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Biomedical subjects

A Alanen

Publications and source records attributed to A Alanen.

At least 55 records · Page 3Linked to original sources
PubMed1996

MR imaging in the presence of small circular metallic implants. Assessment of thermal injuries.

PURPOSE: The thermal effects of MR imaging in the presence of circular nonferro-magnetic metallic implants were studied in 6 rabbits. MATERIAL AND METHODS: A sternotomy was performed and fixed with stainless steel wires, and small titanium rings (diameter 3 mm) were placed on the surface of the ascending aorta and subcutaneous tissue of the thigh. Four of the rabbits were exposed to an imaging procedure with a 1.5 T scanner applying a T1-weighted spin-echo sequence and a gradient echo sequence. Two of the animals served as unexposed controls. Thirty-six hours after the exposure, tissues adjacent to the implants were examined histologically and compared with corresponding samples of the control animals. RESULTS: In the area of the titanium rings, histologic analysis revealed slight inflammatory changes apparently caused by the operation. No evidence of thermal injury was found, suggesting that the presence of the rings does not contraindicate MR examinations. Necrosis was noted in all of the sternal specimens. This was probably post-operative, but it impaired the assessment of thermal injury in this area.

Animals↗
PubMed1996

Absence of bacterial DNA in the bladder of patients with interstitial cystitis.

PURPOSE: Although bacterial infection has been long considered a possible cause of interstitial cystitis (IC), no definitive proof for or against this hypothesis has been presented so far. We have used 16S rDNA bacterial polymerase chain reaction to study bladder biopsies and sterile urine samples from patients suffering from IC. This method is sensitive and detects all known eubacteria. MATERIALS AND METHODS: Bladder biopsies and sterile urine samples obtained by transabdominal puncture were studied from 11 patients with IC. As controls we studied 4 patients with other urological problems leading to partly similar symptoms and 5 healthy individuals. RESULTS: All samples from the IC patients were negative. One positive sample was obtained from a woman with a history of urinary tract infections who suffered from nonIC ulcerative cystitis. Her sterile urine sample yielded Lactobacillus acidophilus. CONCLUSION: These results indicate that an ongoing bacterial infection is not the cause of interstitial cystitis.

Cystitis, Interstitial↗
PubMed1995

Magnetic resonance imaging and magnetization transfer in experimental myonecrosis in the rat.

Experimental myonecrosis--induced by injection of notexin into rat tibialis anterior muscle--and subsequent regeneration were studied from 1 h to 20 days postinjury with magnetic resonance imaging using conventional and magnetization transfer sequences, and these findings were correlated with histopathology. MR images revealed necrosis within 1 h postinjection. Histopathologically, necrotized fibers enlarged and intercellular spaces widened, indicating intracellular and extracellular edema, which began to decrease after 48 h, whereafter the formation of new myofibers predominated. T2 increased progressively until 7.5 h, while T1 increased until 24 h. Magnetization transfer contrast (MTC) and magnetization transfer rate (Rwm) decreased rapidly postinjection; the decrease in Rwm lasted longer than in MTC (96 h versus 48 h, respectively). Spin echo, inversion recovery and magnetization transfer sequences revealed the lesions equally effectively. MR images and relaxation parameters reflect well the extent of histopathological injury and edema in the acute phase, whereas specific tissue changes in the regenerative phase were not detectable by MRI. MT imaging and especially magnetization transfer rate are as sensitive as conventional T2 contrast to alterations in water imbalance.

Animals↗
PubMed1995

Cross-sectional areas of lumbar muscles after surgical treatment of lumbar disc herniation. A study with magnetic resonance imaging after microdiscectomy or percutaneous nucleotomy.

We assessed in this study the potential development of postoperative muscle atrophy in the operation area in 39 patients treated by either microdiscectomy or percutaneous nucleotomy for lumbar disc herniation. The cross-sectional areas of the lumbar muscles were measured on magnetic resonance images created on the day preceding the operation and 6 months postoperatively. The cross-sections of the lumbar muscles remained unchanged during the observation period in all treated patients indicating that no muscle atrophy had developed in the operation area. Since peroperative tissue trauma may correlate with subsequent muscle denervation and atrophy, this finding may be due to the tissue sparing nature of microdiscectomy and percutaneous nucleotomy, thus encouraging the use of these techniques in the treatment of lumbar disc herniation.

Adult↗
PubMed1995

Disc degeneration of pediatric patients in lumbar MRI.

Magnetic resonance imaging (MRI) is widely used in pediatric spinal disorders, but the prevalence of associated lumbar disc degeneration (DD) has not been evaluated previously. In this study we investigated whether children with suspected spinal disease had increased tendency to early DD. We analyzed lumbar MRI scans of 32 patients and 49 control subjects under 15 years old. Only four patients (13%) had DD on T2-weighted MRI and they were all over 10 years old. Eleven subjects (22%) in the control group had DD. It seems that disc degeneration is seldom found in patients under 10 years old.

Case-Control Studies↗
PubMed1995

Magnetic resonance imaging of Achilles tendon xanthomas using a fat-water discrimination technique at 0.1 T.

RATIONALE AND OBJECTIVES: Tendon xanthomas are atherosclerotic plaque like collections of lipids that develop with age in the Achilles tendons of patients having familial hypercholesterolemia (FH). We tested a fat-water discrimination technique for imaging Achilles tendon xanthomatosis. METHODS: We used the spin-warp imaging technique optimized for low-field magnetic resonance (MR) imaging to obtain separate fat and water images of the Achilles tendon. Seven patients with FH, two patients with normal tendons, and three patients with other tendon pathology were studied. RESULTS: Normal tendons showed an intensity near or equal to that of the noisy background in all images. Compared with the background, the intensity of the FH tendons was approximately fivefold greater in magnitude images, fourfold in fat images, and 10-fold in water images. CONCLUSION: The method sensitively detected even subtle xanthomatosis in young patients, but differentiation of xanthomas from other pathologic lesions was possible with this method only when the tendons were significantly thickened.

Achilles Tendon↗
PubMed1995

The value of magnetic resonance imaging in screening myeloma lesions of the lumbar spine.

Screening of the skeleton by plain radiography was compared to magnetic resonance imaging (MRI) of the lumbar spine in 41 patients with multiple myeloma. In the lumbar spine, myeloma lesions were detected in 15 patients with radiography and in 28 patients with MRI. Radiography of the lumbar spine was not positive in any of the 13 cases with negative MRI, but in two of them radiography was positive elsewhere in the skeleton. We suggest that plain radiography is the most suitable method for screening all bone areas in multiple myeloma, but MRI of the lumbar spine is needed to study patients with normal radiographs.

Humans↗
PubMed1995

Intraoperative sonography in patients with suspected liver metastases.

The correlation of preoperative sonography and intraoperative inspection and palpation of the liver with intraoperative sonography was studied in 77 patients. All underwent elective abdominal surgery for the treatment of verified malignant intra-abdominal tumours. Preoperative sonography findings differed from the intraoperative findings in 22 of the 77 patients (29%), intraoperative sonography being more reliable. Palpation differed from intraoperative sonography in 16 of 77 patients (21%), in three of whom the findings at intraoperative sonography altered therapy. Intraoperative sonography was most effective in detecting small previously undetected, nonpalable lesions deep in the liver parenchyma. There were no complications due to sonography. We recommend intraoperative sonography as a safe and diagnostically effective procedure for routine use in abdominal surgery.

Abdominal Neoplasms↗
PubMed1995

Artifacts in MR imaging caused by small quantities of powdered iron.

The MR image artifacts caused by minute metallic particles were investigated by imaging small powdered iron quantities from 0.01 mg to 1.7 mg in water phantoms. Images with T1-weighted GRE 3-D and T2-weighted SE 2-D sequences were reconstructed with 5 MR imagers: at 0.04 T, 0.1 T (2 scanners), 1.0 T and 1.5 T. In GRE 3-D images the artifacts were round, clearly demarcated black areas, whereas in SE 2-D images artifact areas were elliptic and surrounded by a bright irregular rim with ghost veils in the direction of frequency encoding. The area of the artifact increased slightly up to 0.1 mg of iron, but grew clearly with larger samples. It appeared to behave independently on the MR imager system for all iron samples. This study shows that even microscopic magnetic particles cause a notable distortion in the MR image independently of the MR equipment used.

Artifacts↗
PubMed1994

Diurnal fluid changes of lumbar discs measured indirectly by magnetic resonance imaging.

The feasibility of magnetic resonance imaging and the magnetization transfer technique for measurement of diurnal fluid changes in lumbar discs was studied with the use of 13 healthy subjects. The diurnal height loss of the subjects ranged from 13 to 21 mm. The disc signal in T2-weighted magnetic resonance imaging increased as much as 25% after overnight bed rest, presumably due to the enhanced influx of water. The change in magnetization transfer parameters also suggested increased hydration of the disc after bed rest. Magnetic resonance imaging techniques can be used for indirect measurement of the changes in fluid content and the interaction of water with macromolecules in the disc.

Adult↗
PubMed1994

Magnetic resonance image changes and clinical outcome after microdiscectomy or nucleotomy for ruptured disc.

Preoperative and postoperative magnetic resonance imaging (MRI) of the lumbar spine was performed on 41 patients treated either microsurgically or with percutaneous nucleotomy for lumbar disc herniation. On the first postoperative day, MRI revealed an edematous mass effect at the level of surgery in 25 (61%) patients. The mass effect caused compression of the anterior dural sac mimicking preoperative disc herniation. After the follow-up of 6 months, the mass effect had disappeared in all patients, and the MRI finding in the operated disc space was that of a prolapse in six (15%) patients and that of a protrusion in 16 (39%) patients. Postoperative scarring was detected in 23 (56%) patients. The amount of the epidural scar tissue was significantly (p = 0.0002) associated with the extent of the early postoperative hemorrhagic changes detected in these patients with MRI. No association was observed between these MRI findings (mass effect, disc herniation, epidural scarring) and the clinical outcome of the patients.

Adult↗
PubMed1994

Postoperative hematomas after successful lumbar microdiscectomy or percutaneous nucleotomy: a magnetic resonance imaging study.

We evaluated the incidence of postoperative extradural hematomas by means of magnetic resonance imaging (MRI) technique in 44 patients who underwent successful surgery for a virgin lumbar disc herniation. Of these patients, 28 were treated with microdiscectomy and 16 with percutaneous nucleotomy. Postoperative hematoma proved to be a universal MRI finding in the microsurgically treated patients: hematomas were found in all patients in the microdiscectomy group. In 12 (43%) patients the hematoma extended into the dural sack. The incidence of hematomas was significantly (p = 0.001) lower in the patients treated with percutaneous nucleotomy: hematomas were detected in only 10 (63%) of the 16 patients in the nucleotomy group. The hematomas in these patients were also smaller in size and none of them connected with the dural sac. Correlation between the hematomas and clinical findings showed that the presence of a hematoma had no obvious effect on the immediate postoperative recovery of a patient.

Adult↗
PubMed1994

Magnetization transfer in fatty and low-fat livers.

The magnetization transfer technique was applied to imaging of liver tissue at 0.1 T in order to examine the dependence of proton relaxation parameters on protein concentration. The effect of the fat signal on the values of these parameters was also evaluated by using the special fat/water separation method for low fields. The livers of pigs as a model for low-fat tissue and those of burbots as a model for fatty tissue were examined. For the low-fat liver tissue, the magnetization transfer rate Rwm correlated linearly with the total protein concentration very significantly (p = 0.0086). For the fatty liver, the relaxation parameters did not correlate well with the total protein concentration. After fat/water separation, the relaxation times T1 and T1w, the magnetization transfer rate Rwm and magnetization transfer contrast (MTC), measured from the water image, increased significantly. This indicates that the presence of fat in the liver will affect the measured values of magnetization transfer parameters.

Animals↗
PubMed1994

Sonography in the detection of achilles tendon xanthomata in children with familial hypercholesterolaemia.

Patients with heterozygous familial hypercholesterolaemia (FH) are at high risk for the development of coronary artery disease. Achilles tendon xanthomata are often the first clinical manifestation of FH, but are seldom palpable earlier than during the third decade. Twenty-one FH children aged 3-18 years underwent high-frequency ultrasound examination of the achilles tendon. Hypoechoic infiltration of the normal tendon structure was demonstrated in 8 of 21 (38%) of the FH children. The findings were similar in boys and girls. Control subjects (n = 68) aged 1-25 years had no sonographically detectable tendon abnormalities. The thickness of the achilles tendon of the FH children was (mean +/- SD) 7.1 +/- 1.5 mm (range 5-10 mm). The respective values for the controls were 5.8 +/- 1.0 mm (3-7 mm. We conclude that ultrasound examination sensitively detects cholesterol accumulation in the achilles tendon of FH children before tendon xanthomata are clinically evident.

Achilles Tendon↗
PubMed1994

Sonographic technique in diagnosis of urethral strictures in men.

Sixteen male patients were examined by sonography, urethrography and urethroscopy because of a clinical suspicion of urethral stricture. For sonography the urethra was filled with anesthetic gel using an inflexible plastic syringe. Ten strictures were identified by urethroscopy; 9 of them were also seen in urethrography and 5 in sonography. All the membrane-like strictures (4), and 1 very proximal stricture remained unvisualized in sonography. Sonography revealed also 1 diverticulum and 1 posttraumatic fistula, which were also seen in urethrography. The presented sonographic method for visualizing the male urethra proved to be useful.

Adult↗
PubMed1993

Sonography of the Achilles tendon in hypercholesterolaemia.

OBJECTIVES: Tendon xanthomas cause thickening of the tendon and are an important sign in monogenic familial hypercholesterolaemia (FH). The aim of our study was to investigate the usefulness of achilles tendon sonography in detecting FH patients. Special attention was paid to structural abnormalities of the achilles tendon. DESIGN: A clinical study with methodological testing. SETTING: Patients suspected of having FH were sent to the out-patient Department of Medicine from other departments of Turku University Central Hospital and from primary care units. The patients were studied by high-frequency ultrasound before more exact typing of the lipid disorder. An additional study of normolipidaemic volunteers and a phantom study were also carried out. SUBJECTS: Forty FH patients, 51 non-FH hypercholesterolaemia patients and 41 normolipidaemic volunteers were included in the study. MAIN OUTCOME OF MEASURES: The thickness of the tendon was measured and the tendon structure and its echogenicity were recorded. RESULTS: Twenty-five out of 40 (63%) FH patients had distinctly thickened tendons (men more than 10 mm, women more than 9 mm). Thirty-six (90%) had a typical structural alteration of low or mixed echogenicity of the tendon. Three non-FH patients were found to have xanthomas on sonography. CONCLUSIONS: We conclude that ultrasonography is a sensitive method of detecting xanthomas that reveals the altered tendon structure even in xanthomatous tendons of normal thickness.

Achilles Tendon↗