A. Kivisaari

MRI abnormalities of foot and ankle in asymptomatic, physically active individuals.

Abstract Objective. To assess MRI changes in the ankle and foot after physical exercise. Design and patients. Nineteen non-professional marathon runners and 19 age- and sex-matched controls volunteered for the study. All had ankle and foot MR images (1.5 T) taken in three perpendicular planes (STIR, T2F and T1FS sequences) within 3 h of running a full-length marathon (42.125 km). Three radiologists independently analysed the groups on a masked basis using a predefined form. Results. Severe bone marrow oedema was seen in one and slight bone marrow oedema in three marathon runners. Slight bone marrow oedema was found in three control subjects. Signal alteration within the soleus muscle, consistent with a grade 1 strain, was found in one marathon runner. Small punctate hyperintensities within the Achilles tendon were seen in 26% of the marathon runners and in 63% of controls (P=0.016). An increased amount of fluid in the retrocalcaneal bursa was found in one control and in none of the marathon runners. Small amounts of fluid in the retrocalcaneal bursa were seen in 68% of marathon runners and in 53% of controls. Grade 1 or 2 peritendinous joint fluid was found around 22% of tendons, among both marathon runners and controls, most often involving the tendon sheath of the flexor hallucis longus muscle. An increased amount of joint fluid was noted in 34% of the joints of the marathon runners, and in 18% of the controls. Conclusion. MRI shows several abnormalities in the ankle and foot both after marathon races and in asymptomatic physically active individuals without any preceding extraordinary strain. Recreational sports may lead to a number of positive MRI findings without correlation with clinical findings.

Evaluation of pleural disease using MR and CT. With special reference to malignant pleural mesothelioma.

Purpose: To evaluate MR imaging and CT in differentiating malignant pleural mesothelioma from other malignancies or benign pleural disease. Material and Methods: Thirty-four patients (18 pleural mesotheliomas, 9 other malignancies, 7 benign pleural diseases) were examined using enhanced CT and MR. Two radiologists reviewed the CT and two others the MR images. Comparisons were made between the diagnostic groups and the imaging methods. Results: The abnormalities commonly found in malignant disease, but significantly less frequently in benign pleural disease, were focal thickening and enhancement of interlobar fissures. In mesothelioma, enhancement of interlobar fissures, tumour invasion of the diaphragm, mediastinal soft tissue or chest wall, were significantly more often observed than in other malignancies and MR was the most sensitive method. In other malignancies, invasion of bony structures was a more common finding and was also better shown by MR. The contrast-enhanced T1 fat-suppressed (CET1fs) sequence detected these features better than other MR sequences. Conclusion: MR, especially the CET1fs sequence in three planes, gave more information than enhanced CT. Focal thickening and enhancement of interlobar fissures were early abnormalities indicating malignant pleural disease. MR could be clinically useful for differentiating mesothelioma from other pleural diseases.

Acute paediatric ankle trauma: MRI versus plain radiography

Abstract.Objective: To evaluate the diagnosis of acute physeal ankle fractures on plain radiographs using MRI as the gold standard. Methods: Sixty consecutive children, 29 with a clinical diagnosis of lateral ligament injury and 31 with physeal ankle fractures, were examined using both radiographs and MRI in the acute period. The imaging data were reviewed by three ”masked” radiologists. The fracture diagnosis and Slater-Harris classification of radiographs were compared with findings on MRI. Results: Plain radiography produced five of 28 (18%) false negative and 12 of 92 (13%) false positive fracture diagnoses compared with MRI. Six of the 12 false positive fractures were due to a misclassification of lateral ligament disruption as SH1 fractures. Altogether a difference was found in 21% of cases in either the diagnosis or the classification of the fractures according to Salter- Harris. All bone bruises in the distal tibia and fibula and 64% of bone bruises in the talus were seen in association with lateral ligament injuries. Talar bone bruises in association with fractures occurred on the same side as the malleolar fracture; talar bone bruises in association with lateral ligament disruption were seen in different locations. The errors identified on radiographs by MRI did not affect the management of the injury. Conclusions: The incidence of false negative ankle fractures in plain radiographs was small and no complex ankle fractures were missed on radiographs. The total extent of complex fractures was, however, not always obvious on radiographs. In an unselected series of relatively mild ankle injuries, we were unable to show a single case where the treatment or prognosis based on plain radiography should have been significantly altered after having done a routine MRI examination. Plain radiography is still the diagnostic cornerstone of paediatric ankle injuries.

The clinical importance of magnetic resonance imaging versus computed tomography in malignant pleural mesothelioma

There is no standard therapy for malignant pleural mesothelioma (MPM), but recent reports have shown that extensive surgery combined with chemo- and radiotherapy prolongs the survival of selected patients with early stage disease. This emphasises the need for accurate staging procedures at diagnosis and reliable imaging methods to assess response to treatment. Computed tomography (CT) of the chest has been the standard imaging method for these purposes for the last decade, but it is limited in its ability to demonstrate accurately the platelike growth pattern of MPM within the thorax due to the partial volume effect on curved surfaces. In order to define the value of magnetic resonance imaging (MRI) in the imaging of MPM, we have compared the findings from 26 parallel paired CT and MRI scans of mesothelioma patients at various stages of the disease. MRI showed tumour spread into the interlobar fissures, tumour invasion of the diaphragm and through the diaphragm, and invasion of bony structures better than CT. Invasion of the chest wall and mediastinal soft tissue and tumour growth into the lung parenchyma were equally well seen on both imaging methods. CT was better for detecting the inactive pleural calcifications. MRI is a sensitive detector of the characteristic growth pattern and extension of MPM and we recommend its use more widely for the clinical management of MPM especially when evaluating tumour resectability and in research protocols when an accurate evaluation of disease extent is essential.

MRI in the assessment of growth arrest.

Objective: To compare MRI with X-ray tomography in the assessment of bone bridges across the growth plate. Materials and methods: The investigation consisted of two parts. (1) Eleven children with 13 epiphyses suspected of physeal growth arrests were examined with conventional X-ray tomography and MRI. The bar was post-traumatic in eight children, postinfectious in two and due to a congenital, operated pes equinovarus in one. Three blinded radiologists separately evaluated the examinations retrospectively. (2) The images of four children with known physeal bars in the ankle were mixed with 36 normal examinations obtained 1-year after trauma and evaluated blindly by three radiologists. Results: In 5 of 13 epiphysis, the bony bridge was considered smaller on MRI than on X-ray tomography, in 7 of 13 it was considered equal, while it was larger only in one. The interobserver agreement (weighted kappa) was 0.8 (very good) for MRI, 0.76 (good) for X-ray tomography and 0.60 (moderate) for radiographs. The four bony bridges were easily detected on MRI. Conclusions: Compared to MRI, the size of bridges was estimated larger by tomography in about half of the patients.

MR Imaging in Suspected Acute Trauma of Wrist Bones

Objective: the purpose of this study was to evaluate the findings of MR imaging compared to plain radiography in acute wrist trauma. Methods: Radiography and MR imaging (obtained at 1.5 T) of 67 patients (38 female, 29 male, aged 15–80 years) were analysed by three senior radiologists in a blinded random fashion. Results: One-third (n=13) of the 37 fractures observed on MR images were missed on the radiographs. the McNemar test indicated significant differences in diagnoses between radiography and MR. Conclusion: We recommend that MR imaging should be considered in the diagnosis of acute wrist trauma when: 1) There is a clear discrepancy between the clinical status and a negative radiography and when splint treatment would increase cost by causing occupational restrictions; and 2) Healing of trauma diagnosed as contusion or distension does not occur within the expected time.

Feasibility of abdominal plain film images in evaluation suspected drug smuggler

OBJECTIVE Drug smuggling in the gastrointestinal tract has soared within the last 20 years. Though illegal substances in the gastrointestinal tract can be visualized with ultrasound, MRI and CT, the abdominal radiograph has by far remained the most frequently used way of detecting smuggled drugs. The purpose of the study was to evaluate the inter-radiologist interpretation error and the reliability of the abdominal radiograph in detecting smuggled drugs. MATERIALS AND METHODS A total of 279 abdominal radiographs of suspected smugglers were classified by three radiologists as clearly positive or negative for drug smuggling. All available information about the cases was collected from the customs officers and police. RESULTS Out of these cases 203 (73%) were interpreted as negative and 35 (13%) as positive by all three radiologists. In 86% of the cases there was, therefore, an inter-radiological agreement in interpreting the images. In 41 (14%) cases, however, there was an inter-radiologist disagreement. Kappa-value for inter-observer variability was 0.70. CONCLUSIONS In up to a seventh of the abdominal radiographs the interpretation can be challenging even for an experienced radiologist. False positive interpretation can lead to innocent passengers being detained in vain. As negatively interpreted images usually result in releasing of the suspect, there is no way of knowing how many false negative occur. This makes the abdominal radiograph a suboptimal examination, and low dose CT should be considered as the screening modality for gastrointestinal drug smugglers.

MR Imaging in Biofix-Osteosynthesis

Purpose: Osteosynthesis by means of bioresorbable implants, mostly of self-reinforced poly-L-lactide (SR-PLLA), has been used in humans for about 10 years. The aim of this study was to examine the controversy between histological studies confirming fragmentation of the biomaterial and radiological studies showing no breaking of the material. Material and Methods: Six patients with displaced malleolar fractures operatively treated with biodegradable SR-PLLA screws underwent MR examinations at 1.5 T, immediately postoperatively and after one to two years. Results: The biodegradable osteosynthetic screws were clearly seen on all MR images. Of 12 screws, 6 were broken at the final examination (5 syndesmotic transfixation screws and 1 screw through the growth cartilage). Conclusion: The breaking of a biodegradable osteosynthesis is possible to document on MR images.

Computed radiography and image workstation from the radiologist's point of view

A computed radiography system (Digiscan, Siemens) connected to an image workstation (Siemens) has been used for 1 1/2 years in our department. The image quality is good and it has been possible to reduce radiation dose by about 30% without any appreciable loss of image quality. The image workstation has been used in cases where image postprocessing is considered to be useful. For routine reporting of X-ray images the workstation is too slow although the image quality is comparable to that of the computed radiography film.

Detection of Soft-Tissue and Skeletal Infections with Ultra Low-Field (0.02 T) MR Imaging

To evaluate the use of ultra low-field (0.02 T) magnetic resonance (MR) imaging in the diagnosis of musculoskeletal infection, MR examinations with T2 weighted sequences were performed in 61 patients thought to be suffering from one of four major diagnostic categories: Soft-tissue abscesses (n=22), osteomyelitis (n=21), septic arthritis (n=9) and spondylitis (n=9). Infection was confirmed for 37 of these 61 patients. The verified abscesses, arthritis, spondylitis and acute osteomyelitis could be detected by 0.02 T MR. The sensitivity was poor in cases of chronic osteomyelitis. There was one false positive finding in a patient with a possible soft tissue infection. The 0.02 T MR examination failed four times. Two patients were too heavy and another 2 patients had magnetic material in or near the scanning field. Compared with computed tomography and isotope scanning, 0.02 T MR proved a little more informative, but without any statistical significance.