Bremsstrahlung Imaging Research Articles

Possibility analysis of bremsstrahlung x-ray imaging of C-14 radionuclide using a LaGPS radiation imaging system

The in-vivo imaging of C-14 is thought to be impossible because it is a pure beta-emitting radionuclide and the energy of beta particles is low. However, beta particles emit bremsstrahlung x-rays in subjects that may be imaged from the outside subjects. Thus, we imaged bremsstrahlung x-rays from a C-14 solution using a high resolution Ce-doped (Gd, La)2Si2O7 (LaGPS) radiation imaging system. With a LaGPS radiation imaging system, we conducted bremsstrahlung x-ray imaging from a C-14 solution in a plastic container with 37 MBq radioactivity with and without a parallel hole collimator. Without it, images were obtained with a spatial resolution of ∼1 mm FWHM in less than 1 min of acquisition time. The energy spectrum of the bremsstrahlung x-rays from a C-14 solution showed a broad distribution with an average energy of ∼30 keV. With a parallel hole collimator, images of the C-14 solutions were also possible although the detected counts decreased to 2.4% of those without a collimator. The measured sensitivities of the LaGPS imaging system without and with a collimator for bremsstrahlung x-rays from C-14 solutions in a plastic container were 3.5 × 10−5 and 8.5 × 10−7, respectively. We conclude that the imaging of bremsstrahlung x-rays from C-14 might be a new method for the in-vivo distribution imaging of small animals or plants.

04:21 PM Abstract No. 121 Quantitative and qualitative 99mTc MAA SPECT/CT imaging predicts response to therapy for patients treated with Yttrium-90 (90Y) radioembolization

Selective 90Y radioembolization therapy for hepatic malignancies involves planning angiography and 99mTc macroaggregated albumin scintigraphy (99mTc -MAA) to assess lung shunt fraction and extrahepatic perfusion. The purpose of this study is to assess the relationship between tumor MAA uptake by SPECT/CT and response following radioembolization. 22 patients with primary hepatic malignancies (non-colorectal) or hepatic colorectal metastases underwent 99mTc -MAA hepatic artery perfusion with SPECT/CT. Qualitative evaluation and quantitative evaluation with tumor to disease free liver parenchyma background ratios (TBR) of SPECT were correlated with CT response. Post-radioembolization Bremsstrahlung SPECT imaging was also performed to assess for similar correlations. The mean MAA tumor TBR in the patients that did not progress was 11.0 ±13.8 (n=14), significantly higher than the TBR of patients that progressed (2.7±1.3 (n=8) (P<0.05). The pattern of 99mTc -MAA distribution was predictive of therapy response. In all cases, intense homogeneous uptake was seen in patients who responded; absent uptake was seen in those who progressed. Uptake on post-radioembolization Bremsstrahlung SPECT did not correlate with response. Our findings suggest that the pattern of uptake on planning 99mTc -MAA imaging can predict response to subsequent radioembolization. Bremsstrahlung SPECT imaging, which is not typically performed, did not correlate with response. Evaluation of 99mTc -MAA uptake on routine pre-therapy studies could potentially serve as a critical decision node in the pre-treatment assessment of patients for radioembolization. Such analysis would extend the utility of this routine study beyond a simple assessment for extrahepatic perfusion, thereby leveraging information inherent to the scan.

Energy Window and Contrast Optimization for Single-photon Emission Computed Tomography Bremsstrahlung Imaging with Yttrium-90.

Purpose:In yttrium-90 (Y-90) single-photon emission computed tomography (SPECT) imaging, the choice of the acquisition energy window is not trivial, due to the continuous and broad energy distribution of the bremsstrahlung photons. In this work, we investigate the effects of the energy windows on the image contrast to noise ratio (CNR), in order to select the optimal energy window for Y-90 imaging.Materials and Methods:We used the Monte Carlo SIMIND code to simulate the Jaszczak phantom which consists of the six hot spheres filled with Y-90 and ranging from 9.5 to 31.8 mm in diameter. Siemens Symbia gamma camera fitted with a high-energy collimator was simulated. To evaluate the effect of the energy windows on the image contrast, five narrow and large energy windows were assessed.Results:The optimal energy window obtained for Y-90 bremsstrahlung SPECT imaging was 120–150 keV. Furthermore, the results obtained for CNR indicate that the high detection is only for the three large spheres.Conclusion:The optimization of energy window in Y-90 bremsstrahlung has the potential to improve the image quality.

Optimization of Bremsstrahlung imaging in Yttrium internal radiation therapy

Introduction: Treatment efficacy of radiation therapy using Yttrium-90 radionuclide is evaluated by the bremsstrahlung SPECT imaging following radiation therapy. The radioisotopic images have the ability to provide reliable activity map of 90Y distribution. But these images have a low quantitative accuracy in the 90Y bremsstrahlung SPECT imaging, therefore the optimization of some imaging important indicators i.e. the energy window width and collimator geometry, which heavily affect acquisition images quality, is necessary. The aim of this paper is to estimate the effects of the energy window width and the hole diameter of a ME collimator on the image contrast of the 90Y bremsstrahlung SPECT images obtained using SIMIND Monte Carlo simulation program and improve image quality which could be used to estimate activity distribution after radiation therapy. Materials and Methods: In this paper we simulated the SPECT system and a Jaszczak phantom consist of six hot spheres in different diameters by use of the SIMIND Monte Carlo simulation program to study 90Y SPECT images by assessment of the holes diameter of a ME collimator including 2.35, 2.59, 2.82, 2.94, 3.06 and 3.3 mm with fixed values of the collimator and septa thicknesses (3.2 cm and 1.14mm, respectively) in the two energy windows including 60- 160 keV and 60-400 keV. SPECT imaging protocol is selected according to the clinical study. An activity of 1.5GBq 90Y was considered for the hot spheres without background activity. We used OS-EM algorithm to reconstruct projections and evaluated the contrast of the reconstructed images of six hot spheres of Jaszczak phantom with selection of proper ROIs. Results: The comparison of the images contrast of Jaszczak phantom spheres indicated that generally with increasing the hole diameter of collimator, the images contrast of the spheres were decreased. In order to, in comparison to the 1st energy window (60–160 keV), the 2nd energy window (60-400 keV) was increased the image contrast. The results showed that for a fixed collimator and septa thickness values (3.2 cm and 1.14mm, respectively), the optimal value of the hole diameter was found 2.35 mm. Also from the stand point of the image contrast, the optimal energy window was found ranging from 60 to 400 keV. Conclusion: By use of the evaluation of the images contrast of Jaszczak phantom by SIMIND Monte Carlo simulation study, the best contrast is obtained when by use of the wide energy window ranging from 60 to 400 keV, which increased the imaging system sensitivity and decreased variance of the activity estimation. Moreover, a ME collimator with fixed values of 3.2 cm and 1.14 mm for the collimator and septa thicknesses, respectively and a hole diameter of 2.35 mm can improve the 90Y activity estimation and provide a suitable image quality for the 90Y bremsstrahlung SPECT imaging.

Effects of collimator on imaging performance of Yttrium-90 Bremsstrahlung photons: Monte Carlo simulation

Abstract Yttrium-90 is a useful therapeutic radioisotope for tumor treatment because of its high-energy-emitting beta rays. However, it has been difficult to select appropriate collimators and main energy windows for Y-90 Bremsstrahlung imaging using gamma cameras because of the broad energy spectra of Y-90. We used a Monte Carlo simulation to investigate the effects of collimator selection and energy windows on Y-90 Bremsstrahlung imaging. We considered both MELP and HE collimators. Various phantoms were employed in the simulation to determine the main energy window using primary-to-scatter ratios (PSRs). Imaging performance was evaluated using spatial resolution indices, imaging counts, scatter fractions, and contrast-to-noise ratios. Collimator choice slightly affected energy spectrum shapes and improved PSRs. The HE collimator performed better than the MELP collimator on all imaging performance indices (except for imaging count). We observed minor differences in SR and SF values for the HE collimator among the five simulated energy windows. The combination of an HE collimator and improved-PSR energy window produced the best CNR value. In conclusion, appropriate collimator selection is an important component of Bremsstrahlung Y-90 photon imaging and main energy window determination. We found HE collimators to be more appropriate for improving the imaging performance of Bremsstrahlung Y-90 photons.

Abstract ID: 247 Patient specific scatter reduction in SIRT gamma camera images

Clinical Bremsstrahlung imaging with gamma cameras or SPECT scanners, for example used in selective internal radiation therapy (SIRT) [1], suffers from low contrast due to a continuous spectrum and a high amount of scatter. Information about the scattering of the radionuclide within the patient's body can be obtained from Monte-Carlo simulations and subsequently being used to improve image quality. An MAA-acquisition (CT+SPECT) of a HCC patient with a unifocal uptake in the right liver lobe is segmented (lesion) and loaded into the MC simulation framework GATE [2]. The voxelized lesion is used as Y90 source (1.5 GBq, 'fastY90' [3] is used yielding a speedup of 2.3×), the CT dataset is used for attenuation by converting HUs into corresponding materials. A mini gamma camera (Crystal Photonics, Germany) with a LEHR collimator and 4 × 4 cm2 detector size is positioned close to liver on the patient's skin, pointing towards the lesion. A simulation (60 s acquisition time) is performed on a cluster with 512 cores (2.2-2.5 Ghz each). The total number of counts, the energy spectrum and the order of scattered particles within each geometric volume are obtained from the ROOT output. Particles that have not scattered at all are defined as primary events. Scattering is only calculated within the phantom. The simulation took 172 min on the cluster with input data voxel size of 1 × 1 × 3.75 mm3. The number of emitted particles is 7.6 M with 600 k detected counts (∼8% ratio). 13.3% of the detected particles are primary events. Additionally, scatter of multiple orders has been observed (41%, 24% and 13% and 8% for the first four orders). The energy-spectrum of the simulated 2D gamma camera image can be analyzed and used to correct the actual image acquired of that specific patient to achieve improved image quality and subsequently also dosimetry.

Improved quantitative 90 Y bremsstrahlung SPECT/CT reconstruction with Monte Carlo scatter modeling.

In 90 Y microsphere radioembolization (RE), accurate post-therapy imaging-based dosimetry is important for establishing absorbed dose versus outcome relationships for developing future treatment planning strategies. Additionally, accurately assessing microsphere distributions is important because of concerns for unexpected activity deposition outside the liver. Quantitative 90 Y imaging by either SPECT or PET is challenging. In 90 Y SPECT model based methods are necessary for scatter correction because energy window-based methods are not feasible with the continuous bremsstrahlung energy spectrum. The objective of this work was to implement and evaluate a scatter estimation method for accurate 90 Y bremsstrahlung SPECT/CT imaging. Since a fully Monte Carlo (MC) approach to 90 Y SPECT reconstruction is computationally very demanding, in the present study the scatter estimate generated by a MC simulator was combined with an analytical projector in the 3D OS-EM reconstruction model. A single window (105 to 195-keV) was used for both the acquisition and the projector modeling. A liver/lung torso phantom with intrahepatic lesions and low-uptake extrahepatic objects was imaged to evaluate SPECT/CT reconstruction without and with scatter correction. Clinical application was demonstrated by applying the reconstruction approach to five patients treated with RE to determine lesion and normal liver activity concentrations using a (liver) relative calibration. There was convergence of the scatter estimate after just two updates, greatly reducing computational requirements. In the phantom study, compared with reconstruction without scatter correction, with MC scatter modeling there was substantial improvement in activity recovery in intrahepatic lesions (from >55% to >86%), normal liver (from 113% to 104%), and lungs (from 227% to 104%) with only a small degradation in noise (13% vs. 17%). Similarly, with scatter modeling contrast improved substantially both visually and in terms of a detectability index, which was especially relevant for the low uptake extrahepatic objects. The trends observed for the phantom were also seen in the patient studies where lesion activity concentrations and lesion-to-liver concentration ratios were lower for SPECT without scatter correction compared with reconstruction with just two MC scatter updates: in eleven lesions the mean uptake was 4.9 vs. 7.1MBq/mL (P=0.0547), the mean normal liver uptake was 1.6 vs. 1.5MBq/mL (P=0.056) and the mean lesion-to-liver uptake ratio was 2.7 vs. 4.3 (P=0.0402) for reconstruction without and with scatter correction respectively. Quantitative accuracy of 90 Y bremsstrahlung imaging can be substantially improved with MC scatter modeling without significant degradation in image noise or intensive computational requirements.

Clinical feasibility of 90Y digital PET/CT for imaging microsphere biodistribution following radioembolization

The purpose of this study was to evaluate the clinical feasibility of next generation solid-state digital photon counting PET/CT (dPET/CT) technology and imaging findings in patients following 90Y microsphere radioembolization in comparison with standard of care (SOC) bremsstrahlung SPECT/CT (bSPECT/CT). Five patients underwent SOC 90Y bremsstrahlung imaging immediately following routine radioembolization with 3.5±1.7GBq of 90Y-labeled glass microspheres. All patients also underwent dPET/CT imaging at 29±11h following radioembolization. Matched pairs comparison was used to compare image quality, image contrast and 90Y biodistribution between dPET/CT and bSPECT/CT images. Volumetric assessments of 90Y activity using different isocontour thresholds on dPET/CT and bSPECT/CT images were also compared. Digital PET/CT consistently provided better visual image quality and 90Y-to-background image contrast while depicting 90Y biodistribution than bSPECT/CT. Isocontour volumetric assessment using a 1% threshold precisely outlined 90Y activity and the treatment volume on dPET/CT images, whereas a more restrictive 20% threshold on bSPECT/CT images was needed to obtain comparable treatment volumes. The use of a less restrictive 10% threshold isocontour on bSPECT/CT images grossly overestimated the treatment volume when compared with the 1% threshold on dPET/CT images. Digital PET/CT is clinically feasible for the assessment of 90Y microsphere biodistribution following radioembolization, and provides better visual image quality and image contrast than routine bSPECT/CT with comparable acquisition times. With further optimization and clinical validation, dPET technology may allow faster and more accurate imaging-based assessment of 90Y microsphere biodistribution.

Quantitative Imaging for Targeted Radionuclide Therapy Dosimetry - Technical Review.

Targeted radionuclide therapy (TRT) is a promising technique for cancer therapy. However, in order to deliver the required dose to the tumor, minimize potential toxicity in normal organs, as well as monitor therapeutic effects, it is important to assess the individualized internal dosimetry based on patient-specific data. Advanced imaging techniques, especially radionuclide imaging, can be used to determine the spatial distribution of administered tracers for calculating the organ-absorbed dose. While planar scintigraphy is still the mainstream imaging method, SPECT, PET and bremsstrahlung imaging have promising properties to improve accuracy in quantification. This article reviews the basic principles of TRT and discusses the latest development in radionuclide imaging techniques for different theranostic agents, with emphasis on their potential to improve personalized TRT dosimetry.

Optimization of Image Reconstruction for 90Y Selective Internal Radiotherapy on a Lutetium Yttrium Orthosilicate PET/CT System Using a Bayesian Penalized Likelihood Reconstruction Algorithm.

Imaging on a γ-camera with 90Y after selective internal radiotherapy (SIRT) may allow for verification of treatment delivery but suffers relatively poor spatial resolution and imprecise dosimetry calculation. 90Y PET/CT imaging is possible on 3-dimensional, time-of-flight machines; however, images are usually poor because of low count statistics and noise. A new PET reconstruction software using a Bayesian penalized likelihood (BPL) reconstruction algorithm (termed Q.Clear) was investigated using phantom and patient scans to optimize the reconstruction for post-SIRT imaging and clarify whether BPL leads to an improvement in clinical image quality using 90Y. Methods: Phantom studies over an activity range of 0.5-4.2 GBq were performed to assess the contrast recovery, background variability, and contrast-to-noise ratio for a range of BPL and ordered-subset expectation maximization (OSEM) reconstructions on a PET/CT scanner. Patient images after SIRT were reconstructed using the same parameters and were scored and ranked on the basis of image quality, as assessed by visual evaluation, with the corresponding SPECT/CT Bremsstrahlung images by 2 experienced radiologists. Results: Contrast-to-noise ratio was significantly better in BPL reconstructions when compared with OSEM in phantom studies. The patient-derived BPL and matching Bremsstrahlung images scored higher than OSEM reconstructions when scored by radiologists. BPL with a β value of 4,000 was ranked the highest of all images. Deadtime was apparent in the system above a total phantom activity of 3.3 GBq. Conclusion: BPL with a β value of 4,000 is the optimal image reconstruction in PET/CT for confident radiologic reading when compared with other reconstruction parameters for 90Y imaging after SIRT imaging. Activity in the field of view should be below 3.3 GBq at the time of PET imaging to avoid deadtime losses for this scanner.

Feasibility of gamma camera system with CdWO4 detector for quantitation of yttrium-90 bremsstrahlung imaging: Monte Carlo simulation study

Yttrium-90 (Y-90) has attracted great attention as a therapeutic radionuclide because of higher emitted particle energy and pure beta emitter. In Y-90 bremsstrahlung imaging, NaI(Tl) and GSO detectors are widely used in detecting photon but these detectors cannot be easily applied to this imaging because of relatively low sensitivity. Among detector candidates, cadmium tungstate (CdWO4) can acquire high detection efficiency due to the high density and good light yield. The purpose of this study was to evaluate the feasibility of gamma camera system with CdWO4 detector for quantitation of Y-90 bremsstrahlung imaging using a Geant4 Application for Tomographic Emission (GATE). To evaluate performance of the imaging system, a Y-90 point source was designed in GATE simulation. These detectors using CdWO4, NaI(Tl), and GSO were equipped with low energy general purpose (LEGP), medium energy general purpose (MEGP), and high energy general purpose (HEGP) parallel-hole collimators. According to the results, the average sensitivities of the CdWO4 detector with LEGP, MEGP, and HEGP were 43.76, 37.16, and 28.22cps/MBq, respectively. In addition, the sensitivity was higher for CdWO4 detector system than for NaI(Tl) or GSO detector systems for all parallel-hole collimator system with 55–285keV energy window. However, differences of scatter fraction for three detectors were very similar. Our results showed that the effect and feasibility of CdWO4 detector for Y-90 bremsstrahlung imaging can be investigated by a GATE simulation. In conclusion, the results of this study suggest that CdWO4 detector can be achieved improved performance of Y-90 bremsstrahlung imaging.

Practical reconstruction protocol for quantitative (90)Y bremsstrahlung SPECT/CT.

To develop a practical background compensation (BC) technique to improve quantitative (90)Y-bremsstrahlung single-photon emission computed tomography (SPECT)/computed tomography (CT) using a commercially available imaging system. All images were acquired using medium-energy collimation in six energy windows (EWs), ranging from 70 to 410 keV. The EWs were determined based on the signal-to-background ratio in planar images of an acrylic phantom of different thicknesses (2-16 cm) positioned below a (90)Y source and set at different distances (15-35 cm) from a gamma camera. The authors adapted the widely used EW-based scatter-correction technique by modeling the BC as scaled images. The BC EW was determined empirically in SPECT/CT studies using an IEC phantom based on the sphere activity recovery and residual activity in the cold lung insert. The scaling factor was calculated from 20 clinical planar (90)Y images. Reconstruction parameters were optimized in the same SPECT images for improved image quantification and contrast. A count-to-activity calibration factor was calculated from 30 clinical (90)Y images. The authors found that the most appropriate imaging EW range was 90-125 keV. BC was modeled as 0.53× images in the EW of 310-410 keV. The background-compensated clinical images had higher image contrast than uncompensated images. The maximum deviation of their SPECT calibration in clinical studies was lowest (<10%) for SPECT with attenuation correction (AC) and SPECT with AC + BC. Using the proposed SPECT-with-AC + BC reconstruction protocol, the authors found that the recovery coefficient of a 37-mm sphere (in a 10-mm volume of interest) increased from 39% to 90% and that the residual activity in the lung insert decreased from 44% to 14% over that of SPECT images with AC alone. The proposed EW-based BC model was developed for (90)Y bremsstrahlung imaging. SPECT with AC + BC gave improved lesion detectability and activity quantification compared to SPECT with AC only. The proposed methodology can readily be used to tailor (90)Y SPECT/CT acquisition and reconstruction protocols with different SPECT/CT systems for quantification and improved image quality in clinical settings.

Analysis of the influence of 111In on 90Y-bremsstrahlung SPECT based on Monte Carlo simulation.

90Y-ibritumomab tiuxetan (Zevalin) which is used for the treatment of malignant lymphomas can be used for SPECT imaging based on bremsstrahlung from 90Y beta particles. However, gamma rays emitted by 111In, which is administered to evaluate the indication for the treatment, contaminate the 90Y bremsstrahlung images. Our objective is to investigate the influence of 111In on the 90Y SPECT images using Monte Carlo simulation. We used an in-house developed simulation code for the Monte Carlo simulation of electrons and photons (MCEP). Two hot spheres with diameters of 40mm were put in an elliptical phantom. Both spheres ("sphere 1" and "sphere 2") were filled with 90Y and 111In mixed solutions. The activities of 90Y in sphere 1 and sphere 2 were 241 and 394kBq/mL, respectively, and the ones of 111In were 8.14 and 13.3kBq/mL, respectively. The background activity of 90Y was 38.6kBq/mL, whereas that of 111In was 1.30kBq/mL; moreover, the acquisition time was 30min. Two energy windows were used: one is 90-190keV included the 111In photopeak; the other is 90-160keV. To evaluate the quality of the SPECT images, the contrast recovery coefficient (CRC) and the constant noise ratio (CNR) of the SPECT images were derived. For the energy window between 90 and 160keV, the 111In count was 74% of the total. In that case, the CRC values were 30.1 and 30.7% for "sphere 1" and "sphere 2", respectively, whereas the CNR values were 6.8 and 12.1, respectively. For the energy window between 90 and 190keV, the 111In count reached 85% of the total count. The CRC and CNR values were 38.6 and 40.0% and 10.6 and 19.4, respectively. Our simulation study revealed that the cross talk between 111In and 90Y in SPECT imaging is rather serious. Even for the energy window excluding the 111In photopeak, the count ratio of 90Y was less than 30% of the total. However, the influence of 111In on 90Y-SPECT imaging cannot be ignored, and the count ratio because of 111In is important to estimate the density of 90Y.

Monte Carlo feasibility study for image guided surgery: from direct beta minus detection to Cerenkov luminescence imaging

The goal of this work is to compare the performances of different beta minus detection strategies for image guided surgery or ex vivo tissue analysis. In particular we investigated Cerenkov luminescence imaging (CLI) with and without the use of a radiator, direct and indirect beta detection and bremsstrahlung imaging using beta emitters commonly employed in Nuclear Medicine. Monte Carlo simulations were implemented using the GAMOS plug-in for GEANT4 considering a slab of muscle and a radioactive source (32P or 90Y) placed at 0.5 mm depth. We estimated the gain that can be obtained in terms of produced photons using different materials placed on the slab used as Cerenkov radiators, we then focused on the number of exiting photons and their spatial distribution for the different strategies. The use of radiator to enhance Cerenkov signal reduces the spatial resolution because of the increased optical spread. We found that direct beta detection and CLI are best approaches in term of resolution while the use of a thin scintillator increases the signal but the spatial resolution is degraded. Bremsstrahlung presents lower signal and it does not represent the best choice for image guided surgery. CLI represents a more flexible approach for image guided surgery using or ex vivo tissue analysis using beta-emitter imaging.

Correlation of clinical outcomes with bremsstrahlung and Y-90 PET/CT imaging findings following Y-90 radiosynoviorthesis: a prospective study

BackgroundIt is unclear how to predict which patients will respond to Y-90 radiosynoviorthesis. The aim of this study is to correlate clinical outcomes following Y-90 radiosynoviorthesis with bremsstrahlung and Y-90 PET/CT imaging findings.MethodsFifty-one joints underwent bremsstrahlung planar and Y-90 PET/CT imaging following Y-90 radiosynoviorthesis. The Y-90 distribution pattern on bremsstrahlung planar imaging was classified as diffuse or non-diffuse and compared with the intra or extra-articular location of activity on Y-90 PET/CT. Treatment response was assessed by patients and clinicians at 6 months. In patients who underwent bremsstrahlung SPECT, side-by-side comparison with PET was performed with image quality/resolution scored using a five-point-scale.FindingsBremsstrahlung planar images were classified as diffuse in 33/51 (65 %) and non-diffuse in 18/51 (35 %) scans. There was no association between treatment response and the bremsstrahlung planar imaging pattern. PET/CT confirmed an intra-articular location in all 33/33 (100 %) diffuse scans and an extra-articular location in 3/18 (17 %) non-diffuse scans. Of the three joints with extra-articular activity, none had any treatment response. Excluding these three joints, there remained no association between the bremsstrahlung planar imaging pattern and treatment response. Of the 42 joints imaged with SPECT, PET image quality/resolution was classified as superior in 40 (95 %). In one patient with extra-articular activity on PET/CT, SPECT/CT was unable to definitively localise the activity to the intra or extra-articular space.ConclusionsThe distribution pattern on bremsstrahlung planar imaging did not correlate with clinical outcome following Y-90 radiosynoviorthesis in our study population. However, in patients with non-diffuse planar imaging patterns, Y-90 PET/CT should be considered to exclude extra-articular activity with PET providing superior image quality compared to SPECT.

Bremsstrahlung radiation detection for small animal imaging using a CCD detector

The use of optical methods for the detection of radionuclides is becoming an established tool for preclinical molecular imaging experiments. In this paper we present a set of proof of principle experiments showing that planar bremsstrahlung radiation images can be detected with an intensifying screen using a small animal optical imager based on charge coupled device detector.We develop a bremsstrahlung source using a 32P-ATP vial placed in a Plexiglas box, the source with an intensifying screen on top was placed inside a small animal optical imaging system. Bremsstrahlung radiation images were produced with the 32P-ATP source only and also with a pair of pliers placed between the source and the screen. We found that the pair of pliers absorption image matches the shape of the object.Spatial resolution measurements were not performed however, the bremsstrahlung image of the pliers show that the resolution is relatively poor due to a large penumbra effect.We conclude that it is possible to produce planar bremsstrahlung images using optical imaging devices.

Monte Carlo studies for medical imaging detector optimization

This work reports on the Monte Carlo optimization studies of detection systems for Molecular Breast Imaging with radionuclides and Bremsstrahlung Imaging in nuclear medicine.Molecular Breast Imaging requires competing performances of the detectors: high efficiency and high spatial resolutions; in this direction, it has been proposed an innovative device which combines images from two different, and somehow complementary, detectors at the opposite sides of the breast. The dual detector design allows for spot compression and improves significantly the performance of the overall system if all components are well tuned, layout and processing carefully optimized; in this direction the Monte Carlo simulation represents a valuable tools.In recent years, Bremsstrahlung Imaging potentiality in internal radiotherapy (with beta-radiopharmaceuticals) has been clearly emerged; Bremsstrahlung Imaging is currently performed with existing detector generally used for single photon radioisotopes. We are evaluating the possibility to adapt an existing compact gamma camera and optimize by Monte Carlo its performance for Bremsstrahlung imaging with photons emitted by the beta- from 90Y.

Collimator and energy window optimization for 90Y bremsstrahlung SPECT imaging: A SIMIND Monte Carlo study

Treatment efficacy of radioembolization using Yttrium-90 (90Y) microspheres is assessed by the 90Y bremsstrahlung single photon emission computed tomography (SPECT) imaging following radioembolization. The radioisotopic image has the potential of providing reliable activity map of 90Y microspheres distribution. One of the main reasons of the poor image quality in 90Y bremsstrahlung SPECT imaging is the continuous and broad energy spectrum of the related bremsstrahlung photons. Furthermore, collimator geometry plays an impressive role in the spatial resolution, sensitivity and image contrast. Due to the relatively poor quality of the 90Y bremsstrahlung SPECT images, we intend to optimize the medium-energy (ME) parallel-hole collimator and energy window. The Siemens e.cam gamma camera equipped with a ME collimator and a voxelized phantom was simulated by the SImulating Medical Imaging Nuclear Detectors (SIMIND) program. We used the SIMIND Monte Carlo program to generate the 90Y bremsstrahlung SPECT projection of the digital Jaszczak phantom. The phantom consist of the six hot spheres ranging from 9.5 to 31.8mm in diameter, which are used to evaluate the image contrast. In order to assess the effect of the energy window on the image contrast, three energy windows ranging from 60 to 160KeV, 160 to 400KeV, and 60 to 400KeV were set on a 90Y bremsstrahlung spectrum. As well, the effect of the hole diameter of a ME collimator on the image contrast and bremsstrahlung spectrum were investigated. For the fixed collimator and septa thickness values (3.28cm and 1.14mm, respectively), a hole diameter range (2.35–3.3mm) was chosen based on the appropriate balance between the spatial resolution and sensitivity. The optimal energy window for 90Y bremsstrahlung SPECT imaging was extended energy window from 60 to 400KeV. Besides, The optimal value of the hole diameter of ME collimator was obtained 3.3mm. Geometry of the ME parallel-hole collimator and energy window are indeed important indicators of the image quality in 90Y bremsstrahlung imaging. The obtained optimal ME collimator and optimal energy window have the potential to improve the image contrast of 90Y bremsstrahlung images. Subsequently, high quality 90Y bremsstrahlung images can provide reliable estimate of the 90Y microsphere activity distribution after radioembolization.

Theranostic Imaging of Yttrium-90.

This paper overviews Yttrium-90 (90Y) as a theranostic and nuclear medicine imaging of 90Y radioactivity with bremsstrahlung imaging and positron emission tomography. In addition, detection and optical imaging of 90Y radioactivity using Cerenkov luminescence will also be reviewed. Methods and approaches for qualitative and quantitative 90Y imaging will be briefly discussed. Although challenges remain for 90Y imaging, continued clinical demand for predictive imaging response assessment and target/nontarget dosimetry will drive research and technical innovation to provide greater clinical utility of 90Y as a theranostic agent.

Arthroscopic Surgery and Radiosynovectomy to the Hip Joint with Diffuse Pigmented Villonodular Synovitis

A 32-year-old female patient admitted with right hip pain that was diagnosed of diffuse PVNS in right hip joint with magnetic resonance imaging. She went arthoscopic synovectomy for this lesion. Six weeks after the surgery, RS was applied. Before RS three phase bone scintigraphy was taken and minimal increased perfusion, minimal hyperemias were detected in right hip joint. On the late phase images relatively increased activity accumulation in right hip joint was seen. 3 mCi (111 MBq) yttrium-90 colloid was administered to the hip joint under fluoroscopy guidance. The Bremsstrahlung imaging was performed using a gamma camera equiped four hours after RS. In the six and nine months control after RS patient did not have any complaints. In nine months control, MRI and three phase bone scintigraphy were taken and no pathologic radioactivity accumulation on bone scan, any residual lesion or recurrence on MRI was present. To our best knowledge, this is the first case with arthroscopic surgery and adjuvant RS with Y-90 colloid which rarely applied in routine practice for treatment of diffuse PVNS of the hip.