[Show abstract][Hide abstract] ABSTRACT: While the performance of most current commercially available PET scanners is sufficient for many standard clinical applications, some specific tasks likely require specialized imaging systems. The goal of this project is to explore the capabilities and limitations of a small, high-resolution prototype system for obtaining PET images. The scanner consists of a tandem of detectors. One is a small detector consisting of a 20 × 20 array of 0.7 × 0.7 × 3 mm(3) (pitch 0.8 mm) LYSO elements. The scintillator array is coupled to an array of silicon photomultipliers. The second detector is a 96 × 72 array of 2 × 2 × 15 mm(3) (pitch = 2.1 mm) LYSO elements coupled to PSPMTs. Separation between the two devices is 180 mm. The detectors are operated in coincidence with each other. Image reconstruction is performed using a limited angle, Maximum Likelihood Expectation Maximization (MLEM) algorithm. Evaluation of the device included measurements of spatial resolution and detection sensitivity as a function of distance. The transaxial radial and tangential spatial resolution of the system ranged from 0.6 mm to 0.9 mm FWHM; axial resolution ranged from 2.7 mm to 4.6 mm FWHM. Detection sensitivity ranged from 0.05 to 0.28%. Spatial resolution and field-of-view vary as a function of distance from the small detector. The tandem detector insert permitted differentiation of the smallest (1 mm diameter) rods in a mini-hot rod phantom. The results indicate that a tandem PET imaging scheme can be potentially employed in applications where high-resolution images over a small region are required.
[Show abstract][Hide abstract] ABSTRACT: One of the drawbacks of silicon-based photomultipliers is variation of performance with even small temperature fluctuations. The purpose of this work is to investigate a novel method of temperature stabilization of SiPM-based imaging device. Our prototype cooling system utilizes optically transparent cooling fluid as means of removing heat from the light detector and spreading scintillation light among several SiPM units. Cooled liquid passes through a 2 mm opening between two Mylar sheets. The Mylar sheets are held together with an aluminum frame. An array of SiPMs and an array of LYSO scintillation crystals are attached to opposite sides of the cooling light guide. Temperature uniformity of the optical surface was evaluated with an infrared camera. A temperature gradient of 0.09 °C/cm was measured along the direction of the coolant flow. The system was tested with a 5 × 5 array of Hamamatsu S10943 SiPMs coupled to a 16 × 16 matrix of 1.5×1.5×10 mm LYSO crystals. Testing procedures included evaluation of temperature dependence of detector gain, integrated noise, ability to resolve individual crystals and energy resolution. Detector gain varied by 9.3% over the range of 5 °C. Energy resolution change of 5% was observed over the same temperature range. Integrated noise contribution showed moderate increase of 2.2% over the range of 7 °C. The separation of individual crystals was found adequate with only a weak dependence of peak-to-valley contrast ratios on temperature. An assessment of performance stability at constant temperature revealed 0.2% variation in gain and 0.7% variation in energy resolution during an hour-long acquisition. It is concluded that the proposed method is a viable option for cooling and temperature stabilizing of SiPM-based systems.
[Show abstract][Hide abstract] ABSTRACT: The goal of this initial clinical study was to test a new positron emission/tomography imager and biopsy system (PEM/PET) in a small group of selected subjects to assess its clinical imaging capabilities. Specifically, the main task of this study is to determine whether the new system can successfully be used to produce images of known breast cancer and compare them to those acquired by standard techniques.
The PEM/PET system consists of two pairs of rotating radiation detectors located beneath a patient table. The scanner has a spatial resolution of ∼2 mm in all three dimensions. The subjects consisted of five patients diagnosed with locally advanced breast cancer ranging in age from 40 to 55 years old scheduled for pre-treatment, conventional whole body PET imaging with F-18 Fluorodeoxyglucose (FDG). The primary lesions were at least 2 cm in diameter.
The images from the PEM/PET system demonstrated that this system is capable of identifying some lesions not visible in standard mammograms. Furthermore, while the relatively large lesions imaged in this study where all visualised by a standard whole body PET/CT scanner, some of the morphology of the tumours (ductal infiltration, for example) was better defined with the PEM/PET system. Significantly, these images were obtained immediately following a standard whole body PET scan.
The initial testing of the new PEM/PET system demonstrated that the new system is capable of producing good quality breast-PET images compared standard methods.
Journal of Medical Imaging and Radiation Oncology 02/2011; 55(1):58-64. · 0.98 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We are developing the charge division (“resistive”) readout for several arrangements of Silicon Photomultiplier (SiPM) arrays, based on devices from Hamamatsu and SensL. The challenge with the SiPM arrays, as opposed to position sensitive photomultipliers (PSPMTs), is that the noise level is known to be high, and signal to noise ratio (S/N) is lower than in PMTs. In addition, the S/N decreases quickly with the increasing size of the module and with increasing temperatures. Key parameters to optimize are: size and coverage of the SiPM arrays, operational temperature (potential necessity of introducing system cooling), and bias voltage. All these parameters have impact on the S/N, and in consequence on the spatial resolution and the energy resolution of the detector modules. Our somewhat arbitrary but practical goal is to achieve operation similar to the one offered by H8500/H9500 flat panel PSPMTs when using LYSO scintillation arrays in applications to small PET imaging modules. Ultimately we would like to use the reduced channel number readout in the depth-of interaction (DOI) modules. Our first application is to construct ∼5cm×5cm compact PET modules for the HelmetPET brain imager prototype under construction at WVU.
[Show abstract][Hide abstract] ABSTRACT: Parallax error in PET modules can be reduced by measuring the annihilation photon depth of interaction (DOI) in the scintillation crystal on an event-by-event basis. Following implementations described in prior literature, we selected a dual-sided readout PET module design in which SiPMs are placed at both ends of a scintillation array and the ratio of the signal from one photodetector (A) divided by the signal sum of both detectors (A+B), as well as the plot of Signal A vs. Signal B are used to measure DOI. Our experimental apparatus consisted of a 12×12 scintillation array with 1×1×10mm<sup>3</sup> pixels [from Proteus] with 50μ Toray Lumirror septa for DOI optimization. Both polished ends of the scintillation array were optically coupled to a 12×12×2mm<sup>3</sup> anti-reflection coated UV fused silica light spreader window [from Edmund Optics]. The reverse side of each window was optically coupled to a low profile (~1mm thick) 4×4 element SiPM with 3 × 3mm<sup>2</sup> active area pixels [SPMArray2 from sensL]. Flexible Printed Circuit (FPC) cables were used to interface the DOI PET module to custom 16 channel differential pre-amplifiers connected to evaluation/power supply boards [SPMArray2-A0 and SPMArray2-A1, respectively, from sensL]. Average DOI resolution of 1.5±0.1mm FWHM and energy resolution of 20% FWHM was obtained. We conclude that for the limited instances of parallax error expected in realistic PET systems combined with ~1mm spatial resolution in the scintillation plane, the obtained result for DOI spatial resolution indicates that ~1mm spatial reconstruction resolution PET imaging is possible with the selected technical approach. Applications for such a compact high DOI resolution PET module include a prostate PET probe working in conjunction with a standard clinical PET imager or a dedicated prostate PET imager aiding in prostate cancer diagnosis and biopsy guidance, as well as-
a carotid artery PET probe imaging vulnerable plaque or a surgical breast imaging probe.
Nuclear Science Symposium Conference Record (NSS/MIC), 2010 IEEE; 12/2010
[Show abstract][Hide abstract] ABSTRACT: In this paper we consider the task of image reconstruction in positron emission tomography (PET) with the planogram frequency-distance rebinning (PFDR) algorithm. The PFDR algorithm is a rebinning algorithm for PET systems with panel detectors. The algorithm is derived in the planogram coordinate system which is a native data format for PET systems with panel detectors. A rebinning algorithm averages over the redundant four-dimensional set of PET data to produce a three-dimensional set of data. Images can be reconstructed from this rebinned three-dimensional set of data. This process enables one to reconstruct PET images more quickly than reconstructing directly from the four-dimensional PET data. The PFDR algorithm is an approximate rebinning algorithm. We show that implementing the PFDR algorithm followed by the (ramp) filtered backprojection (FBP) algorithm in linogram coordinates from multiple views reconstructs a filtered version of our image. We develop an explicit formula for this filter which can be used to achieve exact reconstruction by means of a modified FBP algorithm applied to the stack of rebinned linograms and can also be used to quantify the errors introduced by the PFDR algorithm. This filter is similar to the filter in the planogram filtered backprojection algorithm derived by Brasse et al. The planogram filtered backprojection and exact reconstruction with the PFDR algorithm require complete projections which can be completed with a reprojection algorithm. The PFDR algorithm is similar to the rebinning algorithm developed by Kao et al. By expressing the PFDR algorithm in detector coordinates, we provide a comparative analysis between the two algorithms. Numerical experiments using both simulated data and measured data from a positron emission mammography/tomography (PEM/PET) system are performed. Images are reconstructed by PFDR+FBP (PFDR followed by 2D FBP reconstruction), PFDRX (PFDR followed by the modified FBP algorithm for exact reconstruction) and planogram filtered backprojection image reconstruction algorithms. We show that the PFDRX algorithm produces images that are nearly as accurate as images reconstructed with the planogram filtered backprojection algorithm and more accurate than images reconstructed with the PFDR+FBP algorithm. Both the PFDR+FBP and PFDRX algorithms provide a dramatic improvement in computation time over the planogram filtered backprojection algorithm.
[Show abstract][Hide abstract] ABSTRACT: We have implemented the low-profile SENSL 16ch SPMArray2 module in a small prototype of a beta/positron imager. The SiPM sensor has a 0.5–1mm thick plastic scintillator optically coupled via thin (1–2mm) glass window for better light spread between the sixteen 3mm SiPM pads to allow center of gravity position calculations of the scintillation light flashes. In the initial studies, aluminized Mylar foil and Teflon tape were used for a top surface reflector, and black Tedlar foil for a light-tight mechanical barrier. Sensitivity of 3–5 counts/sec per nanoCi was measured with one layer of 50 micron Teflon and 50 micron Tedlar each. For two Tedlar layers the sensitivity was lower by about 10 percent with the applied broad energy window. Intrinsic spatial resolution was estimated at approximately 2.5mm, with the un-collimated positron beam distribution limiting the measurement. The position information can be used as a finer indication when the hot spots are located within the ∼10mm×10mm useful FOV of the device. According to the initial plans, the imager will be evaluated as a tool assisting with checking the cancer margin adequacy in breast cancer excision (lumpectomy). Before surgery, the patient will obtain systemic injection of positron biomarker, such as F18-FDG, the same that was used to detect the cancer in the PET procedure. Attached to the surgeons fingertip, the imager will be used to scan the surface of the post-extraction cavity for residual positron activity as an indication of non-sufficient cancer margins, to allow for immediate in-situ correction. The imager is planned as another instrument in the set of complementary imaging and non-imaging tools to assist with breast cancer surgeries, not to replace other tools.
[Show abstract][Hide abstract] ABSTRACT: Efforts to create dedicated nuclear medicine breast imaging scanners are maturing as they approach more routine clinical use. These systems promise to improve the detection of small lesions, especially those in breasts that are not definitively imaged with standard methods. Since these techniques lack sufficient specificity for accurate diagnoses of cancer, a method for guiding biopsies with these new devices must be developed. In this investigation, a technique that capitalizes upon the three-dimensional, multi-angle positron emission tomography (PET) breast images created by our new positron emission mammography/tomography imaging and biopsy device (PEM-PET) to guide breast biopsies was tested. Specifically, the accuracy and precision of the needle positioning system was measured for each of the three axes of motion. In addition, a biopsy of a simulated breast lesion was performed under realistic imaging conditions. The results from the positioning tests revealed that the system had very good accuracy and precision in all three axes. The maximum positioning error was plusmn 0.27 mm, sufficient to obtain samples from most lesions detected with PEM-PET. In addition, the simulated biopsy was performed successfully on a single attempt in obtaining a sample from a 5-mm-diameter target sphere. This successful test moves the project closer to the next phase of development, initiation of limited human testing.
IEEE Transactions on Nuclear Science 07/2009; · 1.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Proton (1H) MRS enables non-invasive biochemical assay with the potential to characterize malignant, benign and healthy breast tissues. In vitro studies using perchloric acid extracts and ex vivo magic angle spinning spectroscopy of intact biopsy tissues have been used to identify detectable metabolic alterations in breast cancer. The challenges of 1H MRS in vivo include low sensitivity and significant overlap of resonances due to limited chemical shift dispersion and significant inhomogeneous broadening at most clinical magnetic field strengths. Improvement in spectral resolution can be achieved in vivo and in vitro by recording the MR spectra spread over more than one dimension, thus facilitating unambiguous assignment of metabolite and lipid resonances in breast cancer. This article reviews the recent progress with two-dimensional MRS of breast cancer in vitro, ex vivo and in vivo. The discussion includes unambiguous detection of saturated and unsaturated fatty acids, as well as choline-containing groups such as free choline, phosphocholine, glycerophosphocholine and ethanolamines using two-dimensional MRS. In addition, characterization of invasive ductal carcinomas and healthy fatty/glandular breast tissues non-invasively using the classification and regression tree (CART) analysis of two-dimensional MRS data is reviewed.
NMR in Biomedicine 12/2008; 22(1):77-91. · 3.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A major goal of this article is to summarize the current status of evaluating prostate metabolites non-invasively using spatially resolved two-dimensional (2D) MR Spectroscopy (MRS).
Due to various technical challenges, the spatially resolved versions of 2D MRS techniques are currently going through the developmental stage. During the last decade, four different versions of 2D MRS sequences have been successfully implemented on 3T and 1.5T MRI scanners manufactured by three different vendors. These sequences include half and maximum echo sampled J-resolved spectroscopy (JPRESS), S-PRESS and L-COSY, which are single volume localizing sequences, and the multi-voxel based JPRESS sequence.
Even though greater than 1ml voxels have been used, preliminary evaluations of 2D JPRESS, S-PRESS and L-COSY sequences have demonstrated unambiguous detection of citrate, creatine, choline, spermine and more metabolites in human prostates. ProFIT-based quantitation of JPRESS and L-COSY data clearly shows the superiority of 2D MRS over conventional one-dimensional (1D) MRS and more than six metabolites have been successfully quantified. These sequences have been evaluated in a small group of prostate pathologies and pilot investigations using these sequences show promising results in prostate pathologies.
Implementation of the state-of-the-art 2D MRS techniques and preliminary evaluation in prostate pathologies are discussed in this review. Even though these techniques are going through developmental and early testing phases, it is evident that 2D MRS can be easily added on to any clinical Magnetic Resonance Imaging (MRI) protocol to non-invasively record the biochemical contents of the prostate.
MAGMA Magnetic Resonance Materials in Physics Biology and Medicine 11/2008; 21(6):443-58. · 1.86 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The link between body weight, lipid metabolism, and health risks is poorly understood and difficult to study. Magnetic resonance spectroscopy (MRS) permits noninvasive investigation of lipid metabolism. We extended existing two-dimensional MRS techniques to permit quantification of intra- and extramyocellular lipid (IMCL and EMCL, respectively) compartments and their degree of unsaturation in human subjects and correlated these results with body mass index (BMI). Using muscle creatine for normalization, we observed a statistically significant (P < 0.01) increase in the IMCL-to-creatine ratio with BMI (n = 8 subjects per group): 5.9 +/- 1.7 at BMI < 25, 10.9 +/- 1.82 at 25 < BMI < 30, and 13.1 +/- 0.87 at BMI > 30. Similarly, the degree of IMCL unsaturation decreased significantly (P < 0.01) with BMI: 1.51 +/- 0.08 at BMI < 25, 1.30 +/- 0.11 at 25 < BMI < 30, and 0.90 +/- 0.14 at BMI > 30. We conclude that important aspects of lipid metabolism can be evaluated by two-dimensional MRS and propose that degree of unsaturation measured noninvasively may serve as a biomarker for lipid metabolic defects associated with obesity.
[Show abstract][Hide abstract] ABSTRACT: Tomographic breast imaging techniques can potentially improve detection and diagnosis of cancer in women with radiodense and/or fibrocystic breasts. We have developed a high-resolution positron emission mammography/tomography imaging and biopsy device (called PEM/PET) to detect and guide the biopsy of suspicious breast lesions. PET images are acquired to detect suspicious focal uptake of the radiotracer and guide biopsy of the area. Limited-angle PEM images could then be used to verify the biopsy needle position prior to tissue sampling. The PEM/PET scanner consists of two sets of rotating planar detector heads. Each detector consists of a 4 x 3 array of Hamamatsu H8500 flat panel position sensitive photomultipliers (PSPMTs) coupled to a 96 x 72 array of 2 x 2 x 15 mm(3) LYSO detector elements (pitch = 2.1 mm). Image reconstruction is performed with a three-dimensional, ordered set expectation maximization (OSEM) algorithm parallelized to run on a multi-processor computer system. The reconstructed field of view (FOV) is 15 x 15 x 15 cm(3). Initial phantom-based testing of the device is focusing upon its PET imaging capabilities. Specifically, spatial resolution and detection sensitivity were assessed. The results from these measurements yielded a spatial resolution at the center of the FOV of 2.01 +/- 0.09 mm (radial), 2.04 +/- 0.08 mm (tangential) and 1.84 +/- 0.07 mm (axial). At a radius of 7 cm from the center of the scanner, the results were 2.11 +/- 0.08 mm (radial), 2.16 +/- 0.07 mm (tangential) and 1.87 +/- 0.08 mm (axial). Maximum system detection sensitivity of the scanner is 488.9 kcps microCi(-1) ml(-1) (6.88%). These promising findings indicate that PEM/PET may be an effective system for the detection and diagnosis of breast cancer.
Physics in Medicine and Biology 03/2008; 53(3):637-53. · 2.70 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present an efficient rebinning algorithm for positron emission tomography (PET) systems with panel detectors. The rebinning algorithm is derived in the planogram coordinate system which is the native data format for PET systems with panel detectors and is the 3-D extension of the 2-D linogram transform developed by Edholm. Theoretical error bounds and numerical results are included.
IEEE transactions on medical imaging. 02/2008; 27(7):925-33.
[Show abstract][Hide abstract] ABSTRACT: Gender differences in lipid metabolism are poorly understood and difficult to study using conventional approaches. Magnetic resonance spectroscopy (MRS) permits non-invasive investigation of lipid metabolism. We employed novel two- dimensional MRS techniques to quantify intramyocellular (IMCL) and extramyocellular (EMCL) lipid compartments and their degree of unsaturation in normal weight adult male and female subjects. Using muscle creatine (Cr) for normalization, a statistically significant (p 0.05) increase in IMCL/Cr (7.8 ± 1.6) and EMCL/Cr (22.5 ± 3.6) for female subjects was observed (n = 8), as compared to IMCL/Cr (5.9 ± 1.7) and EMCL/Cr (18.4 ± 2.64) for male subjects. The degree of unsaturation within IMCL and EMCL was lower in female subjects, 1.3 ± 0.075 and 1.04 ± 0.06, respectively, as compared to that observed in males (n = 8), 1.5 ± 0.08 and 1.12 ± 0.03, respectively (p 0.05 male vs female for both comparisons). We conclude that certain salient gender differences in lipid metabolism can be assessed noninvasively by advanced MRS approaches.
[Show abstract][Hide abstract] ABSTRACT: Longitudinal multispin orders can be created in spin systems that exhibit scalar, dipolar or quadrupolar couplings. They provide an effective way for measurement of scalar couplings and also to probe molecular interactions and dynamics. They cannot be separated by phase cycling or gradient selection methods which are the only known modes of separating different coherences. In this review we describe the frequency cycling procedure for separating various orders in weakly and strongly coupled spin systems. We provide the analytical solutions that permit determination of the frequency cycle for different spin systems. We also discuss the creation of longitudinal orders through relaxation. Finally we highlight the potential applications including spectral editing, measurement of relative signs of scalar couplings and structural properties of molecules.
Current Analytical Chemistry 12/2007; 4(1):40-54. · 1.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To implement and evaluate a novel single-volume two-dimensional localized constant-time-based correlated spectroscopy (2D LCT-COSY) sequence on a clinical 3T MR scanner. This sequence exhibits homonuclear decoupling along the F1 dimension, leading to improved spectral resolution compared to that of non-constant-time localized correlated spectroscopy (L-COSY).
A GE 3T MR scanner equipped with a quadrature transmit and receive extremity coil was used in this study. The 2D LCT-COSY sequence was programmed using General Electric's EPIC compiler. Simulations for a two-spin 1/2 system were performed using GAMMA libraries to evaluate the theoretical performance of the sequences, and were also compared with corresponding phantom experiments using trans-cinnamic acid. Finally, spectra were acquired from the soleus muscle of healthy volunteers in order to evaluate performance in vivo.
Simulations and experimental results confirmed the improved spectral resolution of LCT-COSY over L-COSY, as well as its homonuclear decoupling performance. The behavior of resonance amplitudes as a function of evolution time in the experiment also was appropriately reflected by the simulation. Corresponding results were obtained for the in vivo muscle spectra, in which separation of overlapping olefinic and allylic methylene protons from the intra- and extramyocellular lipids (IMCL and EMCL, respectively) was achieved.
Simulations and experimental results in vitro and in vivo demonstrate the strengths of LCT-COSY. This technique can be implemented on systems of any field strength, and has the potential to separate overlapping metabolites in tissue when employed on high-field clinical MRI scanners equipped for proton spectroscopy.
Journal of Magnetic Resonance Imaging 09/2007; 26(2):410-7. · 2.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To compare point-resolved spectroscopy (PRESS) and localized two-dimensional (2D) correlated spectroscopy (L-COSY) in the detection of cerebral metabolites in humans on a clinical scanner at 3T and to estimate their respective inter- and intrasubject variances.
Measurements were made on nine healthy subjects to assess intersubject variance, and daily on a single subject over a period of seven days to assess intrasubject variance. All L-COSY measurements were performed with a voxel size of 27 mL (3 x 3 x 3 cm(3)) and a measurement time of approximately 34 minutes in the occipitoparietal lobe of the brain. Relative metabolite concentrations were estimated with respect to N-methyl creatine.
While the sensitivity of PRESS is twice that of L-COSY, the greater spectral resolution offered by L-COSY resulted in greater consistency in estimates of the concentrations of several cerebral metabolites, as indicated by a superior intraclass correlation and a significantly lower standard deviation (SD) in a matched pair intrasubject analysis.
Our pilot results demonstrate that L-COSY is an effective approach for resolving cerebral metabolites, and demonstrates a lower coefficient of variance (CV) than the conventional 1D localized spectroscopic approach using LC Model for quantification.
Journal of Magnetic Resonance Imaging 09/2007; 26(2):405-9. · 2.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Multi-modality imaging (such as PET–CT) is rapidly becoming a valuable tool in the diagnosis of disease and in the development of new drugs. Functional images produced with PET, fused with anatomical images created by MRI, allow the correlation of form with function. Perhaps more exciting than the combination of anatomical MRI with PET, is the melding of PET with MR spectroscopy (MRS). Thus, two aspects of physiology could be combined in novel ways to produce new insights into the physiology of normal and pathological processes. Our team is developing a system to acquire MRI images and MRS spectra, and PET images contemporaneously. The prototype MR-compatible PET system consists of two opposed detector heads (appropriate in size for small animal imaging), operating in coincidence mode with an active field-of-view of ∼14 cm in diameter. Each detector consists of an array of LSO detector elements coupled through a 2-m long fiber optic light guide to a single position-sensitive photomultiplier tube. The use of light guides allows these magnetic field-sensitive elements of the PET imager to be positioned outside the strong magnetic field of our 3T MRI scanner. The PET scanner imager was integrated with a 12-cm diameter, 12-leg custom, birdcage coil. Simultaneous MRS spectra and PET images were successfully acquired from a multi-modality phantom consisting of a sphere filled with 17 brain relevant substances and a positron-emitting radionuclide. There were no significant changes in MRI or PET scanner performance when both were present in the MRI magnet bore. This successful initial test demonstrates the potential for using such a multi-modality to obtain complementary MRS and PET data.
Journal of Magnetic Resonance 07/2007; · 2.30 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Multi-modality imaging is rapidly becoming a valuable tool in the diagnosis of disease and in the development of new drugs. Functional images produced with PET fused with anatomical structure images created by MRI will allow the correlation of form with function. Our group is developing a system to acquire MRI and PET images contemporaneously. The prototype device consists of two opposed detector heads, operating in coincidence mode. Each MRI-PET detector module consists of an array of LSO detector elements coupled through a long fibre optic light guide to a single Hamamatsu flat panel position-sensitive photomultiplier tube (PSPMT). The use of light guides allows the PSPMTs to be positioned outside the bore of a 3T MRI scanner where the magnetic field is relatively small. To test the device, simultaneous MRI and PET images of the brain of a male Sprague Dawley rat injected with FDG were successfully obtained. The images revealed no noticeable artefacts in either image set. Future work includes the construction of a full ring PET scanner, improved light guides and construction of a specialized MRI coil to permit higher quality MRI imaging.
Physics in Medicine and Biology 01/2007; 51(24):6371-9. · 2.70 Impact Factor