ABSTRACT
Radiosynoviorthesis (RSO) is a minimally invasive treatment aiming for the necrosis of the pannus tissue by the use of radionuclide. The method suggested here starts with the segmentation of the joint effusion, synovial thickness, and area of the synovial membrane using the 3D Slicer software. The last step is the estimated value of the activity to be injected without considering the leakage of the radiopharmaceutical into the articular cavity. It includes the S-values obtained by Monte Carlo simulation coupled with the calculated therapeutic distance (ST90).
Subject(s)
Joint Diseases/radiotherapy , Radiopharmaceuticals/therapeutic use , Synovial Membrane/radiation effects , Hemophilia A/complications , Humans , Joint Diseases/complications , Magnetic Resonance Imaging , Monte Carlo Method , Synovial Membrane/diagnostic imagingABSTRACT
Although there are several radionuclides suitable for radiosynoviorthesis (RSO), not all of them can irradiate deeper synovium. Yttrium-90 (Y) is the beta radionuclide with more penetration range; therefore, it is predominantly used to treat knees. The aim of this paper is to highlight several dosimetry concepts to compare Y and Sm, also discussing the feasibility of implementing a dose planning methodology for both in RSO. The MCNPX Monte Carlo nuclear code version 2.6 was used for calculating S-values from which the activity to be injected into the joint was obtained. This activity is considered sufficient to deliver a 100-Gy absorbed dose in 1 mm of synovial tissue. The simulated mathematical model consisted of a system formed by several cylindrical slabs of 1-mm thickness, aligned consecutively. The different areas of the cylinder base simulate several synovial membrane sizes. The effective treatment range for each radionuclide was also calculated. Quantification of the synovial joint features (synovial thickness and synovial surface) by diagnostic imaging, such as magnetic resonance (MRI) combined with a Monte Carlo simulation, can be used to achieve a treatment planning strategy in RSO with the available radionuclides.
Subject(s)
Radioisotopes/therapeutic use , Radiopharmaceuticals/therapeutic use , Samarium/therapeutic use , Synovectomy/methods , Synovitis/radiotherapy , Yttrium Radioisotopes/therapeutic use , Cartilage, Articular/pathology , Computer Simulation , Electrons , Humans , Magnetic Resonance Imaging , Monte Carlo Method , Radiotherapy Dosage , Radiotherapy Planning, Computer-Assisted/methods , Synovial Membrane/pathologyABSTRACT
PURPOSE: Recently, there has been a growing interest in a methodology for dose planning in radiosynoviorthesis to substitute fixed activity. Clinical practice based on fixed activity frequently does not embrace radiopharmaceutical dose optimization in patients. The aim of this paper is to propose and discuss a dose planning methodology considering the radiological findings of interest obtained by three-dimensional magnetic resonance imaging combined with Monte Carlo simulation in radiosynoviorthesis treatment applied to hemophilic arthropathy. METHOD: The parameters analyzed were: surface area of the synovial membrane (synovial size), synovial thickness and joint effusion obtained by 3D MRI of nine knees from nine patients on a SIEMENS AVANTO 1.5 T scanner using a knee coil. The 3D Slicer software performed both the semiautomatic segmentation and quantitation of these radiological findings. A Lucite phantom 3D MRI validated the quantitation methodology. The study used Monte Carlo N-Particle eXtended code version 2.6 for calculating the S-values required to set up the injected activity to deliver a 100 Gy absorbed dose at a determined synovial thickness. The radionuclides assessed were: 90Y, 32P, 188Re, 186Re, 153Sm, and 177Lu, and the present study shows their effective treatment ranges. RESULT: The quantitation methodology was successfully tested, with an error below 5% for different materials. S-values calculated could provide data on the activity to be injected into the joint, considering no extra-articular leakage from joint cavity. Calculation of effective treatment range could assist with the therapeutic decision, with an optimized protocol for dose prescription in RSO. CONCLUSION: Using 3D Slicer software, this study focused on segmentation and quantitation of radiological features such as joint effusion, synovial size, and thickness, all obtained by 3D MRI in patients' knees with hemophilic arthropathy. The combination of synovial size and thickness with the parameters obtained by Monte Carlo simulation such as effective treatment range and S-value, from which is calculated the injected activity, could be used for treatment planning in RSO. Data from this methodology could be a potential aid to clinical decision making by selecting the most suitable radionuclide; justifying the procedure, fractioning the dose, and the calculated injected activity for children and adolescents, considering both the synovial size and thickness.
Subject(s)
Magnetic Resonance Imaging , Radiopharmaceuticals , Radiotherapy Planning, Computer-Assisted , Humans , Monte Carlo Method , Phantoms, Imaging , Radioisotopes , Radiotherapy DosageABSTRACT
RESUMEN La primera fase del ensayo clínico del anticuerpo monoclonal humanizado h-R3 (Nimotuzumab) marcado con 
, para la radioinmunoterapia de tumores cerebrales malignos fue ejecutada durante el período 2002-2005 en Cuba. El objetivo del trabajo fue analizar los datos de la vigilancia radiológica realizada durante el estudio, con respecto a las dosis estimadas inicialmente. Estas últimas se calcularon para cada nivel de actividad, operación y cantidad total de pacientes, considerando el decaimiento radiactivo del y que una misma persona realizaba todas las operaciones. Se demostró que el riesgo radiológico de la práctica es aceptable. Las hipótesis conservadoras empleadas para los cálculos y el cumplimiento de los procedimientos de seguridad establecidos, determinaron que la exposición medida fuera inferior a la estimada. La realización de este trabajo constituye una referencia para la introducción y desarrollo de la radioinmunoterapia en Cuba.
ABSTRACT The first phase of the clinical trial using the humanized monoclonal antibody h-R3 (Nimotuzumab) labelled with , for radioimmunotherapy of brain malignant was performed during the period 2002-2005 in Cuba. The aim of this work was to analyze data from the radiological surveillance of this research compared to initially estimated doses. These latter were calculated for each activity level, operation and total quantity of patients, considering the radioactive decay of and taking into account that only one person carries out all of the operations. It was demonstrated that the radiation risk of the practice is acceptable. The conservative hypotheses for dose assessment and the compliance with established safety procedures during this trial showed that the measured exposure was lower than that estimated. This paper is a reference useful to introduce and develop the RIT in Cuba.
