was found to be limited as long as ordinary Poisson ordered subsets expectation maximization reconstruction algorithms with random smoothing are used. Adding PSF correction and TOF information to the reconstruction greatly improves the image quality in terms of bias, variability, noise reduction, and detectability. On the patient studies, the total activity in the field of view is in general accurately measured by Biograph mCT and slightly overestimated by the Biograph TruePoint.

Preliminary direct evidence of a dose-response relationship for [Y-90]-microsphere selective internal radionuclide therapy (SIRT) in hepatic malignancy.

11064 Background: [Y-90]-SIRT has an established role in managing patients with primary and secondary hepatic neoplasia. Recently, imaging of the regional distribution of the implanted [Y-90]-micro...

Neutrophil/lymphocyte ratio (NLR) and FDG PET as predictive measures of response and prognosis in patients treated with Y-90 microsphere selective internal radionuclide therapy (SIRT).

e22137 Background: Y-90 SIRT has been increasingly utilized for treatment of liver predominant malignancies, whether primary or metastatic. Relatively little data exist regarding the prognostic val...

MIRD Pamphlet No. 24: Guidelines for Quantitative 131I SPECT in Dosimetry Applications

The reliability of radiation dose estimates in internal radionuclide therapy is directly related to the accuracy of activity estimates obtained at each imaging time point. The recently published MIRD pamphlet no. 23 provided a general overview of quantitative SPECT imaging for dosimetry. The present document is the first in a series of isotope-specific guidelines that will follow MIRD 23 and focuses on one of the most commonly used therapeutic radionuclides, (131)I. The purpose of this document is to provide guidance on the development of protocols for quantitative (131)I SPECT in radionuclide therapy applications that require regional (normal organs, lesions) and 3-dimensional dosimetry.