Radiation exposure of the operator during cardiac catheter ablation procedures was assessed for an experienced cardiologist adopting various measures of radiation protection and utilised electroanatomic navigation. Chip thermoluminescent dosemeters were placed at the eyes, chest, wrists and legs of the operator. The ranges of fluoroscopy time and air kerma area product values associated with cardiac ablation procedures were wide (6.3-48.3 min and 1.7-80.3 Gy cm(2), respectively). The measured median radiation doses per procedure for each monitored position were 23.6 and 21.3 μSv to the left and right wrists, respectively, 25.3 and 30.4 μSv to the left and right legs, respectively. The doses to the eyes were below the minimum detectable dose of 9 μSv. The estimated median effective dose was 22.5 μSv. Considering the actual workload of the operator, the calculated annual doses to the hands, legs and eyes, as well as the annual effective dose, were all below the corresponding limits. The findings of this study indicate that cardiac ablation procedures performed at a modern laboratory do not impose a high radiation hazard to the operator when radiation protection measures are routinely adopted.

LiF is a well-known thermoluminescent (TL) material used in individual monitoring, and its fading characteristics have been studied for years. In the present study, the fading characteristics (for a period of 150 d) of various commercial LiF materials with different dopants have been evaluated. The materials used in the study are those used in routine procedures by the Personal Dosimetry Department of Greek Atomic Energy Commission and in particular, LiF:Mg,Ti (MTS-N, TL Poland), LiF:Mg,Cu,P (MCP-N, TL Poland), LiF:Mg,Cu,P (MCP-Ns, thin active layer detector, TL Poland) and LiF:Mg,Cu,P (TLD100H, Harshaw). The study showed that there is a sensitivity loss in signal of up to 20 % for the MTS-N material for a 150-d period in the pre-irradiation fading phase. The MCP-N has a stable behaviour in the pre-irradiation fading phase, but this also depends on the readout system. As far as the post-irradiation fading effect is concerned, a decrease of up to 20 % for the MTS-N material is observed for the same time period. On the other hand, the LiF:Mg,Cu,P material presents a stable behaviour within ± 5 %. These results show that the fading effect is different for each material and should be taken into account when estimating doses from dosemeters that are in use for >2 months.

In the present study scintillating screens prepared from Y3Al5O12:Ce (YAG:Ce) powder phosphor were evaluated for use in digital mammography. YAG:Ce has never been previously used in x-ray medical imaging, however since it emits yellow light (i.e peak at 550nm), it is expected to match well the spectral sensitivities of most photodetectors (photodiodes, CCDs and amorphous silicon sensors) incorporated in various digital mammography detectors. YAG:Ce was purchased in powder form and was used to prepare test screens in laboratory. Screens were evaluated by determining the absolute luminescence efficiency, the light emission spectrum, the x-ray to light intrinsic conversion efficiency and the spectral compatibility with photodetectors. Results were compared with phosphor materials commercially employed in x-ray imaging. Maximum YAG:Ce emission efficiency was observed for the 63 mg/cm(2) screen at 49 kV. Emission spectra peaked at 553 nm. The spectral compatibility with amorphous silicon photodiodes (0.93) and CCDs (0.95) was found to be very high, better than the corresponding compatibility of the CsI:Tl, mostly used in current digital radiography detectors. Taking into account the YAG:Ce overall performance, its short decay time as well as its spectral compatibility with amorphous silicon detectors and CCDs, this phosphor could be of interest for further investigation for use in digital mammography detectors.

Currently, the basis for standard clinical X-ray radiography is absorption, tracking attenuation of radiation when X-ray beams pass through a particular part of the body. The fundamental interaction processes are dependent on variations in the atomic number and density of the target medium; consequentially radiographic contrast can be poor, particularly in regard to soft tissue imaging. Over the past several years considerable interest has been paid to utilising phase properties of the X-ray field to enhance radiographic contrast in challenging circumstances, particularly with respect to soft-tissue imaging. Surrey is among an increasing number of institutes in which a programme of investigation of phase contrast X-ray imaging has been established. We briefly review some basic ideas in X-ray phase contrast imaging and then examine the radiographic contrast enhancement that can be obtained, use being made of the method of free-space propagation and investigating a number of test objects, including biological samples. The equipment used at Surrey is relatively simple, comprising of bench-top X-ray tubes with focal spot sizes from a few microns up to 100 microns and a position sensitive 12 bit CCD detector.

Clinical radiography has traditionally been based on contrast obtained from absorption when X-rays pass through the body. The contrast obtained from traditional radiography can be rather poor, particularly when it comes to soft tissue. A wide range of media of interest in materials science, biology and medicine exhibit very weak absorption contrast, but they nevertheless produce significant phase shifts with X-rays. The use of phase information for imaging purposes is therefore an attractive prospect. Some of the X-ray phase-contrast imaging methods require highly monochromatic plane wave radiation and sophisticated X-ray optics. However, the propagation-based phase-contrast imaging method adapted in this paper is a relatively simple method to implement, essentially requiring only a microfocal X-ray tube and electronic detection. In this paper, we present imaging results obtained from two different benchtop X-ray sources employing the free space propagation method. X-ray phase-contrast imaging provides higher contrast in many samples, including biological tissues that have negligible absorption contrast.

ABSTRAK Pada masa ini, asas dalam radiografi sinar-X klinikal piawai adalah penyerapan, menjejaki pengecilan sinaran apabila bim sinar-X melepasi suatu anggota badan tertentu. Proses interaksi asas adalah bergantung kepada variasi dalam nombor atom dan ketumpatan medium sasaran; akibatnya kontras radiograf boleh menjadi lemah, terutamanya untuk pengimejan tisu lembut. Beberapa tahun kebelakangan ini banyak usaha telah ditumpukan dalam penggunaan ciri fasa medan sinar-X untuk meningkatkan kontras radiografi dalam keadaan yang mencabar, terutamanya yang berkait dengan pengimejan tisu lembut. Surrey adalah salah sebuah daripada bilangan institut yang semakin bertambah dalam mana suatu program penyelidikan pengimejan sinar-X kontras fasa telah diwujudkan. Kami dengan ringkas mengkaji semula beberapa idea asas dalam pengimejan sinar-X kontras fasa dan kemudiannya menyelidiki penonjolan kontras radiografi yang dapat diperolehi, kegunaan perambatan ruang bebas yang digunakan dan menyelidiki beberapa objek kajian termasuk sampel biologi. Peralatan yang digunakan di Surrey adalah secara relatifnya mudah, mengandungi tiub sinar-X di atas bangku dengan saiz titik fokus dari beberapa mikron hingga 100 mikron dan pengesan CCD 12 bit yang sensitif kepada kedudukan. ABSTRACT Currently, the basis for standard clinical X-ray radiography is absorption, tracking attenuation of radiation when X-ray beams pass through a particular part of the body. The fundamental interaction processes are dependent on variations in the atomic number and density of the target medium; consequentially radiographic contrast can be poor, particularly in regard to soft tissue imaging. Over the past several years considerable interest has been paid to utilising phase properties of the X-ray field to enhance radiographic

The aim of this study was to examine Y3Al5O12:Ce (also known as YAG:Ce) powder scintillator under X-ray imaging conditions. This material shows a very fast scintillation decay time and it has never been used in X-ray medical imaging. In the present study various scintillator layers (screens) with coating thickness ranging from 13 to 166mg/cm2 were prepared in our laboratory by sedimentation of Y3Al5O12: Ce powder. Optical emission spectra and light emission efficiency (spectrum area over X-ray exposure) of the layers were measured under X-ray excitation using X-ray tube voltages (80–120kVp) often employed in general medical radiography and fluoroscopy. Spectral compatibility with various optical photon detectors (photodiodes, photocathodes, charge coupled devices, films) and intrinsic conversion efficiency values were determined using emission spectrum data. In addition, parameters related to X-ray detection, energy absorption efficiency and K-fluorescence characteristic emission were calculated. A theoretical model describing radiation and light transfer through scattering media was used to fit experimental data. Intrinsic conversion efficiency (ηC≈0.03–0.05) and light attenuation coefficients (σ≈26.5cm2/g) were derived through this fitting. Y3Al5O12:Ce showed peak emission in the wavelength range 530–550nm. The light emission efficiency was found to be maximum for the 107mg/cm2 layer. Due to its “green” emission spectrum, Y3Al5O12:Ce showed excellent compatibility (of the order of 0.9) with the sensitivity of many currently used photodetectors. Taking into account its very fast response Y3Al5O12:Ce could be considered for application in X-ray imaging especially in various digital detectors.

In this study Y3Al5O12: Ce powder scintillator was evaluated for use in X-ray imaging detectors. This phosphor, also known as YAG: Ce scintillator or P-46 phosphor, is a non-hygroscopic, emitting green light with very short decay time. These properties are very attractive for X-ray imaging. Y3Al5O12: Ce powder was used to prepare various test screens (33–166 mg/cm2). Absolute luminescence efficiency measurements were performed for various X-ray tube voltages (50–130 kVp). In addition parameters related to image quality such as the modulation transfer function and the detective quantum efficiency were examined. A theoretical model, describing radiation and light transfer, was employed to fit experimental data and to estimate values of optical parameters. Absolute efficiency was found to decrease with X-ray tube voltage. Highest efficiency was obtained for the 107 mg/cm2 screen. Light attenuation coefficients were close to those of green emitting rare earth scintillators. At low spatial frequencies the detective quantum efficiency was high for the 107–166 mg/cm2 screens. The light emission efficiency and imaging performance of Y3Al5O12: Ce was not better than currently employed scintillators. However due to its very fast response and high spectral compatibility to optical sensors it may be considered for use in digital imaging detectors.