Biomedical subjects
Publications and source records attributed to L Ekelund.
A series of 55 percutaneous nephrostomy patients is presented. Techniques and presently available catheter types are discussed as well as the specific problems arising when the procedure is used for urinary diversion in neoplastic disease.
Twelve patients with cavernous hemangiomas of the liver were studied with computed tomography (CT) and ultra-low field magnetic resonance imaging (MRI). Seven patients were examined at a field strength of 0.02 T and 5 patients at 0.04 T, while 3 patients were studied at both field strengths. On T2-weighted images all hemangiomas had the same characteristic appearance of a homogeneous high signal intensity that has been described at higher field strengths. Signal characteristics of the hemangiomas were the same at 0.02 and 0.04 T, but the higher field strength provided better signal-to-noise (S/N) ratio and hence improved image quality. Homogeneous contrast enhancement was seen in three hemangiomas examined after intravenous administration of gadopentetate dimeglumine. Our results indicate that ultra-low field MRI can be useful in the differential diagnosis of hepatic hemangiomas.
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The diagnostic utility of extremely low field magnetic resonance (MR) (0.02 T) was evaluated in various parts of the body outside the head. The areas investigated included the spine (104 patients), kidneys (19 patients), female pelvis (21 patients), and hips (15 patients). The results were compared with those of other imaging modalities, e.g., ultrasound, CT, and scintigraphy. Available pulse sequences and typical examination times for different types of studies are reported. Poor spatial resolution and long imaging times limit the application of this technique to the whole body. Due to poor signal-to-noise ratio, image quality is not comparable with that obtained at higher field strengths. In spite of these restrictions it was possible to demonstrate lumbar disk herniations, to differentiate renal and ovarian cysts from tumors, and to detect early avascular necrosis of the femoral head. Extremely low field MR imaging may eventually be used in screening spinal pathology and in the diagnosis of early avascular necrosis of the femoral head. At present, this technique can not replace ultrasound or CT in abdominal examinations.
A new type of balloon catheter for rapid nephrostomy track dilatation from 3 to 10 mm is described. The balloon has a length of 10 cm, which means that the tract can be dilated in its entire length in one step. The catheter system is recommended for use, especially in patients previously not operated upon.
The effect on the renal parenchyma caused by rapid dilatation of a nephrostomy track to 24 F to 30 F was studied on 9 kidneys in 5 pigs. Angiography at different intervals up to 5 weeks was used in combination with histology. Moderate bleeding and short lacerations were observed around the puncture site in all kidneys. Complications included one transient pyelovenous reflux, one organized abscess following perforation of the upper pole, and two cases of hydronephrosis caused by abscess and inflammation. These infections were probably due to the prevailing sanitary conditions. No arteriovenous fistula formation was seen. Minimal scars were encountered after 4 to 5 weeks follow-up. Transparenchymal access to the pelvocaliceal system through percutaneously established large tracks seems to cause limited damage which resolves in minor scars provided perforations are avoided by an optimum technique and infections are prevented or treated appropriately.
The diagnostic utility of extremely low field magnetic resonance (MR) imaging was evaluated in 25 patients with focal hepatic masses, including 17 with primary (n = 7) or secondary (n = 10) malignant neoplasms and 8 with benign lesions (6 hemangiomas). The findings were compared with the results of computed tomography (CT). Out of 16 patients with malignant tumors demonstrated by both modalities, the diagnostic information from MR imaging was equal to or better than that from CT in 6 patients and inferior to CT in 10. Shortcomings of MR were mainly due to low signal-to-noise ratio and poor spatial resolution, resulting in an image quality inferior to that obtained at higher field strengths. Considering these facts, together with the long imaging times required, low field MR cannot be recommended for general use in the evaluation of hepatic masses. On the other hand, our results indicate that this technique may be useful in establishing the diagnosis of hepatic hemangioma.
Fourteen patients with cervical hip fractures were treated with internal fixation using titanium screws. The femoral head vitality was evaluated with 99Tcm-MDP scintigraphy and scintimetry within 2 weeks postoperatively and by serial low field magnetic resonance imaging (MR). Two patients with reduced radionuclide uptake (femoral head ratio less than 1.0) developed radiographic signs of femoral head necrosis. MR disclosed the definite area of the necrosis at 2 and 12 months after fracture, respectively. In three of the patients with a high scintimetric uptake (femoral head ratio greater than or equal to 1.0), MR revealed a focal decrease of the signal intensity in the femoral head or neck at 2, 3 and 7 months after fracture, respectively. The radiographs in one of these patients were normal at 7 months after fracture. The second one showed signs of necrosis at 16 months and the last one developed delayed/non-union. With a non-ferromagnetic osteosynthesis the healing course after femoral neck fracture can be studied with low field MR equipment without disturbing artifacts. The time period between ischaemia and definite abnormalities on MR may embrace several months.
Magnetic resonance (MR) examination of the lumbar spine was performed in 51 patients using a resistive magnet with a field strength of 0.02 T. The results at 105 intervertebral levels were compared with those of computed tomography (CT). Due to the extremely low field strength, an unfavourable signal-to-noise ratio degraded the image quality. Some improvement was achieved with the development of a dedicated surface coil. The diagnostic information was not comparable with that obtained with CT, nor was the image quality comparable to that obtained at higher field strengths. Compared with CT there was no false information. Therefore, it is suggested that extremely low field units may permit exclusion of pathology on the basis of a normal examination and in this way help in the selection of those patients who need further investigation and treatment.
Fibrotic stenosing anastomoses of the common bile duct were surgically created in pigs in order to investigate the effects of percutaneous transhepatic balloon catheter dilatation. In a group of 6 animals, not treated with balloon dilatation, percutaneous transhepatic cholangiography and microscopic examination of the stricture were performed 5 to 25 weeks postoperatively. A persistent stenosis and slight to moderate fibrosis of the bile duct wall and peribiliary tissue were observed. In 5 animals the stenotic anastomosis was dilated 4 to 10 weeks postoperatively and this resulted in widening of the stricture and necrosis of the mucosa at the stricture site. Rupture of the fibrotic tissue in the bile duct wall and thrombus formation in the peribiliary veins also occurred in one of these 5 animals. Short-term follow-up in 3 animals 4 to 6 weeks after balloon dilatation showed almost complete fibrotic healing and partial re-stenosis of the anastomoses.
The digital moving slit technique as used by most CT scanners for overview images, was used for antero-posterior and lateral views of the pelvis for pelvimetry. The method was evaluated in phantom experiments and clinical examinations were performed in 23 patients. The method was compared with conventional pelvimetry in 14 patients. Estimated ovarian dose was reduced by a factor of 14.2. The discrepancy in measurements of the pelvic diameters by computed tomography compared with conventional pelvimetry was considered to be without practical importance from an obstetric point of view. Digital pelvimetry is easier for the patient, faster and the need for repeated exposures is eliminated. Based on these facts it is suggested that digital pelvimetry should replace the conventional method whenever possible.
To determine the usefulness of extremely low field magnetic resonance imaging (MRI) in the evaluation of renal masses 19 patients with 15 tumors (13 renal and 2 renal pelvic carcinomas) and 8 cysts were examined in a 0.02 tesla MRI unit. The findings were compared with results of computed tomography (CT) and ultrasound. Cavography was performed in 6 patients. MRI enabled differentiation between cysts and solid tumors. Tumor extension into the inferior vena cava could be demonstrated in one case and liver metastases in two patients. The image quality was inferior to that reported at higher field strengths and the tumors were more precisely staged by CT and ultrasound. At present, it is unlikely that low field MRI will play any substantial role in the evaluation of renal masses.
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Chronic compartmental syndromes have been reported in various locations in the upper and lower extremities, but to the best of the authors' knowledge it has not been described in the tensor fasciae latae muscle. Two patients, men of about 60 years of age, complained of pain on exertion and sitting associated with swelling of the tensor muscle. In both cases CT scans showed muscle enlargement. Intracompartmental pressure values were high both at rest and during exercise. After fasciotomy the patients were relieved of pain, and intracompartmental pressure values were normalized.