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Biomedical subjects

D Ahn

Publications and source records attributed to D Ahn.

28 records · Page 2Linked to original sources
PubMed1992

Charged particle radiotherapy of paraspinal tumors.

Between 1976 and 1987, 52 patients with tumors adjacent to and/or involving the cervical, thoracic, or lumbar spinal cord were treated with charged particles at the University of California Lawrence Berkeley Laboratory. The histologies included chordoma and chondrosarcoma (24 pts), other bone and soft tissue sarcoma (14 pts), and metastatic or unusual histology tumors (14 pts). Radiation doses ranged from 29 to 80 Gray-equivalent (GyE), with a median dose of 70 GyE. Twenty-one patients received a portion of their treatment with photons. Median followup was 28 months. For 36 previously untreated patients, local control was achieved in 21/36 patients and the 3-year actuarial survival was 61%. Of 16 patients treated for recurrent disease, 7/16 were locally controlled and the 3-year actuarial survival was 51%. For patients treated for chordoma and chondrosarcoma, probability of local control was influenced by tumor volume (less than 100 cc or greater than 150 cc) and whether disease was recurrent or previously untreated. Complications occurred in 6/52 patients, including one spinal cord injury, one cauda equina and one brachial plexus injury, and three instances of skin or subcutaneous fibrosis. Charged particle radiotherapy can safely deliver high tumor doses to paraspinal tumors with good local control.

Adolescent↗
PubMed1991

Uveal melanoma: development of metastases after helium ion irradiation.

Forty-two (16%) of 261 patients with ocular melanoma who were treated with helium ions between January 1978 and November 1986 have developed metastatic disease. The time between start of helium ion treatment and recognition of metastatic disease ranged from 3 to 67 months (median, 27 months). The mean pretreatment tumor height in the patients with metastases was 7.7 mm. All 42 patients who developed metastatic disease have died. The median survival after diagnosis of metastatic disease was 5 months; the longest survival was 49 months. The most common site of metastasis was the liver (n = 34). Four (10%) of the 42 patients with metastases also had local recurrence of the tumor. Multivariate analysis identified three variables that predicted independently the development of metastases and lack of survival. These variables are anterior location of tumor (P = .027), tumor height greater than 5 mm (P = .02), and tumor diameter greater than 10 mm (P = .0075).

Actuarial Analysis↗
PubMed1990

The effects of TMB-8 on acetylcholine release from frog motor nerve: interactions with adenosine.

The putative intracellular calcium (Ca) antagonist TMB-8 was shown to reduce postjunctional sensitivity and quantal acetylcholine (ACh) release at low micromolar concentrations. At 10-fold higher concentrations, TMB-8 also blocked caffeine-induced Ca release (as monitored electrophysiologically by changes in ACh release) but did not impair the ability of adenosine to inhibit quantal ACh release. This last result implies that TMB-8 and adenosine exert their inhibitory actions at different steps in the depolarization-secretion coupling sequence.

Acetylcholine↗
PubMed1990

Long-term results of helium ion irradiation of uveal melanoma.

Between 1978 and 1988, 307 patients with uveal melanoma were irradiated using helium ions at Lawrence Berkeley Laboratory. The length of follow-up ranged from 1-115 months (median 42 months). The 5-year actuarial treatment results were: local control rate, 96.8%, determinate survival rate, 81%, freedom from distant metastases, 76%, eye retention rate, 83%, and risk of developing neovascular glaucoma, 36%. Long-term vision outcome was analyzed in 81 patients with a minimum follow-up of 5 years. Forty-seven percent of patients retained vision of 20/200 or better. The median change in vision was a loss of four lines on the standard eye chart. Thirty-eight percent of patients had visual acuity either improve or remain within two lines of their pretreatment vision. A multivariate analysis identified tumor size as the only independently significant risk factor affecting survival, development of neovascular glaucoma, or the risk of enucleation; no risk factor correlated with local recurrence. Tumor size, tumor-fovea distance, and pretreatment visual acuity were independently significant risk factors influencing vision outcome. These results confirm that helium ion irradiation is an effective treatment for uveal melanoma which combines high rates of local control, survival, and eye retention with a substantial likelihood of long-term vision preservation.

Adult↗
PubMed1990

Ciliary body melanoma treated with helium particle irradiation.

Melanoma involving the ciliary body is a rare tumor which carries a poor prognosis when compared to all uveal melanoma. We have treated 54 patients with ciliary body melanoma using helium ions from 1978 to 1985. Because of the high rate of metastatic disease, the 5-year disease specific survival rate is only 59% despite a 5-year local control rate of 98%. The greatest diameter of the tumor was predictive of loss of vision and enucleation (p = .05, p = .04, respectively). Multivariate analysis showed that the greatest diameter of the tumor was the most important predictor of death from metastases. The incidence of neovascular glaucoma at 5 years is 43%. The 5-year actuarial rate of enucleation is 26%. Enucleation was done for pain and/or neovascular glaucoma. Univariate analysis showed treatment volume to be a statistically significant predictor for the development of neovascular glaucoma (p = .0017) and enucleation (p = .0078). Seventy percent of neovascular glaucoma occurred in patients with treatment volume greater than 5.5 cc. Seventy-four percent occurred in patients with an initial ultrasound height greater than 9.2 mm. Using this information, patients at high risk for neovascular glaucoma could be considered for prophylactic treatment with panretinal photocoagulation.

Adult↗
PubMedDate not supplied

Brain injury rehabilitation settings: a gold mine for student and staff learning.

This article explores cognitive, psychomotor, and affective learning relative to the professional development of senior nursing students and staff in a long-term brain injury rehabilitation setting. Valuable opportunities for learning exist in this environment. Nursing students acquire a much different perspective toward caring for patients in rehabilitation settings than in acute care; they also gain tremendous opportunities to strengthen the clinical judgement and psychomotor skills applicable to most clinical work environments following graduation. In addition, they assume professional attitudes toward and interest in caring for long-term brain-injured patients as they work closely with expert rehabilitation nurses. When staff nurses interact with students, they receive reciprocal benefits. Staff nurses profit by refining and broadening the scope of their own practice; they also develop a positive self-image and a feeling of pride in their work. More importantly, staff nurses in a long-term brain injury rehabilitation setting regain the feeling that their daily efforts are really worthwhile.

Brain Injuries↗