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D M Healy

Publications and source records attributed to D M Healy.

4 recordsLinked to original sources

Wavelet-encoded MR imaging.

Wavelet encoding is presented and compared to phase encoding. In wavelet encoding a distribution of spins is excited by a slice selective RF pulse; for each repetition time the distribution excited has the profile of a wavelet at different scale and translation. The spin density can be reconstructed with an inverse wavelet transform. Wavelet encoding has three advantages over phase encoding: (1) there is no Gibb's ringing from partial volume effects, (2) the effective repetition time can be 36 times the repetition time for a 256 x 256 image, and (3) motion artifacts are local and dramatically reduced. Using wavelet encoding, a 256 x 256 T2-weighted projection image can be acquired in 33 s.

Artifacts

Filtering noise from images with wavelet transforms.

A new method of filtering MR images is presented that uses wavelet transforms instead of Fourier transforms. The new filtering method does not reduce the sharpness of edges. However, the new method does eliminate any small structures that are similar in size to the noise eliminated. There are many possible extensions of the filter.

Artifacts

Prophylactic minitracheotomy in lung resections. A randomized controlled study.

Thirty consecutive patients undergoing lung resections were randomized into two groups: Group A (n = 15) received minitracheotomy postoperatively and group B (n = 15) were control patients. Postoperative respiratory course was monitored by serial clinical assessments, chest x-ray examination, arterial blood gases, sputa bacterial cultures, and the patient's requirement and response to chest physiotherpy. The two groups were similarly matched in age (mean 58.5 years), smoking habits, pulmonary functions, and surgical procedures. Postoperative pulmonary complications of collapse/consolidation developed in 11 patients (two in group A and nine in group B) (p less than 0.03). Four patients (all in group B) required nimitracheotomy in addition to antibiotics and chest physiotherapy to treat their pneumonia. Chest physiotherapy requirement was less in group A than in group B, with a mean number of sessions of seven in group A and eight in group B and a mean total time of 92 minutes in group A and 112 minutes in group B. The mean duration of minitracheotomy was 4.13 days. Minor temporary symptoms resulted from the minitracheotomy in eight patients (42%) and included discomfort, voice changes, subcutaneous emphysema, and stridor. There was one case of long-term morbidity (5%)-skin scarring from wound infection at the site of the minitracheotomy. No postoperative deaths resulted. We conclude that the prophylactic use of minitracheotomy is safe and effective in decreasing postoperative respiratory complications in patients undergoing lung resections.

Adult