Activation of the sensorimotor cortex at 1.0 T: comparison of echo-planar and gradient-echo imaging.

PURPOSE: The increasing demand for the clinical application of functional MR imaging raises the question of whether this technique can be routinely performed on 1.0-T MR scanners. To this end, we assessed the feasibility of functional MR imaging at 1.0 T. METHODS: Healthy volunteers were scanned during the performance of a motor task. Functional data were acquired with echo-planar imaging (EPI) and with gradient-echo (GRE) and dual-echo GRE sequences. The signal intensity variations of the EPI and GRE sequences were compared, and the influence of inflow and blood oxygen level-dependent (BOLD) effects on the signal variations was assessed with the dual-echo GRE sequences. RESULTS: In 11 of the 12 subjects we found activation in the primary motor cortex with both the GRE and EPI sequences. Active voxels had a significantly higher mean percentage of signal changes with the EPI sequence than with the GRE sequence (EPI: 1% to 6.1%, mean 2.4%; GRE: 1% to 4.5%, mean 1.9%). The EPI sequence was less sensitive to motion artifacts and enabled imaging of a larger brain volume in a shorter time. With a dual-echo sequence we found an increasing contribution of inflow effect with an increasing percentage of signal changes. CONCLUSION: Functional MR imaging of the sensorimotor cortex can be routinely performed at 1.0 T.

Hemispheric language dominance studied with functional MR: preliminary study in healthy volunteers and patients with epilepsy.

PURPOSE: We used functional MR imaging to compare hemispheric language dominance in healthy volunteers and in patients with epilepsy. METHODS: We retrospectively reviewed the functional MR images of 23 healthy volunteers and 16 patients with epilepsy obtained by using an echo-planar technique designed for whole-brain imaging. The activation paradigm used was a silent word generation task. Hemispheric language dominance was assessed as the percentage of activated pixels in the left hemisphere minus the percentage of activated pixels in the right hemisphere x 100. RESULTS: We found no significant difference in language lateralization between right-handed male and right-handed female volunteers. However, a statistically significant difference in language distribution was found between left- and right-handed female volunteers. The left-handed female volunteers showed a more bilateral hemispheric language lateralization. Language lateralization in right-handed male epilepsy patients with early age at seizure onset and seizure locus in the left temporal lobe was not significantly different from that of healthy right-handed male volunteers. Similarly, we found no difference in language lateralization between right-handed female volunteers and right-handed female epilepsy patients with late age at seizure onset and seizures in the left temporal lobe. CONCLUSION: Handedness has a significant influence on hemispheric language dominance in healthy volunteers. Sex has no influence on hemispheric language dominance, regardless of the task used to assess such dominance, nor does age at seizure onset influence language lateralization in patients with left temporal lobe epilepsy. Therefore, hemispheric language dominance can be assessed and compared effectively with functional MR imaging.

[Functional MRI: imaging of motor cortex function]. / Functionele MRI: het afbeelden van motorische hersenfuncties.

OBJECTIVE: To image the motor cortex with functional MRI (fMRI), and locate the activated area with the proportional grid of Talairach. DESIGN: Descriptive. SETTING: St. Radboud Academic Hospital Nijmegen. METHODS: In ten volunteers functional images of the motor cortex were made during execution of a motor task (finger movements). From the functional images the positions of activated areas were calculated using the 3D Talairach grid system. RESULTS: fMRI of the motor cortex was possible using a 1.5 T MRI scanner. Task activation of the motor cortex gave a signal increase in Brodmann's area 4, the precentral gyrus. CONCLUSION: Imaging of the active motor cortex with fMRI is feasible. The use of the 3D Talairach proportional grid system for the calculation of the position of an activated area in the motor cortex is possible with adequate accuracy.

MR characterization of suspicious breast lesions with a gadolinium-enhanced TurboFLASH subtraction technique.

PURPOSE: To assess the utility of gadolinium-enhanced dynamic magnetic resonance (MR) imaging with turbo fast low-angle shot (TurboFLASH) technique in the differentiation of benign from malignant lesions of the breast. MATERIALS AND METHODS: Contrast material-enhanced MR images were obtained at intervals of 2.3 seconds for 2 minutes. After the first four images were obtained, contrast medium was intravenously injected within 10 seconds. Lesions that enhanced within 11.5 seconds after the aorta opacified were regarded as malignant. Lesions that enhanced more than 11.5 seconds after the aorta were regarded as benign. A centrifugal pattern of enhancement was regarded as a sign that a lesion was benign. RESULTS: Eighty-seven lesions were evaluated. Histologic examination showed 65 lesions were malignant and 22 were benign. Gadolinium-enhanced TurboFLASH imaging had a sensitivity of 95%, a specificity of 86%, and an overall accuracy of 93% in differentiating benign from malignant lesions. CONCLUSION: Gadolinium-enhanced TurboFLASH imaging is a valuable method in the examination of breast lesions suspected of being malignant.

Magnetic resonance imaging of urinary bladder cancer: an overview and new developments.

The role of magnetic resonance (MR) imaging in the management of carcinoma of the urinary bladder is reviewed and illustrated. In vivo and in vitro MR images of the normal urinary bladder, carcinoma, and surrounding structures are presented. Factors for optimal MR imaging of urinary bladder carcinoma are reviewed. Pulse sequence optimization, (endorectal) surface coils, and other new developments such as fast spin echo, subtraction turbo-fast low angle shot (FLASH), three-dimensional rapid acquisition gradient echo sequences, and the use of contrast agents are discussed. Finally, the value of MR imaging in staging urinary bladder carcinoma is compared with clinical staging, staging based on findings from computed tomography and intravesical sonography.

Low-dose prednisone induces rapid reversible axial bone loss in patients with rheumatoid arthritis. A randomized, controlled study.

OBJECTIVE: To determine the effects of a short course of a low dose of a glucocorticoid agent on bone mass. DESIGN: Double-blind, placebo-controlled, randomized study. SETTING: Outpatient clinic of a university hospital. PATIENTS: Forty patients with active rheumatoid arthritis. INTERVENTION: All patients started receiving intramuscular gold salts. In addition, they were randomly allocated to receive either prednisone or placebo. The initial dose was 10 mg/d, which was tapered between weeks 12 and 20. Thereafter, patients were followed for an additional 24 weeks. MEASUREMENTS: Lumbar bone mineral density was measured with dual-energy, quantitative computed tomography in a trabecular and a cortical region of interest. RESULTS: Despite favorable effects on disease activity and functional capacity, trabecular bone mineral density decreased in the prednisone-treated patients between baseline and week 20 (mean change, -8.2%; 95% CI, -12.7% to -3.7%; P = 0.001). Little change was found in the placebo-treated patients (P > 0.2), and the prednisone group had a greater mean bone loss than the placebo group (9.5%; CI, 3.4% to 15.6%; P = 0.003). After discontinuation of prednisone, an increase was found in trabecular bone mineral density between weeks 20 and 44 (mean change, 5.3%; CI, 0.7% to 9.9%; P = 0.03). Little change was found after withdrawal of placebo (P > 0.2). The mean improvement in the prednisone group was 6.8% (CI, 0.8% to 12.8%; P = 0.03) greater than for placebo. In both treatment groups, cortical bone mineral density did not change markedly in either period (P > or = 0.2). CONCLUSIONS: Low doses of glucocorticoid agents cause marked vertebral trabecular bone loss in the initial months of therapy in patients with active rheumatoid arthritis. After discontinuation of treatment, this bone loss seems to be (partially) reversible.

Differential effects of glucocorticoids on cortical appendicular and cortical vertebral bone mineral content.

The susceptibility to glucocorticoid-induced bone loss may vary in different parts of the skeleton. We studied 62 patients with rheumatoid arthritis, 26 of whom were on low-dose glucocorticoid treatment. Bone mineral content (BMC) in the forearm was measured by single photon absorptiometry at a cortical, diaphyseal, and at a mixed cortical and trabecular, metaphyseal site. Lumbar BMC was measured by dual energy computed tomography in a trabecular and a cortical region of interest. The presence of vertebral deformities was evaluated on lateral spine radiographs. After correction for possibly confounding variables, prednisone therapy significantly influenced BMC at both the trabecular (-22.0%, 95% confidence interval -36.0% to -8.1%) and cortical (-24.8%, 95% confidence interval -39.3% to -10.3%) lumbar site. A significant effect was also seen at the metaphyseal (-15.7%, 95% confidence interval -27.1% to -4.2%), but not the diaphyseal (-3.9%, 95% confidence interval -14.1% to 6.4%) site in the forearm. Correlations between peripheral and vertebral BMC were moderate at best. The diaphyseal to metaphyseal BMC ratio did not identify patients with vertebral osteoporosis. It is concluded that the anterior cortical rim of the vertebral body is more susceptible to the effects of glucocorticoids than the cortical bone in the forearm, and that measurements of trabecular and anterior cortical vertebral BMC are essential in the management of patients with possible glucocorticoid-associated osteoporosis.

Single- versus dual-energy quantitative computed tomography for spinal densitometry in patients with rheumatoid arthritis.

Lumbar bone mineral density was measured by both single- and dual-energy quantitative computed tomography in 109 patients with rheumatoid arthritis. The results were corrected for the age-related increase in vertebral fat content by converting them to percentages of expected densities, using sex and energy-level specific regression equations obtained in a normal reference population. The percentages of expected density are approximately 10% lower in the single- than in the dual-energy mode, both in the patients with and without prednisone therapy. This difference is statistically highly significant, and is positively correlated with the duration of the disease and with the degree of radiological joint destruction. The data suggest that the vertebral fat content may be increased in patients with rheumatoid arthritis, as a consequence of disease-dependent mechanisms.

Overview of CAPACITY data.

This paper presents an overview of the data from 15 cases collected with the CAPACITY software for cost analysis of PACS. The data suggest that both hospital wide and partial PACS implementations do not pay back yet. Only Nuclear Medicine PACS systems may be introduced cost-neutral in the near future. Because of the assumed price drop of hardware components of 5-25% per year, hospital wide and partial PACS may allow cost savings within the next 10-20 years. There are major differences in viewpoints concerning the required PACS configurations and their costs. The experiences with the CAPACITY software suggest the need for the establishment of key rules, for designing a PACS configuration and for estimating PACS costs.

A view from the Nijmegen PACS project.

A view on PACS is given from a radiology department involved in PACS as part of its medical research environment. Special attention is payed to historical developments in medical imaging to study the context of actual PACS developments. Some directions of future diagnostic developments are indicated. Both image data-acquisition and presentation techniques are of interest to medical as well as industrial applications. It is pointed out how PACS is thought to depend on contextual factors.

Comparison of digital and conventional mammography: a ROC study of 270 mammograms.

Observer performance tests were conducted to study the visibility of malignancies in digital mammography. Detectabilities of tumours and of microcalcifications were studied separately. For this purpose two sets of images were used, one for tumours consisting of 150 mammograms and one for microcalcifications containing 120 mammograms. Images were digitized at a resolution of 2048 x 2048 pixels using a 12-bit CCD camera. Conventional film mammograms were read on a lightbox, whereas digital mammograms were viewed on a high-resolution monitor. Two experienced radiologists read both sets independently, and ranked their judgements about the presence or absence of tumours or microcalcifications on a confidence-rating scale. Results were evaluated using receiver operating characteristic (ROC) analysis. No statistical differences were found between judgements based on conventional and digitized mammography.

Vertebral osteoporosis in rheumatoid arthritis patients: effect of low dose prednisone therapy.

The effect of low dose prednisone therapy on spinal bone mass is controversial. We measured lumbar trabecular and cortical bone mineral density (BMD) in 74 rheumatoid arthritis (RA) patients by dual energy quantitative computerized tomography in a cross-sectional study. The presence of vertebral deformities was evaluated on a lateral spine radiograph. Patients who had never been treated with corticosteroids (n = 44) were compared with patients on long-term low dose (less than or equal to 10 mg/day) prednisone therapy (n = 30). After correction for confounding variables the lumbar BMD was highly significantly influenced by prednisone therapy in postmenopausal patients (estimated influence -31.2% on trabecular BMD and -37.2% on cortical BMD). Vertebral deformities were also significantly more frequent in prednisone treated postmenopausal patients. No negative effect of prednisone treatment could be demonstrated in male patients. In contradiction to previous reports we conclude that long-term prednisone therapy may be associated with development of spinal osteoporosis in postmenopausal RA patients, even when low doses are used.

[Digital mammography is very useful in mass screening of breast cancer]. / Digitale mammografie is goed bruikbaar in het bevolkingsonderzoek naar borstkanker.

Mammograms made between 1981 and 1989 in the Nijmegen screening programme for breast cancer were retrospectively reviewed. Those made before detection of breast cancer showed signs of tumour growth in the place of the subsequently detected malignancy in 22% of the cases. A work station was set up for image digitization and image processing. Display with optimal contrast and image processing of mammograms is possible. Diagnoses based on digitized mammograms displayed on a monitor were as good as those based on the conventional images on film. Automatic detection of image features has been investigated. A procedure for automatic detection of microcalcifications was developed. This research is important for optimalization of diagnosis in screening and because of the expected introduction of direct digital imaging techniques.

PACS in practice: on-line communications in daily routine.

After a preparatory phase in which a software link was realized, on-line communications between a diagnostic reporting console and a computed tomography (CT) apparatus were set-up. Two specific groups of CT investigations were selected to be diagnosed in a 'digital' as well as a 'conventional' manner. The 'digital' diagnosis implies medical as well as organizational aspects. The latter will be illustrated by an organization study based on activity diagrams performed to set-up a prototype digital archive (PDA). The PDA was developed to determine the information to be stored in a digital archive and the requirements that users have in accessing image data and corresponding attributes. First experiences with respect to the organizational aspects of this clinical picture archiving and communication systems (PACS) project, in which on-line communications are used in daily routine, will be presented.

PACS in practice: the status of the PACS project at the St. Radboud University Hospital. Part A: Introduction and the picture system.

A so-called bottom-up approach of a Picture Archiving and Communication System (PACS) is initiated by existing clinical questions. It is investigated how far existing Data-Acquisition (DA) modalities combined with the existing computer infrastructure of the hospital can provide soil to a, at first local, PACS system. Examples of current research projects in Digital Subtraction Angiography (DSA), Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) demonstrate how image and raw data processing evolve from applications based on a general matrix manipulation software package to projects within the field of PACS. Starting from the existing facilities a stepwise increase of connections and expansions of required features is going to be brought about by separately considering the picture system, the communication system and the archive system. A three step phasing is proposed: (1) Software linking; (2) Hardware linking: small scale; and (3) Hardware linking: local area network. Examples are given from the first phase, i.e. the development and expansion of software on existing DA-modalities or processing hardware to receive the data on floppy disk, hard disk or tape. Data are converted and transported for further processing: (a) within the department; (b) between hospital departments; and (c) between research centres. With regard to the picture system special attention has to be given to the requirements for digitizing analogue film images and the reading of images from monitor screens instead of films on lightboxes.

PACS in practice: the status of the PACS project at the St. Radboud University Hospital. Part B. A digital image archive: information analysis and development.

In accordance with the bottom-up approach in the field of the Picture Archiving and Communication System (PACS), a pilot study was performed with regard to the archiving of digital diagnostic images. A prototype has been developed to determine what information has to be stored in the digital archive and what requirements the users have in accessing these data. Firstly an organization analysis of the department of diagnostic radiology with respect to the archiving of images was performed. A variant of the ISAC method was used for this purpose. This resulted in a set of activity diagrams. Thereafter an information analysis was performed according to the Nijssen Informal Analysis Method (NIAM). This resulted in a Conceptual Schema (CS). Two other prototypes of relational Image Database Management Systems (IDBMS) are described and a description of a general modular structure of an IDBMS is given. By means of a Prototype of a Digital Archive (PDA) the department of diagnostic radiology was shown what might be expected from a digital archive and how the information will be presented to the users.

Recognition of organs in CT-image sequences: a model guided approach.

A method is proposed for segmentation of organs in CT-image sequences. An important feature of the method is the use of search areas to guide the segmentation process. Time consuming, data-directed operations are restricted to these areas, instead of being applied to the whole image. A search area for a particular anatomical structure is determined by constraints, derived from a model of the imaged scene and by results already obtained in the recognition process. The method has been successfully applied on recognition of the spleen in abdominal X-ray CT scans.

Afterimages: a collective term for percepts of different origin.

Exposure of the eye to a strong photoflash results in a so-called "afterimage", which may last for 20 min or longer. In contrast, the true afterimage, which fluctuates in brightness and is best seen in complete darkness, lasts only a few minutes. This true afterimage can be attributed to the strong oscillatory neuronal responses immediately initiated by the flash. Thereafter dark and light regions, insensitivity percepts, are observable against bright and dark backgrounds, respectively. These percepts can be adequately explained by a reversal of the response behaviour of rod and cone driven ganglion cells situated along the contour of the flash-exposed area. The slow recovery of the rods explains why insensitivity percepts can be seen for many minutes.

Apparent size and receptive field properties.

A light square against a dark background besides an equisized dark square against a light background shows a difference in apparent size such that the light square seems larger than the dark one. This illusion was studied for squares of 109 x 109 min arc. Their centres were located 90 min arc out of the centre of the fovea. The apparent size appeared to be dependent on the contrast between the square and the background and not on the mean luminance in the vicinity of the contour. The addition of a small white or dark line to the luminance step that constituted the border of the square changed the illusion dramatically. It is argued that this explains the observations where an inversion of the illusion for very small contrast values was found. The results are explained on the basis of a model with receptive fields of different sizes overlapping the same retinal location and having different sensitivities.