This paper describes the design of a coincidence processing board for a dual-head Positron Emission Tomography (PET) scanner for breast imaging. The proposed block-oriented data acquisition system ...relies on a high-speed DSP processor for fully digital trigger and on-line event processing that surpasses the performance of traditional analog coincidence detection systems. A mixed-signal board has been designed and manufactured. The analog section comprises 12 coaxial inputs (six per head) which are digitized by means of two 8-channel 12-bit 40-MHz ADCs in order to acquire the scintillation pulse, the charge division signals and the depth of interaction within the scintillator. At the digital section, a state-of-the-art FPGA is used as deserializer and also implements the DMA interface to the DSP processor by storing each digitized channel into a fast embedded FIFO memory. The system incorporates a high-speed USB 2.0 interface to the host computer.
The Gamma Functional Navigator Benlloch, J.M.; Alcaniz, M.; Escat, B. ...
IEEE transactions on nuclear science,
2004-June, 2004-06-00, 20040601, Letnik:
51, Številka:
3
Journal Article
Recenzirano
We have developed a new device that allows precise guided surgery through gamma-camera images in real time. It consists of a portable mini gamma camera combined with an image guided surgery system. ...We call this new instrument the "Gamma Functional Navigator." The small gamma camera has been built by our group and has a spatial resolution of about 2 mm. The position and orientation of the gamma camera and the surgical instruments is determined by the navigator through infrared reflectors. A software program combines the images obtained by the gamma camera at two different positions to form a stereoscopic image of the object under study. We have focused our interest, as a starting point, to the simplest problem of quasi-punctual objects, such as lymph nodes or small tumors. We have tested the "Gamma Functional Navigator" with different phantoms finding the position of the node in 3-D space with a resolution better than 3 mm for node-camera head distances lower than 5 cm. This allows to locate and distinguish cancerous nodes from its neighbors during surgery.
Medium field of view multiflat panel-based portable gamma camera Giménez, M; Benlloch, J.M; Cerdá, J ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2004, Letnik:
525, Številka:
1
Journal Article
Recenzirano
A portable gamma camera based on the multianode technology has been built and tested. The camera consists in optically coupling four “Flat Panel” H8500 PSPMTs to a 100×100×4
mm
3 CsI(Na) continuous ...scintillation crystal. The dimensions of the camera are 17×12×12
cm
3 including the pinhole collimator and it weighs a total of 2
kg. Its average spatial resolution is 2
mm, its energy resolution is about 15%, and it shows a field of view of 95
mm. Because of its portability, its FOV and its cost, it is a convenient choice for osteological, renal, mammary, and endocrine (thyroid, parathyroid and suprarenal) scintigraphies, as well as other important applications such as intraoperatory detection of lymph nodes and surgical oncology. We describe the simulations performed which explain the crystal choice, the mechanical design of the camera and the method of calibration and algorithms used for position, energy and uniformity correction. We present images taken from phantoms. We plan to increase the camera sensitivity by using a four-holes collimator in combination with the MLEM algorithm, in order to decrease the exploration time and to reduce the dose given to the patient.
MAMMI is a dedicated breast positron emission tomograph (PET) based on monolythic LYSO crystals, with a transaxial field of view (FOV) of 170 mm. It has been upgraded by adding a second ring of ...detectors that extends the axial FOV from 40 mm to 94.4 mm, in order to improve its sensitivity and reduce the acquisition time. In this work we present the performance evaluation of the dual ring MAMMI breast PET and a discussion about the contribution of the addition of a second ring of detectors, the compensation of the detector blur and the increase of the scintillator thickness. Experimental measurements suggested on NEMA NU 4-2008 and NEMA NU 2-2007 have been conveniently adapted to the dimensions of the MAMMI. The addition of the second ring of detectors leads to a rise of the sensitivity from 1.8% to 3.6%. The spatial resolution at one-fourth of the axial FOV (1.5 mm axial, 1.6 mm tangential, 1.7 mm radial) is slightly better than that measured at the axial center (1.9 mm axial, 1.8 mm tangential and radial), because of the 14 mm gap in between detection rings. The results obtained after the evaluation reflect a substantial performance improvement, specially in the absolute sensitivity, because of the changes introduced in the MAMMI PET.
Pancreatitis in children is uncommon, but can be associated with severe morbidity rates. Eleven patients (14 months to 9.5 years of age) with acute pancreatitis and one patient with chronic ...idiopathic pancreatitis beginning the second year of life, were treated over a 11-year period. Half of them had history of blunt abdominal trauma. The most frequent clinical presentations included abdominal pain and vomiting. Diagnosis of pancreatic injury was suggested by hypera-amylasemia, being the computerized tomography scan the most useful radiologic investigation. Medical treatment consisted of intravenous fluids, nasogastric suction and total parenteral nutrition. One third of the patients developed pancreatic pseudocysts (4); spontaneous resolution after observation and conservative therapy occurred in two and the others were treated by surgery. Ranson and Imrie scores can help predicting the severity of this disease in children; three of four pancreatic pseudocysts were judged to have severe pancreatitis by this criteria.
The LM-EM algorithm has the advantage to calculate the emission probabilities needed for the reconstruction process on the fly, without the need of a pre-calculated system matrix. The reconstruction ...time for this algorithm strongly depends on the used backprojector and the available statistics. This algorithm when implemented in systems using monolithic crystals to detect gamma radiation allows one to extensively exploit the virtual pixilation feature, not available for systems based on pixilated crystals. In this work we present a backprojector for LM-EM, the TOR method, which achieves a tradeoff between computational efficiency and image quality. Its temporal subset algorithm optimization (LM-OS) has also been implemented in order to achieve real-time reconstructions. To evaluate the performances of LM-OS algorithm with the TOR method backprojector and only with one iteration on the datasets, studies based on the system spatial resolution, uniformity, and contrast coefficients were carried out and they were compared with those obtained with LM-EM and MLEM algorithms using twelve iteration. Finally, a study on reconstruction time using LM-OS has been performed with breast patients data.
PDF
