Source-detector Distance Research Articles

Multi-distance frequency-domain optical measurements of coherent cerebral hemodynamics.

We report non-invasive, bilateral optical measurements on the forehead of five healthy human subjects, of 0.1 Hz oscillatory hemodynamics elicited either by cyclic inflation of pneumatic thigh cuffs, or by paced breathing. Optical intensity and the phase of photon-density waves were collected with frequency-domain near-infrared spectroscopy at seven source-detector distances (11-40 mm). Coherent hemodynamic oscillations are represented by phasors of oxyhemoglobin (O) and deoxyhemoglobin (D) concentrations, and by the vector D/O that represents the amplitude ratio and phase difference of D and O. We found that, on average, the amplitude ratio (|D/O|) and the phase difference (∠(D/O)) obtained with single-distance intensity at 11-40 mm increase from 0.1 and −330°, to 0.2 and −200°, respectively. Single-distance phase and the intensity slope featured a weaker dependence on source-detector separation, and yielded |D/O| and ∠(D/O) values of about 0.5 and −200°, respectively, at distances greater than 20 mm. The key findings are: (1) single-distance phase and intensity slope are sensitive to deeper tissue compared to single-distance intensity; (2) deeper tissue hemodynamic oscillations, which more closely represent the brain, feature D and O phasors that are consistent with a greater relative flow-to-volume contributions in brain tissue compared to extracerebral, superficial tissue.

335. Uncertainty in quantification of cumulative activity in bone metastasis dosimetry with 223Ra

Purpose Ra-223 therapy of prostate cancer bone metastases is being used to treat patients routinely. Accurate activity quantification through imaging is essential to calculate the absorbed dose in organs and sub-units in radiopharmaceutical therapy, enabling personalized absorbed dose-based treatment planning methodologies and more effective and optimal treatments. This work was aimed to estimate the error in quantifying cumulated activity in simulated case applying specific SPECT calibration procedure [1] , [2] . Methods Calibrations with Ra-223 were performed with the SPECT/CT Infinia Hawkeye 4 GE (3/8-inch crystal) acquiring planar static images with double-peak (82 and 154 keV, 20% wide) and MEGP collimator. The sensitivity was measured in air by varying activity, source–detector distance, and source diameter. Acquisition times were 10 min. Transmission curves were measured for attenuation and scatter correction with the pseudo-extrapolation number method. A real case has been simulated placing on the source a bone equivalent material and PMMA thickness simulating human condition. Results The calibration factors is 63.4 cps/MBq. The table attenuation affects less than 11.5%. Sensitivity values for each head varies by 0.4% respect to the mean value with the source-detector distance and the activity. The effect of the partial volume decreases the calibration factor of the smaller source by 10%. The quantified activity in the real case differs by less than 15% respect to the measured activity. Conclusions The calibration factor found is higher than the literature value (45.7 cps/MBq [2] ). This result and the variation of the sensibility factor with source and acquisition setup stress the needed to characterize the system to perform a proper dosimetry estimation for any SPECT scanner. The error in determining the cumulated activity is less than 15%. Further studies including variation in source depth and acquisition time are needed to confirm these results including analysis in anthropomorphic phantom or human.

Depth dependence of coherent hemodynamics in the human head.

We report a near-infrared spectroscopy (NIRS) study of coherent hemodynamic oscillations measured on the human forehead at multiple source-detector distances (1 to 4cm). The physiological source of the coherent hemodynamics is arterial blood pressure oscillations at a frequency of 0.1Hz, induced by cyclic inflation (to a pressure of 200mmHg) and deflation of two thigh cuffs wrapped around the subject's thighs. To interpret our results, we use a recently developed hemodynamic model and a phasor representation of the oscillations of oxyhemoglobin, deoxyhemoglobin, and total hemoglobin concentrations in the tissue (phasors O, D, and T, respectively). The increase in the phase angle between D and O at larger source-detector separations is assigned to greater flow versus volume contributions and to a stronger blood flow autoregulation in deeper tissue (brain cortex) with respect to superficial tissue (scalp and skull). The relatively constant phase lag of T versus arterial blood pressure oscillations at all source-detector distances was assigned to competing effects from stronger autoregulation and smaller arterial-to-venous contributions in deeper tissue with respect to superficial tissue. We demonstrate the application of a hemodynamic model to interpret coherent hemodynamics measured with NIRS and to assess the different nature of shallow (extracerebral) versus deep (cerebral) tissue hemodynamics.

Toward complete oral cavity cancer resection using a handheld diffuse reflectance spectroscopy probe.

This ex-vivo study evaluates the feasibility of diffuse reflectance spectroscopy (DRS) for discriminating tumor from healthy tissue, with the aim to develop a technology that can assess resection margins for the presence of tumor cells during oral cavity cancer surgery. Diffuse reflectance spectra were acquired on fresh surgical specimens from 28 patients with oral cavity squamous cell carcinoma. The spectra (400 to 1600nm) were detected after illuminating tissue with a source fiber at 0.3-, 0.7-, 1.0-, and 2.0-mm distances from a detection fiber, obtaining spectral information from different sampling depths. The spectra were correlated with histopathology. A total of 76 spectra were obtained from tumor tissue and 110 spectra from healthy muscle tissue. The first- and second-order derivatives of the spectra were calculated and a classification algorithm was developed using fivefold cross validation with a linear support vector machine. The best results were obtained by the reflectance measured with a 1-mm source-detector distance (sensitivity, specificity, and accuracy are 89%, 82%, and 86%, respectively). DRS can accurately discriminate tumor from healthy tissue in an ex-vivo setting using a 1-mm source-detector distance. Accurate validation methods are warranted for larger sampling depths to allow for guidance during oral cavity cancer excision.

Monte Carlo modeling of a holder for irradiation of dosimeters in beta radiation beams

A study of the influence of a dosimetric holder and its cover for the irradiation of the dosimeters in the Beta Secondary Standard BSS2 radiation fields is reported. The correction factors for attenuation or scattering were calculated taking into account the BSS2 beta source energy, as well as the detector source distance. The study and the determination of these factors were carried out using the Monte Carlo Method. The results of the correction factors showed that the absorption and scattering of the electrons depend greatly on the energy of beta radionuclides. The determined correction factors are in agreement with the international report ISO 6980.

Instrumental, optical and geometrical parameters affecting time-gated diffuse optical measurements: a systematic study.

In time-domain diffuse optics the sensitivity to localized absorption changes buried inside a diffusive medium depends strongly on the interplay between instrumental, optical and geometrical parameters, which can hinder the theoretical advantages of novel measurement strategies like the short source-detector distance approach. Here, we present a study based on experimental measurements and simulations to comprehensively evaluate the effect of all different parameters. Results are evaluated exploiting standardized figures of merit, like contrast and contrast-to-noise ratio, to quantify the system sensitivity to deep localized absorption perturbations. Key findings show that the most critical hardware parameter is the memory effect which ultimately limits the dynamic range. Further, a choice of the source-detector distance around 10 mm seems to be a good compromise to compensate non-idealities in practical systems still preserving the advantages of short distances. This work provides both indications for users about the best measurement conditions and strategies, and for technology developers to identify the most crucial hardware features in view of next generation diffuse optics systems.

Quantitative subsurface imaging in strongly scattering media.

We present a method to obtain quantitatively accurate images of small obstacles or inhomogeneities situated near the surface of a strongly scattering medium. The method uses time-resolved measurements of backscattered light to form the images. Using the asymptotic solution of the radiative transfer equation for this problem, we determine that the key information content in measurements is modeled by a diffusion approximation that is valid for small source-detector distances, and shallow penetration depths. We simplify this model further by linearizing the effect of the inhomogeneities about the known background optical properties using the Born approximation. The resulting model is used in a two-stage imaging algorithm. First, the spatial location of the inhomogeneities are determined using a modification of the multiple signal classification (MUSIC) method. Using those results, we then determine the quantitative values of the inhomogeneities through a least-squares approximation. We find that this two-stage method is most effective for reconstructing a sequence of one-dimensional images along the penetration depth corresponding to null source-detector separations rather than simultaneously using measurements over several source-detector distances. This method is limited to penetration depths and distances between boundary measurements on the order of the scattering mean-free path.

Deficit in selective attention in children with hypoxic-ischaemic encephalopathy

The nuclear spectroscopy method has long been used for advanced studies on nuclear physics. In order to decrease costs and increase the efficiency of nuclear radiation investigations, quick and efficient solutions are required. The purpose of this research was to calculate the whole energy peak efficiency values for a range of gamma-ray energies, from 30.973 keV to 1408 keV, at various source-detector distances using the MCNPX Monte Carlo code, which is extensively used in nuclear medicine, industry, and scientific research. As a result, the modeled detectors' full-energy peak efficiencies were calculated and compared to both experimental data and Monte Carlo simulations. Experiment results and prior studies using Monte Carlo simulations were found to be very consistent with these results. The counting efficiency against source-detector distance is then calculated using the modeled detectors. The data we have show that LaBr3(Ce) has outstanding detection properties. This study’s findings might be used to improve the design of detectors for use in wide range of high-tech gamma spectroscopy and nuclear research applications.

Efficiency response of an aged PIPS detector used in high-resolution alpha-particle spectrometry

The experimental characterization of an aged PIPS detector used in an alpha-particle spectrometry is performed using a standard mixed source of 238U, 234U, 239Pu, and 241Am. The variations in the detector efficiency and resolution (FWHM) at the main energy lines of the 238U, 234U, 239Pu and 241Am source were investigated at all possible source–detector distances under chamber air pressure of ∼ 1.33 Pa. Finding shows that on average, the counting efficiency data obtained from measurements are lower than those obtained by theoretical data and Monte Carlo simulation (SOLANG and AASI) methods. A combination of polymeric strippable coating and both traditional wiping and cleaning method for the detector decontamination works only show a significant reduction in the background activity. The counting efficiency improvement process by an increase of the higher voltages within the recommended range results in a good agreement in the counting efficiency comparison and a slight decrease of the detector dead layer thickness. Novel method to evaluate the dead layer thickness for PIPS detector via the variations in experimental energy loss with respect source to detector distance using alpha standard sources of 242Pu has been proposed. This method can help to predict a default dead layer thickness value which will be as close as it was originally, is less than 50 nm from the manufacturer.

I006] How to calibrate gamma camera for 223Ra Dosimetry

Purpose The purpose of this study was to calibrate different gamma cameras in the framework of a multicentre research for lesion dosimetry in 223Ra therapy of bone metastases. Equipment of several manufacturers and different models were available. Moreover, differences in gamma camera calibration procedures into activity quantification were explored. Methods Eleven gamma cameras of different crystal thickness (3/8- and 5/8-inches) were used, acquiring planar static images with double-peak windows (at 82 and 154 keV, 20% wide) and a MEGP collimator in all cases. Sensitivity was measured in air, varying the activity, the source-detector distance and the diameter of the source. Transmission curves were measured, calculating the parameters used for attenuation/scatter correction with the pseudo-extrapolation number method, and assessing their variations with the source size. Results The values of the calibration factors (considering the geometric mean of both detector sensitivities) ranged from 41 to 114 cps/MBq. For the smallest source (diameter of 3.5 cm), the calibration factor decrease ranged from 30% to 4%, highlighting the importance of partial volume effect according to the equipment involved. Partial volume effects were negligible for an object area of 960 mm2. The sensitivity was nearly constant varying activity and distance, and its variation with the source-detector distance, with respect to the 15 cm-value, reached 10% (in absolute value) in the range of 5–30 cm. Fixing the distance between the two heads, the calibration factor variation with the distance from the midline was within 3.6%. Examining the results obtained with six gamma cameras, appreciable variation of the transmission curves with the source size and experimental setup were observed, leading to activity quantification errors up to 20%. Conclusion The calibration protocol that should be regularly implemented for Ra22 acquisitions requires sensitivity and transmission curve measurements varying the source size, and performing a careful procedure of standardisation. The results of this study represent a compendium useful for dosimetric purposes.

P056] Dose distribution from computed tomograghy in anthropomorphic phantom using gafchromic XR-QA2 AND TLD100H

Purpose The Directive 2013/59/Euratom, in the transposition phase, pays particular attention to the radioprotection of the patients and therefore to the absorbed doses evaluation by diagnostic phases. In Computed Tomography (CT), this evaluation is closely linked to the CTDI calculation in homogeneous phantom. Aim of this work is to make an assessment of the dose distribution inside the organs with an anthropomorphic Rando phantom in CT, through the use of Gafchromic™XR-QA2 and TLD100H. Methods Dose mapping were obtained by using Gafchromic™XR-QA2 film and individual TLD100H dosimeters included in RANDO® Woman anthropomorphic phantom by Computed Tomography. Luminescence emissions from TLD100H, were carried out with low constant heating rate of 1 K/s and 513.15 K maximum temperature using a Riso TL/OSL-DA-10 reader. For thermoluminescence intensity evaluation a theoretical glow curve fitting, using the General-Order kinetics (GOK) expressions was applied to experimental glow curves. Gafchromic™XR-QA2 film dosimetry were digitized with Epson 10000 XL with the pixel-to-pixel veil subtraction method. For calibration curve, both for the film and for the TLD, irradiation was delivered with an X-ray tube (Samsung GC 80) in following experimental conditions: ΔV = 140 kVp, source-detector distance (SDD) = 60 cm, 10 × 10 cm2 open field. The dosimeters was placed on 30 × 30 × 10 cm3 of RW3. Calibration of the X-ray tube was done in terms of radiation output (mGy/mAs), using a Multi-Purpose Detector (MPD). Delivered doses were in the range between 0 and 100 mGy. Results A dose distribution between about 10 mGy and 30 mGy was obtained both with gafcromic film and TLDs. While in the pulmonary areas a good homogeneity of dose distribution was found. Along the sagittal sternal axis, a dose gradient was observed, especially in the area of the medulla, where dose distribution reached minimum levels. TLD and Gafchromic dose measured discrepancy was of 5% −20%. Conclusion Dose gradients found in the particular area such as the sternal/ mammary area and the medullary area are the starting point for a deepening and a critical treatment to the CDTI index until now used.

P153] A comparison of different dosimetry systems for surface and buildup region dose measurements

Purpose In this study, the surface doses obtained by optically stimulated luminescence (OSL), thermoluminescence (TLD) and markus parallel plane ion chamber were compared with TPS results and the availability of the systems in surface dosimetry was investigated. Methods The percentage depth dose (PDD) measurements of buildup region were made by TLD, OSL and markus pp ion chamber, at the surface, 1, 2, 5, 10 and 15 mm water equivalent depth at 100 cm source-detector distance for 5×5, 10×10, and 20×20 cm 2 field sizes.DD values were measured at the depth of 0.07 mm, which was suggested for surface dose measurements by ICRU Report 39. The effective measurement depth of each dosimeter was taken into account. The water equivalent thickness (WET) was considered to make an accurate comparison. Interpolations and extrapolations were performed for all systems to obtain the doses at the same depths. Under the same conditions, surface doses were calculated by TPS for different field sizes and were recorded. The buildup region doses measured by different dosimetry systems and calculated by TPS were compared for different field sizes. Results The overdoses occured in the buildup region were corrected for Markus chamber according to Gerbi’s method. The surface doses using 6 MV photon beams for 5×5, 10×10, and 20×20 cm 2 field sizes at 0.07 mm were found to be 14%, 24.75%, 13.17%, 7.74%; 19.69%, 31.78%, 21.63%, 11.04%; 30.87%, 43.80%, 28.71%, 13.61% for Markus chamber, TLD, OSL and TPS, respectively. Conclusions The lowest build-up region PDD values in all field sizes were obtained with the TPS. At 0.07 mm water equivalent depth, while the OSL and Markus pp. ion chamber results are close to each other, TLD results are higher in all field sizes. However, it is seen that the TLD gives closer results to Markus pp. ion chamber than OSL after 3 mm depth in all field sizes.

Using a simulation approach to optimize time-domain diffuse correlation spectroscopy measurement on human head.

Time-domain diffuse correlation spectroscopy (TD-DCS) has been recently proposed to improve detection of deep blood flow dynamics in a biological tissue, such as human brain. To obtain a high sensitive measurement, several experimental parameters such as the source-detector (SD) distance, gate opening time, and width need to be considered and optimized. We use a simulation approach to optimize these parameters based on Monte Carlo computations using a realistic human head model. Two cortical regions are investigated including the frontal and temporal lobes. SD distance ranging from 0 to 45mm, gate opening time from 400 to 1000ps, and gate width from 50 to 3000ps are considered. The goal is to find out the optimal combinations of these parameters by which the higher contrast measurement on the cortical dynamics can be achieved. The simulations show that with an acceptable input power of light, the combinations of SD distance ranging from 0 to 15mm, gate opening time at 700 to 800ps, and gate width of 800ps are optimal for achieving higher contrast measurement on the cortical dynamics. The simulation approach and results are helpful for the optimization of TD-DCS experimental design focused on brain functional detection.

Assessment of tomato soluble solids content and pH by spatially-resolved and conventional Vis/NIR spectroscopy

Spatially-resolved spectroscopy (SRS) enables better interrogation of tissue properties at different depths, and it thus has the potential for enhancing quality assessment of horticultural products like tomato, which are heterogeneous in structure and chemical composition. This research was aimed at assessing quality of tomato fruit by using a newly developed SRS system with 30 detection optic fibers covering the wavelength range of 550–1650 nm and comparing its performance with two conventional single-point (SP) spectroscopic instruments covering the visible and shortwave near-infrared (Vis/SWNIR) (400–1100 nm) and near-infrared (NIR) (900–1300 nm) regions, respectively. Spatially-resolved (SR) spectra and SP interactance spectra were acquired for 600 ‘Sun Bright’ tomato fruit. Partial least squares (PLS) models for individual SR spectra and their combinations and for SP Vis/SWNIR and NIR spectra were developed for prediction of soluble solids content (SSC) and pH. Results showed that SSC and pH predictions by SRS varied depending on the light source-detector distance, with the correlation coefficient of prediction (rp) ranging 0.608–0.791 and 0.688–0.800, respectively. Combinations of two or more SR spectra resulted in better, more consistent SSC and pH predictions. SR predictions of pH (rp = 0.819) were better than for SP Vis/SWNIR (rp = 0.743) and NIR (rp = 0.741) predictions, whereas SR predictions of SSC (rp = 0.800) were comparable to SP NIR predictions (rp = 0.810) but better than SP Vis/SWNIR predictions (rp = 0.729). This research showed that owning to its ability of acquiring spatially-resolved spectral information, the SRS technique has advantages over conventional SP spectroscopy for enhancing quality assessment of tomatoes.

Voxel-based measurement sensitivity of spatially resolved near-infrared spectroscopy in layered tissues.

We quantitatively investigated the measurement sensitivity of spatially resolved spectroscopy (SRS) across six tissue models: cerebral tissue, a small animal brain, the forehead of a fetus, an adult brain, forearm muscle, and thigh muscle. The optical path length in the voxel of the model was analyzed using Monte Carlo simulations. It was found that the measurement sensitivity can be represented as the product of the change in the absorption coefficient and the difference in optical path length in two states with different source-detector distances. The results clarified the sensitivity ratio between the surface layer and the deep layer at each source-detector distance for each model and identified changes in the deep measurement area when one of the detectors was close to the light source. A comparison was made with the results from continuous-wave spectroscopy. The study also identified measurement challenges that arise when the surface layer is inhomogeneous. Findings on the measurement sensitivity of SRS at each voxel and in each layer can support the correct interpretation of measured values when near-infrared oximetry or functional near-infrared spectroscopy is used to investigate different tissue structures.

Prediction of tomato firmness using spatially-resolved spectroscopy

This paper reports on evaluating the firmness of tomato fruit using a newly developed spatially-resolved spectroscopy (SRS) system with an illumination optic fiber and 30 detection optic fibers arranged at the source-detector distances of 1.5–36 mm. Spatially-resolved (SR) spectra of 550–1650 nm were acquired for 600 ‘Sun Bright’ tomatoes at six maturity stages. The firmness of tomatoes was measured using acoustic/impact, compression and puncture tests. Partial least squares (PLS) models for individual SR spectra and their combinations were developed to determine optimal prediction models for the firmness parameters. The results indicated that firmness predictions varied with the light source-detector distance or SR spectra, and the optimal single spectrum was different for prediction of different firmness parameters. Those spectra acquired for the light source-detector distances of 6–24 mm resulted in better prediction results. Combinations of SR spectra gave consistently better predictions for the multiple firmness parameters than the optimal single SR spectra, with the correlation coefficients (rp) of 0.760 and 0.911 for acoustic and impact measurement, rp = 0.935 for compression, and rp = 0.917, 0.948 and 0.859 for puncture maximum force, slope and flesh firmness. Overall, the SRS technique gave excellent predictions of firmness parameters for impact, compression and puncture tests that measured the local properties of tomato tissues, and combinations of SR spectra improved prediction results.

Prefrontal hemodynamic changes measured using near-infrared spectroscopy during the Valsalva maneuver in patients with orthostatic intolerance.

The Valsalva maneuver (VM) with beat-to-beat blood pressure and heart rate monitoring are used to evaluate orthostatic intolerance (OI). However, they lack the ability to detect cerebral hemodynamic changes, which may be a cause of OI symptoms. Therefore, we utilized near-infrared spectroscopy during VM. Patients with OI symptoms and normal healthy subjects were recruited. Patients were subgrouped according to VM results: patients with normal VM (NVM) and abnormal VM (AbVM). Oxyhemoglobin (HbO), deoxyhemoglobin, and total hemoglobin changes were measured at four different source-detector distances (SD) (15, 30, 36, and 45mm), and latency, amplitude, duration, and integrated total signal were calculated. Those parameters were compared between a normal healthy control (HC) group and the two OI patient subgroups. We found that HbO increment latency at 30-mm SD in the HC, NVM, and AbVM groups was as follows: [Formula: see text], [Formula: see text], and [Formula: see text], respectively ([Formula: see text]). Among the four parameters we evaluated, latency of HbO increment was the best marker for differentiating OI.

Investigation of Confounding Factors in Measuring Tissue Saturation with NIRS Spatially Resolved Spectroscopy.

Performing absolute measurements of tissue saturation of the brain with near-infrared spectroscopy (NIRS) is a clinically desirable brain monitoring tool. Tissue oxygenation index (TOI) is an indicator of absolute tissue mixed arterial and venous oxygen saturation, and can be calculated using a NIRS technique called spatially resolved spectroscopy (SRS). SRS instruments measure the change of light attenuation with distance by using multiple light source-detector distances at two or more wavelengths. The aim of the study is to use broadband NIRS SRS data to investigate the effects on the calculation of TOI of different parameters: wavelength selection, scattering dependence, source-detector distance, and resolving for water. In total, 55 neonates with hypoxic-ischemic encephalopathy were monitored using a broadband multi-distance continuous wave NIRS system; 172 datasets were recorded. Using a “Standard” approach, TOI values between 0 and 100% (“good”) were calculated in 157/172 datasets with a mean TOI of 50%. By changing the wavelength selection, the number of “good” data sets increases to 165/172 with a mean of 60%. Alteration of the dependence of scattering on wavelength acts as a constant which shifts the absolute value of TOI significantly (p < 0.05), demonstrating the importance of having a subject-appropriate estimation of scattering dependence. In general, changing the combination of source-detector distances does not significantly alter the TOI (the mean TOI ranges from 41% to 53%) which suggests that the algorithm is robust to different source-detector combinations. The study shows the broadband NIRS SRS algorithm gives the opportunity to explore the calculation of TOI and could further improve the measurement of tissue saturation in a clinical setting.

Evaluation of Dosimetic Characteristics of Electronic Portal Imaging Device (EPID) for Flattening Filter Free (FFF) Beams

Objective: To evaluatethe dosimetric characteristics of electronics portal imaging device (EPID) for 6 and 10 megavoltage(MV) of flattening filter-free (FFF) beams.Material and Method: The EPID characteristicsfor FFF beams have been evaluated as follows; saturation with sourcedetector-distance (SDD), saturation with dose rate, dose linearity response with monitor unit (MU), and the scatterd radiation with field size.Results: The saturation of signal was not occurred at 150 cm and 180 cm SDD for 6 and 10 MV of FFF beams, respectively. When the signals were measured with optimal SSD according to vendor suggestion (150 cm and 180 cm), the standard deviation for all dose rate were ±1.35 and ±1.64 CU for 6 and 10 MV of FFF beams,respectively. The dose linearity response showed that EPID has a good linearity response between signals and MU forthe both of 6 and 10 MV of FFF beams. The results of scatterd radiation with field size were found that FFF beams have different respose from flattening filter (FF) beams with the highest differences of 5.50% and 6.78% for 6 and 10 MV of FFF beams, respectively.Conclusion: EPID has a good characteristic for FFF beams, and an extended SSD can be used to reduce the satured signal effects in FFF beams.

Hard X-ray dosimetry of a plasma focus suitable for industrial radiography

Dosimetric measurements of the hard X-ray emission by a small-chamber 4.7kJ Mather-type plasma focus device capable of producing neat radiographs of metallic objects, were carried out with a set of thermoluminescent detectors TLD 700 (LiF:Mg,Ti). Measurements of the hard X-ray dose dependence with the angular position relative to the electrodes axis, are presented. The source-detector distance was changed in the range from 50 to 100cm, and the angular positions were explored between ± 70°, relative to the symmetry axis of the electrodes. On-axis measurements show that the X-ray intensity is uniform within a half aperture angle of 6°, in which the source delivers an average dose of (1.5 ± 0.1)mGy/sr per shot. Monte Carlo calculations suggest that the energy of the electron beam responsible for the X-ray emission ranges 100–600keV.