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H K Genant

Publications and source records attributed to H K Genant.

At least 235 records · Page 13Linked to original sources
PubMed1995

The European Spine Phantom--a tool for standardization and quality control in spinal bone mineral measurements by DXA and QCT.

The lack of standardization in bone mineral measurements of the lumbar spine and other skeletal sites is generally recognized as an important and unresolved issue. We report and discuss efforts at standardization and cross-calibration of DXA and QCT equipment. We have designed and tested a geometrically defined, semi-anthropomorphic phantom, the European Spine Phantom (ESP). It contains a spine insert consisting of three vertebrae of increasing bone mineral densities and thicknesses of cortical structures; the respective parameters are given in tabular form for the final phantom design. Results for cross-calibration with the ESP compare well with patient results. Measurements on the first 30 phantoms confirmed that the ESP can be manufactured with a variation of about 1%. We conclude that the ESP is suitable for daily quality assurance, cross-calibration of instruments and universal standardization. The ESP was used to establish standardized BMD (sBMD) units for DXA equipment going into effect in late 1995. Its acceptance by manufacturers as a calibration standard for DXA and QCT measurements appears imminent.

Absorptiometry, Photon↗
PubMed1995

Alendronate treatment of the postmenopausal osteoporotic woman: effect of multiple dosages on bone mass and bone remodeling.

BACKGROUND: The effects of the aminobisphosphonate alendronate sodium on bone mass and markers of bone remodeling were investigated. PATIENTS AND METHODS: In a multicenter, randomized, double-blind, placebo-controlled, 2-year study, 188 postmenopausal women, aged 42 to 75 years, with low bone mineral density (BMD) of the lumbar spine were randomly assigned to 1 of 6 daily treatment groups: placebo for 2 years, alendronate 5 or 10 mg for 2 years, alendronate 20 or 40 mg for 1 year followed by placebo for 1 year, or alendronate 40 mg for 3 months followed by 2.5 mg for 21 months. All subjects were given 500 mg/d of elemental calcium as calcium carbonate. RESULTS: At each dose, alendronate produced significant reductions in markers of bone resorption and formation, and significantly increased bone mass at the lumbar spine, hip, and total body, as compared with decreases (significant at lumbar spine) in subjects receiving placebo. In the 10-mg group, mean urinary deoxypyridinoline/creatinine had declined by 47% at 3 months, and mean serum osteocalcin by 53% at 6 months. Mean changes in BMD over 24 months with 10 mg alendronate were +7.21% +/- 0.49% for the lumbar spine, +5.27% +/- 0.70% for total hip, and +2.53% +/- 0.68% for total body (each P < 0.01) compared to changes of -1.35% +/- 0.61%, -1.20% +/- 0.64% and -0.31% +/- 0.44% at these sites, respectively, with placebo treatment. Progressive increases in BMD of both lumbar spine and total hip were observed in the second year of treatment with 10 mg alendronate (both P < 0.05). CONCLUSION: Alendronate, a potent inhibitor of bone resorption, reduces markers of bone remodeling and significantly increases BMD at the lumbar spine, hip, and total body, and is well tolerated at therapeutic doses (5 or 10 mg daily) in the treatment of osteoporosis in postmenopausal women.

Adult↗
PubMed1995

[Spontaneous osteonecrosis of the knee joint: MRT compared to CT, scintigraphy and histology].

PURPOSE: We compared MR imaging with scintigraphy and CT in eight patients with spontaneous osteonecrosis of the knee. The histological changes accounting for the MR signal abnormalities were evaluated. METHODS: Eight patients with spontaneous osteonecrosis of the knee joint underwent MR imaging before and after i.v. administration of Gd-DTPA. Nuclear scintigraphy was performed in all 8 patients, three patients also had CT scans of the knee area. Histologic correlation was available in three patients. RESULTS: Increased radionuclide uptake was observed in all patients. In one patient, however, scintigraphy showed increased radionuclide uptake consistent with osteonecrosis only in the medial femoral condyle, while MR imaging demonstrated osteonecrosis both in the medial as well as the lateral femoral condyles. MR demonstrated areas of low signal intensity on precontrast T1-weighted images in the femoral condyle in all patients. All these areas showed high signal intensity on T2-weighted images. On postcontrast T1-weighted images, signal intensity increase was either homogeneous throughout the lesion or it was seen at the periphery of the lesion in a band-like pattern. Histologically, the areas of high signal intensity on T2-weighted and on postcontrast T1-weighted images corresponded to granulation tissue. CONCLUSION: MR imaging detects granulation tissue adjacent to the necrotic zone. Using morphological and signal intensity criteria, MR imaging can be utilised to differentiate spontaneous osteonecrosis of the knee from osteochondritis dissecans, degenerative osteoarthritis, and other conditions affecting the knee joint.

Aged↗
PubMed1995

Transient osteoporosis of the hip in pregnancy: natural history of changes in bone mineral density.

A 31-year-old white female developed severe bilateral hip pain during the third trimester of pregnancy that persisted after parturition. Laboratory abnormalities (elevated alkaline phosphatase and erythrocyte sedimentation rate) and radiographic changes (faint demineralization of the femur in the more symptomatic hip on plain films with evidence of bone marrow oedema and small joint effusions bilaterally on MRI) in the absence of other causes of focal osteoporosis were consistent with the diagnosis of transient osteoporosis of the hip in pregnancy. Although loss of bone mineral density (BMD) characterizes this syndrome, serial BMD measurements in symptomatic transient osteoporosis of the hip in pregnancy have not previously been reported. In the case reported here, serial bone density measurements were obtained over a 4-year period following the onset of symptoms. BMD in both femoral necks, which initially was approximately 20% lower than the average for age matched controls, increased markedly during the first year, plateaued during the following year, and then rapidly increased again following cessation of lactation. Unexpectedly, BMD in the lumbar spine, an asymptomatic site, was also markedly decreased at the time of presentation (31% lower than the mean of age-matched controls). Recovery of spinal density did not occur during the first year. However, spinal BMD did begin to increase during the second year and continued to rise after the cessation of lactation. In contrast to the marked reduction in bone density at these site of trabecular bone, cortical bone density in the forearm was normal. Possible aetiologies of pregnancy associated osteoporosis are discussed.

Adult↗
PubMed1995

Meniscal ossicle: radiographic and MR imaging findings.

PURPOSE: To determine the magnetic resonance (MR) imaging appearance of meniscal ossicles and correlate that with the radiographic and clinical features. MATERIALS AND METHODS: Radiographs and MR images were studied retrospectively in six patients with meniscal ossicles; all patients had intermittent discomfort in the knee, and five patients had experienced knee trauma. Imaging findings were correlated with the clinical history. Four patients underwent arthroscopy. RESULTS: All patients had a visible ossicle on conventional radiographs initially interpreted as a loose joint body. MR imaging features included a corticated marrow-containing structure within the substance of the medial meniscus near the tibial attachment that appeared as a rounded focus of increased signal intensity on T1-weighted images that decreased in signal intensity on T2-weighted images. CONCLUSION: Meniscal ossicles have a characteristic MR appearance that may help distinguish them from loose bodies. They should be considered diagnostically when a circumscribed ossification is identified near the posterior horn of the medial meniscus on radiographs.

Adolescent↗
PubMed1995

Musculoskeletal neoplasm: perineoplastic edema versus tumor on dynamic postcontrast MR images with spatial mapping of instantaneous enhancement rates.

PURPOSE: To evaluate the utility of fast, contrast-enhanced, sequential magnetic resonance (MR) imaging in differentiating between extraosseous tumor and perineoplastic edema. MATERIALS AND METHODS: Fourteen patients underwent sequential MR imaging (3.5 seconds per image) after bolus administration of gadopentetate dimeglumine. Initial rates of enhancement (initial slope) were calculated on a pixel-by-pixel basis and displayed as a "slope image"' in which pixel intensity reflected the slope value. Close correlation with wedge biopsy specimens was performed. RESULTS: Mean initial slope values were viable extraosseous tumor, 9.33 (standard deviation, 2.23); infiltrated muscle, 9.07 (2.31); edematous muscle without tumor infiltration, 5.48 (1.27); normal muscle, 1.11 (0.65). Differences in initial slope between all neoplastic and nonneoplastic tissues were statistically significant. Within individual patients, initial slope of edematous muscle was always 20% or more lower than that of neoplastic tissue. Slope images highlighted areas of viable extraosseous tumor and infiltrated muscle against edematous and normal tissues. CONCLUSION: Computer-generated slope images derived from sequential postcontrast MR images allow differentiation between tumor and nonneoplastic edema and may thereby guide the surgeon in planning limb-sparing procedures.

Adolescent↗
PubMed1995

A comparison of bone densitometry measurements of the central skeleton in post-menopausal women with and without vertebral fracture.

The purpose of this investigation was to compare the ability of two different bone densitometry techniques (quantitative computed tomography and dual X-ray absorptiometry) to discriminate subjects without any vertebral fracture from those with definite vertebral fractures. Bone mineral density (BMD) was determined in 112 post-menopausal women. 83 women were classified free of vertebral fracture and 29 were considered to have definite vertebral fractures. Quantitative computed tomography (QCT) was performed using three different spinal regions of interest. Dual X-ray absorptiometry (DXA) was measured at the spine (both in posteroanterior (PA) and lateral (L-DXA) projection, and at hip (total, neck and Ward regions). An additional estimated volumetric BMD was derived from the PA and L-DXA spine scans. Individuals with definite vertebral fractures had lower bone mineral density for each of the methods and regions of interest (ROI). Spinal QCT results, total and Ward hip DXA results showed the greatest percentage decrement. Odds ratio estimates revealed a significant relationship between BMD and fracture with spinal QCT, hip, and volumetric spinal DXA. The greatest areas under the receiver operating characteristic (ROC) curves were found with results of spinal QCT, total and Ward hip DXA, and volumetric spinal DXA measurements. It is concluded that spinal QCT and femoral total DXA measurement may be preferred to PA and lateral L3 DXA measurements.

Absorptiometry, Photon↗
PubMed1995

Primary bone tumors: value of MR angiography for preoperative planning and monitoring response to chemotherapy.

OBJECTIVE: The purposes of our study were to investigate the use of MR angiography with two- (2D) and three-dimensional (3D) displays in evaluating vascular morphology of musculoskeletal neoplasms for preoperative planning of limb-salvage surgery and to assess the use of MR angiography for monitoring changes in neovascularity and evaluating response to chemotherapy. SUBJECTS AND METHODS: We used MR angiography (2D time-of-flight) to study 13 patients with primary bone tumors (nine osteogenic sarcomas, two Ewing's sarcomas, and two primary lymphomas of bone) at the time of initial presentation. Eight patients (all of whom had osteogenic sarcoma) also underwent MR angiography following chemotherapy before limb-salvage surgery. Two-dimensional maximum intensity projections were obtained. Three-dimensional reconstructions of vascular structures were created from the angiographic source images and were displayed simultaneously with 3D reconstructions of tumor and normal bone generated from conventional MR images. RESULTS: Two-dimensional maximum intensity projections were useful for evaluating small vessel neovascularity; 3D displays demonstrated spatial relationships of tumor, feeder vessels, and normal vascular structures. Tumor encroachment onto or encasement of normal vascular structures was shown in four patients on 2D maximum intensity projections and on 3D displays. The eight patients with osteogenic sarcoma who had follow-up imaging showed marked neovascularity prior to chemotherapy. Five patients responded to chemotherapy (> or = 90% tumor necrosis at histology); MR angiography showed marked reduction in tumor neovascularity in these patients. Three patients did not respond to chemotherapy; MR angiography showed unchanged neovascularity in one and increased neovascularity in two of these patients. CONCLUSION: MR angiography provides good visualization of peripheral vascular branches and tumor neovascularity in patients with primary bone tumors. MR angiography demonstrates encroachment onto and encasement of major vessels by the tumor mass and appears to be useful for assessing response to chemotherapy in osteogenic sarcoma and possibly other primary bone tumors by detecting treatment-induced changes in tumor neovascularity.

Adolescent↗
PubMed1995

Quantification of the volume of articular cartilage in the metacarpophalangeal joints of the hand: accuracy and precision of three-dimensional MR imaging.

OBJECTIVE: Cartilage loss is central to the development of joint failure in arthritis. However, radiographic assessment of cartilage loss is highly unreliable. This study examined the accuracy and reproducibility of a noninvasive technique for quantifying the volume of articular cartilage in the metacarpophalangeal joints of the hand by use of three-dimensional (3D) MR imaging. SUBJECTS AND METHODS: Eight metacarpophalangeal joints (four normal, one rheumatoid arthritic, and three normal cadaveric) each were imaged three times with a 1.5-T clinical MR imaging scanner with a small partial volume coil and a fat-saturated 3D spoiled gradient-echo sequence optimized for delineating articular cartilage. The volumes of cartilage over the metacarpal and phalangeal surfaces were quantified by summing the voxels within segmented 3D reconstructions of the images. Cartilage volumes in the three cadaver joints also were estimated by scraping cartilage off the articular surfaces and measuring water displacement in graduated cylinders. These values were used as the gold standard for assessing the accuracy of cartilage volume quantification by MR imaging. RESULTS: The fat-saturated sequence discriminated the articular cartilage from adjacent joint structures with high contrast and high spatial resolution. Cartilage volumes determined by MR imaging for the different subjects ranged from 115 microliters to 222 microliters for metacarpal cartilage and from 34 microliters to 86 microliters for proximal phalangeal cartilage. Accuracy errors for quantifying cartilage volume by MR imaging were -1.8% (95% confidence interval, -3.5% to -0.7%) for metacarpal cartilage and 9.1% (4.3% to 14.7%) for proximal phalangeal cartilage. Reproducibility errors were 5.2% (95% confidence interval, 2.9% to 7.6%) and 9.9% (5.4% to 15.1%), respectively. CONCLUSION: Fat-suppressed T1-weighted 3D MR imaging provides sufficient contrast and spatial resolution to allow accurate and reproducible quantification of articular cartilage volume in the metacarpophalangeal joints of the hand. This technique may be useful for monitoring cartilage loss in patients with arthritis.

Adult↗
PubMed1995

Current methods and advances in bone densitometry.

Bone mass is the primary, although not the only, determinant of fracture. Over the past few years a number of noninvasive techniques have been developed to more sensitively quantitate bone mass. These include single and dual photon absorptiometry (SPA and DPA), single and dual X-ray absorptiometry (SXA and DXA) and quantitative computed tomography (QCT). While differing in anatomic sites measured and in their estimates of precision, accuracy, and fracture discrimination, all of these methods provide clinically useful measurements of skeletal status. It is the intent of this review to discuss the pros and cons of these techniques and to present the new applications of ultrasound (US) and magnetic resonance (MRI) in the detection and management of osteoporosis.

Absorptiometry, Photon↗
PubMed1995

The impact of bone size on broadband ultrasound attenuation.

Quantitative ultrasound (QUS) is a simple, inexpensive and radiation-free technique to study skeletal status in osteoporosis. Broadband ultrasound attenuation (BUA) is typically used without normalizing for bone thickness. We investigated the impact of bone thickness on BUA, both in in vitro and in vivo, using commercially available ultrasound scanners (Walker Sonix UBA 575 and 575+). For the study in vitro, we analyzed 12 paired cubes (12 x 12 x 12 mm3) of bovine trabecular bone cut from six "parent" blocks (24 x 12 x 12 mm3). These "parent" blocks showed a fairly homogeneous structure as assessed by conventional radiography. BUA and dual x-ray absorptiometry (DXA) measurements of bone mineral density (BMD) were obtained. The difference between the paired cubes was significant for BUA (p < 0.001), but not for BMD (p > 0.05). The BUA of the "parent" blocks was larger by 32-92% than the average BUA of the corresponding paired cubes, and always less than the sum of the paired cubes (5-34%). BUA thus added up in a complex and nonlinear fashion. Measurements in vivo of the calcaneal bone width demonstrated on radiographs (study in vivo I, 28 postmenopausal women) and CT images (study in vivo II, 17 women) showed a small, positive but not significant correlation with BUA (r2 = 0.13 and r2 = 0.007, p > 0.05). The magnitude of this effect provides further evidence that BUA does not scale linearly with bone size. Our results indicate that simple normalization of BUA data by specifying the results in decibels per megahertz per millimeter units may not be appropriate.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗