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Biomedical subjects

B W Chang

Publications and source records attributed to B W Chang.

13 recordsLinked to original sources
PubMed1995

Single- and double- lumen silicone breast implant integrity: prospective evaluation of MR and US criteria.

PURPOSE: To evaluate the accuracy of magnetic resonance (MR) and ultrasound (US) criteria for breast implant integrity. MATERIALS AND METHODS: One hundred twenty-two single-lumen silicone breast implants and 22 bilumen implants were evaluated with surface coil MR imaging and US and surgically removed. MR criteria for implant failure were a collapsed implant shell ("linguine sign"), foci of silicone outside the shell ("noose sign"), and extracapsular gel, US criteria were collapsed shell, low-level echoes within the gel, and "snowstorm" echoes of extracapsular silicone. RESULTS: Among single-lumen implants, MR imaging depicted 39 of 40 ruptures, 14 of 28 with minimal leakage; 49 of 54 intact implants were correctly interpreted. US depicted 26 of 40 ruptured implants, four of 28 with minimal leakage, and 30 of 54 intact implants. Among bilumen implants, MR imaging depicted four of five implants with rupture of both lumina and nine of 10 as intact; US depicted one rupture and helped identify two of 10 as intact. Mammography accurately depicted the status of 29 of 30 bilumen implants with MR imaging correlation. CONCLUSION: MR imaging depicts implant integrity more accurately than US; neither method reliably depicts minimal leakage with shell collapse. Mammography is useful in screening bilumen implant integrity.

Breast Implants↗
PubMed1994

Breast implant rupture: diagnosis with US.

PURPOSE: To characterize sonographic criteria for the detection of implant rupture. MATERIALS AND METHODS: One hundred nineteen symptomatic women (221 silicone implants) were evaluated with ultrasound (US) over 11 months to detect implant rupture. Fifty-nine breast prostheses in 31 women were surgically removed. RESULTS: Five sonographic findings associated with rupture were identified: echogenic noise, low-level homogeneous echoes within the implant, echogenic lines coursing within the implant, a contour bulge of the implant, and peri-implant fluid accumulations. The most useful finding in the detection of implant rupture was low-level homogeneous echoes, which were associated with 55% of ruptured implants and 16% of intact implants. This was statistically significant, achieving a 55% sensitivity and 84% specificity for the detection of implant rupture. Nine of 22 ruptured implants (41%) displayed none of the described criteria. CONCLUSION: US may be useful to detect implant rupture; however, a larger prospective study is necessary for adequate evaluation.

Equipment Failure↗
PubMed1994

Color Doppler flow mapping of abdominal wall perforating arteries for transverse rectus abdominis myocutaneous flap in breast reconstruction: method and preliminary results.

PURPOSE: To describe the use of color Doppler flow ultrasound (US) in preoperative mapping of small perforating arteries in the abdominal wall that supply the transverse rectus abdominis myocutaneous (TRAM) flap used primarily for breast reconstruction. MATERIALS AND METHODS: With a grid (clear x-ray film) and a high-frequency linear-array transducer, the size and position of perforating arteries as they exit the rectus abdominis muscle were mapped preoperatively in 35 patients. Twenty-three of these patients had previously undergone abdominal surgery; 26 underwent reconstruction and clinical follow-up. RESULTS: Operating time was decreased and flap design was planned to include the largest perforating arteries and minimize the overall abdominal wall defect. Two of the 26 patients who underwent TRAM flap reconstruction had partial flap loss: One continued to smoke, which may have caused microvascular compromise; and a paucity of perforating arteries was seen in the second patient. CONCLUSION: Preoperative mapping of perforating arteries for TRAM flap reconstruction provides a rational basis for flap design and patient selection, which may affect flap survival.

Abdominal Muscles↗
PubMed1994

MR imaging of the breast in patients with silicone breast implants: normal postoperative variants and diagnostic pitfalls.

Because of the wide variety of types of silicone breast implants, modifications, and surgical procedures, a number of normal variants and potentially misleading appearances can be encountered on MR images of breast implants. Familiarity with these findings is essential to proper interpretation of these images. The purpose of this essay is to illustrate the overlap in appearances of MR images in different clinical scenarios. When confusing findings are present, confirmation of the surgical history can usually clarify the matter.

Adult↗
PubMed1993

Diagnosing breast implant rupture with MR imaging, US, and mammography.

A total of 135 symptomatic women with 262 breast implants were examined with magnetic resonance (MR) imaging performed with a body coil, ultrasound (US), or both to determine imaging features of implant rupture. Surgical proof was available for 33 women with 62 implants; 24 were ruptured and 38 were intact. Complicated internal structure was the most reliable predictor of implant rupture: Diffuse low-level echoes were seen on sonograms in 56% of ruptured implants; internal membranes (which correspond to the collapsed implant shell) were seen on MR images in 58% of ruptured implants. Fluid droplets were seen within the silicone in 26% of ruptured implants on MR images. Irregular implant contour can be a sign of rupture but is unreliable. Fluid collections around silicone implants are not a sign of rupture. At present, neither US nor conventional MR imaging with a body coil is sufficiently reliable to advocate routine screening of asymptomatic women with breast implants. Evaluation with MR imaging performed with a surface coil is more reliable.

Breast↗
PubMed1992

A systematic approach to repair of syndactylism.

An approach to the repair of syndactyly is presented whereby the web space is dissected in anatomically defined planes. This technique is preferred because it allows a reliable means of removing interdigital fibrofatty tissue while preserving the neurovascular bundles. Digital contour is improved and wound healing is promoted by less skin tension due to removal of the fibrofatty tissue.

Adipose Tissue↗
PubMed1992

Technical modifications for on-site nipple-areola reconstruction.

There have been numerous techniques and refinements for nipple-areola reconstruction described that have required the use of distant donor sites. A further modification of the skate flap is described, whereby the entire reconstruction can be performed on site, thus avoiding a second scar and any subsequent morbidity. This technique is easy to perform and has all the advantages of the skate flap as described by Little.

Female↗
PubMed1991

Experimental cholelitholysis with the pulsed tunable dye laser.

This study evaluates the pulsed tunable dye laser with wavelength 504 nm, frequency 10 Hz, and pulse width 1.2 microseconds for cholelitholysis. Power of 10-40 kW was directed through a 250-microns quartz fiber optic to ablate 55 gallstones (removed from 14 patients). The fiber was positioned in direct contact with the stones under saline. Power delivery was begun at 10 kW and increased in 10-kW increments until litholysis began. The range of power and energy necessary to fragment the gallstones was evaluated on four common bile ducts (fresh autopsy specimens). Following fragmentation, all stones were analyzed. There were 35 cholesterol stones (3 calcified) and 20 bilirubin stones (4 calcified). Size ranged from 0.012 to 7.56 cm3 (mean 0.96 +/- 1.41 cm3). Energy necessary for fragmentation ranged from 0.4 to 11.2 J (exposure time 1.0-28 s). Power necessary for fragmentation was 20 kW for 2/55 stones and 40 kW for 53/55 stones. At 40 kW (40 mJ/pulse), common bile duct perforation occurred within 1.1 +/- 0.1 s (0.44 +/- 0.04 J). The pulsed tunable dye laser can fragment gallstones of all compositions. The threshold for fragmentation is 40 kW, but common bile duct perforation occurs at this power. We conclude that laser radiation sufficient to fragment gallstones can injure the common bile duct.

Cholelithiasis↗
PubMed1982

Reproducibility of electron diffraction intensity data obtained from hydrated microcrystals of rat hemoglobin.

Analysis of electron diffraction patterns from rat hemoglobin taken at 200 kV on a wet stage yields intensity data to a resolution of 2-3 A which are as reproducible as those from typical X-ray diffraction. Some crystals were so similar that the differences in measured intensities were insignificant (R = 0.056), but in other cases real differences between crystals were observed (R = 0.33). Dynamic scattering was insignificant under our diffraction conditions; however, exposures to electron doses as low as 10(-2) e/A2 produced detectable changes in measured intensities. Limits to the reproducibility of the data are set by radiation damage and errors in microdensitometry.

Animals↗