Radiation Detectors and Sensors in Medical Imaging.

Medical imaging instrumentation design and construction is based on radiation sources and radiation detectors/sensors. This review focuses on the detectors and sensors of medical imaging systems. These systems are subdivided into various categories depending on their structure, the type of radiation they capture, how the radiation is measured, how the images are formed, and the medical goals they serve.

A phantom based evaluation of the clinical imaging performance of electronic portal imaging devices.

Purpose: In this study an evaluation of the imaging performance of an electronic portal imaging device (EPID) is presented. The evaluation performed employing the QC-3V image quality phantom.

Methods: An EPID system of a 6 MV LINAC, was used to obtain images of a QC-3V EPID phantom.

A Novel Method for Developing Thin Resin Scintillator Screens and Application in an X-ray CMOS Imaging Sensor.

Scintillating screens for X-ray imaging applications are prepared with various methods. Among them, the classic sedimentation method presents certain weak points. In this context, a novel fabrication process was developed that offers simplicity, economy of resources and time, while the screens exhibit adequate durability and image quality performance.

A Novel Method to Model Image Creation Based on Mammographic Sensors Performance Parameters: A Theoretical Study.

Background: Mammographic digital imaging is based on X-ray sensors with solid image quality characteristics. These primarily include (a) a response curve that yields high contrast and image latitude, (b) a frequency response given by the Modulation Transfer Function (), which enables small detail imaging and (c) the Normalize Noise Power Spectrum () that shows the extent of the noise effect on image clarity.

Methods: In this work, a methodological approach is introduced and described for creating digital phantom images based on the measured image quality properties of the sensor.

Grain Size Distribution Analysis of Different Activator Doped GdOS Powder Phosphors for Use in Medical Image Sensors.

The structural properties of phosphor materials, such as their grain size distribution (GSD), affect their overall optical emission performance. In the widely used gadolinium oxysulfide (GdOS) host material, the type of activator is one significant parameter that also changes the GSD of the powder phosphor. For this reason, in this study, different phosphors samples of GdOS:Tb, GdOS:Eu, and GdOS:Pr,Ce,F, were analyzed, their GSDs were experimentally determined using the scanning electron microscopy (SEM) technique, and thereafter, their optical emission profiles were investigated using the LIGHTAWE Monte Carlo simulation package.

On the Response of a Micro Non-Destructive Testing X-ray Detector.

Certain imaging performance metrics are examined for a state-of-the-art 20 μm pixel pitch CMOS sensor (RadEye HR), coupled to a GdOS:Tb scintillator screen. The signal transfer property (STP), the modulation transfer function (MTF), the normalized noise power spectrum (NNPS) and the detective quantum efficiency (DQE) were estimated according to the IEC 62220-1-1:2015 standard. The detector exhibits excellent linearity (coefficient of determination of the STP linear regression fit, R was 0.

Characterization of breast calcification types using dual energy x-ray method.

Calcifications are products of mineralization whose presence is usually associated with pathological conditions. The minerals mostly seen in several diseases are calcium oxalate (CaCO), calcium carbonate (CaCO) and hydroxyapatite (HAp). Up to date, there is no in vivo method that could discriminate between minerals.

Detective quantum efficiency (DQE) in PET scanners: A simulation study.

The aim of the present study is to introduce the detective quantum efficiency (DQE) for the image quality assessment of positron emission tomography (PET) scanners. For this purpose, a thin layer chromatography (TLC) plane source was simulated using a previously validated, scanner and source geometry, Monte Carlo (MC) model. The model was developed with the Geant4 application for tomographic emission (GATE) MC package and reconstructed images obtained with the software for tomographic image reconstruction (STIR), with cluster computing.

A novel method for the optimization of positron emission tomography scanners imaging performance.

Objective: The aim of the present study was to propose a comprehensive method for positron emission tomography (PET) scanners image quality assessment, by simulation of a thin layer chromatography (TLC) flood source with a previously validated Monte Carlo model.

Methods And Materials: We used the GATE Monte Carlo package (GEANT4 application for tomographic emission) and the reconstructed images were obtained using the software for tomographic image reconstruction (STIR), with cluster computing. The PET scanner used in this simulation study was the General Electric Discovery-ST (USA).

Polynomial dual energy inverse functions for bone Calcium/Phosphorus ratio determination and experimental evaluation.

An X-ray dual energy (XRDE) method was examined, using polynomial nonlinear approximation of inverse functions for the determination of the bone Calcium-to-Phosphorus (Ca/P) mass ratio. Inverse fitting functions with the least-squares estimation were used, to determine calcium and phosphate thicknesses. The method was verified by measuring test bone phantoms with a dedicated dual energy system and compared with previously published dual energy data.

Dual Energy Method for Breast Imaging: A Simulation Study.

Dual energy methods can suppress the contrast between adipose and glandular tissues in the breast and therefore enhance the visibility of calcifications. In this study, a dual energy method based on analytical modeling was developed for the detection of minimum microcalcification thickness. To this aim, a modified radiographic X-ray unit was considered, in order to overcome the limited kVp range of mammographic units used in previous DE studies, combined with a high resolution CMOS sensor (pixel size of 22.

Bone calcium/phosphorus ratio determination using dual energy X-ray method.

Non-invasive dual energy methods have been used extensively on osteoporosis diagnosis estimating parameters, such as, Bone Mineral Density (BMD) and Bone Mineral Content (BMC). In this study, an X-ray dual energy method (XRDE) was developed for the estimation of the bone Calcium-to-Phosphorous (Ca/P) mass ratio, as a bone quality index. The optimized irradiation parameters were assessed by performing analytical model simulations.

A robust method, based on a novel source, for performance and diagnostic capabilities assessment of the positron emission tomography system.

The aim of our work was to provide a robust method for evaluating imaging performance of positron emission tomography (PET) systems and particularly to estimate the modulation transfer function (MTF) using the line spread function (LSF) method. A novel plane source was prepared using thin layer chromatography (TLC) of a fluorine-18-fluorodeoxyglucose ((18)F-FDG) solution. The source was placed within a phantom, and imaged using the whole body (WB) two dimensional (2D) and three dimensional (3D) standard imaging protocols in a GE Discovery ST hybrid PET/CT scanner.

A new PET resolution measurement method through Monte-Carlo simulations.

Objective: The aim of this study was to propose a novel method for image quality assessment in PET scanners through estimation of the modulation transfer function (MTF) of a plane source. The simulation was implemented using the previously validated Monte-Carlo model. A comparison of the proposed method with the more traditional technique, based on a line source, was also performed.

Figure of image quality and information capacity in digital mammography.

Objectives: In this work, a simple technique to assess the image quality characteristics of the postprocessed image is developed and an easy to use figure of image quality (FIQ) is introduced. This FIQ characterizes images in terms of resolution and noise. In addition information capacity, defined within the context of Shannon's information theory, was used as an overall image quality index.

Towards the optimization of nuclear medicine procedures for better spatial resolution, sensitivity, scan image quality and quantitation measurements by using a new Monte Carlo model featuring PET imaging.

The aim of this study was to develop a Monte-Carlo model that can be used for the optimization of positron emission tomography (PET) procedures and image quality metrics. This model was developed using the Monte Carlo package of Geant4 application for tomographic emission (GATE) and the software for tomographic image reconstruction (STIR) with cluster computing to obtain reconstructed images. The PET scanner used in this study was the General Electric Discovery-ST (US).

Acute radiation syndrome and chronic radiation syndrome.

Acute radiation syndrome (ARS) or sickness or poisoning or toxicity is induced after a whole body exposure of men to high doses of radiation between 1-12Gy. First symptoms are from the gastrointestinal system, which together with bone marrow are the most sensitive parts of our body. Chronic radiation syndrome (CRS) may be induced by smaller than 1Gy radiation doses or after a mild form of ARS.

A novel easy-to-use phantom for the determination of MTF in SPECT scanners.

Purpose: To evaluate modulation transfer function (MTF) in single photon emission computed tomography (SPECT) systems using the line spread function (LSF) method and a novel flood source which can be easily fabricated with materials accessible in hospital facilities.

Methods: A Tc-99m-based flood source (E(γ) = 140 keV) consisting of a radiopharmaceutical bound to the grains of a radiographic film was prepared in laboratory. Various films and radiopharmaceuticals were examined, in order to obtain a thin homogenous and reproducible flood source.

[Is major depression in middle-aged men correlated with bone density decrease? A study on Greek population].

During the last 10 years there has been an increasing interest in studying the coexistence of osteoporosis and depression in the male population, due to the increased morbidity and mortality in the patients' life. The present retrospective study evaluates the effect of major depression on the bone density of Greek middle-aged men. By using the method of dual-energy X-rays absorptiometry (DEXA) we reviewed the bone mineral density (BMD) studies performed in the lumbar spine (LS) and/or femoral neck, in 97 men of the white race, aged 55 years with mean age±standard deviation (SD)= 65±10.

Light emission efficiency and imaging performance of Gd2O2S: Eu powder scintillator under x-ray radiography conditions.

Purpose: To evaluate Gd2O2S:Eu powder phosphor as a radiographic image receptor and to compare it to phosphors often used in radiography. Gd2O2S:Eu is nonhygroscopic, emitting red light with decay time close to that of Gd2O2S:Tb.

Methods: The light intensity emitted per unit of x-ray exposure rate (absolute luminescence efficiency) was measured for laboratory prepared screens with coating thicknesses of 33.

Erdheim-Chester disease: symmetric uptake in the (99m)Tc-MDP bone scan.

Erdheim-Chester disease (E-C D) is a rare clinicopathologic entity with nearly pathognomonic radiographic features. About half of the affected exhibit extraskeletal manifestations, including involvement of the hypothalamus-pituitary axis, lung, heart, retroperitoneum, skin, liver, kidneys, spleen and orbit. This disease usually affects individuals in their fifties to their seventies and has a male preponderance.

The physician should benefit, not harm the patient.

Six hundred years before Christ, Hippocrates said that physicians on exercising their medical duties, should benefit but not harm their patients. Seventy years ago increased medical radiation caused radiologists in the US an excess risk of leukemia, lymphoma and multiple myeloma. Now medical radiation is rather safe for the physician but the question remains if proper prophylactic measures are being taken to make it safe for the subjects examined.

In vivo measurement of radius calcium/phosphorus ratio by X-ray absorptiometry.

We describe a new method for assessing the skeletal Ca/P ratio in vivo using X-ray absorptiometry. By placing cerium (Ce) and samarium (Sm) filters in the X-ray beam from a commercial X-ray source (Norland), mean photon energies of 39 and 89 keV were obtained. The instrument was designed to take measurements of the forearm, at a site located at the distal 1/3 of the radius.

The influence of inflammation-mediated osteopenia (IMO) on the structure of rabbit bone and skin collagen fibrils.

The influence of Inflammation Mediated Osteopenia (IMO) on rabbit skin and bone (trabecular and cortical) collagen fibrils was studied by electron microscopy. Severe abnormalities in collagen fibril structure were detected, at the ultrastructural level, in skin and bone specimens from IMO rabbits. In treated animals the arrangement of fibrils is anarchic.