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K T Mattila

Publications and source records attributed to K T Mattila.

11 recordsLinked to original sources
PubMed2005

Comparison of digital and conventional radiostereometric image analysis in an ankle phantom model.

BACKGROUND AND AIMS: Radiostereometric analysis (RSA) allows accurate three-dimensional measurements of micromotion in skeletal structures. The current RSA techniques are based on the analysis of scanned plain films. This study was undertaken to compare digital filmless RSA technique to conventional scanning technique using a phantom model of the ankle mortise. MATERIAL AND METHODS: In the first experiment, the relative displacement of the markers inserted to the fibula in relation to the markers inserted to the tibia was studied by means of double examinations and the precision of DICOM images were compared to scanned images of printed radiographs. In the second experiment, the film pair of double examination was re-imported or re-scanned and self-compared in order to show merely the error related to the image processing. RESULTS: The precision of RSA using scanned images of printed radiographs was compatible to DICOM images. However, the mean error of rigid body fitting (ME) values were significantly lower in use of DICOM images compared with scanned radiographs, indicating less deformation of rigid body segments in filmless analysis. CONCLUSIONS: Precision of the RSA method was improved under the completely filmless environment. Therefore, this technique can be recommended for clinical studies of radiostereometric analysis.

Ankle Joint↗
PubMed2001

Dynamic contrast-enhanced MR imaging and MR-guided bone biopsy on a 0.23 T open imager.

OBJECTIVE: To assess the feasibility of MR (magnetic resonance)-guided bone biopsies. DESIGN AND PATIENTS: Thirty-six consecutive patients with known or suspected benign or malignant bone lesions underwent comprehensive MR imaging. A dynamic contrast-enhanced sequence followed by stationary T1-weighted sequences were obtained and MR-guided bone biopsy of the tumor at the site with fastest enhancement was performed using an open 0.23 T MR imager. RESULTS: All MR-guided bone biopsies samples were estimated to be sufficient by the pathologists. The biopsy specimens were diagnostic in 34 of 36 cases. CONCLUSION: MR-guided bone biopsies combined with dynamic contrast-enhanced imaging are feasible and safe for the diagnostic investigation of equivocal bone lesions.

Adolescent↗
PubMed2001

MR-guided core biopsies of soft tissue tumours on an open 0.23 T imager.

PURPOSE: To assess the feasibility of MR-guided soft tissue core biopsies on an open 0.23 T magnet. MATERIAL AND METHODS: Twenty-nine consecutive patients with known or suspected benign or malignant soft tissue tumours underwent MR imaging. A one-slice dynamic enhancement sequence was used to obtain an enhancement curve of the tumour. MR-guided core biopsy of the tumour was performed in the same session. RESULTS: All biopsies could be performed on an open 0.23 T magnet. Standard MR images and dynamic enhancement curves were used in deciding biopsy route and target. The MR-guided core biopsy specimens were sufficient for histopathological diagnosis in 27 of 29 cases. CONCLUSION: Open magnet configuration allows easy access to the patient and near real-time imaging guidance of soft tissue tumours. Minimally invasive MR-guided core biopsies of soft tissue tumours are feasible and help to avoid open surgical biopsies.

Adult↗
PubMed1999

Medial tibial pain: a dynamic contrast-enhanced MRI study.

The purpose of this study was to compare the sensitivity of different magnetic resonance imaging (MRI) sequences to depict periosteal edema in patients with medial tibial pain. Additionally, we evaluated the ability of dynamic contrast-enhanced imaging (DCES) to depict possible temporal alterations in muscular perfusion within compartments of the leg. Fifteen patients with medial tibial pain were examined with MRI. T1-, T2-weighted, proton density axial images and dynamic and static phase post-contrast images were compared in ability to depict periosteal edema. STIR was used in seven cases to depict bone marrow edema. Images were analyzed to detect signs of compartment edema. Region-of-interest measurements in compartments were performed during DCES and compared with controls. In detecting periosteal edema, post-contrast T1-weighted images were better than spin echo T2-weighted and proton density images or STIR images, but STIR depicted the bone marrow edema best. DCES best demonstrated the gradually enhancing periostitis. Four subjects with severe periosteal edema had visually detectable pathologic enhancement during DCES in the deep posterior compartment of the leg. Percentage enhancement in the deep posterior compartment of the leg was greater in patients than in controls. The fast enhancement phase in the deep posterior compartment began slightly slower in patients than in controls, but it continued longer. We believe that periosteal edema in bone stress reaction can cause impairment of venous flow in the deep posterior compartment. MRI can depict both these conditions. In patients with medial tibial pain, MR imaging protocol should include axial STIR images (to depict bone pathology) with T1-weighted axial pre and post-contrast images, and dynamic contrast enhanced imaging to show periosteal edema and abnormal contrast enhancement within a compartment.

Adolescent↗
PubMed1997

Stress fracture of the ulnar diaphysis in a recreational golfer.

PURPOSE: To report a very rare presentation of a stress fracture in a golfer: a stress fracture of the ulnar diaphysis. CASE SUMMARY: A 44-year-old woman had a 4-week history of a sore left wrist. She had been playing golf daily and had had no sudden trauma. Extensor tendinitis was suspected. Symptomatic treatment was given. Radiographs showed a spiculated periosteal reaction of the distal ulnar diaphysis with no signs of fracture or bone destruction. The suggestion of a malignant lesion was raised. Magnetic resonance imaging showed a healing ulnar fracture and edema of the interosseous membrane. DISCUSSION: In golfers, stress fractures may be seen in ribs laterally and in tibias. We believe supination together with overuse of the hand flexor muscles caused the stress fracture presented, which has not previously been reported in golfers. RELEVANCE: Physicians should be aware of the potential for ulnar stress fracture in golfers with wrist pain.

Adult↗
PubMed1996

Knee extension dynamometer: a new device for dynamic isokinetic magnetic resonance spectroscopy experiments.

In the present study we introduce a new device for exercise magnetic resonance spectroscopy (MRS). It operates in a standard whole-body scanner. Mechanical exertion unit allows maximal 10 degrees to 15 degrees short-arc knee extensions. The device operates hydraulically and is based on isokinetic movement. The force and work conducted are automatically controlled by the electronic control and computer unit. A small surface coil placed on the vastus medialis muscle allows the collection of spectra without interfering spectra from nearby resting muscles. The force used for the extensions can be followed simultaneously as a curve on the screen in the operator's room and the data is transferred to a personal computer for later analysis. Total work and fatigue percentage are also calculated by the device. It also allows the use of different isokinetic exercise protocols. The measurements of force proved reliable in repeat measurements using an isokinetic test device as a control. This device has been used clinically for over a year, is easy to operate, and offers reliable measurements. It is well suited to trials where muscle energy states versus time are followed since it allows noninvasive simultaneous quantification of muscle performance and collecting MRS spectra at rest, during exercise, and in the recovery phase.

Ergometry↗
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

Massive osteoarticular knee allografts: structural changes evaluated with CT.

PURPOSE: To analyze the structural changes seen at computed tomography (CT), particularly the findings that precede insufficiency (fatigue) fractures in massive osteoarticular knee allografts. MATERIALS AND METHODS: The subchondral and cancellous bone of 12 allografts were retrospectively evaluated with repeat transaxial CT (mean follow-up, 53 months). RESULTS: Early cortical graft resorption was followed by slow thickening after 6 months. Formation of resorptive cysts increased the cortical irregularity, which leveled off after 2 years. Late remodeling was evident as a subcortical sclerotic rim, "neocortex." Initially, the cancellous graft bone showed higher attenuation than the host bone; this difference subsided gradually during the first 3 years. Four insufficiency fractures were detected after the 1st postoperative year. Poor remodeling preceded these fractures. CONCLUSION: CT effectively depicted the structural changes during allograft incorporation and was superior to plain radiography for the detection of insufficiency fractures. The use of CT for follow-up of massive osteoarticular knee allografts provides additional information concerning the readiness of the graft for weight bearing.

Adolescent↗
PubMed1993

Exercise-induced changes in magnetization transfer contrast of muscles.

Magnetization transfer contrast (MTC) technique provides a new type of contrast in MR imaging. The MTC method is based on the interaction between the spins of free protons and those with restricted motion. Exercise-induced changes in signal intensity and MTC were measured in the forearm muscles of 10 volunteers at 0.1 T. There was 26% increase in signal intensity of active flexor muscles after exercise when imaged with ordinary gradient echo sequence. Despite this marked intensity increase, the postexercise values of MTC did not differ from the preexercise ones.

Adult↗
PubMed1990

Long-term follow-up of St. Jude Medical valve.

St. Jude Medical bileaflet valve replacement was performed on 182 patients--aortic in 90, mitral in 70, both sites in 20 and tricuspid in two. The 30-day mortality was 4.3%, and was related to poor preoperative condition (NYHA class III or IV). The late mortality during observation up to 8 years was 9.3%, with actuarial survival 87.4% at 5 years and 86.3% at 8 years. For aortic, mitral and double valve replacement the respective 8-year figures were 88, 87.3 and 76.2%. Late death was associated with high preoperative pulmonary vascular resistance in five cases, dysrhythmia in four, myocardial infarction in two, thromboembolism, paravalvular leakage, prosthetic endocarditis or bleeding, each in one case, and was accidental in two cases. Calculated per 100 patient years the incidence of late thromboembolic events was 1.0, of bleeding complications 0.9 and of prosthetic valve endocarditis and paravalvular leak 0.26 (8, 7, 2 and 2 cases). The NYHA class in the 144 cases available for follow-up was I in 63%, II in 27% and III in 10%. The St. Jude Medical prosthesis thus was reliable, with good long-term performance.

Aortic Valve↗