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O Tervonen

Publications and source records attributed to O Tervonen.

At least 55 records · Page 3Linked to original sources
PubMed1995

Use of a neural network and a multiple regression model to predict histologic grade of astrocytoma from MRI appearances.

Several MRI features of supratentorial astrocytomas are associated with high histologic grade by statistically significant p values. We sought to apply this information prospectively to a group of astrocytomas in the prediction of tumor grade. We used 10 MRI features of fibrillary astrocytomas from 52 patient studies to develop neural network and multiple linear regression models for practical use in predicting tumor grade. The models were tested prospectively on MR images from 29 patients studies. The performance of the models was compared against that of a radiologist. Neural network accuracy was 61% in distinguishing between low and high grade tumors. Multiple linear regression achieved an accuracy of 59%. Assessment of the images by a radiologist yielded 57% accuracy. We conclude that while certain MRI parameters may be statistically related to astrocytoma histologic grade, neural network and linear regression models cannot reliably use them to predict tumor grade.

Astrocytoma↗
PubMed1995

Low-cost digital teleradiology.

A teleradiology link based on standard personal computers and a flat-bed CCD scanner was tested. A 64 kbit/s dial-up digital ISDN telephone line was used for transmission. A total of 254 films (174 uncompressed, 80 compressed) were sent. Ninety-six per cent of the uncompressed images and 98% of the compressed images were considered technically acceptable. The total diagnostic agreement between the acceptable transmitted images and the original films was 98%. Image quality was sufficient for diagnosis in CT and conventional chest and bone radiographs. However, a 256-step gray scale of the scanner was not sufficient for demanding situations, such as overexposed images with a high contrast gradient. The average speed of transmission was 60 kbit/s, which was considered adequate. The tested system suggests that a teleradiology link based on standard personal computers and programs works in situations where instant consultation is needed. However, the image digitization time with the prototype system was quite long, and a better user interface is under development.

Microcomputers↗
PubMed1995

Clinical and MRI findings of the temporomandibular joint in relation to occlusion in young adults.

Magnetic resonance imaging (MRI) is excellent for visualizing soft tissues of the temporomandibular joint (TMJ) . Because it has no harmful effects, it can be used in asymptomatic subjects. MRI and clinical findings relating to TMJs were correlated with findings relating to occlusion in 20 medical and dental students (13 women, 7 men) who volunteered to participate in our study. Subjects with clinically evident joint signs such as clicking, crepitation or tenderness on palpation also exhibited pathologic MRI findings, especially in regards to configuration, position and function of the disk, and, often, disturbances of occlusal relationships between the upper and lower teeth.

Adult↗
PubMed1994

Temporomandibular joint findings obtained by brain MRI.

Magnetic resonance imaging (MRI) is an excellent method for examining the temporomandibular joint (TMJ). Forty-five patients, 29 females and 16 males (mean age 44, range 17-77 years), who had been referred for MRI examination of the brain were asked about their TMJ problems by questionnaire. Subjectively, 29 of the 45 were symptom-free, 11 had mild symptoms, while five experienced severe ones. Symptoms of TMJ dysfunction were correlated with MRI findings that applied to the TMJ emerging in connection with a brain MRI. This study was performed in order to obtain valuable information about the structure of the TMJs. Seven of the 29 patients who anamnestically reported no symptoms of TMJ dysfunction had changes in the configuration and/or position of the disk. In this study, MRI findings concerning the TMJ did not clearly correlate with subjective symptoms of TMJ dysfunction.

Adolescent↗
PubMed1992

Diffuse "fibrillary" astrocytomas: correlation of MRI features with histopathologic parameters and tumor grade.

MR images in 54 patients with biopsy-proven diffuse or "fibrillary" astrocytomas were analyzed and compared with the histopathologic features in order to determine which histopathologic characteristics underlie the radiographic findings in these gliomas and whether radiographic findings are more closely correlated with individual histopathologic characteristics than with histologically determined tumor grade. The MRI features studies included tumor heterogeneity, edema, mass effect, border sharpness, "anatomic invasion", contrast enhancement, hemorrhage, and the presence of flow voids, calcium and cyst formation. The histopathologic characteristics studied included cellular atypia, mitoses, cellularity, endothelial proliferation, necrosis and tumor grade. Edema (P less than 0.01), flow voids (P = 0.02) and contrast enhancement (P less than 0.01) demonstrated a direct correlation with tumor grade, but edema (P less than 0.01) and contrast enhancement (P less than 0.01) also demonstrated a significant correlation to tumor cellularity. Tumor heterogeneity was associated with the presence of necrosis (P = 0.01). Hemorrhage occurred only in high grade tumors, where it correlated with endothelial proliferation (P = 0.04).

Astrocytoma↗
PubMed1992

Clinically occult avascular necrosis of the hip: prevalence in an asymptomatic population at risk.

An abbreviated screening magnetic resonance (MR) imaging examination was used to determine the prevalence of clinically occult avascular necrosis (AVN) of the hip in 100 asymptomatic renal transplantation patients treated with corticosteroids. All patients were more than 18 years old, had been treated with corticosteroids for at least 6 months, and had no symptoms of AVN before MR imaging. Of the 100 patients screened, six were found to have clinically occult AVN at MR imaging (rate: 6%, with a 95% confidence interval of 2.2%-12.6%). No significant differences were found regarding the total dose of corticosteroids and exposure time between patients with and patients without asymptomatic AVN. The authors conclude that there is a significant prevalence of asymptomatic, clinically occult AVN among renal transplantation patients treated with corticosteroids and that a potentially low-cost screening MR imaging examination can be used to detect such disease.

Female↗
PubMed1991

Ultrasound diagnosis of lumbar disc degeneration. Comparison with computed tomography/discography.

Transabdominal ultrasound (US) imaging was compared with computed tomography (CT)/discography in order to assess whether the former could be used for screening discs to be examined by CT/discography, or could be used to replace CT/discography. A total of 56 discs in 29 patients was examined by both methods. The US findings were classified as local or generalized disc lesions, and the CT/discography findings according to the Dallas Discogram Description. The sensitivity of US for recognizing a discographically painful and deteriorated disc was 0.95, and its specificity was 0.38. Correspondingly, the predictive value of a positive US finding was 1.53, and that of a negative finding was 0.13. US is considered suitable for screening discs prior to CT/discography.

Adult↗
PubMed1991

Traumatic trabecular lesions observed on MR imaging of the knee.

Examinations carried out on 302 consecutive patients with MR of the knee between January 1988 and March 1989 were reviewed for detection of trabecular lesion. Twenty-seven patients found presenting trabecular lesion were further reviewed with specific reference to their activity level and need for specific therapy to determine the clinical significance of the trabecular lesion. Twenty-one of the trabecular lesions were in the femur, 5 were in the tibia, and one was in the fibula. Three of them were associated with a direct trauma, 12 with a valgus type injury, 3 with pure rotation mechanism, and 5 with a combination of valgus and rotation. In 17 cases trabecular lesion was a single finding, in 10 cases it was associated with some ligamentous tear. At the follow-up visit, 26 of the 27 patients with trabecular lesion had no symptoms, and the patient with moderate knee symptoms had had similar knee symptoms prior to the accident due to an osteochondral defect. We conclude that a trabecular lesion in an MR image is a benign bone change associated with knee trauma which heals without sequelae.

Adolescent↗
PubMed1990

Lumbar disc degeneration. Correlation between CT and CT/discography.

Computed tomography (CT) images of 59 discs in 30 patients suffering from low back pain were compared with CT/discography images of the same discs in order to assess the correlation between intradiscal damage and changes in annular configuration and density. The discs were graded in CT as not bulging, slight protrusion, advanced protrusion or disc herniation, and were checked for local areas of hypodensity. General degeneration and annular disruption in CT/discography were evaluated separately according to the Dallas Discogram Description, on a scale of non-existent, slight, moderate, or severe. Most discs with a slight protrusion in CT showed severe annular disruption in CT/discography. Discs with advanced protrusion showed in addition a severe general degeneration. Disc herniation was associated only with severe annular disruption. Local hypodensity proved to be a specific but insensitive sign of annular disruption. It is concluded that a bulging disc is a sign of intradiscal damage and should be noted even when there is no nerve entrapment present.

Adolescent↗
PubMed1989

Intraoperative ultrasound imaging in lumbar disc herniation surgery.

The diagnosis of lumbar disc herniation has improved with metrizamide rhizography and CT. Also, visualization of the operative site has been enhanced with use of the operating microscope. However, evaluation of the completeness of herniated disc removal can be difficult, especially in the case of medially located lesions. Also, intradural extension of the herniation can be impossible to rule out in some cases without intradural exploration. Intraoperative ultrasound imaging is safe, rapid and readily available in most hospitals. Its application to real-time imaging control of 10 selected cases of herniated lumbar disc showed that the herniated material could be visualized in relation to the interspace and dural sac in all cases. The effect of removal of the herniation on nerve root compression could also be evaluated. Especially in cases involving extension of the herniation to the medial region under the dura, or into the intradural space, the removal of herniated material could be adequately confirmed without the need for further manipulation with surgical instruments. With appropriate transducer design and frequency, the method can be applied to microsurgical technique to rule out sequestration outside of the surgical exposure.

Adult↗
PubMed1989

Transabdominal ultrasound measurement of the lumbar spinal canal. Its value for evaluation of lumbar spinal stenosis.

Lumbar spinal stenosis, most commonly caused by hypertrophic changes in the soft tissues of the spinal canal, is itself a clinical entity, but in the early phase it can also serve as a factor influencing general back disorder morbidity. It can be identified reliably by measuring the anteroposterior diameter of the dural sac on myelography films and/or the transverse area of the dural sac on computed tomography (CT) scans. In the present study, 76 patients with general back disorders were examined with ultrasound (US) transabdominally through the intervertebral disc. In those 50 patients (66%) in which all three of the lowest lumbar intervertebral spaces could be visualized, the measurements made by US differed by +/- 5 mm from those obtained by myelography and +/- 25 mm2 from those made by CT. In a subset of ten patients with spinal stenosis, US was able to demonstrate the small size of the dural sac, but the cause of the stenosis could not be reliably evaluated. In addition to diagnosing central spinal stenosis, ultrasonography is also well suited for screening purposes.

Abdomen↗
PubMed1989

Completely computer-focused ultrasound imaging. First clinical imaging results.

Completely computer-focused ultrasound imaging has been achieved using the UHB (ultrasound holographic B) method. This is a synthetic aperture method that combines ultrasonic holography and the conventional B-scan method. A wide-angle ultrasound burst (4 MHz) is transmitted into the object and the reflected echoes are measured as a function of the propagation time, but both the amplitude and phase angle are recorded, giving multiple one-dimensional holograms in a cross-sectional plane. This UHB data is rearranged to obtain one-dimensional wave fields, which represent the wave fronts reflected from each depth. The image is then reconstructed by propagating these wave fields backward to their original positions on the image using Fourier transform, a spectrum shift theorem, and inverse Fourier transform. The whole UHB image is obtained by calculating the intensity lines from these wave fields and by scanning these lines one by on the cathode ray tube (CRT) monitor. Following extensive laboratory testing with single and multielement transducers, special 32- and 64-element linear array transducers were fabricated, as was computer software capable of producing a UHB image in 40 seconds. Tissue imaging tests followed by clinical imaging of 30 patients showed that images obtained with this prototype compared favorably with those obtained by state-of-the-art conventional ultrasound scanners. The potential advantages of the new method are enhanced lateral resolution and the incorporation of phase information in tissue characterization. This would be important in diagnostic and intraoperative, especially neurosurgical, imaging.

Brain↗
PubMed1987

CT detection and location of intraorbital foreign bodies. Experiments with wood and glass.

The series comprises 27 patients examined by CT to detect, locate or exclude a foreign body. 22 of them actually had an orbital foreign body. In three cases CT was the primary method and showed the foreign body correctly, while in 18 it was first detected in plain films and CT was performed to locate it. 20 metallic foreign bodies were hyperdense in appearance. Two cases had wooden foreign bodies, one with a density of +10 HU and the other hypodense with a value of about -434 to -446 HU. The latter piece of wood was first interpreted falsely as a bubble of gas. The results proved that the detection of metal is easy, but differentiation between wood and gas is problematical. Experiments conducted to determine the CT densities of different pieces of wood gave results varying from -618 HU to +23 HU. The highest densities obtained for glass varied from +522 HU to +2000 HU. The density of a plastic lens was -105 HU.

Adolescent↗
PubMed1986

Sensitivity of ultrasonography for detecting gallstones.

Previous studies have overestimated the accuracy of ultrasonography for the diagnosis of gallstones by neglecting the systematic checking of false negative findings. In the present series only 80% of 331 cases of gallstones seen at autopsy had been detected by ultrasonography. The most frequent reason for a false negative finding was the small size of the gallstones.

Aged↗
PubMedDate not supplied

MR imaging of knee hyaline cartilage: evaluation of two- and three-dimensional sequences.

Magnetic resonance (MR) imaging of cadaveric knees was performed to determine optimal sequences for visualization of hyaline cartilage. Full-thickness cartilage lesions ranging in diameter from 1 to 5 mm and a partial-thickness cartilage lesion 15 mm in diameter were created in the femoral articular surfaces of three cadaveric knees. The knees were then imaged with a 1.5-T imager with various two-dimensional and high-resolution three-dimensional (3D) techniques. After imaging, the knee specimens were sectioned for evaluation. Measurements of cartilage thickness in fast spin-echo images correlated best with those in the gross specimen. Diffuse areas of cartilage thinning were also most accurately identified with fast spin-echo images. Small, focal cartilage defects were best delineated in 3D SPGR (spoiled GRASS [gradient-recalled acquisition in the steady state]) images.

Cadaver↗