A popular method for gamma ray detection utilizes scintillation detectors which consist of crystals optically coupled to a photomultiplier tubes (PMTs). Scintillators are widely used in the medical radiation fields such as CT scanners, gamma cameras and positron emission tomography (PET) scanners [1]-[5]. The scintillation crystal responds to the absorption of gamma ray by the emission of a light pulse. This light pulse is characterized by the special properties of the crystal such as the decay time constant. Then the PMT generates an electrical pulse relative to the absorbed gamma energy. The phenomenon known as a parallax-error or depth-of-interaction (DOI) error [5] which reduces the sensitivity and reconstruction quality of PET, most probably happened when the photons enter to the detector with non-perpendicular angle. Phosphor sandwich (phoswich) detectors [1] are considered as one of the methods used to reduce the parallax-error. The phoswich detector is a stack of two or more different scintillation crystals; i.e. with different decay time constants, optically coupled to a single PMT. Hence the DOI error is reduced when the scintillated crystal is identified. The crystal identification (CI) requires applying one of the pulse shape discrimination (PSD) methods [6] - [20]. Different PSD algorithms were developed which can be classified into two categories: time domain and frequency domain. In the time domain, the cross correlation [10], fuzzy logic [11] and neural network [12] were employed in the PSD and CI methods. On the other hand, the Fast Fourier Transform (FFT) of the pulses improved the CI performance [13]. Moreover, the normalized least sample (NLS) method [14], which is dependent strongly on ... ... middle of paper ... .... Saleh, and M. A. Ashour, "A Zernike Moment Method for Pulse Shape Discrimination in PMT-Based PET Detectors," Nuclear Science, IEEE Transactions on, pp. 1-9, 2013. [25] V. Vapnik, “Statistical Learning Theory,” John Wiley & Sons Inc., New York, 1998. [26] V. Vapnik, “The Nature of Statistical Learning Theory,” Springer Verlag, Berlin, 1995. [27] G. Amayeh, A. Erol, G. Bebis, M. Nicolescu, "Accurate and Efficient Calculation of High Order Zernike Moments", International Symposium on Visual Computing, (LNCS, Vol.3804), Lake Tahoe, Nevada, pp. 462-469, 2005. [28] J. Gu, H.Z. Shu, C. Toumoulin, L.M. Luo, "A novel algorithm for fast computation of Zernike moments", Pattern Recognition, vol. 35, no. 12, pp. 2905- 2911, 2002. [29] S. Hwang, W. Kim, "A novel approach to the fast computation of Zernike moments", Pattern Recognition, vol. 39, no. 11, pp. 2065–76, 2006.
The careful familial and patient history is imperative for this exam and procedure. And as the video indicated, is this really an effective screening tool for a healthy person more so than seeing the primary care physician. According to the research in the Indian Journal of Medical Research, the “PET/CT doses were found to be higher than many other conventional diagnostic radiology examinations suggesting that all efforts should be made to clinically justify and carefully weigh the risk-benefit ratios prior to every 18FDG whole body PET/CT investigation” (Kaushik et al,
The description of PET scans in detail requires the understanding of the radioactive substance injected into the subject. First, a small amount of a biochemical substance is tagged with a positron-emitting radioisotope. A positron is an “anti-electron.” Positrons are given off during the decay of the nuclei of the radioisotope. When the positron emitted collides with an electron in the tissue of the subject, both the positron and the electron are annihilated. When this happens, the collision produces two gamma rays having the same energy (511 KeV), but going in opposite directions.
Zhang, B., & Mészáros, P. (2004). GAMMA-RAY BURSTS: PROGRESS, PROBLEMS & PROSPECTS. International Journal of Modern Physics A, 17, 223-241.
Position emission tomography. (1998, August 12). Retrieved October 06, 2008, from TRIUMF - Canada's national laboratory for particle and nuclear physics: http://www.triumf.ca/welcome/
The usage of the iris technology is very fast. The capturing and the testing of the images is very fast, it must require some training. The glasses must be removed during the enrollment in the recognition system will ensure the best image will be captured without any reflections from the glasses or the lenses.
To test these hypotheses, we first collected a two point discriminator containing a variety of distances for two points. The point distances on the discriminator included values of.25 millimeters being the smallest, ...
When taking a radiograph there are some precautions that can be taken to reduce some of the radiation that can be exposed to a patient, what would be used on all patients is call a lead apron and thyroid collar, these aprons are used to protect the patients that may be a bit more radiosensitive and also may give the patient a little of reassurance that they will be protected. “Radiosensitivity is the relative susceptibility of cells, tissues, organs, organisms, or other substances to the injurious action of radiation.”
In this section, the results of the research are presented. For each task carried out, the most important information obtained is presented.
Radioisotopes have helped create advanced imaging techniques. Beforehand, X rays could only provide so much information such as broken bones, abnormal growths, and locating foreign objects in the body. Now it is possible to obtain much more information from medical imaging. Not only can this advanced imaging give imaging of tiny structures in the body, but it can also provide details such as cancerous cells and damaged heart tissue from a heart...
The large width Gaussian masks are not preferred as detector's sensitivity to noise is low and moreover, the localization error in the detected edges also increases with increase in Gaussian mask width. Step 2:- After the initial pre-processing steps of smoothening and removal of noise, the edge strength is calculated by taking the gradient of the image. For the purpose of edge detection in an image, the Sobel operator first performs a 2-D spatial gradient measurement with the help of convolution masks. The convolution masks used are of the size 3X3, where one is used to calculate the horizontal gradient(Gx) while the other is used to calculate the vertical gradient(Gy). Then, the approximate absolute edge strength can be calculated at each point.
[5] Kresimir Delac, Mislav Grgic, Panos Liatsis. (March 2005). Appearance based statistical methods for face recognition. The 47th international symposium EL, Croatia.
Gamma cameras and Single Photon emission computerized Tomography (SPECT) scanners are used for planer and tomographic imaging of gamma
e) Ghosh, P. & Kelly, M. (2010). Expanding the power of PET with PERCIST. [Siemens Healthcare White Paper]. URL http://usa.healthcare.siemens.com/siemens_hwem-hwem_ssxa_websites-context-root/wcm/idc/groups/public/@us/@imaging/@molecular/documents/download/mdaw/nduz/~edisp/white_paper_10_percist-00309714.pdf
Iris recognition is very accurate and distinctive because iris has a complex texture that can produce a substantial amount of information to identify a person. Furthermore, the iris remains almost unchanged from childhood, only minuscule variations are presented. The biometric data is captured using a small and high definition camera that is able to recognize different characteristics of the iris. Moreover, the system can detect the use of contact lens with a fake iris and can realize with the natural movement of the eye if the sample object is a living being. Although initially iris recognition systems were expensive and complex to use, new technology developments have improved these weaknesses.
The most important use of radioiactivity is in the production of nuclear energy. There are two basic ways in which nuclear energy can be released from ...