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Biomedical subjects

M D Murphey

Publications and source records attributed to M D Murphey.

At least 19 recordsLinked to original sources
PubMed1992

Titanium-induced arthropathy associated with polyethylene-metal separation after total joint replacement.

Complications of total joint replacements are not infrequent. The authors describe five patients with displacement of the polyethylene component in two knee (metal-backed patellar component) and three hip joint replacements. Clinical, radiographic, surgical, and pathologic findings were reviewed in all cases. Conventional radiographs revealed abnormal position of the metal components in all patients and opaque curvilinear periarticular deposits in four. Arthropathy caused by deposition of small titanium particles from metal friction (in the absence of interposed polyethylene) was pathologically proved to correspond to the periarticular opacity. The subtle radiolucent polyethylene component was identified in all patients; adequate visualization in some cases may necessitate imaging with additional methods such as magnification, phosphor plate, and soft-tissue radiographic techniques; conventional tomography; and arthrography. Early recognition of these abnormalities in patients with painful joint replacements may allow less extensive surgical revision and prevent development of titanium-induced arthropathy.

Aged↗
PubMed1992

Computed radiography in musculoskeletal imaging: state of the art.

Computed radiography is a 2K x 2K x 10 bit digital radiographic system that replaces the film-screen combination with a photo-stimulable phosphor plate. The advantages of this relatively new technology include linear detector response, improved detector efficiency, and digital processing capabilities. Musculoskeletal applications benefit significantly from these attributes, which result clinically in the ability to reduce both radiation dose and number of exposures. Studies of observers' performance have shown no statistically significant difference in diagnostic accuracy between film-screen and computed radiographic musculoskeletal images. Computed radiography is particularly useful in the evaluation of the musculoskeletal system in traumatized patients with portable radiographs, spine radiographs, scoliosis studies, and depiction of soft-tissue abnormalities. Limitations include change in image format and size, high cost, decreased spatial resolution, restricted throughput, increased perception of noise, and new artifacts that must be recognized. Spatial resolution limitations of computed radiography in identification of fine detail information can be improved by using magnification techniques. Radiation dose reduction with an exposure decrease of 25-50% can be achieved without loss of diagnostic accuracy, although this depends on the examination and the abnormality. An interactive workstation is important in the use of a computed radiographic system with capabilities to adjust display parameters to best depict images and disease. We conclude that computed radiography is an alternative to film-screen radiography without significant differences in diagnostic quality in the evaluation of musculoskeletal images.

Humans↗
PubMed1991

Image data compression using a new floating-point digital signal processor.

A new dual-ported, floating-point, digital signal processor has been evaluated for compressing 512 and 1,024 digital radiographic images using a full-frame, two-dimensional, discrete cosine transform (2D-DCT). The floating point digital signal processor operates at 49.5 million floating point instructions per second (MFLOPS). The level of compression can be changed by varying four parameters in the lossy compression algorithm. Throughput times were measured for both 2D-DCT compression and decompression. For a 1,024 x 1,024 x 10-bit image with a compression ratio of 316:1, the throughput was 75.73 seconds (compression plus decompression throughput). For a digital fluorography 1,024 x 1,024 x 8-bit image and a compression ratio of 26:1, the total throughput time was 63.23 seconds. For a computed tomography image of 512 x 512 x 12 bits and a compression ratio of 10:1 the throughput time was 19.65 seconds.

Algorithms↗
PubMed1991

Wide area networks for teleradiology.

Teleradiology networks transmit digital radiographic images from one location to another. These networks are wide area networks. Teleradiology networks are used for diagnostic purposes and preview tasks. Wide area networks for teleradiology use public service switching. The use of fiber optics networks provide reduced costs and increased flexibility. An example is presented that compares the cost of teleradiology networks.

Computer Communication Networks↗
PubMed1991

Clinical experience in the use of photostimulable phosphor radiographic systems.

The experience with CR systems gained at the three institutions described in this report demonstrates numerous advantages over the conventional screen-film system. These include: (1) a reduction in the radiation exposure delivered to the patient (25% to 50%); (2) a decrease in the number of repeat examinations needed, especially in portable units where technical difficulties are common with screen-film examinations; this is attributable to the linear, wider dynamic range of CR systems compared with screen-film combinations; (3) the capability to archive electronically all images by means of a digital optical storage system; (4) automatic electronic setting of the laser scanner for the latitude and sensitivity on each image; (5) the digital images are available for transmission to all image display workstations on a local or wide-area network; and (6) the ability to adjust interactively the display parameters to best depict images and pathology as well as salvage technically suboptimal examinations. Several disadvantages of CR systems compared with conventional screen-film examinations have also been identified.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1991

State-of-the-art digital radiography.

Technologic advances in digital radiography have improved the ways in which radiographic images are acquired, displayed, transmitted, recorded, and archived. With computed radiography, performed with storage phosphor plates and interactive high-resolution workstations, radiation dose is reduced and repeat exposures necessitated due to technical errors are eliminated. Digital fluorography allows reductions in dose, procedure time, and film costs. These digital imaging modalities have been well accepted clinically and are equal in diagnostic accuracy to conventional methods. Teleradiology has advanced with the development of laser film digitization, fiberoptic networks, and dial-up circuit switching technology. Laser film printers yield improved hard copies of transmitted images, but further work is needed to faithfully reproduce the images displayed on high-resolution work-stations. Although the capacity for archiving digital image data has increased (260,000 examinations or 23,500 Gbytes can be stored in a six-unit optical disc library), higher capacity storage media are needed. Further technologic advances in the speed of image transmission and storage capacity are anticipated.

Humans↗
PubMed1991

Sacroiliitis: MR imaging findings.

Magnetic resonance (MR) imaging was performed in seven asymptomatic volunteers and 17 patients with clinical and radiologic evidence of sacroiliitis. MR imaging findings were compared with those at computed tomography (CT) to determine the MR imaging appearance of the sacroiliac joint when normal and in sacroiliitis. The normal articulation was well depicted with MR imaging. Findings of sacroiliitis were identified in 20 sacroiliac joints (12 patients). MR imaging findings characteristic of sacroiliitis included abnormal cartilage signal intensity (95% of joints) and erosions (75% of joints) on T1-weighted images. Areas of increased intensity in the articulation (80% of joints) or in erosions (60% of joints) were seen on T2-weighted images. MR imaging was superior to CT for evaluation of cartilage and detection of erosions. Four sacroiliac joints (20%) and two patients (17%) with MR imaging findings of sacroiliitis were negative at CT. The authors conclude that MR imaging is a valuable method for detecting sacroiliitis, particularly when results of other imaging techniques are inconclusive.

Adolescent↗
PubMed1990

Cytogenetic findings and biologic behavior of giant cell tumors of bone.

Giant cell tumor of bone is a benign but often aggressive lesion with a distinct tendency toward local recurrence and, rarely, malignant transformation. Over a 3-year period, 20 giant cell tumors from 14 different patients were cytogenetically characterized. Random chromosomal abnormalities were detected in 14 of the 20 specimens and clonal chromosomal abnormalities were detected in six. An unusual anomaly, telomeric fusion, was the most striking random chromosomal abnormality detected. A comparison of the presence or absence of cytogenetic aberrations and the clinical behavior of these neoplasms was studied as well as a comparison of the aberrations in the initial specimen with those in subsequent specimens. Chromosomal abnormalities were detected in all but one of the ten tumors shown to be locally aggressive, recurrent, or metastatic. (The abnormalities observed in five of these tumors were clonal). There were no chromosomal abnormalities present in three of four tumors that behaved in an innocent fashion. These findings support the presence of chromosomal abnormalities in giant cell tumors (telomeric fusion in particular) and suggest that cytogenetic analysis may be useful in predicting the biologic behavior of these neoplasms.

Adolescent↗
PubMed1990

Experience in the use of an image-processing workstation for a photostimulable phosphor radiographic system.

Photostimulable phosphor radiographic (computed radiographic) systems are being installed and evaluated by radiology departments. The use of interactive image-processing workstations are a major advantage for any computed radiography system. An interactive image-processing workstation enables rapid image retrieval, reduces the examination repeat rate, provides for image enhancement, and rapidly sets the desired display parameters for laser-printed images. The authors have conducted over 2,500 radiographic examinations using a computed radiographic system equipped with an interactive image-processing workstation. Their experience supports the necessity of such a workstation.

Computer Systems↗
PubMed1990

Perimeter encoding for teleradiology.

Perimeter encoding is a technique of data compression that is done simply by outlining the area of interest on an examination. In a sample of 92 emergency room examinations (excluding chest, abdomen, and pelvic exams), 304 films were interpreted by a resident radiologist who indicated the area of interest by marking four corners of a rectangle. The adequacy of the area of interest was determined by a staff osteoradiologist during subsequent review of the films. The amount of data reduction was measured by determining the ratio of the area of interest inside a rectangle to the area of the film (compression ratio). The overall average compression ratio was 3 to 1. This preliminary study suggests that further evaluation of perimeter encoding is warranted.

Emergency Medical Service Communication Systems↗
PubMed1990

Nondisplaced fractures: spatial resolution requirements for detection with digital skeletal imaging.

Fifty-six radiographs of nondisplaced or minimally displaced fractures of the extremities and an equal number of studies with normal findings were selected and digitized to produce spatial resolution varying from 5.75 to 0.72 line pairs per millimeter (1p/mm), corresponding to pixel sizes ranging from 0.08 to 0.64 mm. The conventional and digitized images were evaluated by 10 radiologists, who gave their decision confidence on a graded scale. Receiver operating characteristic analyses were performed from these data to compare the digital images with the conventional radiographs. There was a progressive improvement in observer performance as the pixel size decreased. A pixel size greater than 0.16 mm (2.88 1p/mm) resulted in a significant loss of diagnostic accuracy in comparison with conventional radiographs. Specific fractures in which a larger pixel size adversely affected the evaluation included torus injuries, corner fractures in child abuse, minimal avulsion injuries, and fractures that demonstrated only trabecular disruption.

Adult↗
PubMed1990

Teleradiology: an assessment.

A teleradiology system acquires radiographic images at one location and transmits them to one or more remote sites, where they are displayed and/or converted to hard copy. These systems often employ wide area networks. Their goal is to provide improved radiologic services at all sites on the network. Experience in the use of teleradiology systems has demonstrated the need for a laser film digitizer, an optical disk, and a high-quality display and/or laser film printer at each site. Single-site hardware purchase costs average $196,000, plus an additional 20% for yearly network services. Hardware purchased for a consultation or central referral facility approximates $344,000.

Computer Communication Networks↗
PubMed1989

Image data compression in magnification hand radiographs.

A study was conducted on the use of an irreversible compression technique, Fourier quantization, to reduce the amount of digital data needed for an image. The effect of image compression was studied in radiographs obtained to diagnose subperiosteal bone resorption. Magnification radiographs of 44 hands were digitized to an array size of 4,096 X 4,096 X 12 bits. Selected subregions containing a single middle phalanx were compressed and reconstructed. A subset of the resultant 12-bit uncompressed and 8-, 7-, and 6-bit compressed images were read by four radiologists whose responses were analyzed with receiver operating characteristic (ROC) techniques. There were 81 images used in the ROC analysis, of which 48 were normal and 33 showed subperiosteal resorption. No statistically significant loss of diagnostic quality was detected for 8- or 7-bit compressed images, with average compression ratios of 16:1 and 28:1, respectively. Diagnostic quality was lost with 6-bit images, with an average compression ratio of 107:1.

Arthritis↗
PubMed1989

Digital skeletal radiography: spatial resolution requirements for detection of subperiosteal resorption.

Forty direct-magnification (2:1 enlargement) radiographs showing various severities of subperiosteal resorption and 40 normal studies were selected and digitized. Images were processed to produce varying resolution, from 1.42 to 11.4 Ip/mm, corresponding to pixel sizes ranging from 0.04 to 0.32 mm. The conventional and digitized images were evaluated by six radiologists giving their decision confidence on a graded scale. Receiver operating characteristic analyses were performed from these data to compare the digital images with the conventional films. The results show significant improvement in diagnostic accuracy as pixel size decreases to the level of 0.08 mm. Digital images with pixel sizes of 0.04 mm (11.4 Ip/mm) were not significantly different from the magnification radiographs in terms of observer performance. In conclusion, for high-resolution skeletal imaging as needed for detection of subperiosteal resorption, spatial resolution of 5.7 Ip/mm or less resulted in a significant loss of diagnostic accuracy, as compared with conventional films.

Bone Resorption↗
PubMed1989

Diagnostic imaging of spinal trauma.

The radiologist has a pivotal role in evaluation of spinal trauma patients because proper treatment cannot begin before the abnormality is diagnosed. Plain films remain the screening modality of choice, and by understanding the radiographic signs of injury, patterns produced by various traumatic mechanisms can be recognized. As radiologists we can then provide insight to our clinical colleagues into the optimal methods of further investigation. The objective is to eliminate the possibility of further damage and to identify lesions amenable to correction.

Fractures, Bone↗