Accurate molecular imaging of small animals taking into account animal models, handling, anaesthesia, quality control and imaging system performance

Small-animal imaging has become an important technique for the development of new radiotracers, drugs and therapies. Many laboratories have now a combination of different small-animal imaging systems, which are being used by biologists, pharmacists, medical doctors and physicists. The aim of this paper is to give an overview of the important factors in the design of a small animal, nuclear medicine and imaging experiment. Different experts summarize one specific aspect important for a good design of a small-animal experiment

End-to-End QoS Support for a Medical Grid Service Infrastructure

Quality of Service support is an important prerequisite for the adoption of Grid technologies for medical applications. The GEMSS Grid infrastructure addressed this issue by offering end-to-end QoS in the form of explicit timeliness guarantees for compute-intensive medical simulation services. Within GEMSS, parallel applications installed on clusters or other HPC hardware may be exposed as QoS-aware Grid services for which clients may dynamically negotiate QoS constraints with respect to response time and price using Service Level Agreements. The GEMSS infrastructure and middleware is based on standard Web services technology and relies on a reservation based approach to QoS coupled with application specific performance models. In this paper we present an overview of the GEMSS infrastructure, describe the available QoS and security mechanisms, and demonstrate the effectiveness of our methods with a Grid-enabled medical imaging service

BIAS AND VARIABILITY IN IMAGE-BASED VOLUMETRIC YTTRIUM-90 DOSIMETRY

90Y-microsphere therapy has been widely accepted as a treatment option for both primary and metastatic liver tumors where the patients are ineligible for surgical resection and external beam radiation therapy. The prognosis of untreated patient having liver cancer is very poor with life expectancy less than a year at advance stage. Hence the ability to predict treatment efficacy right after the treatment from post-therapy imaging will help personalize treatment strategies and achieve better outcome. Such prediction can be modeled from correlation of dose and tumor response metrics. It has been shown that local dose deposition method can generate dose map from 90Y emission images with accuracy comparable to dose-point kernel and Monte Carlo simulation methods. The bias and variability of the input images remain to be the weakest link in volumetric dosimetry. The objectives of this dissertation project were to improve image-based volumetric 90Y dose quantification using current commercially available systems and to determine its limitation (bias/variability). We have developed a practical image reconstruction method for 90Y bremsstrahlung SPECT/CT (bSPECT/CT) images with CT attenuation correction and energy-window based background compensation. Although the volumetric quantitative accuracy of our bSPECT/CT images is limited by partial volume effect, the images can be used to accurately quantify the total 90Y activity delivered to the patient, which allow gross treatment delivery verification and limited outcome prediction. We have also characterized the accuracy and variability of volumetric 90Y dosimetry calculated from count-limited 90Y-PET/CT images. Knowledge of overall errors (systematic and random) in volumetric 90Y dosimetry is important to derive statistically significant dose-response model, which in turn allowing prediction of treatment outcome and personalization of treatment strategy

Theranostic SPECT reconstruction for improved resolution: application to radionuclide therapy dosimetry

BACKGROUND: SPECT-derived dose estimates in tissues of diameter less than 3× system resolution are subject to significant losses due to the limited spatial resolution of the gamma camera. Incorporating resolution modelling (RM) into the SPECT reconstruction has been proposed as a possible solution; however, the images produced are prone to noise amplification and Gibbs artefacts. We propose a novel approach to SPECT reconstruction in a theranostic setting, which we term SPECTRE (single photon emission computed theranostic reconstruction); using a diagnostic PET image, with its superior resolution, to guide the SPECT reconstruction of the therapeutic equivalent. This report demonstrates a proof in principle of this approach. METHODS: We have employed the hybrid kernelised expectation maximisation (HKEM) algorithm implemented in STIR, with the aim of producing SPECT images with PET-equivalent resolution. We demonstrate its application in both a dual 68Ga/177Lu IEC phantom study and a clinical example using 64Cu/67Cu. RESULTS: SPECTRE is shown to produce images comparable in accuracy and recovery to PET with minimal introduction of artefacts and amplification of noise. CONCLUSION: The SPECTRE approach to image reconstruction shows improved quantitative accuracy with a reduction in noise amplification. SPECTRE shows great promise as a method of improving SPECT radioactivity concentrations, directly leading to more accurate dosimetry estimates in small structures and target lesions. Further investigation and optimisation of the algorithm parameters is needed before this reconstruction method can be utilised in a clinical setting

New Imaging Protocols for New Single Photon Emission CT Technologies

Nuclear cardiology practitioners have several new technologies available with which to perform myocardial perfusion single photon emission CT (MPS). These include dedicated small-footprint cardiac scanners, new stationary or semi-stationary three-dimensional detectors, and advanced software algorithms for optimal image reconstruction. These new technologies have been employed to reduce imaging time and radiation exposure. They require less technologist and camera time and offer improved patient comfort. They have potential for the overall cost reduction of MPS and at the same time for improved accuracy by increased resolution, or accurate attenuation correction. Furthermore, these new technologies offer potential for new protocols such as simultaneous dual isotope, new combinations of isotopes, stress only MPS, or dynamic first-pass imaging. In addition, new imaging technologies in coronary CT angiography (CCTA) allow novel hybrid stress only MPS/CCTA protocols with reduced radiation burden. Additional developments further improving efficiency and diagnostic accuracy of MPS are on the horizon

Phantom-based evaluation of yttrium-90 datasets using biograph vision quadra.

PURPOSE The image quality characteristics of two NEMA phantoms with yttrium-90 (90Y) were evaluated on a long axial field-of-view (AFOV) PET/CT. The purpose was to identify the optimized reconstruction setup for the imaging of patients with hepatocellular carcinoma after 90Y radioembolization. METHODS Two NEMA phantoms were used, where one had a 1:10 sphere to background activity concentration ratio and the second had cold background. Reconstruction parameters used are as follows: iterations 2 to 8, Gaussian filter 2- to 6-mm full-width-at-half-maximum, reconstruction matrices 440 × 440 and 220 × 220, high sensitivity (HS), and ultra-high sensitivity (UHS) modes. 50-, 40-, 30-, 20-, 10-, and 5-min acquisitions were reconstructed. The measurements included recovery coefficients (RC), signal-to-noise ratio (SNR), background variability, and lung error which measures the residual error in the corrections. Patient data were reconstructed with 20-, 10-, 5-, and 1-min time frames and evaluated in terms of SNR. RESULTS The RC for the hot phantom was 0.36, 0.45, 0.53, 0.63, 0.68, and 0.84 for the spheres with diameters of 10, 13, 17, 22, 28, and 37 mm, respectively, for UHS 2 iterations, a 220 × 220 matrix, and 50-min acquisition. The RC values did not differ with acquisition times down to 20 min. The SNR was the highest for 2 iterations, measured 11.7, 16.6, 17.6, 19.4, 21.9, and 27.7 while the background variability was the lowest (27.59, 27.08, 27.36, 26.44, 30.11, and 33.51%). The lung error was 18%. For the patient dataset, the SNR was 19%, 20%, 24%, and 31% higher for 2 iterations compared to 4 iterations for 20-, 10-, 5-, and 1-min time frames, respectively. CONCLUSIONS This study evaluates the NEMA image quality of a long AFOV PET/CT scanner with 90Y. It provides high RC for the smallest sphere compared to other standard AFOV scanners at shorter scan times. The maximum patient SNR was for 2 iterations, 20 min, while 5 min delivers images with acceptable SNR

Monte Carlo simulations for system modeling in emission tomography

Non-invasive diagnostic imaging can be performed with different technologies:X-ray radiography, computed radiography, direct radiography, mammography,Computed Tomography (CT), UltraSound (US), and Magnetic Resonance Imaging (MRI), which all give anatomical information, and also with functional MRI (fMRI), optical imaging, thermography, planar isotope imaging,Single Photon Emission Tomography (SPECT), Positron Emission Tomography (PET), and gamma camera PET which return functional information.Recent devices combine two modalities on the same gantry in order to achieve hardware fusion of anatomical and functional images. Given the demographic aging in Western Europe, there exists a large interest in what is popularly referred to as a GPS-tool for cancer, i.e. a diagnostic tool for oncology that detects small malignant lesions in a very early stadium and that can be used for disease staging. Therefore research in nuclear medicine has a social support and bearing. In nuclear medicine examinations, a radiopharmaceutical is injected in the patient, marked with a radionuclide emitting one single photon with an energy of 100-200 keV in SPECT and a positron emitting radionuclide in PET. The emission of a positron finally results in two annihilation photons of 511 keV. Those photons are detected, mostly using a scintillation crystal that generates optical photons which travel through a light guide before reaching the PhotoMultiplierTubes (PMTs). Those PMTs convert the optical photons to electrons, which are in their turn used to generate a position and energy encoding signal. In PET there is an electronic collimation to acquire directional information while this information is obtained by applying a lead collimator in SPECT. The acquired data is afterwards reconstructed to result in a threedimensional radioactive tracer distribution within the patient. Optimization,evaluation and (re)design of all elements in this detection chain is mostly done using simulations. Given the possibility of modeling different physical processes, the Monte Carlo method has also been applied in nuclear medicine to a wide range of problems that could not be addressed by experimental or analytical approaches