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D A Rubin

Publications and source records attributed to D A Rubin.

At least 37 records · Page 2Linked to original sources
PubMed1997

Forced choice and ordinal discrete rating assessment of image quality: a comparison.

This study compared a five-category ordinal scale and a two-alternative forced-choice subjective rating of image quality preferences in a multiabnormality environment. 140 pairs of laser-printed posteroanterior (PA) chest images were evaluated twice by three radiologists who were asked to select during a side-by-side review which image in each pair was the "better" one for the determination of the presence or absence of specific abnormalities. Each pair included one image (the digitized film at 100 microns pixel resolution and laser printed onto film) and a highly compressed (approximately 60:1) and decompressed version of the digitized film that was laser printed onto film. Ratings were performed once with a five-category ordinal scale and once with a two-alternative forced-choice scale. The selection process was significantly affected by the rating scale used. The "comparable" or "equivalent for diagnosis "category was used in 88.5% of the ratings with the ordinal scale. When using the two-alternative forced-choice approach, noncompressed images were selected 66.8% of the time as being the "better" images. This resulted in a significantly lower ability to detect small differences in perceived image quality between the noncompressed and compressed images when the ordinal rating scale is used. Observer behavior can be affected by the type of question asked and the rating scale used. Observers are highly sensitive to small differences in image presentation during a side-by-side review.

Fourier Analysis↗
PubMed1997

Anterolateral soft-tissue impingement in the ankle: diagnosis using MR imaging.

OBJECTIVE: This study was performed to elucidate the MR imaging findings and pitfalls for the diagnosis of anterolateral soft-tissue impingement in the ankle, a cause of chronic ankle pain that can be relieved by arthroscopic resection. MATERIALS AND METHODS: We retrospectively reviewed MR imaging examinations of 18 patients with arthroscopically confirmed anterolateral ankle impingement. The MR images of 18 additional subjects with symptoms that could mimic anterolateral impingement, but who had a surgically confirmed alternate diagnosis (instability, peroneal tendon injury, osteochondral defect, normal arthroscopy) and no evidence of impingement at arthroscopy, served as controls. RESULTS: On the MR imaging studies, nine patients had an ankle effusion, eight of whom showed an abnormal soft-tissue structure in the anterolateral gutter, 2-15 mm in maximal diameter. No soft-tissue mass was seen in the patients without joint fluid. Four control subjects with instability had a similar soft-tissue structure in the anterolateral gutter, but in the control subjects the finding represented a portion of the torn anterior talofibular ligament. CONCLUSION: Anterolateral soft-tissue impingement of the ankle can be suggested by MR imaging when fluid in the lateral gutter outlines an abnormal soft-tissue structure separate from the anterior talofibular ligament.

Adolescent↗
PubMed1997

MR imaging of the knee menisci.

MR imaging of the knee is highly accurate for the noninvasive diagnosis of meniscal tears and other meniscal pathology. Familiarity with the normal anatomy and common pitfalls reduces errant interpretations, but does not eliminate them entirely. The two MR imaging signs of a meniscal tear are abnormal intrameniscal signal on a short-TE image that unequivocally contacts the meniscal surface, and abnormal meniscal morphology in the absence of prior meniscal surgery. To help guide the treatment of meniscal injuries, which continues to evolve, the MR imaging report should thoroughly describe tears, and not simply indicate whether a meniscal tear is present. In the patient with an ACL tear, the accuracy of MR imaging examination for meniscal tears, especially lateral tears, diminishes but still surpasses that of physical examination. The MR imaging criteria for meniscal tears need to be modified in patients who have undergone meniscal surgery.

Humans↗
PubMed1996

Is it possible to construct phylogenetic trees using polypeptide hormone sequences?

Because of the high degree of primary sequence conservation in neuropeptides and low molecular weight polypeptide hormones, these polypeptides are not useful for constructing phylogenetic trees based on maximum parsimony analysis. This review focuses on the organization of neuropeptide and polypeptide hormone precursors and discusses strategies for aligning polypeptide precursors for phylogenetic analysis. Examples are provided to support the hypothesis that some neuropeptide and polypeptide precursors and some high molecular weight polypeptide hormones can be used as data sets for resolving deep divergences among vertebrate taxa.

Amino Acid Sequence↗
PubMed1996

Subjective quality assessment of computed radiography hand images.

To evaluate the sensitivity of a non-receiver-operating characteristic (ROC) study in assessing small differences of perceived image quality of hand images acquired by computed radiography (CR) and conventional screen-film systems, hand images were acquired on 12 patients with both conventional screen-film and CR. Each CR image was then processed with three different edge-enhancement algorithms. One conventional film and four CR images were then viewed side by side by five radiologists. Observers rated perceived image quality of each radiograph using a 10-category discrete scale. The study was repeated after 6 weeks using a different block randomization scheme. Despite the small sample size, significant differences (P < .05) in assigned image quality were detected among CR images acquired at low, medium, and high resolutions. Image processing routines did not fully compensate for differences in quality between conventional film and CR-acquired images. The quality rating of the reference conventional image was found to be dependent on the quality of images with which it was compared. Small, highly sensitive study designs can be used to identify radiologists' perceived differences in image quality. "Reference" or "gold standard" quality are important in such studies. Edge-enhancement schemes cannot fully compensate for perceived image quality degradations because of reduced image resolution.

Algorithms↗
PubMed1996

The radiology of early arthritis.

Accurate diagnosis of early arthritis is important because successful treatment with preservation of joint structure and function is most likely when specific therapeutic interventions are instituted early in the disease. Early arthritis may be difficult to accurately diagnose clinically, even for experience practitioners. High-yield radiologic studies are possible, but the radiologist must realize that for each patient and each disease, how and where to look, and what to look for, may differ. Conventional radiographs remain the most important screening studies for both the axial and appendicular skeleton. Other modalities, especially MRI, have limitations but can be powerful tools in problem cases. Each disease has target areas of early involvement that may differ from the classic distribution seen once the process is established. A careful examination of these areas for subtle but characteristic early findings will often be rewarding.

Adult↗
PubMed1996

The seronegative spondyloarthropathies.

The four seronegative spondyloarthropathies can be divided into two main groups by their pattern of sacroiliitis and spondylitis (Table 1). The axial skeletal changes of ankylosing spondylitis and enteropathic arthropathy are often indistinguishable, as are those of psoriatic arthritis and Reiter's syndrome. Early proximal appendicular joint involvement in ankylosing spondylitis is a poor prognostic sign except in women where peripheral arthritis is more common, but has a more benign course. Peripheral joint destruction in enteropathic arthropathy is rare because treatment of the bowel disease also treats the arthritis. Distal appendicular involvement is characteristic of psoriatic arthritis and Reiter's syndrome. Proliferative erosions and enthesitis, periostitis, and normal mineralization aid in differentiating psoriatic arthritis and Reiter's syndrome from rheumatoid arthritis. The distribution of arthritis also differs from that seen in classic rheumatoid arthritis, with asymmetry and involvement of the distal interphalangeal joints more common in psoriatic disease and Reiter's syndrome.

Arthritis, Psoriatic↗
PubMed1996

Radioscaphocapitate ligament of the wrist: volar filling defect during radiocarpal arthrography.

PURPOSE: To determine whether a filling defect seen at radiocarpal arthrography represents the volar radioscaphocapitate ligament and to establish how frequently this finding is seen in patients referred for wrist arthrography. MATERIALS AND METHODS: Radiopaque markers were surgically placed along the borders of the radioscaphocapitate ligament in three cadaveric wrist specimens. Each cadaveric wrist was examined at arthrography. Seventy contrast material-enhanced wrist arthrograms were retrospectively reviewed for visualization of the radioscaphocapitate ligament. The arthrographic appearance of the ligament was compared with its reported appearance at dissection, radiography, and magnetic resonance arthrography. RESULTS: The cadaveric study, together with an analysis of the appearance of the ligament, confirmed that the radioscaphocapitate ligament can be seen as a filling defect at radiocarpal arthrography. Fifty-five (78%) of the 70 clinical arthrograms unequivocally demonstrated the radioscaphocapitate ligament. The ligament was most conspicuous early during the injection, especially with the wrist in ulnar deviation. CONCLUSION: The radioscaphocapitate ligament of the wrist can be visualized during routine radiocarpal arthrography. Future studies will need to determine whether abnormalities of the radioscaphocapitate ligament can be diagnosed at arthrography.

Adult↗
PubMed1996

Are MR imaging signs of meniscocapsular separation valid?

PURPOSE: To define the positive predictive value (PPV) for the magnetic resonance (MR) imaging diagnosis of meniscocapsular separation in the knee. MATERIALS AND METHODS: The MR reports of 52 patients aged 16-75 years who had a prospective MR diagnosis of meniscocapsular injury were correlated with arthroscopic results. MR images obtained in 50 of these patients were retrospectively reviewed for specific signs of meniscocapsular separation, which included meniscal displacement, peripheral meniscal corner tears, increased perimeniscal signal intensity, fluid deep to the medial collateral ligament, and abnormal lateral fascicles. MR findings were correlated with arthroscopic findings. RESULTS: For the prospective MR interpretations, the PPV for meniscocapsular separation was 9% medially and 13% laterally. Meniscal displacement (measured from the meniscal edge to the tibia) was as great as 10 mm medially or 13 mm laterally without meniscocapsular tears at arthroscopy. Meniscal displacement did not correlate with effusion. Meniscal corner tears had a PPV of 0% medially and 50% laterally. Fluid at the meniscocapsular border and fluid deep to the medial collateral ligament were poor predictors of meniscocapsular abnormalities. Abnormal-appearing meniscal fascicles had a PPV of 8% for lateral meniscocapsular separation. CONCLUSION: The PPV for the MR diagnosis of meniscocapsular separation is low; the reported MR signs correlate poorly with arthroscopic findings.

Adolescent↗
PubMed1996

Cloning of a gar (Lepisosteus osseus) GH cDNA: trends in actinopterygian GH structure.

A cDNA containing the sequence of GH was cloned and sequenced from a pituitary cDNA library for the holostean fish Lepisosteus osseus (common name: gar). The gar GH cDNA contained an open reading frame of 633 nucleotides and a 3' untranslated region (including the terminal codon TAG) of 1058 nucleotides. The overall length of the gar GH cDNA including leader sequence, signal sequence, hormone sequence and 3' untranslated region was 1713 nucleotides. Thus, the gar GH cDNA is the largest vertebrate GH cDNA yet cloned. A comparison of GH sequences from ancient (holostean fishes-gar and bowfin; one chondrostean fish-the Russian sturgeon) and more modern (27 species of teleosts) members of class Actinopterygii indicate that members of this class have maintained many of the invariant residues deemed necessary for GH folding motifs (intramolecular relationships) observed in mammals.

Amino Acid Sequence↗
PubMed1996

Flexor tendon tears in the hand: use of MR imaging to diagnose degree of injury in a cadaver model.

OBJECTIVE: Treatment of flexor tendon lacerations of the finger partly depends on the degree of injury, which is difficult to determine clinically. We used a cadaver model to investigate the potential of MR imaging in evaluating these injuries. MATERIALS AND METHODS: A scalpel was drawn transversely across the volar surface of four cadaver hands, producing various flexor tendon injuries. MR imaging of each hand was performed using axial two-dimensional spin-echo and three-dimensional gradient-recalled-echo sequences. The three-dimensional data sets were interactively reformatted along the long axis of each tendon. The hands were then dissected; injury to each digit was categorized, measured, and compared with the prospective MR interpretations. RESULTS: Twelve high-grade flexor tendon tears (10 complete tears, with 1- to 14-mm separation of the torn ends, and two partial tears involving 50% or more of the total tendon cross-sectional area) and two partial tears of less than 50% of tendon area were produced; four tendons were not injured. Using MR imaging, we diagnosed 11 of the 12 high-grade lesions (those involving at least 50% of the total tendon cross-sectional area); the MR images did not show one complete tear whose separation measured 2 mm long at dissection. All intact tendons were correctly identified. We underestimated the extent of five lesions but overestimated none. Using the reformatted images, we reduced the number of errors that we would have made interpreting the transverse images alone. CONCLUSION: In this cadaver model, using MR imaging we accurately distinguished different degrees of flexor tendon tears. The potential of this technique for noninvasively diagnosing flexor tendon injury in patients awaits clinical studies.

Cadaver↗
PubMed1996

MR imaging of the foot: utility of complex oblique imaging planes.

Successful MR imaging of the foot presents special challenges to the radiologist. Accurate and confident diagnosis presupposes the ability to produce high-resolution images of obliquely oriented, relatively small structures. Orienting the foot within an appropriate local coil to bring such structures into an orthogonal imaging plane, or even into a conventional oblique plane, may be impossible or intolerably uncomfortable for the patient. The frequent result is motion artifacts, which are accentuated when using a small field of view. However, when patients are comfortably positioned, the anatomy of interest often lies in a plane that is not orthogonal to any of the conventional imaging planes. Fortunately, commercially available MR imaging equipment can produce images in complex oblique planes with relative ease. In this pictorial essay, we discuss the technical considerations for expedient diagnostic MR imaging of the complex anatomy of the foot and illustrate our experiences with this technique.

Adolescent↗
PubMed1995

Obtaining a more resolute teleost growth hormone phylogeny by the introduction of gaps in sequence alignment.

In order to obtain a more resolute phylogeny of teleosts based on growth hormone (GH) sequences, phylogenetic analyses were performed in which deletions (gaps), which appear to be order specific, were upheld to maintain GH's structural information. Sequences were analyzed at 194 amino acid positions. In addition, the two closest genealogically related groups to the teleosts, Amia calva and Acipenser guldenstadti, were used as outgroups. Modified sequence alignments were also analyzed to determine clade stability. Analyses indicated, in the most parsimonious cladogram, that molecular and morphological relationships for the orders of fishes are congruent. With GH molecular sequence data it was possible to resolve all clades at the familial level. Analyses of the primary sequence data indicate that: (a) the halecomorphean and chondrostean GH sequences are the appropriate outgroups for generating the most parsimonious cladogram for teleosts; (b) proper alignment of teleost GH sequence by the inclusion of gaps is necessary for resolution of the Percomorpha; and (c) removal of sequence information by deleting improperly aligned sequence decreases the phylogenetic signal obtained.

Amino Acid Sequence↗