1.
Eriksson, Joakim, et al.
(författare)
Measurements of Kinematic Properties of the Cervical Spine Using Magnetic Resonance Imaging
1998
Annan publikation (övrigt vetenskapligt/konstnärligt) abstract
This paper presents kinematic data on the cervical and upper thoracic spine, based on measurements made on 20 Scandinavian healthy, female volunteers, aged 22-58 years (mean age 40.4). The aim was to provide anatomical in vivo data, primarily intended as data for biomechanical modelling of the upper spine. Together with the measurements of standard anthropometric body dimensions, magnetic resonance imaging (MRI) was used to capture the inner anatomy for each subject. A rigid linkage system is described for the vertebrae C1 –Tvi, with one link per vertebra. Measurements include link lengths, link rotations, and antero-posterior endpoints of the spinous process. Furthermore, correlation coefficients are calculated between link lengths and anthropometric measurements. Also presented are regression equations for each link length, with stature as a predictor. Using additional images of lower accuracy, a sub-study (N=15) investigated possible differences in link length and link rotation between non-flexion and maximum-flexion of the neck. The differences in link lengths were significant (p>0.05) for only 1 of 16 measured links (Cii-Tx). Regarding link rotation, differences were significant for 4 links (Cv–T1). Finally, the precision of the results was evaluated using two methods: by using a phantom for determining the geometrical uncertainties caused by the scanner; and by comparing results between two repeated measurement rounds. The phantom test revealed that the pixel resolution and magnetic field inhomogenities had only a minor influence on the results. The comparisons of repeated measurements revealed a significant difference for the links Ci and Cii, indicating that the landmarks for determining the occipital and Ci/Cii joints were the most difficult to identify on the images.
2.
3.
Norgren, L, et al.
(författare)
Endovaskulär teknik vid aortaaneurysm. Lovande alternativ till öppen kirurgi
1998
Ingår i: Läkartidningen. - 0023-7205. ; 95:6, s. 508-512
Tidskriftsartikel (refereegranskat) abstract
The article consists in a presentation of endovascular surgery for abdominal aortic aneurysm repair in 23 cases. Two cases required conversion to open surgery, but the procedure could be completed in the remaining 21 cases, with a current duration of follow-up of up to 30 months. There was early leakage in one case, and late leakage in five cases. Late conversion has been necessary in three instances, and supplementary endovascular measures have been required in a further two instances. All complications have occurred in those cases operated during the first half of the study period. Modification of the endoprosthesis used and increasing skill have reduced both operation time and the complication rate. Intensive care is no longer required, and the median duration of hospitalisation is three days. Follow-up with magnetic resonance imaging has yielded new and important information.
4.
Svensson, Jonas, et al.
(författare)
Image artifacts due to a time-varying contrast medium concentration in 3D contrast-enhanced MRA
1999
Ingår i: Journal of Magnetic Resonance Imaging. - 1522-2586. ; 10:6, s. 919-928
Tidskriftsartikel (refereegranskat) abstract
The purpose of this work was to study image effects due to time-varying contrast medium concentration in contrast-enhanced three dimensional (3D) magnetic resonance angiography (MRA) images. Two different simulation models (1D and 3D) and two different contrast medium variation schemes were used. Phantom measurements were also performed. Experiments were performed for several different bolus timings. Similar sequence and image object parameters were used in both simulations and measurements (TE/TR 2. 1/7.8 mses, flip angle 30 degrees, T1/T2 1200-80/150-40 msec, flow velocity 100 cm/sec). A small variation in bolus timing yielded large variations in the appearance of the image effects, especially if the center of k-space was sampled in the vicinity of rapid contrast medium concentration variation. For a typical bolus injection in a patient, a severe signal loss but only minor ringing and edge artifacts appeared if the bolus injection was poorly timed. Effects of pulsatile flow were minor. The 3D model proved to be a useful tool in these studies.
5.
Åkeson, Per, et al.
(författare)
Brain metastases--comparison of gadodiamide injection-enhanced MR imaging at standard and high dose, contrast-enhanced CT and non-contrast-enhanced MR imaging
1995
Ingår i: Acta Radiologica. - 1600-0455. ; 36:3, s. 300-306
Tidskriftsartikel (refereegranskat) abstract
The aim was to compare the abilities of contrast-enhanced CT, non-contrast-enhanced MR imaging and contrast-enhanced MR imaging using standard (0.1 mmol/kg b.w.) and high (0.3 mmol/kg b.w.) doses of Gadodiamide injection to detect brain metastases (i.e. blood-brain barrier damage). Sixteen patients with at least 2 metastases found by CT were evaluated by MR imaging using non-contrast-enhanced spin-echo, T1-weighted, T2-weighted sequences, and contrast-enhanced spin-echo T1-weighted sequences at 2 dose levels. Gadodiamide injection was first given at the dose of 0.1 mmol/kg b.w. After imaging, another 0.2 mmol/kg b.w. was given, yielding a cumulative dose of 0.3 mmol/kg b.w. No contrast media-related adverse events were recorded. The images were evaluated openly by one and blindly by 2 investigators and the number of metastases, size, delineation (open study) and diagnostic certainty (blind study) of each individual metastasis noted. High-dose MR imaging showed significantly more and smaller metastases than any other examination, and gave a higher diagnostic certainty. All high-dose images were superior to those with the standard dose MR imaging when compared blindly in pairs. We conclude that spin-echo MR imaging with a high dose of Gadodiamide injection is an efficient way to improve the detection of brain metastases, in particular of small ones.
