Spin warp NMR imaging and applications to human whole-body imaging.

Using the tracer theory of Rescigno, adapted for an open mammillary system, a method is given of finding (1) metabolic rate, (2) ratios of masses of protein in extravascular compartments to mass of protein in intravascular compartment, (3) capillary permeabilities, when 131I-labelled protein is injected into the blood stream of animals. Examples are given for human, rabbit and rat. 0031-9155/04/040001+04$30.00 © 2004 IOP Publishing Ltd Printed in the UK L1 L2 Letter to the Editor Phys. Med. Biol. 25 (July 1980) 751–756 LETTER TO THE EDITOR Spin warp NMR imaging and applications to human whole-body imaging W A Edelstein, J M S Hutchison, G Johnson and T Redpath Dept. of Bio-Medical Phys. & Bio-Engng, Univ. of Aberdeen, Aberdeen, UK Abstract. Describes a new nuclear magnetic resonance (NMR) imaging technique which the authors call ‘spin warp imaging’ and gives examples of its application to human wholebody imaging. The apparatus is based on a four-coil, air cored magnet (made by the Oxford Instrument Company) capable of accepting the whole human body. The magnet produces a static field of 0.04 T giving a proton NMR frequency of 1.7 MHz. The maximum field inhomogeneity is about 6 × 10−4 at a radius of 0.23 m, approximately twice the amount theoretically attainable with this configuration. The pulse sequence used is shown. Phys. Med. Biol. 21 (September 1976) 689–732 REVIEW ARTICLE Principles of computer assisted tomography (CAT) in radiographic and radioisotopic imaging R A Brooks and G Di Chiro Section Neuroradiology, Nat. Inst. of Neurological & Communicative Disorders & Stroke, Bethesda, MD, USA Abstract. Reconstructive tomography is compared with conventional focal plane tomography. Methods of reconstruction-back projection, iterative reconstruction and analytic reconstruction are described. The limitations of present techniques, and new developments and trends are outlined. Phys. Med. Biol. 32 (January 1987) 11–22 Basic mathematical and electromagnetic concepts of the biomagnetic inverse problem J Sarvas Low Temp. Lab., Helsinki Univ. of Technol., Espoo, Finland Abstract. Basic mathematical and physical concepts of the biomagnetic inverse problem are reviewed with some new approaches. The forward problem is discussed for both homogeneous and inhomogeneous media. Geselowitz’s formulae and a surface integral equation are presented to handle a piecewise homogeneous conductor. The special cases of a spherically symmetric conductor and a horizontally layered medium are discussed in detail. The nonuniqueness of the solution of the magnetic inverse problem is discussed and the difficulty caused by the contribution of the electric potential to the magnetic field outside the conductor is studied. As practical methods of solving the inverse problem, a weighted least-squares search with confidence limits and the method of minimum norm estimate are discussed. Phys. Med. Biol. 33 (December 1988) 1433–1442 Estimation of optical pathlength through tissue from direct time of flight measurement D T Delpy, M Cope, P van der Zee, S Arridge, S Wray and J Wyatt Dept. of Med. Phys., Univ. Coll. London, UK Letter to the Editor L3 Abstract. Quantitation of near infrared spectroscopic data in a scattering medium such as tissue requires knowledge of the optical pathlength in the medium. This can now be estimated directly from the time of flight of picosecond length light pulses. Monte Carlo modelling of light pulses in tissue has shown that the mean value of the time dispersed light pulse correlates with the pathlength used in quantitative spectroscopic calculations. This result has been verified in a phantom material. Time of flight measurements of pathlength across the rat head give a pathlength of 5.3 ± 0.3 times the head diameter. Quantitation of near infrared spectroscopic data in a scattering medium such as tissue requires knowledge of the optical pathlength in the medium. This can now be estimated directly from the time of flight of picosecond length light pulses. Monte Carlo modelling of light pulses in tissue has shown that the mean value of the time dispersed light pulse correlates with the pathlength used in quantitative spectroscopic calculations. This result has been verified in a phantom material. Time of flight measurements of pathlength across the rat head give a pathlength of 5.3 ± 0.3 times the head diameter. Phys. Med. Biol. 30 (April 1985) 341–344 TECHNICAL NOTE 1H NMR chemical shift selective (CHESS) imaging A Haase, J Frahm, W Hanicke and D Matthaei Max-Planck-Inst. für Biophys. Chem., Göttingen, West Germany Abstract. 1H NMR images of human or animal tissues reflect the spatial distribution of both water (H2O) and methylene (CH2) proton resonance signals. There are several reasons for a separation of these contributions: (i) the large chemical shift dispersion in high magnetic fields ( 1.5 T) which leads to an apparent spatial shift in ‘composite’ images between the superimposed H2O and CH2 images; (ii) the evaluation and interpretation of proton H2O and CH2 relaxation times from NMR images; and (iii) the physiological implications of ‘water’ and ‘fat’ distributions for medical diagnosis. The authors describe a chemical shift selective (CHESS) imaging technique which destroys the unwanted signal component by means of a selective 90 degrees excitation pulse and a subsequent magnetic field gradient (‘homogeneity spoiling gradient’) prior to imaging of the wanted component. The new method allows the creation of either a pure ‘water’ or ‘fat’ image. Phys. Med. Biol. 18 (January 1973) 78–87 A molecular theory of cell survival K H Chadwick and H P Leenhouts Euration ITAL, Wageningen, The Netherlands Abstract. A theory is presented to explain the effect of radiation on cell survival. Phys. Med. Biol. 32 (August 1987) 933–970 REVIEW ARTICLE The passive electrical properties of biological systems: their significance in physiology, biophysics and biotechnology R Pethig and D B Kell Inst. of Molecular & Biomolecular Electron., Univ. Coll. of North Wales, Bangor, UK Abstract. The following topics are discussed: a summary of dielectric theory; amino acids, peptides, proteins and DNA; bound water in biological systems; biological electrolytes; membranes and cells; tissues. L4 Letter to the Editor Phys. Med. Biol. 37 (August 1992) 1637–1655 Physical performance of a positron tomograph for brain imaging with retractable septa T J Spinks, T Jones, D L Bailey, D W Townsend, S Grootoonk, P M Bloomfield, M-C Gilardi, M E Casey, B Sipe and J Reed MRC Cyclotron Univ., Hammersmith Hosp., London, UK Abstract. Performance characteristics of a new design of positron tomograph with automatically retractable septa for brain imaging have been studied. The device, consisting of block BGO detectors (8 × 8 elements per block), has a ring diameter of 76 cm and an axial FOV of 106.5 mm. The in-plane resolution is on average 5.8 mm and 5.0 mm (FWHM) for stationary and wobble sampling, respectively, over the central 18 cm of the transaxial FOV. Its unique feature is the capability of data acquisition both in the ‘conventional’ 2D mode (with septa) or 3D mode (septa retracted) where coincidences between any of the 16 detector rings are acquired. In spite of the increase in scatter when septa are retracted, the increased efficiency in the 3D mode of acquisition yields distinct advantages, particularly in the many studies where tracer concentration is low and consequently where dead time and random rates are less important. Phys. Med. Biol. 26 (May 1981) 445–459 Electron beam dose calculations K R Hogstrom, M D Mills and P R Almond Dept. of Phys., Univ. of Texas System Cancer Center, Houston, TX, USA Abstract. Electron beam dose distributions in the presence of inhomogeneous tissue are calculated by an algorithm that sums the dose distribution of individual pencil beams. The off-axis dependence of the pencil beam dose distribution is described by the Fermi–Eyges theory of thick-target multiple Coulomb scattering. Measured square-field depth-dose data serve as input for the calculations. Air gap corrections are incorporated and use data from ‘in-air’ measurements in the penumbra of the beam. The effective depth, used to evaluate depth-dose, and the sigma of the off-axis Gaussian spread against depth are calculated by recursion relations from a CT data matrix for the material underlying individual pencil beams. The correlation of CT number with relative linear stopping power and relative linear scattering power for various tissues is shown. The results of calculations are verified by comparison with measurements in a 17 MeV electron beam from the Therac 20 linear accelerator. Calculated isodose lines agree nominally to within 2 mm of measurements in a water phantom. Similar agreement is observed in cork slabs simulating lung. Calculations beneath a bone substitute illustrate a weakness in the calculation. Finally a case of carcinoma in the maxillary antrum is studied. The theory suggests an alternative method for the calculation of depth-dose of rectangular fields. Michael S Patterson, Juravinski Cancer Centre and McMaster University, 699 Concession Street, Hamilton, Ontario, Canada L8V 5C2