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Biomedical subjects

E K Ho

Publications and source records attributed to E K Ho.

At least 19 recordsLinked to original sources
PubMed2006

The spectrum of myelodysplastic syndromes post-solid organ transplantation: a single institutional experience.

An increased incidence of acute myeloid leukemia (AML) has recently been documented in patients post-solid organ transplantation but the incidence and types of myelodysplastic syndromes (MDS) occurring in this patient population are not known. We identified 5 patients (3M, 2F, age 48-64 years) who developed MDS ranging from 1.8 to 25 years (median 4.2 years) post-solid organ transplantation, only 2 patients had received azathioprine. The cumulative incidence of MDS in heart and lung transplant recipients at 15 years was 0.5% and 1.8%, respectively, which is markedly higher compared to the general population. Low-risk types of MDS predominated, 3 of 5 patients are alive (median 3.9 years) since diagnosis. Deletions of chromosome 20q, which have not been previously reported in post-transplant MDS/AML, were identified in 3 cases. Our findings expand the morphologic and cytogenetic spectrum of MDS occurring post-solid organ transplantation and suggest that mechanisms beside azathioprine toxicity might be important in disease pathogenesis.

Biopsy↗
PubMed2001

Analyzing holistic parsers: implications for robust parsing and systematicity.

Holistic parsers offer a viable alternative to traditional algorithmic parsers. They have good generalization performance and are robust inherently. In a holistic parser, parsing is achieved by mapping the connectionist representation of the input sentence to the connectionist representation of the target parse tree directly. Little prior knowledge of the underlying parsing mechanism thus needs to be assumed. However, it also makes holistic parsing difficult to understand. In this article, an analysis is presented for studying the operations of the confluent preorder parser (CPP). In the analysis, the CPP is viewed as a dynamical system, and holistic parsing is perceived as a sequence of state transitions through its state-space. The seemingly one-shot parsing mechanism can thus be elucidated as a step-by-step inference process, with the intermediate parsing decisions being reflected by the states visited during parsing. The study serves two purposes. First, it improves our understanding of how grammatical errors are corrected by the CPP. The occurrence of an error in a sentence will cause the CPP to deviate from the normal track that is followed when the original sentence is parsed. But as the remaining terminals are read, the two trajectories will gradually converge until finally the correct parse tree is produced. Second, it reveals that having systematic parse tree representations alone cannot guarantee good generalization performance in holistic parsing. More important, they need to be distributed in certain useful locations of the representational space. Sentences with similar trailing terminals should have their corresponding parse tree representations mapped to nearby locations in the representational space. The study provides concrete evidence that encoding the linearized parse trees as obtained via preorder traversal can satisfy such a requirement.

Algorithms↗
PubMed1999

How to design a connectionist holistic parser.

Connectionist holistic parsing offers a viable and attractive alternative to traditional algorithmic parsers. With exposure to a limited subset of grammatical sentences and their corresponding parse trees only, a holistic parser is capable of learning inductively the grammatical regularity underlying the training examples that affects the parsing process. In the past, various connectionist parsers have been proposed. Each approach had its own unique characteristics, and yet some techniques were shared in common. In this article, various dimensions underlying the design of a holistic parser are explored, including the methods to encode sentences and parse trees, whether a sentence and its corresponding parse tree share the same representation, the use of confluent inference, and the inclusion of phrases in the training set. Different combinations of these design factors give rise to different holistic parsers. In succeeding discussions, we scrutinize these design techniques and compare the performances of a few parsers on language parsing, including the confluent preorder parser, the backpropagation parsing network, the XERIC parser of Berg (1992), the modular connectionist parser of Sharkey and Sharkey (1992), Reilly's (1992) model, and their derivatives. Experiments are performed to evaluate their generalization capability and robustness. The results reveal a number of issues essential for building an effective holistic parser.

Artificial Intelligence↗
PubMed1998

A new method for casting discrepancy: some results for a phosphate-bonded investment.

OBJECTIVES: An accurate and realistic casting discrepancy method applicable to base metal alloys has hitherto been lacking. The purpose of this study was to develop a method for determining casting discrepancy free of interference from oxide, slag and surface defects, working under realistic conditions. In addition, a variable was sought that could be used for calibrating the casting process to allow for local errors. METHODS: A crown pattern was designed to incorporate circular V-grooves on the margin and the inside surface of the occlusal part for determination of the 'groove root diameter' (GRD) with a measuring microscope. Castings using a phosphate-bonded investment were made to test the effects of 'hygroscopic' expansion, burn-out temperature, powder/liquid ratio and groove location. RESULTS: The tested investment variables showed the expected effects, but the distortion between marginal and pulpal regions was clearly shown, as were interactions between some variables. 'Special liquid' proportion appears to be a good candidate variable for process calibration. CONCLUSIONS: The GRD method was shown to be sensitive and reproducible. It is also applicable to many other casting systems, and in particular to monitoring overall process discrepancy, i.e. from tooth preparation to casting, which is suggested as being the key issue.

Analysis of Variance↗
PubMed1996

Immunologic monitoring in lung allograft recipients.

To identify patients with increased risk of chronic lung allograft rejection, we assessed the utility of an in vitro biopsy-derived lymphocyte growth assay and serum anti-HLA antibody screening as a complement to currently available methods of monitoring lung allograft recipients. Lymphocyte growth assay was performed on bronchoscopic fragments of tissue cultured in medium with rIL-2. Seventy-nine biopsies from 31 lung transplant recipients were tested by lymphocyte growth assay, and results were correlated with histopathology findings. Positive lymphocyte growth was found in 12/26 (46%) episodes of acute rejection, 5/44 biopsies without rejection (11%), and 0/9 episodes of bronchitis. Positive lymphocyte growth was seen in 7/16 (44%) grade A1 rejections and in 5/10 (50%) grade A2 rejections, as opposed to only 5/44 (11%) grade A0 (no rejection) biopsies (P < 0.01 for both A1 and A2 with respect to A0). Actuarial probability of remaining free from obliterative bronchiolitis (OB)* tended to be higher in patients who did not exhibit lymphocyte growth in biopsies. Sequential samples of sera obtained at the time of the biopsy were screened for lymphocytotoxic anti-HLA antibodies. Twenty-two of 44 recipients (50%) developed anti-HLA antibodies during the first postoperative year, exhibiting greater than 10% reactivity to an HLA reference panel of lymphocytes in four or more consecutive serum samples. Actuarial survival of lung allograft recipients with anti-HLA antibodies (n = 22) was lower than in those without anti-HLA antibodies (n = 22; P = 0.03). Of the 22 antibody producers, 7/12 died as a consequence of OB. Of the 22 non-antibody-producers, 1/2 deaths occurred as a consequence of OB. Anti-HLA antibodies were present in 9/11 instances of OB (82% sensitivity) and in 13/33 patients without OB (61% specificity; P = 0.03). These data indicate that lung transplant recipients with positive lymphocyte growth and anti-HLA antibodies are at an increased risk of chronic allograft rejection.

Antibodies↗
PubMed1995

New prognostic factors to predict the final outcome of brace treatment in adolescent idiopathic scoliosis.

STUDY DESIGN: Eighty-five patients with adolescent idiopathic scoliosis treated with Milwaukee or thoracolumbosacral orthoses at The Duchess of Kent Children's Hospital were studied longitudinally at 4-6-month intervals until maturity for spinal curvature and vertebral rotation, or until termination of brace treatment for persons who experienced brace failure who went on to have surgery. OBJECTIVES: To identify radiologic features so that it may be possible to predict outcome of brace treatment early on. SUMMARY OF BACKGROUND DATA: The structural curve with poor flexibility and large rotational prominence have been found to be associated with poor prognosis for brace treatment. However, early response to bracing for spinal deformity and its relationship to final outcome of brace treatment in a longitudinal study is not available in the literature. METHODS: Vertebral rotation and Cobb angles measured from anteroposterior radiographs of the spine obtained before bracing and 1-2 months after bracing were found valuable for prediction. Changes in post-brace Cobb angle and vertebral rotation were considered as an increase or reduction only when there was an increase or reduction of minimum 5 degrees or more from their prebrace measurements. RESULTS: Those patients who showed increase in vertebral rotation and/or in Cobb angle after brace application were shown to have progression of curves leading to brace failure in 93% of patients, and 79% of these required surgery. The patients with no change in both vertebral rotation and Cobb angle after bracing often experienced brace failure (69%). Two patients (15%) required surgery. The results show that reduction of both Cobb angle and vertebral rotation after application of a brace is a prognostic indicator for a good outcome (97%), and no patients required surgery. Most of the patients with lumbar scoliosis (91%) showed such reductions. CONCLUSION: The findings show a strong association between changes in vertebral rotation and the Cobb angle after application of a brace and the final outcome. Reduction in both is indicative of a good outcome, whereas increase in one or both indicates brace failure.

Adolescent↗
PubMed1995

Fracture of the odontoid peg in ankylosing spondylitis: case report.

Fractures in patients with ankylosing spondylitis tend to affect the lower cervical spine. We describe a 50-year-old man who sustained fractures of the odontoid peg and body of the second cervical vertebra after a hyperextension injury. In absence of atlanto-occipital fusion, deformity from previous lower cervical spine injury may have contributed to susceptibility for this very rare combination of fractures. The patient was treated surgically with a good result.

Cervical Vertebrae↗
PubMed1994

Pulmonary functions in congenital scoliosis.

STUDY DESIGN: Thirty-six patients with congenital scoliosis underwent full clinical and radiologic evaluation of their deformity and their full pulmonary functions. OBJECTIVES: This study observed pulmonary functions in congenital scoliosis in detail, evaluated pulmonary functions in nonsurgically treated patients, and established whether, in surgically treated patients, there are any differences between those with multiple thoracic anomalies and those with lumbar or one of two thoracic anomalies. SUMMARY OF BACKGROUND DATA: Eighty-six of our patients in both groups (surgically and nonsurgically treated) showed abnormal increases in residual volumes, indicating a restrictive pattern of lung function. The results of their pulmonary functions were analyzed using predicted values to eliminate age affect. METHODS: Pulmonary functions were assessed using the Gould 5000IV Computerized Pulmonary Function System. RESULTS: Overall, mean total lung capacity was 89% of predicted value, and mean vital capacity and forced vital capacity were 74% of predicted value. The mean residual volume was significantly increased, being 154% of predicted value. Nonsurgically treated patients showed normal total lung capacity (mean 99.8% of predicted value); this mean value was 82% of predicted value in surgically treated patients. CONCLUSION: Vital capacity was found to be significantly reduced in surgically treated patients (68% of predicted value), especially in those patients who had multiple thoracic anomalies. We believe that children with congenital scoliosis due to multiple anomalies should be operated on at an early age before deformity is too severe.

Adolescent↗
PubMed1994

Bone mineral density in ankylosing spondylitis. DEXA comparison of control subjects with mild and advanced cases.

We have used dual-energy X-ray absorptiometry to measure bone mineral density (BMD) in patients with ankylosing spondylitis comparing 41 healthy control subjects and 33 patients with either mild or advanced ankylosing spondylitis. A Norland XR-28 bone densitometer was used to measure the BMD of the lumbar spine and that of the head, trunk, arms, femoral neck, Ward's triangle, legs, pelvis, and total body. Mild ankylosing spondylitis was defined as that showing no or incipient syndesmophytes between L1 and L5 vertebrae: we studied 16 men of mean age 37 years and six women of mean age 37 years. Advanced ankylosing spondylitis, in 11 men of mean age 42 years, showed a bamboo spine with bridging syndesmophytes across all disc spaces between L1 and L5. The mean BMD of the lumbar spine was significantly different in the patients and control subjects of the same sex (0.01 < p < 0.05, analysis of variance), being significantly reduced compared with control subjects in mild disease (0.001 < p < 0.01, t-test) and significantly increased in advanced disease over control subjects (0.01 < p < 0.05; t-test) and over patients with mild disease (0.001 < p < 0.01; t-test). The relevance of these findings to the aetiology and pathogenesis of spinal deformities and other complications in ankylosing spondylitis is discussed.

Absorptiometry, Photon↗
PubMed1993

Nine-year mean follow-up of one-stage anteroposterior excision of hemivertebrae in the lumbosacral spine.

Six patients with lumbosacral hemivertebrae were treated by one-stage anterior and posterior excision of the hemivertebrae. Long-term follow-up is reported. Overall, correction of the lumbosacral curve was 46%, including one case of pseudarthrosis and subsequent loss of correction. More importantly, truncal imbalance was restored unless other congenital thoracic anomalies were present. New methods of calculating rib cage shift on the pelvis as well as vertebral column displacement from the sagittal plane are presented.

Child↗
PubMed1993

New methods of measuring vertebral rotation from computed tomographic scans. An intraobserver and interobserver study on girls with scoliosis.

The purpose of this study was to search for constant and reliable reference points on the computed tomographic scans of scoliotic spines to measure vertebral rotation. Several methods using different sets of reference points on computed tomographic scans were tested for reliability. Two methods that gave minimum variation between the readings are presented here with interobserver and intraobserver reliability on 17 girls with adolescent idiopathic scoliosis. The selection of reference points for the two methods were as follows: In method 1, the vertebral rotation was an angle formed by two lines; one, a line joining the junction of the inner surfaces of two laminae and the midpoint of the posterior surface of the vertebral body and second, the vertical plane of the computed tomographic machine. In method 2, three datum points were marked; one at the junction of the inner surfaces of the laminae, and the other, one each at the junction of the inner surfaces of the lamina and the pedicle. A line bisecting this angle is drawn by the computer and the vertebral rotation was an angle between this line and the vertical plane. The 95% confidence intervals of these two methods for intraobserver variation were between 1.2 to 4.4 degrees. There was no significant difference between the readings obtained by each observer except on three occasions for observer 1. When these methods were tested for interobserver reliability, method 1 showed significant statistical differences between the readings obtained by the two observers. However, the readings obtained using method 2 were not significantly different between the two observers (95% confidence intervals = 3.2 to 5.8 degrees).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Changes in residual volume relative to vital capacity and total lung capacity after arthrodesis of the spine in patients who have adolescent idiopathic scoliosis.

We evaluated pulmonary functions before correction and again after a mean follow-up of three years in thirty-five patients who had adolescent idiopathic scoliosis. The mean age (and standard deviation) at the time of correction was 13.7 +/- 1.8 years, and at the time of follow-up it was 17.1 +/- 2.5 years. The findings in the patients were compared with those in matched normal control subjects. With the exception of forced vital capacity, all of the determinations of absolute pulmonary volume increased postoperatively, but the increases were not all proportional. When the preoperative and follow-up determinations were expressed as percentages of the predicted pulmonary volumes (on the basis of age) to eliminate any effects of the difference in age, there was no change in total lung capacity, but vital capacity and forced vital capacity were significantly reduced. In addition, there was a significant increase in residual volume. Of the mean increase in total lung capacity after correction of the scoliosis, 82 per cent was due to an increase in residual volume and 18 per cent, to an increase in vital capacity. However, in control subjects age-matched at the time of follow-up, the increase in vital capacity contributed 69 per cent of the mean increase in total lung capacity, a very marked difference from the findings in the patients who had scoliosis. In addition, two pulmonary-volume ratios--residual volume to vital capacity and residual volume to total lung capacity--increased in a highly significant fashion (Mann-Whitney test, p < 0.001) after arthrodesis of the spine.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

A comparative study of computed tomographic and plain radiographic methods to measure vertebral rotation in adolescent idiopathic scoliosis.

A comparative analysis of two methods of measuring vertebral rotation in adolescent idiopathic scoliosis is reported in this article. Nash and Moe's pedicle shift method (using plain anteroposterior radiographs) is compared with a new method using computed tomographic scans. The computed tomographic scans of the whole length of the major curve and the scout films obtained from seventeen girls aged 12.5-14 years were measured for rotation of each vertebra of the curve (total number of vertebrae measured by two methods = 173). This study has three interesting new findings: 1) Those vertebrae with Nash & Moe grade 0 had up to 11 degrees of vertebral rotation when measured using the computed tomographic method. Therefore, Nash & Moe's grade '0' is not a neutrally rotated vertebra; 2) For Nash & Moe grade 1 and 2, the computed tomographic method revealed statistically significantly greater rotation for lumbar vertebrae than thoracic vertebrae. There was a similar pattern for Nash & Moe grade 0 but these differences were not statistically significant; and 3) Simple formulae are reported to convert Nash & Moe's grades into angle of vertebral rotation as obtained by CT method separately for thoracic and lumbar vertebrae.

Adolescent↗
PubMed1991

The shoulder girdle in ankylosing spondylitis.

We report the clinical findings in the shoulders of fifty-two patients who had ankylosing spondylitis. The three major patterns that were found included limitation of scapulothoracic motion (forty-one patients), acute inflammatory arthropathy of the sternoclavicular or acromioclavicular joint (six patients), and severe restriction of glenohumeral motion (five patients). Although radiographic abnormalities were common, they correlated with the clinical findings in only minor respects.

Acromioclavicular Joint↗
PubMed1991

Disproportionate body growth in girls with adolescent idiopathic scoliosis. A longitudinal study.

Two thousand, one hundred and eighty-nine southern Chinese women, aged 8-21 years, were studied: 541 with adolescent idiopathic scoliosis (176 treated with posterior spinal fusion and Harrington instrumentation, 150 with brace, and 215 who did not require any treatment), and 1,648 age-matched normal controls from schools and colleges. Scoliotic girls treated at Duchess of Kent Children's Hospital were examined clinically, radiologically, and anthropometrically, including a roentgenogram of the left hand for bone age, at yearly intervals from their first visit to hospital until maturity. Leg:spine and leg:arm ratios were calculated to study the proportionate body growth. The data obtained at first visit and at maturity for each treatment group were compared within treatment groups, and also with normal controls (all age-matched comparisons). The results are summarized as follows: The comparison of leg:spine ratio between fusion, brace, and untreated groups at first visit using uncorrected spinal length showed inconsistent results, but when these ratios were calculated using spinal length corrected for scoliosis, the results were all consistent, showing no significant difference between these groups at first visit. At maturity, leg:spine ratios, using either uncorrected spinal length or corrected spinal length, were highly significantly greater for the fusion group compared to the brace and untreated groups. The leg:spine ratio comparisons of scoliosis groups against normals showed that brace and fusion groups had highly significantly greater ratios at first visit and at maturity, using uncorrected spinal length. Similar comparison using corrected spinal length showed minimum or no difference at first visit, but at maturity, only the fusion group had a significantly greater ratio than normals.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Postsurgical recurrent stress fracture in the spine affected by ankylosing spondylitis.

Stress fracture in the dorsolumbar region is a well-known complication of the rigid spine usually occurring at the end stages of ankylosing spondylitis. When indicated, surgical treatment by anterior spinal fusion is prescribed. Three cases illustrating the appearance of new stress fractures in different parts of the spine after the successful anterior surgical fusion of a previous lesion indicate the possibility of recurrence. This explains the persistence of back pain postoperatively. These stress fractures seem unrelated to spinal deformities. External bracing is useful, but additional surgical fusions may become necessary.

Adult↗