Abstract：
:A radiofrequency and field-gradient pulse sequence is presented permitting the non-invasive, volume-selective and spectroscopically resolved determination of incoherent transport parameters with the aid of an NMR field-gradient method. With proton NMR, diffusion or (quasi-incoherent) perfusion coefficients as low as 10(-12) m2 s-1 are accessible with gradients G less than or equal to 100 mT m-1 for T2 greater than or equal to 0.3 s. If coherent motions like flow are superimposed, the gradient pulses can be compensated for phase shifts arising from uniform or accelerated motions. The efficiency of the suppression of the influence of coherent motions was demonstrated in test experiments with phantom sample arrangements. As a biophysical application, the local diffusion coefficients D and relaxation times T1 and T2 of hen eggs were studied during the first days of incubation. In the yolk, strongly non-exponential decay curves were observed for the CH2 line. The translational displacements of water were found to be restricted. The relaxation and diffusion parameters turned out to be constant during the incubation. Medical applications of the pulse sequences are discussed. In one case we demonstrate that attempts to assign resonance lines can be checked by the condition that resonances of the same compound must have identical diffusion coefficients.
journal_name
Phys Med Bioljournal_title
Physics in medicine and biologyauthors
Klammler F,Kimmich Rdoi
10.1088/0031-9155/35/1/007subject
Has Abstractpub_date
1990-01-01 00:00:00pages
67-79issue
1eissn
0031-9155issn
1361-6560journal_volume
35pub_type
杂志文章abstract：:The purpose of this study was to determine the performance of a single lutetium oxy-orthosilicate (LSO) crystal layer High Resolution Research Tomograph (HRRT) positron emission tomography (PET) scanner. The HRRT is a high resolution PET scanner designed for human brain and small animal imaging. The scanner consists o...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/48/4/302
更新日期：2003-02-21 00:00:00
abstract：:Physical properties of a position-sensitive camera for the analysis of biodistributions of gamma- and beta-emitting radiopharmaceuticals in small animals have been studied, in order to achieve optimal operating conditions. The camera consisted of a highly segmented yttrium-aluminate perovskite (YAP) scintillator, coup...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/50/3/n01
更新日期：2005-02-07 00:00:00
abstract：:Segmentation of liver in abdominal computed tomography (CT) is an important step for radiation therapy planning of hepatocellular carcinoma. Practically, a fully automatic segmentation of liver remains challenging because of low soft tissue contrast between liver and its surrounding organs, and its highly deformable s...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/1361-6560/aabd19
更新日期：2018-05-04 00:00:00
abstract：:Sparse-view CT reconstruction algorithms via total variation (TV) optimize the data iteratively on the basis of a noise- and artifact-reducing model, resulting in significant radiation dose reduction while maintaining image quality. However, the piecewise constant assumption of TV minimization often leads to the appea...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/59/12/2997
更新日期：2014-06-21 00:00:00
abstract：:We have numerically modelled the thermal effects of yellow (577 or 578 nm) light illumination on the ectatic blood vessels of port wine stains. We investigated the effect of the laser treatment parameters of light irradiance and illumination time on the extent of coagulation (coagulation thickness) of the endothelial ...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/34/9/010
更新日期：1989-09-01 00:00:00
abstract：:Many of the inadequacies of the system presently used for surveying environments containing penetrating radiation stem from the impossibility of defining a radiation parameter which is additive, measurable and closely related to peak dose equivalent in the body. Many of the present conceptual difficulties would be eli...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/20/6/012
更新日期：1975-11-01 00:00:00
abstract：:Coronary flow rate remains complex to assess in clinical practice using non-invasive, non-ionizing imaging tools. In this study, we introduce 3D ultrafast Doppler coronary angiography (3D UDCA), an ultrasound-based method to assess coronary blood flows in three-dimensions at high volume-rate and in one single heartbea...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/1361-6560/ab8d78
更新日期：2020-06-05 00:00:00
abstract：:The purpose of this paper is to evaluate the ability of a prototype Compton camera (CC) to measure prompt gamma rays (PG) emitted during delivery of clinical proton pencil beams for prompt gamma imaging (PGI) as a means of providing in vivo verification of the delivered proton radiotherapy beams. A water phantom was i...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/60/18/7085
更新日期：2015-09-21 00:00:00
abstract：:The optical properties (absorption and scattering coefficients and the scattering anisotropy factor) were measured in vitro for cartilage, liver, lung, muscle, myocardium, skin, and tumour (colon adenocarcinoma CC 531) at 630, 632.8, 790, 850 and 1064 nm. Rabbits, rats, piglets, goats, and dogs were used to obtain the...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/42/11/017
更新日期：1997-11-01 00:00:00
abstract：:In this paper we present the results of a dosimetric evaluation of a 2D ionization chamber array with the objective of its implementation for quality assurance in clinical routine. The pixel ionization chamber MatriXX (Scanditronix Wellhofer, Germany) consists of 32x32 chambers with a distance of 7.6 mm between chambe...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/52/4/023
更新日期：2007-02-21 00:00:00
abstract：:Recent acute shortage of medical radioisotopes prompted investigations into alternative methods of production and the use of a cyclotron and ¹⁰⁰Mo(p,2n)(99m)Tc reaction has been considered. In this context, the production yields of (99m)Tc and various other radioactive and stable isotopes which will be created in the ...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/56/17/002
更新日期：2011-09-07 00:00:00
abstract：:Backscatter factors for orthovoltage x-ray beams are fitted with the expression BSF = 1 + ms/(s + n), where s is field size and m and n are adjustable parameters. The accuracy is better than 0.5%. Good results were also obtained for Cs-137 gamma rays at depth 0.12 cm and Co-60 gamma rays at depth 0.5 cm using the same...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/43/5/021
更新日期：1998-05-01 00:00:00
abstract：:Magnetic resonance and ultrasound elastography techniques are now important tools for staging high-grade fibrosis in patients with chronic liver disease. However, uncertainty remains about the effects of simple accumulation of fat (steatosis) and inflammation (steatohepatitis) on the parameters that can be measured us...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/1361-6560/aac09a
更新日期：2018-05-17 00:00:00
abstract：:We present a new version of STIR (Software for Tomographic Image Reconstruction), an open source object-oriented library implemented in C++ for 3D positron emission tomography reconstruction. This library has been designed such that it can be used for many algorithms and scanner geometries, while being portable to var...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/57/4/867
更新日期：2012-02-21 00:00:00
abstract：:Iterative image reconstruction algorithms have the potential to produce low noise images. Early stopping of the iteration process is problematic because some features of the image may converge slowly. On the other hand, there may be noise build-up with increased number of iterations. Therefore, we examined the stabili...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/49/20/004
更新日期：2004-10-21 00:00:00
abstract：:A significant timer error has been found on a linear accelerator used for intraoperative radiation therapy. Since typical treatment doses range up to 20 Gy, calibrations that do not account for this effect can incur a large dosimetry error. The effect is dose rate dependent, but energy independent. For a dose rate of ...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/43/10/031
更新日期：1998-10-01 00:00:00
abstract：:The function of the placenta is challenging to characterize and as a result is understudied, despite the growing awareness of the impact of the placental environment on human health and development. Medical imaging has the potential to improve our ability to screen for diseases associated with placental insufficiency,...
journal_title：Physics in medicine and biology
pub_type： 杂志文章,评审
doi：10.1088/1361-6560/aaccd9
更新日期：2018-07-09 00:00:00
abstract：:In critical organ in vivo x-ray dosimetry, the relative contaminating electron contribution to the total dose and total detector response outside the field will be different to the corresponding contributions at the central axis detector calibration position, mainly due to the effects of shielding in the linear accele...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/51/24/013
更新日期：2006-12-21 00:00:00
abstract：:Mean glandular dose (MGD) is the figure of merit to assess breast dose after a mammographic acquisition. The use of normalized MGD obtained from Monte Carlo computations with measured incident air kerma determines the MGD delivered to patients. The Geant4 Application for Tomographic Emission (GATE) toolkit is a modern...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/58/7/2247
更新日期：2013-04-07 00:00:00
abstract：:Two dosimetry protocols based on absorbed dose to water have recently been implemented: TG-51 and TRS-398. These protocols use different beam-quality indices: %dd(10)x and TPR20,10. The effect of electron contamination in measurements of %dd(10)x has been proposed as a disadvantage of the TG-51. For actual measurement...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/49/1/002
更新日期：2004-01-07 00:00:00
abstract：:The temperature sensitivities of absorption and reduced scattering coefficients in the range 700-1000 nm are determined for the liquid phantom Intralipid using spatially resolved continuous wave measurements. The measurements were conducted on a 10 L heated volume of 1% Intralipid subjected to a 40-30 degrees C coolin...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/52/9/003
更新日期：2007-05-07 00:00:00
abstract：:This paper presents finite-difference time-domain (FDTD) calculations of the whole-body averaged SAR in an anatomically realistic voxel model of the human body. This model, NORMAN, consists of approximately 9 million voxels, of 2 mm dimension in the adult phantom, segmented into 37 tissue types. SAR values are present...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/42/3/003
更新日期：1997-03-01 00:00:00
abstract：:Using conventional scintillation detection, the fundamental limit in positron emission tomography (PET) time resolution is strongly dependent on the inherent temporal variances generated during the scintillation process, yielding an intrinsic physical limit for the coincidence time resolution of around 100 ps. On the ...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/61/21/7600
更新日期：2016-11-07 00:00:00
abstract：:Today, new single photon emission computed tomography (SPECT) reconstruction techniques rely on accurate Monte Carlo (MC) simulations to optimize reconstructed images. However, existing MC scintillation camera models which usually include an accurate description of the collimator and crystal, lack correct implementati...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/56/1/006
更新日期：2011-01-07 00:00:00
abstract：:Delivery of pencil beam scanning (PBS) requires the on-line measurement of several beam parameters. If the measurement is outside of specified tolerances and a binary threshold algorithm is used, the beam will be paused. Given instrumentation and statistical noise such a system can lead to many pauses which could incr...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/61/1/400
更新日期：2016-01-07 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
pub_type： 杂志文章
doi：10.1088/0031-9155/28/12/001
更新日期：1983-12-01 00:00:00
abstract：:This paper presents a method to obtain the pencil-beam kernels that characterize a megavoltage photon beam generated in a flattening filter free (FFF) linear accelerator (linac) by deconvolution from experimental measurements at different depths. The formalism is applied to perform independent dose calculations in mod...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/61/1/50
更新日期：2016-01-07 00:00:00
abstract：:Fast heat extraction is critically important to obtain the maximal benefit of cryogen spray cooling (CSC) during laser therapy of shallow skin lesions, such as port wine stain birthmarks. However, a film of liquid cryogen can build up on the skin surface, impairing heat transfer due to the relatively low thermal condu...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/47/18/301
更新日期：2002-09-21 00:00:00
abstract：:Cavity theories are used to relate the dose in a medium to the dose in a cavity. No satisfactory analytical approach exists for the case of intermediate cavities, such as TLDs, when interface effects are important. Burlin proposed a general cavity theory that accounts for the cavity size but which ignores interface ef...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/46/4/320
更新日期：2001-04-01 00:00:00
abstract：:An in vivo probe was compared with a gamma camera for the task of detecting radiolabelled tumour models in a water phantom. The probe, which contained a 1 cm diameter NaI(T1) detector, was designed and used by us for surgical staging studies of gynaecological patients. Tumours were spherical sources of different sizes...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/34/6/008
更新日期：1989-06-01 00:00:00
