Biomedical subjects

B C Chan

Publications and source records attributed to B C Chan.

5 recordsLinked to original sources

PubMed2005

Three-dimensional extended imaging: a new display modality for three-dimensional ultrasound examination.

OBJECTIVE: To describe Three-Dimensional eXtended Imaging (3DXI) as a new display modality for three-dimensional (3D) ultrasound examination of the fetus. METHODS: The spine, palate, heart and brain were evaluated using 3D ultrasound examination at a mean gestational age of 22 weeks in 35, 31, 32 and 31 fetuses, respectively. The volume data captured were analyzed using the conventional orthogonal display mode (ODM), as well as the 3DXI, which includes the Multi-Slice View (MSV) mode and the Oblique View (OBV) mode. The MSV mode allows simultaneous display of multiple sequential parallel planes while the OBV mode allows examination of a non-standard straight or curved plane. RESULTS: The MSV mode allowed a simultaneous display of multiple sequential parallel planes of the fetal structures, but we found some uncertainty if an isolated image in one of the multi-slice images represented the exact level of a fetal structure. The MSV mode was advantageous in one of the six cases of facial cleft by allowing the simultaneous display of bilateral clefts that were located in two different axial planes. The multi-slice images were helpful in making the diagnosis in one case of holoprosencephaly. The OBV mode allowed examination of the coronal plane across the curvature of the spine, and the 'in-plane' view of the interventricular septum in a non-gated study. CONCLUSION: The 3DXI can display the volume data in a different manner from that which usually results from the use of more conventional ODM, and provide additional information over conventional two-dimensional sonography.

Cardiovascular Abnormalities↗

PubMed2001

Expression of human BRE in multiple isoforms.

BRE, a putative stress-modulating gene, found able to down-regulate TNF-alpha-induced NF-kappaB activation upon overexpression, is now shown in human cells expressed as multiple mRNA isoforms. A total of six isoforms are produced by alternative splicing predominantly at either end of the gene. Predicted from the cDNA sequences of these isoforms, three of them (alpha(a), alpha(b), and alpha(c)) code for BRE of different C-terminus, and the other three (beta(a), beta(b), and beta(c)) may possibly be the nonfunctional counterparts. All human cells examined coexpress all the predominant splice variants, albeit at different ratios. Comparing with normal cells, immortalized human cell lines uniformly express higher levels of BRE. Interestingly, peripheral blood monocytes responded to LPS by down-regulating the expression of all the BRE isoforms, which was however less obvious in the cell line counterpart, THP-1. Isoform alpha(a), which codes for the canonical BRE with a C-terminal peroxisomal targeting sequence, is the most abundant transcript. We propose that the function of BRE and its isoforms is to regulate peroxisomal activities.

Animals↗

PubMed1999

Influence of parity on the obstetric performance of mothers aged 40 years and above.

We reviewed the delivery records of 205 mothers aged 40 years and above who delivered from 1st January 1994 to 31st December 1996 to examine the influence of parity on their obstetric performance. There were 51 (24.9%) primiparous mothers. The incidences of antenatal complications (antepartum haemorrhage, hypertensive disorder, glucose intolerance, prematurity), labour performance (type of labour, mode of delivery) and neonatal outcome (birth weight, Apgar scores, neonatal intensive care unit admission, perinatal mortality) were compared between the 51 (24.9%) primiparous and the 154 (75.1%) multiparous mothers. Higher incidences of antepartum haemorrhage (17.6 versus 5.8%, P = 0.0188), hypertensive disorder (17.6 versus 5.2%, P = 0.015), labour induction (33.3 versus 14.3%, P = 0.004) and Caesarean section delivery (58.8 versus 20.8%, P < 0.0001) were found among the primiparous mothers than the multiparous group. Neonatal outcome, however, was similar in both groups. We conclude that the primiparous mothers aged 40 years and above had more complicated antenatal and labour courses than multiparous mothers. On the other hand, the neonatal outcomes of two groups were comparable.

Adult↗

PubMed1998

Wavelet analysis of embolic heart sound detected by precordial Doppler ultrasound during continuous venous air embolism in dogs.

UNLABELLED: The spectrum of the embolic heart sounds (EHS) detected by precordial Doppler ultrasound has been previously characterized, but only on small volumes of venous air embolism (VAE). We sought to determine whether real-time wavelet analysis is useful in analyzing the signals of EHS and whether the embolic power of the EHS for larger volumes of air is proportionate to the volume of VAE that has been reported for small volumes of VAE. A series of small air boli (0.01, 0.02, 0.05, 0.07, 0.1, 0.15, 0.2, 0.3, 0.4, and 0.8 mL), followed by continuous infusion of larger volumes of air (0.8, 1.6, 2.4, 4.8, and 9.6 mL), was injected into the external jugular vein through a central catheter in seven pentobarbital-anesthetized dogs. We measured the spectrum of the Doppler heart sound (DHS) in a real-time manner by using wavelet analysis at different scales. Wavelet analysis at scale = 1 yielded satisfactory results in distinguishing abnormal EHS from normal DHS with high sensitivity (100%) and good positive predictive value (100%) compared with the conventional method, which requires an anesthesiologist to listen to the audio DHS signals in a real-time manner. There was a linear relationship (y = 1.08x + 7.89, r = 0.75, P < 0.001) between the cumulative embolic power of the EHS and the air volume introduced in the form of either bolus or continuous infusion. The 95% confidence intervals for slope and intercept were 0.89-1.27 and 7.65-8.13, respectively. Our results suggest that wavelet analysis is effective as a real-time monitor and that it is possible to distinguish larger volumes of air emboli based on previous injections of small volumes of air. IMPLICATIONS: The real-time wavelet analysis of the heart sound detected by precordial Doppler ultrasound may be useful in estimating larger volumes of air emboli based on previous injections of small volumes of air in anesthetized dogs.

Animals↗

PubMed1997

Fast detection of venous air embolism in Doppler heart sound using the wavelet transform.

The introduction of air bubbles into the systemic circulation can result in significant morbidity. Real-time monitoring of continuous heart sound in patients detected by precordial Doppler ultrasound is, thus, vital for early detection of venous air embolism (VAE) during surgery. In this study, the multiscale feature of wavelet transforms (WT's) is exploited to examine the embolic Doppler heart sound (DHS) during intravenous air injections in dogs. As both humans and dogs share similar physiological conditions, our methods and results for dogs are expected to be applicable to humans. The WT of DHS at scale 2j (j = 1, 2) selectively magnified the power of embolic, but not the normal, heart sound. Statistically, the enhanced embolic power was found to be sensitive (P < 0.01 at 0.01 ml of injected air) and correlated significantly (P < 0.0005, r = 0.83) with the volume of injected air from 0.01 to 0.10 ml. A fast detection algorithm of O(N) complexity with unit complexity constant for VAE was developed (processing speed = 8 ms per heartbeat), which confirmed the feasibility of real-time processing for both humans and dogs.

Algorithms↗