Computer assisted characterization of cervical intervertebral disc degeneration in MRI

A texture-based pattern recognition system is proposed for the automatic characterization of cervical intervertebral disc degeneration from saggital magnetic resonance images of the spine. A case sample of 50 manually segmented ROIs, corresponding to 25 normal and 25 degenerated discs, was analyzed and textural features were generated from each disc-ROI. Student's t-test verified the existence of statistically significant differences between textural feature values generated from normal and degenerated discs. This finding is indicative of disc image texture differentiation due to the degeneration of the disc. The generated features were employed in the design of a pattern recognition system based on the Least Squares Minimum Distance classifier. The system achieved a classification accuracy of 94{%} and it may be of value to physicians for the assessment of cervical intervertebral disc degeneration in MRI

Initial results on SiPMs performance for use in medical imaging

Silicon photomultiplier (SiPMs) detectors are attractive candidates for replacing position sensitive photomultipliers in nuclear imaging. They are compact, they provide high gain with low bias voltage and show better response. The development of dedicated imaging prototypes based on SiPMs possesses several design challenges, since it is necessary to optimize scintillator and SiPM coupling, as well as signal amplification and digitization. In this work, we have investigated the performance of three SiPM modules constructed by SensL coupled on three scintillators (CsI:Tl, BGO, LYSO:Ce), which are used in SPECT and PET imaging. Irradiation was carried out using different sources, which covered a wide range of energies from 88 to 1275 keV. The parameters measured were output pulses' width and height, energy resolution and linearity as a function of bias voltage and sources energy

Adult patient radiation doses from non-cardiac CT examinations: A review of published results

Objectives: CT is a valuable tool in diagnostic radiology but it is also associated with higher patient radiation doses compared with planar radiography. The aim of this article is to review patient dose for the most common types of CT examinations reported during the past 19 years. Methods: Reported dosimetric quantities were compared with the European diagnostic reference levels (DRLs). Effective doses were assessed with respect to the publication year and scanner technology (i.e. single-slice vs multislice). Results: Considerable variation of reported values among studies was attributed to variations in both examination protocol and scanner design. Median weighted CT dose index (CTDIw) and dose length product (DLP) are below the proposed DRLs; however, for individual studies the DRLs are exceeded. Median reported effective doses for the most frequent CT examinations were: head, 1.9 mSv (0.3-8.2 mSv); chest, 7.5 mSv (0.3-26.0 mSv); abdomen, 7.9 mSv (1.4-31.2 mSv); and pelvis, 7.6 mSv (2.5-36.5 mSv). Conclusion: The introduction of mechanisms for dose reduction resulted in significantly lower patient effective doses for CT examinations of the head, chest and abdomen reported by studies published after 1995. Owing to the limited number of studies reporting patient doses for multislice CT examinations the statistical power to detect differences with single-slice scanners is not yet adequate. © 2011 The British Institute of Radiology

Assessing the information content of phosphor produced medical images: application to Zn2SiO4 : Mn phosphor

In this study a method to assess the information content of medical images produced by phosphors is described. The optical signal emitted by the phosphor after X-ray excitation, the detective quantum efficiency (DQE), expressing the signal-re-noise ratio (SNR) transfer efficiency, and the information;capacity were experimentally determined. The method was based on light flux and modulation transfer function (MTF) measurements and was used to assess the imaging performance of the Zn2SiO4:Mn phosphor. The latter was employed in the form of laboratory prepared phosphor layers (test screens). Results showed that high values for optical signal emission and DQE were obtained for medium thickness phosphor layers (56 and 89 mg/cm(2)) at 20 kVp X-ray tube voltage. The information capacity was found to decrease continuously with phosphor coating weight. (C) 2000 Elsevier Science Ltd, All rights reserved

Design considerations for application of SiPMs in nuclear imaging

Silicon Photomultiplier (SiPM) detectors are attractive candidates for the replacement of Photomultipliers in nuclear imaging. They are compact, provide high gain with low Vbias and have fast response. In addition, SiPMs are not influenced by strong magnetic fields, allowing their use in the emerging field of PET-MRI. The development of small prototypes based on SiPMs posses several design challenges, since it is necessary to optimize scintillator and SiPM coupling, as well as signal amplification and digitization. The aim of this work is the characterization of two SiPM modules, in terms of energy resolution using 3 different scintillator materials and variable Vbias. We have used SensL's SPMM3020 and SPMM3035 combined with LYSO, CsI:Tl and BGO, irradiated with99mTc and 137Cs sources The best energy resolution for Tc was 18% and achieved for the SPMM3020, coupled to CsI:Tl at 31V. For 137Cs energy resolution was 10.0% and achieved for the SPMM3020 coupled to CsI(Tl) at 32.5V. © 2010 IEEE

The effect of a combined tube current modulation system on dose delivered to patients undergoing thoracic and abdominal CT with a 128-slice scanner

Combined tube current modulation techniques (such as Care Dose4D used in this study) during computed tomography (CT) procedures bring together the benefits of the angular and z-axis modulation techniques, measuring X-ray attenuation profile in the z-axis together with the data from the perpendicular x-y direction with a sophisticated algorithm. The purpose of this study was to investigate the radiation dose, in terms of computed tomography dose index (CTDIvol), delivered to patients during thoracic and abdominal CT using this technique and compare it with the corresponding CTDIvol of the fixed tube current CT technique. The results revealed a 5-32% dose reduction for chest CT and a dose reduction of 7.6-60% for the three-sequence abdominal CT scan of normal and overweight patients. In the case of obese patients a 15.4-18.7% dose increase for chest CT and a (21.5) 2 (26.3)% dose increase for the three-stage abdominal examinations for females and males, respectively, was revealed. © The Author 2012. Published by Oxford University Press. All rights reserved