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Biomedical subjects

T M Link

Publications and source records attributed to T M Link.

At least 91 records · Page 5Linked to original sources
PubMed1995

[Spinal metastases. Value of diagnostic procedures in the initial diagnosis and follow-up].

In this retrospective study plain radiographs, radionuclide bone scans, computed tomography (CT) and magnetic resonance (MRT) examinations of 115 patients with metastatic carcinoma of the spine were analyzed. In 32 patients metastases were proven histologically and in the remainder by follow-up studies. Altogether, 513 vertebrae were evaluated. Forty-one patients had histologically proven breast cancer, 14 renal cell carcinoma, 11 prostate cancer, 8 melanoma. 8 tumors of the gastrointestinal system and 7 bronchial carcinoma. Evaluation of the plain films showed that the initial site of metastasis (n = 463) was the vertebral body in 441 cases and the pedicles in 294 cases. In CT scans most of the lesions confined to one part of the vertebral body (36 of 98) were localized in the posterior part. Twelve percent of the metastases were diagnosed with conventional radiography and 17% of those diagnosed with CT were not detected in skeletal scintigraphy. MRI was rarely used in diagnosing occult vertebral metastases (n = 37); 22% of the metastases demonstrated by MRI were not detected in skeletal scintigraphy. We concluded that only in 63.8% was the pedicle sign the initial site of metastasis on plain films. Bone scans and plain films are the most important diagnostic procedures for detecting and monitoring vertebral metastases. CT and MRI are only needed in patients with neurological symptoms and persistent pain.

Diagnostic Imaging↗
PubMed1994

[Significance of intravascular ultrasound in arteriosclerotic calcified intima plaques: in vitro comparison of 20 and 12.5 MHz transducers].

The aim of this in vitro study was to analyze the diagnostic performance of intravascular ultrasound (IVUS) in vessel wall calcifications and to compare the accuracy of mechanical 12.5 and 20 MHz transducers. Fourty-three sections of 10 vessels with signs of arteriosclerotic disease on pathologic examination were examined. Slices 500 microns thick were obtained and examined radiographically at 9 fold magnification. In each section, identical segments were defined, amounting to a total of 344 segments. The IVUS sections were analyzed by 3 experienced readers. For statistical evaluation ROC analysis was performed using magnification radiography as a reference. An area under the curve (AUC) of 0.79 was obtained for the 12.5 transducer and of 0.83 for the 20 MHz transducer. Additionally, sensitivity, specificity, and accuracy were determined. Sensitivity depended on the morphology, size, and density of the calcified lesions. We therefore conclude that the sensitivity of intravascular ultrasound concerning calcified arteriosclerotic plaques is limited and that there is no significant (p < 0.01) difference between mechanical 20 and 12.5 MHz transducers in examining iliac arteries.

Angiography↗
PubMed1994

In vitro correlation of intravascular ultrasound and direct magnification radiography for calcified arterial lesions.

RATIONALE AND OBJECTIVES: Intravascular ultrasound (IVUS) is an adjunct to contrast angiography that gives additional information concerning the morphology of the vascular wall. The authors examined the accuracy of intravascular ultrasound (IVUS) in the evaluation of calcified lesions within the abdominal aorta and the iliac artery. METHODS: Forty-nine human specimens (iliac artery, 26; abdominal aorta, 23) were examined using a 20-MHz 6.0-F ultrasound catheter, followed by magnification radiography of the same specimens using a newly developed microfocus x-ray tube. Magnification radiographs and ultrasound images were divided into identical sectors to analyze the morphology of calcified arteriosclerotic lesions. RESULTS: A total of 644 sectors was analyzed. Sensitivity of intravascular sonography was 70%, specificity 53%. Sensitivity strongly depended on the morphology of the calcified lesions. CONCLUSION: The detection of calcified arteriosclerotic lesions by means of IVUS revealed a sensitivity of 70% in an in vitro study using human specimens. However, the specificity of IVUS was only 53%, which is basically a random chance occurrence.

Aorta, Abdominal↗
PubMed1994

Artificial bone erosions: detection with magnification radiography versus conventional high-resolution radiography.

PURPOSE: To compare the diagnostic performance of direct magnification radiography with computed radiography versus that of conventional radiography in detection of artificial bone erosions. MATERIALS AND METHODS: Thirty-one paws from German shepherd dogs were embedded in paraffin and examined with x6 magnification radiography and conventional radiography before and after creation of artificial bone erosions. A microfocal x-ray unit with a focal spot of 20-130 microns was used for magnification radiography. All 210 images were analyzed by five radiologists, and receiver operating characteristic (ROC) analysis was performed. Interobserver analysis in evaluation of anatomic structures was also performed. RESULTS: ROC analysis of pooled data from all readers showed a larger area under the ROC curve for magnification radiography (0.88) than for conventional radiography (0.72). Magnification radiography produced higher scores in interobserver analysis as well. CONCLUSION: Magnification radiography is superior to conventional radiography in detection of small bone erosions.

Animals↗
PubMed1994

[Fractures of the cervical spine. Diagnosis in multiple trauma patients].

The purpose of our study was to analyze diagnostic procedures of the cervical spine in severely traumatized patients. Findings in plain radiographs and computed radiography of 234 patients were evaluated. The image quality of the plain radiographs was examined. Casualty reports were evaluated retrospectively. Frequency, distribution and morphology of cervical spine fractures were analyzed: 44 fractures in 35 patients were diagnosed, most of the fractures were located in C2 (20/44). Twenty of the fractures diagnosed in CT were not diagnosed in plain radiography and 7 fractures were uncertain findings; 5 fractures were not detected at the casualty site. A new screening procedure in patients with severe head injury is introduced.

Adolescent↗
PubMed1994

[Follow-up of fracture healing--indications and clinical relevance of direct radiographic magnification in comparison with conventional roentgen imaging].

Comparison of 83 magnification radiographs with corresponding conventional X-rays showed that direct radiographic magnification (DIMA) yielded additional information in 39 cases (47%), which had implications for the treatment in 19 cases (22.9%). In 11 cases callus was first visualized in magnification radiography; the earliest evidence of callus was found 14 days after surgery. Since magnification radiography means the region that can be examined is smaller, conventional radiographs were necessary in 32.5% of cases to find the position of the fracture in long bones. For statistical evaluation interobserver analysis was performed, anatomical and pathological structures being graded according to four levels. Magnification radiography proved superior in all structures examined. Magnification radiography can be recommended as an additional method to monitor fracture healing. Computed radiography was used together with magnification radiography to reduce the radiation dose and to perform image processing including simulation of conventional technique and edge enhancement. DIMA is a valuable tool in the evaluation of fracture stability and in the adjustment of distraction rates in limb-lengthening procedures.

Adult↗
PubMed1994

[Value of direct radiographic enlargement (DIMA) in early detection of rheumatic inflammatory lesions. Comparative evaluation with high resolution conventional imaging technique].

Rheumatological joint disorders were examined with mammographic film-screen combinations and high-definition microfocal magnification radiography. Our objective was to evaluate the potentials of magnification radiography in diagnosing arthritis by means of interobserver and ROC analysis. The microfocal X-ray unit had a spot size of 20-130 microns; 5-fold magnification was performed. Digital luminescence radiography was employed; digital image processing included simulation of conventional technique and edge enhancement. Eighty radiographs were obtained with conventional and magnification technique. All films were analyzed by five readers. Anatomical and pathological structures were evaluated. The percentage of uncertain findings in magnification radiography was lower compared to conventional radiographs (14% to 26%); in 8% (compared to 19%) the diagnosis of erosions was uncertain. Additionally ROC analysis was carried out. Magnification radiography was significantly (p < 0.03) better than the conventional films.

Arthritis, Rheumatoid↗
PubMed1993

[Intravascular ultrasound in peripheral calcified vascular lesions: comparison with direct magnification radiography].

Intravascular ultrasound can detect calcified peripheral arteriosclerotic lesions by hyperdense echo patterns and shadowing of subintimal layers. Nevertheless, 20 MHz ultrasound systems have not been validated for the detection of peripheral calcifications; besides, it is unknown whether the depiction of calcified lesions by intravascular ultrasound depends on the morphology of the calcification. Histological evaluation of severely calcified arteries is difficult because the preparation of those specimens often causes artefacts, e.g., fracture of calcified structures. Direct magnification radiography, currently used in forensic medicine or skeleton examination, is based on a minimized focus and enables the edge-enhanced views of calcifications with high discrimination. In this in-vitro-study direct radiological magnification was used to validate intravascular ultrasound. Forty-nine segments of human peripheral arteries were fixed in formalin, examined with intravascular ultrasound and, as a reference, radiographically magnified using a newly developed microfocus x-ray tube. Sensitivity, specificity, positive and negative predictive value, and accuracy of intravascular ultrasound for the detection of calcified wall areas were determined and compared to the appearance (configuration, circumferential and areal expansion, density, number of fragments) of these calcifications. Thicknesses of 110 single calcified structures were estimated on sonograms and radiograms. The overall sensitivity of the 20 MHz intravascular ultrasound system for the detection of calcification in 913 sectors was 70%, specificity 53%, positive predictive value 66%, negative value 58% and accuracy 62%. The depiction of calcified regions by direct magnification radiography showed that the sensitivity strongly depended on the density of the calcification. Sensitivity was 81% with calcified lesions of high density, but only 51% with lesions of low density.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1993

[State of the art of selective small bowel enema. Indications and results].

Medical records of 312 consecutive patients with enteroclysis were reviewed. Clinical indications, symptoms, roentgenologic results and clinical outcome were correlated. The most frequent indications were abdominal pain (22%), suspected inflammatory bowel disease (19%), evaluation of Crohn's disease (17%) and diarrhea (11%). Two-thirds of the studies (67.6%) gave normal results and 32.4%, abnormal. The most common abnormalities detected were pathology of the mucosa (40%), stenosis of the small bowel (34%) and fistulas (26%). A low incidence of pathology as found in cases of gastrointestinal bleeding of unknown origin (0%) and when a primary tumor was sought (13%). In 18% operation followed enteroclysis; results were found to be true-positive in 68% and false-negative in 28%. We conclude that in view of the implications (radiation dose and patient discomfort), the indications should be carefully considered before enteroclysis is performed.

Abdominal Pain↗
PubMed1988

[Preoperative localization of pathologic findings in mammography].

Pre-operative localization of abnormal findings during mammography makes it easier to find the lesions if they are not palpable. Our study is based on 373 procedures, using a "harpoon" needle. Radiographs of the operative specimen showed that 66% of the lesions had been completely removed, 15% had been partially removed and 19% could not be identified unequivocally. 172 patients had subsequent mammograms. Amongst these, the lesion had been completely removed in 70%, partially removed in 14% and in 10% it was still present. In 62% dense scar formation made it impossible to be certain whether excision had been complete.

Biopsy, Needle↗
PubMedDate not supplied

Assessment of trabecular structure using high resolution CT images and texture analysis.

PURPOSE: Our goal was to use high resolution (HR) CT images combined with texture analysis to investigate the trabecular structure of human vertebral specimens and to compare these techniques with bone mineral density (BMD) in the prediction of bone strength. METHOD: HR CT images with a slice thickness of 1 mm were obtained of 28 bone cubes. Four different groups of texture analysis techniques were used to assess these images. In addition, quantitative CT (QCT) was performed and elastic modulus (EM) was determined biomechanically. RESULTS: R2 between EM and BMD was 0.78 (p < 0.01). R2 values for EM versus most of the texture measures were also significant. Texture measures in addition to measures of BMD in a multivariate regression model significantly increased R2 up to 0.87. CONCLUSION: In an experimental setting, texture parameters calculated using HR CT images correlated significantly with EM. Combining texture measures with BMD improved the prediction of EM significantly.

Adult↗
PubMedDate not supplied

Intravertebral vacuum phenomenon following fractures: CT study on frequency and etiology.

PURPOSE: The purpose of this work was to determine the frequency and etiology of the intravertebral vacuum phenomenon (IVP). METHOD: CT examinations of 96 vertebral fractures were evaluated for IVP. Bone mineral density (BMD) was determined in nonfractured vertebrae. For calibration purposes, densities of a standard phantom measured in 30 patients who underwent quantitative CT examinations in the same time period were used and precision was calculated. RESULTS: Eleven of 96 fractures (11.5%) showed IVP. IVP was present in 4 of 20 fractures at T12 (20%), in 4 of 23 at L1 (17.4%), and 1 IVP was found at L2-4 each. Mean +/- SD age of patients with IVP was 68.3 +/- 10.5 years and without 47.8 +/- 19.4 years (p < 0.001). Mean +/- SD density of nonaffected vertebra was 45.9 +/- 17.0 mg of hydroxyapatite/ml for patients with IVP and 139.5 +/- 62.6 mg/ml for those without IVP (p < 0.0005). An average precision of 1.2% was calculated for the density measurements over the investigated time. CONCLUSION: Following vertebral fractures, IVP on CT scans is more common than presumed and increases with age. There exists a significant inverse correlation between the BMD and the frequency of IVP.

Age Factors↗
PubMedDate not supplied

CT of metal implants: reduction of artifacts using an extended CT scale technique.

PURPOSE: The purpose of this work was to use an extended CT scale technique (ECTS) to reduce artifacts due to metal implants and to optimize CT imaging parameters for metal implants using an experimental model. METHOD: Osteotomies were performed in 20 porcine femur specimens. One hundred cobalt-base screws and 24 steel plates were used for osteosynthesis in these specimens. Artificial lesions were produced in 50 screws, such as osteolysis near the screws (mimicking lysis due to infection, tumor, or loosening), displacement of the screws, as well as fractures of the screws. All specimens were examined using eight different CT protocols: four conventional (CCT) and four spiral (SCT) CT protocols with different milliampere-second values (130 and 480 mAs for CCT, 130 and 300 mAs for SCT), kilovolt potentials (120 and 140 kVp), and slice thicknesses (2 and 5 mm). The images were analyzed by three observers using a standard window (maximum window width 4,000 HU) and ECTS (maximum window width 40,000 HU). Receiver operating characteristic analysis was performed, and image quality was assessed according to a five level scale. RESULTS: Metal artifacts were significantly reduced using ECTS (p < 0.05). The highest diagnostic performance was obtained using ECTS with the thinnest slice thickness. Metal artifacts were more pronounced using SCT. In this experimental model, exposure dose and kilovolt potential had no significant impact on diagnostic performance (p > 0.05). CONCLUSION: ECTS improved imaging of metal implants. In this study, no significant effects of exposure dose and kilovolt potential were noted. Metal artifacts were more prominent using SCT than using CCT.

Animals↗
PubMedDate not supplied

Periosteal chondroma: MR characteristics.

PURPOSE: The purpose of this study was to describe the MR characteristics of periosteal chondroma. METHOD: MR images of 12 proven cases of periosteal chondroma were analyzed with reference to tumor morphology and size. MR features were correlated with radiographic and pathologic findings. RESULTS: Tumor size ranged from 1 to 7 cm in maximum diameter with a mean value of 2.6 cm. On MR images, a soft tissue mass at the bone surface with pressure erosion of adjacent cortical bone could be identified in all cases. All lesions were bordered by a hypointense rim (100%) and frequently showed a lobulated configuration (75%). Edema of medullary bone or soft tissues was not observed in any of the cases. Signal intensity of cartilaginous tumor tissue was typically hypo-or isointense relative to muscle on T1-weighted (100%) and hyperintense relative to fat on T2-weighted (92%) and T2*-weighted (100%) MR images. Radiographically significant calcifications of the tumor matrix, present in half of the cases, caused focal signal loss on MR images of all pulse sequences. Contrast enhancement was observed predominantly at the periphery of the lesions (100%), which on pathologic examinations typically contained fibrovascular bundles, surrounding the cartilage lobules. CONCLUSION: Periosteal chondroma appears to have a relatively typical MR appearance, which reflects the histologic composition of the lesion. In addition to radiography, MRI therefore can substantially aid in the preoperative diagnosis of this rare bone lesion.

Adolescent↗