Bo Jung

Cardiac Gated MR Imaging of Cerebrospinal Fluid Flow

This is a preliminary investigation of the cerebrospinal fluid (CSF) spaces using cardiac gated magnetic resonance imaging. A variation of intensity of the signal from the cerebral aqueduct is demonstrated during the cardiac cycle. The pattern of this variation suggests pulsatile CSF flow. Calculations that have been verified by phantom measurements show that CSF flow rates less than I mm/s may be detectable. Magnetic resonance may therefore offer a new method for the demonstration and measurement of CSF flow.

SUPPLEMENTARY TREATMENT OF NASOPHARYNGEAL TUMOURS WITH HIGH ENERGY PROTONS

The administration of a curative dose of conventional roentgen radiation to nasopharyngeal tumours lying deep behind bony structures is not easy. Supplementary irradiation of the tumour with radionuclide applicators has been used, but this procedure is technically difficult and fails to ensure uniform irradiation of the whole tumour mass. The problem of administrating an adequate dose to nasopharyngeal tumours is much simplified with a high-energy proton beam. With a two-field technique the skin dose may be kept below 40 per cent of the tumour dose and the absorption in the bony structures is in fact slightly reduced. These conditions are favourable even when compared with those produced by roentgen rays from a 31 MV betatron (BERDAL & POPPE 1962). Material. This comprised the ten cases of malignant nasopharyngeal tumours admitted to the Department of Radiotherapy between 1964 and 1965. It was considered advisable in this exploratory series to give the proton dose only as a supplement to conventional roentgen therapy in order to decrease the influence of any possible unexpected biologic effect. This policy obviously fails

Soft Tissue Intensification in Frontal Roentgenography of the Larynx

The perception of roentgenographic detail is not completely understood but may well be dependent upon the radiation absorption gradient over the contour of a projected structure (WALLS 1954) and its inference by other structures (TUDDENHAM 1957, EDHOLM 1960). The visibility of the soft tissue structure is disturbed and limited by the spongy bone of the cervical vertebrae in frontal roentgenography of the larynx. Structures of low contrast are thus masked by the closely spaced structures of fairly high contrast. Laryngography is the best method of improving the visibility of laryngeal soft tissue (POWERS et coll, 1957, THORNBURY & LATOURETTE 1967, BRINDLE 1966, LANDMAN 1970, HEMMINGSSON 1972, and others). This technique necessitates premedication and anaesthesia with the contrast media used at present; other techniques with a similar diagnostic accuracy but without this disadvantage are therefore desirable.

Ellipsoidal Body Phantom for Evaluation of CT Scanners

A phantom for study of uniformity, artifacts from dense structures, and consistency in pixel values was constructed. On-site studies of eight computed tomographs belonging to the second, third, and fourth generations showed that the phantom was appropriate for such measurements. The results indicate certain inherent shortcomings in some of the present designs.

Perception of Simulated Lesions in the Lung

The detectability of phi 20 mm, disk-shaped objects on a normal chest film was investigated at viewing distances of 0.3, 1.0 and 3.0 m. Objects with a tapered border were found to be best perceived at longer distances. The photpgraphic density difference between object and background yielding a 50% detection probability was found to increase from 0.025 to 0.060 when the outer gradient zone of the object increased from 0.8 to 4.0 mm.

Perceptibility of experimental and clinical lesions in the CT image with and without image processing.

The Ohio-Nuclear Delta 50 FS whole-body CT scanner and image filtering programs FI and SP:SMOOTH provided with the equipment were used to investigate how the perceptibility in the CT image of artificial lesions in a phantom and of liver lesions in patients was influenced by different reconstruction diameters, radiation doses and section thicknesses and by image filtering and different conditions of viewing. The perceptibility of both artificial and clinical lesions was considerably improved, especially in scans with a low radiation dose, when optimum viewing conditions and image filters were used.

Computed tomography, ultrasonography and gamma camera scintigraphy after renal transplantation.

In routine postoperative observations on 31 transplanted kidneys, computed tomography (CT), ultrasonography (US) and gamma scintigraphy (GS) were compared with respect to diagnosis of abscess or lymphocele in the vicinity of the transplant, rejection and outflow obstruction. The results showed that US was the most reliable procedure for detecting fluid-filled cavities. In cases of graft rejection, GS was of most value. In demonstrating outflow obstruction, there was no definite difference between the three methods.

Image enhancement by digital-analog filtration. II. Tests of filters.

The function of a device for frequency filtration of roentgenograms with digital filters has been tested with the use of different filters. The image was altered in the expected way, which means that the device is suitable for investigating the possibilities of different filters to improve the diagnostic ability. The results of the tests indicate that improvement should be achieved by low-pass filtration.

Structure Enhancement by Subtraction in Magnetic Resonance Imaging

Two patients with tumours in the pituitary gland and the liver, respectively, were studied with MRI. Regions of different transverse relaxation times were found in the tumours. Subtraction of images recorded with different echo times demonstrated the tumour regions better than the original images although these were recorded with 2 repetition times and double and multiple echo sequences. Subtraction techniques may thus aid diagnosis in MRI.

Proton relaxation in a multicompartmental system with exchange, simulating human tissue.

The proton magnetic resonance behaviour of human tissue was simulated with a numerical model in which the resonating nuclei were assumed to belong to five different compartments of defined relative sizes and with distinct relaxation properties. Effects of various proton exchange rates between the compartments were included in the model. The time evolution of longitudinal and transverse macroscopic magnetizations was calculated. Applications of this model in magnetic resonance imaging are discussed.