abstract：:Measurement of total body nitrogen is assuming increasing importance in the nutritional evaluation of seriously ill patients. Nitrogen has been previously measured either by counting (i) the annihilation radiation from 13N immediately after neutron irradiation with 14 MeV neutrons or (ii) the 'prompt' gamma rays from ...

journal_title：Physics in medicine and biology

authors： Spinks TJ,Goode AW,Ranicar AS,Steere E

更新日期：1984-04-01 00:00:00

abstract：:A technique is described by which the regional distribution of bone mineral can be determined in bone samples from small animals. The technique employs an Anger camera interfaced to a medical computer. High resolution (less than 1 mm) imaging is possible by producing magnified images of the bone samples. Regional dens...

journal_title：Physics in medicine and biology

authors： LeBlanc A,Evans H,Jhingran S,Johnson P

更新日期：1984-01-01 00:00:00

abstract：:Electron depth-dose curves and spectra have been measured from an experimental accelerator on which both energy and spectral shape could be varied independently. The measurements were made at nominal energies of 6 and 12 MeV, with the energy spread (FWHM) varied from 1.7% to over 10% of average energy. Changes in dept...

journal_title：Physics in medicine and biology

authors： Johnsen SW,LaRiviere PD,Tanabe E

更新日期：1983-12-01 00:00:00

abstract：:The biological mechanisms of platelet destruction must be correctly identified before platelet survival curves can be interpreted. This report develops a theory of platelet destruction which is compared with experiments performed on platelets labelled with the radioactive isotope 51Cr. Platelet destruction rate is a c...

journal_title：Physics in medicine and biology

authors： Trowbridge EA,Martin JF

更新日期：1983-12-01 00:00:00

abstract：:It seems likely that long term patency of small bore vascular prostheses is dependent upon, among other things, the mechanical properties of their walls. Arteries are visco-elastic but there is no accurate method of measuring the visco-elasticity of arterial substitutes in vivo. The most successful vascular substitute...

journal_title：Physics in medicine and biology

authors： Chapman BL,Charlesworth D

更新日期：1983-09-01 00:00:00

abstract：:Both inhomogeneity in the main magnetic field and non-linearity in the gradient fields introduce errors in NMR images reconstructed from projections. It is found that the image artefacts caused by these two sources are separable. The inhomogeneous main field blurs the image while the nonlinear gradients distort the im...

journal_title：Physics in medicine and biology

authors： Lai CM

更新日期：1983-08-01 00:00:00

abstract：:A method for the calculation of absorbed dose distributions of arbitrarily shaped electron beams is presented. Isodose distributions and output factors of treatment fields can be predicted with good accuracy, without the need for any dose measurement in the actual field. A Gaussian pencil beam model is employed with t...

journal_title：Physics in medicine and biology

authors： Bruinvis IA,Van Amstel A,Elevelt AJ,Van der Laarse R

更新日期：1983-06-01 00:00:00

abstract：:The use of calibrated tissue-equivalent (TE) ionisation chambers is commonly considered to be the most practical method for total absorbed dose determinations in mixed neutron-photon fields for biomedical applications. The total absorbed dose can be derived from the charge produced within the cavity of an ionisation c...

journal_title：Physics in medicine and biology

authors： Zoetelief J,Broerse JJ

更新日期：1983-05-01 00:00:00

abstract：:The radiofrequency dielectric behaviour of packed human erythrocytes has been investigated in normal haemoglobins F and AA and also abnormal haemoglobins homozygous SS and heterozygous AS. Dielectric measurements were made in tightly packed blood cells at an average room temperature of 26.5 +/- 0.5 degrees C in the fr...

journal_title：Physics in medicine and biology

authors： Laogun AA,Ajayi NO,Okafor LO,Osamo NO

更新日期：1983-04-01 00:00:00

abstract：:In vivo neutron activation analysis was used to measure total body sodium and chlorine in 18 male and 18 female normal adults. Corrections for body size were developed. Normalisation factors were derived which enable the prediction of the normal levels of sodium and chlorine in a subject. The coefficient of variation ...

journal_title：Physics in medicine and biology

authors： Kennedy NS,Eastell R,Smith MA,Tothill P

更新日期：1983-03-01 00:00:00

abstract：:A method is described which offers an alternative to conventional Fourier phase/amplitude imaging for analysing representative LV cycles obtained from first-pass cardiac studies. The method involves applying factor analysis to the data and producing functional images of the first two factor loadings after polar transf...

journal_title：Physics in medicine and biology

authors： Houston AS,Elliott AT,Stone DL

更新日期：1982-10-01 00:00:00

abstract：:Monte Carlo methods have been applied to the study of the performance of antiscatter grids in radiography. Photon histories for imaging with a 20 cm thick water phantom irradiated with an 80 kV x-ray spectrum were generated by Monte Carlo simulation. The scattering and absorption of the photons transmitted from the ph...

journal_title：Physics in medicine and biology

authors： Chan HP,Doi K

更新日期：1982-06-01 00:00:00

abstract：:This work studies the effect of age on lung dose commitments arising from the inhalation of an atmosphere containing radionuclides of varying half-lives and physical sizes. This dependence is significant in many cases, approaching a ratio of 2 in several instances when the maximum dose at a given age is compared with ...

journal_title：Physics in medicine and biology

authors： Crawford DJ

更新日期：1982-04-01 00:00:00

abstract：:The established theory for the collection efficiency of an ionisation chamber irradiated by a series of uniform short pulses is extended to the more complex case of irradiation in a pulsed and electromagnetically swept electron beam. The radial variation of exposure rate is assumed to be Gaussian with scale constant e...

journal_title：Physics in medicine and biology

authors： Boag JW

更新日期：1982-02-01 00:00:00

abstract：:A photoluminescent thermometer, based on the transient emission response of a europium-activated calcium sulphide phosphor, is described in detail. This optical thermometry system has special advantages for temperature measurements in microwave and RF fields and potential application in electromagnetically induced cli...

journal_title：Physics in medicine and biology

authors： Samulski TV,Chopping PT,Haas B

更新日期：1982-01-01 00:00:00

abstract：:A theoretical analysis is presented of the biologically effective dose of the solar long wave ultraviolet radiation (UVA) received by patients who are being treated for psoriasis by oral psoralen photochemotherapy. It is shown that patients treated during the summer months in the UK may well receive a UV dose which is...

journal_title：Physics in medicine and biology

authors： Diffey BL

更新日期：1981-11-01 00:00:00

abstract：:Curves relating beam energy, scattering foil thickness, central-axis depth-dose, and beam flatness have been generated using data taken on a Siemens 200A betatron. The curve set allows a single combination of tungsten foil thickness and electron beam energy to be chosen that will provide the optimum depth-dose distrib...

journal_title：Physics in medicine and biology

authors： Marbach JR,Almond PR

更新日期：1981-05-01 00:00:00

abstract：:A rotary positron-emission computed tomography system has been proposed in which detectors are mounted unequally spaced on a ring, so as to provide fine and uniform linear sampling during a 360 degree rotation of the ring around its centre. The usefulness of a simple iterative method for searching for a suitable arran...

journal_title：Physics in medicine and biology

authors： Yamamoto M

更新日期：1981-05-01 00:00:00

abstract：:The exponential edge-gradient effect must arise in any x-ray transmission CT scanner whenever long sharp edges of high contrast are encountered. The effect is non-linear and is due to the interaction of the exponential law of x-ray attenuation and the finite width of the scanning beam in the x-y plane. The error induc...

journal_title：Physics in medicine and biology

authors： Joseph PM,Spital RD

更新日期：1981-05-01 00:00:00

abstract：:The distribution and transport of Hippuran is discussed. The activity leaving both kidneys has been calculated and compared with the bladder activity. It is shown that the Impulse Response Function of the ureter and bladder may be obtained by deconvolution, and data are presented relating to studies on one patient. ...

journal_title：Physics in medicine and biology

authors： Knesaurek K,Spaventi S

更新日期：1981-03-01 00:00:00

abstract：:The sensitivity and detection limit for measurements of the concentration of cadmium in the kidney cortex of man in vivo have been investigated using the technique of X-ray fluorescence. An 11 GB1 241Am source was used to generate the characteristic K alpha X-rays of cadmium. The variation in the sensitivity for the d...

journal_title：Physics in medicine and biology

authors： Ahlgren L,Mattsson S

更新日期：1981-01-01 00:00:00

abstract：:Geometric and penetration responses of a multihole focusing collimator to a point source have been determined using a digital computer and a ray tracing technique. Results are presented as point and line spread functions for collimated rays and penetrating rays, and as plane sensitivities and modulation transfer funct...

journal_title：Physics in medicine and biology

authors： Jahns MJ

更新日期：1981-01-01 00:00:00

abstract：:The correlation between radiation quality and cellular RBE of a mixed n-gamma field produced by a collimated fast-neutron beam produced by the bombardment of 14 MeV deuterons on Be in a water phantom is investigated. The microdosimetric parameters yF and YD are used for a physical description of the local distribution...

journal_title：Physics in medicine and biology

authors： Booz J,Fidorra J

更新日期：1981-01-01 00:00:00

abstract：:Measurements have been made using an air sampler to measure airborne radioactivity produced during the routine handling of large activities of technetium-99m, iodine-125 and iodine-131. The results indicate that 99Tcm can be safely handled in environments without direct exhaust of the ventilated air but that 125I and ...

journal_title：Physics in medicine and biology

authors： Eadie AS,Horton PW,Hilditch TE

更新日期：1980-11-01 00:00:00

abstract：:A single experimental apparatus has been designed to allow measurements of stopping cross-sections of materials in liquid and vapour phase, for alpha particles, using an indirect method. The method, in which residual energies for increasing absorber thicknesses are obtained and differentiated, has been used in a numbe...

journal_title：Physics in medicine and biology

authors： Thwaites DI

更新日期：1980-09-01 00:00:00

abstract：:Calibration methods are investigated for the determination of bone density by the Compton scattering method. The scattered radiation from materials of different densities and dimensions is measured for this purpose. A function for the dependence of the intensity on these parameters is derived and compared with the exp...

journal_title：Physics in medicine and biology

authors： Leichter I,Weinreb A,Hazan G

更新日期：1980-07-01 00:00:00

abstract：:A two-probe technique has been developed to measure 125I in the thyroid. In this technique simultaneous emissions from a source are detected as coincidence events between two probes rather than as a sum peak in a single probe (the sum peak method). The background count rate when counting coincidence events between pro...

journal_title：Physics in medicine and biology

authors： Burns PA,Peggie JR

更新日期：1980-05-01 00:00:00

abstract：:The total ionisation produced by ions stopped in nitrogen, methane and carbon dioxide has been measured in the energy range 25-375 keV using a chamber described previously. The chamber was operated alternately as a proportional counter and as an ionisation chamber to measure respectively the particle rate and the tota...

journal_title：Physics in medicine and biology

authors： Nguyen VD,Chemtob M,Chary J,Posny F,Parmentier N

更新日期：1980-05-01 00:00:00

abstract：:It was observed that the radiation output of x-ray tubes falls off exponentially during an exposure with a time constant of about 120 ms. The equilibrium value is approximately 15% lower than that at the beginning of the exposure. The clinically noticeable consequences are discrepancies in x-ray generator calibration,...

journal_title：Physics in medicine and biology

authors： Brezovich IA,Barnes GT

更新日期：1980-03-01 00:00:00

abstract：:The poor agreement in the photon calibrations of tissue-equivalent ionisation chambers between different participants in two major neutron dosimetry intercomparisons is noted. The methods of converting measurements made with a calibrated secondary standard exposure meter to the absorbed dose in the wall of a tissue-eq...

journal_title：Physics in medicine and biology

authors： Williams JR,Greening JR

更新日期：1980-03-01 00:00:00

abstract：:A Monte Carlo computer program has been developed for the computation of integral radiation dose to the breast in xeromammography. The results are given in terms of the integral dose per unit area of the breast per unit incident exposure. The calculations have been made for monoenergetic incident photons and the resul...

journal_title：Physics in medicine and biology

authors： Dance DR

更新日期：1980-01-01 00:00:00

abstract：:Fully three-dimensional positron emission tomography is considered and a reconstruction algorithm derived. The reconstruction problem is formulated mathematically as a three-dimensional convolution integral of a point spread function with an unknown positron activity distribution and is solved by Fourier transform met...

journal_title：Physics in medicine and biology

authors： Colsher JG

更新日期：1980-01-01 00:00:00

abstract：:Recent developments in the technique of constant infusion and in emission computed tomography have provided a new method for quantitative regional flow measurements. This paper re-examines critically the theoretical relationship between flow and radioactivity during constant infusion of short-lived isotopes. Sensitivi...

journal_title：Physics in medicine and biology

authors： Huang SC,Phelps ME,Hoffman EJ,Kuhl DE

更新日期：1979-11-01 00:00:00

abstract：:Experimental radiobiological investigations of fast neutron beams involve irradiation of thin cell layers. The irradiation of cells is done either in free air or with a material such as graphite, TE plastic or bone-equivalent plastic covering the cells. This paper discusses the computed dose distributions in LET at sh...

journal_title：Physics in medicine and biology

authors： Bhatia DP,Nagarajan PS

更新日期：1979-09-01 00:00:00

abstract：:Various lead attenuation techniques to determine the fast neutron sensitivity kU of a photon dosemeter are reviewed and a modified method is proposed to determine the kU value of a commercially available Geiger--Müller detector. The dependence on the 'effective' photon energy of the gamma-component of the mixed n--gam...

journal_title：Physics in medicine and biology

authors： Hough JH

更新日期：1979-07-01 00:00:00

abstract：:Dose calculations were performed for a tissue phantom irradiated by uniform circular beams of negative pions with an assumed gaussian momentum distribution. The mean momentum of the pions was varied from 104.4 to 171.5 MeV/c (mean range 5-20 cm in unit-density tissue) and the momentum spread from 0 to 5% of the mean. ...

journal_title：Physics in medicine and biology

authors： Hamm RN,Wright HA,Turner JE

更新日期：1979-05-01 00:00:00

abstract：:A method of computing theoretical X-ray spectra in the range 30-150 kV is presented. The theoretical spectra are compared with constant potential, high resolution spectra from a tungsten target measured with a Ge(Li) detector, for a range of target angles, tube voltage and filtrations. Above 100 kV the spectra were al...

journal_title：Physics in medicine and biology

authors： Birch R,Marshall M

更新日期：1979-05-01 00:00:00

abstract：:Plutonium-239 and americium-241 were administered to adult hamsters in various chemical forms and their absorption from the gut was measured. The results have been compared with published data on other species in order to derive values for the estimated absorption of these actinides in man. On the basis of current kno...

journal_title：Physics in medicine and biology

authors： Stather JW,Harrison JD,Rodwell P,David AJ

更新日期：1979-03-01 00:00:00

abstract：:W (the average energy to form an ion pair) for 5.4 MeV 241Am alpha particles in a Rossi-type tissue-equivalent (TE) gas, argon and methane was determined to an accuracy better than 0.2% using a new automated data handling system. A vibrating reed electrometer and current digitiser were used to measure the current prod...

journal_title：Physics in medicine and biology

authors： Krieger GL,Baum JW,Varma MN,Beach JL

更新日期：1979-03-01 00:00:00

abstract：:Users of nuclear and atomic data for biomedical purposes often have difficulty in identifying the most up-to-date and appropriate sources of such data. The biomedical Subcommittee of the UK Nuclear Data Committee have prepared a list of recommended data sources available at the beginning of 1978 on radioactive decay s...

journal_title：Physics in medicine and biology

authors： Holt PD

更新日期：1979-01-01 00:00:00