Diagnostic ultrasound artifacts during imaging of two-body interfaces: part 1--wavelength resonance.

A diagnostic ultrasound technique is to be developed for measuring surface contact areas at the tibio-femoral interface of a total knee replacement in an in vitro industrial engineering setting as a design tool. As a first step, a previous study mathematically characterized the ultrasound behaviour expected at a two-body circular-on-flat interface of known geometry. In the current investigation, a series of test objects was constructed and imaged to experimentally validate the theoretical contact models. Specifically, several unique metal-on-polymer test objects, whose interfaces were point, non-point, and circular contact areas, were ultrasonically imaged. The effects of interface geometry, ultrasound resonance wavelength, lambda/2, and compressive load were studied.

Diagnostic ultrasound artifacts during imaging of two-body interfaces: part 2--beam thickness artifact.

A diagnostic ultrasound method is being developed for measuring surface contact areas at the tibio-femoral interface of a total knee replacement in a non-clinical industrial setting as an engineering design tool. As an initial step towards this, a previous study mathematically predicted the effect of ultrasound beam thickness on contact area measurements at a two-body interface. In the current study, a novel metal-on-polymer acoustic test object was constructed to create circular two-body interfaces of known geometry. The object was ultrasonically imaged, contact areas measured, and the results compared with the theoretical model previously developed.

A digital image analysis method for diagnostic ultrasound calibration.

Acoustic test objects are commonly used for quality assurance testing of diagnostic ultrasound machines. However, the accompanying calibration protocols rely heavily on the judgment of the sonographer, are dependent on machine settings and are semi-quantitative. In the current study, two unique test objects and protocols were designed to quantitatively determine diagnostic ultrasound parameters, namely axial resolution and geometric uniformity, and lateral resolution and geometric uniformity of the ultrasound field. The effect of focal zone, signal gain, and distance from the ultrasound probe on these parameters was assessed. The investigation was performed using a typical low-frequency diagnostic unit equipped with a 7.5 MHz linear pulse-echo probe. Results underline the need to ensure that sensitivity of routine testing regimes is adequate for the measurements to be made. This study is a preliminary part of a larger project developing an ultrasound technique to be used as an engineering design tool in a non-clinical industrial setting for quality assurance testing of total knee replacements immersed in water.

Fuji film and ultrasound measurement of total knee arthroplasty contact areas.

This article describes tibiofemoral contact area measurement results from tests on 1 commercial total knee arthroplasty (TKA) using 2 experimental methods-fuji film and diagnostic ultrasound. The study presents a novel diagnostic ultrasound technique developed specifically for measuring TKA contact areas. Because most experimental investigations have been concerned with interimplant comparison, this article is one of few parametric TKA studies in the literature. Fuji film and ultrasound provide lower and upper bound contact area measurements based on their physical operating principles; this implies that no single measurement method can be relied on exclusively to glean contact area data. Designers should be cautious in using contact area and contact stress as the exclusive predictors of TKA failure.

Real-time sonography to estimate muscle thickness: comparison with MRI and CT.

PURPOSE: We investigated the feasibility of using real-time sonography to measure muscle thickness. Clinically, this technique would be used to measure the thickness of human muscles in which intramuscular microstimulators have been implanted to treat or prevent disuse atrophy. METHODS: Porcine muscles were implanted with microstimulators and imaged with sonography, MRI, and CT to assess image artifacts created by the microstimulators and to design protocols for image alignment between methods. Sonography and MRI were then used to image the deltoid and supraspinatus muscles of 6 healthy human subjects. RESULTS: Microstimulators could be imaged with all 3 methods, producing only small imaging artifacts. Muscle-thickness measurements agreed well between methods, particularly when external markers were used to precisely align the imaging planes. The correlation coefficients for sonographic and MRI measurements were 0.96 for the supraspinatus and 0.97 for the deltoid muscle. Repeated sonographic measurements had a low coefficient of variation: 2.3% for the supraspinatus and 3.1% for the deltoid muscle. CONCLUSIONS: Real-time sonography is a relatively simple and inexpensive method of accurately measuring muscle thickness as long as the operator adheres to a strict imaging protocol and avoids excessive pressure with the transducer.

Cervical spine pseudogout with myelopathy and Charcot joints.

Myelopathy due to calcium pyrophosphate dihydrate (CPPD) crystals in the cervical spine is rare. Neuropathic-like joints are also uncommon manifestations of CPPD crystal disease. We describe a 79-year-old woman with multiple neuropathic joints containing CPPD crystals. She also had a large mass containing CPPD crystals impinging on the cervical spinal cord, causing a myelopathy. She appears to be the first patient with this combination of unusual clinical features with CPPD disease.

Juxtacortical dedifferentiated chondrosarcoma from a primary periosteal chondrosarcoma.

In this report, we describe dedifferentiation in a primary periosteal chondrosarcoma in the proximal tibia of a 73-year-old man. The diagnosis of primary periosteal chondrosarcoma was made by the characteristic radiographic, gross, and microscopic features of the tumor. The presence of dedifferentiation, however, in the form of malignant fibrous histiocytoma, was an unexpected histologic finding. Although rare, dedifferentiation is a well-recognized occurrence in secondary chondrosarcomas arising from precursor osteochondromas. This event has not been previously documented in the setting of primary periosteal chondrosarcoma.

Unilateral hypertrophic osteoarthropathy secondary to infected aortobifemoral graft and aortoenteric fistula.

Localized hypertrophic osteoarthropathy is a reported manifestation of--and an important diagnostic clue to--infection of an aortic graft and aortoenteric fistula, two complications of vascular bypass surgery that carry a significant risk of mortality. This clue may lead to the early diagnosis essential to a successful outcome. The authors describe a patient with localized unilateral hypertrophic osteoarthropathy secondary to infection of an aortobifemoral graft and aortoenteric fistula.

Femoral fracture mimicking acute arthritis in Down's syndrome.

We describe a 38-year-old white woman with Down's syndrome with a history of chronic arthritis and hyperuricemia who presented with acute left knee pain, patellar tenderness and patello-femoral instability. Findings appeared due to a fracture of the lateral femoral condyle, which responded to conservative therapy with a spica cast. Patellofemoral instability in Down's syndrome can be associated with significant morbidity including femoral condyle fracture. Patients with Down's syndrome who present with acute knee arthritis responding poorly to antiinflammatory agents and other conventional therapy should be assessed for fractures related to patellar dislocation, as treatments for the 2 disorders differ.

Clinical Applications of Magnetic Resonance Imaging: Tapping the strengths of this imaging technique.

Magnetic resonance imaging (MRI) is a relatively new diagnostic imaging technique that has substantially affected the diagnosis of a multitude of diseases. It has become the imaging modality of choice for a number of pathologic processes, especially in the central nervous system. The authors discuss the clinical applications of MRI, its current status in radiologic investigations, and radiographic features of some of the common diseases of the central nervous system.