Biomedical subjects

R C Chan

Publications and source records attributed to R C Chan.

At least 127 records · Page 7Linked to original sources

PubMed1979

Management and results of localized Ewing's sarcoma.

Seventy-six patients with localized Ewing's sarcoma who received primary treatment at M.D. Anderson Hospital from 1948 through December 1975 were reviewed. Patients have been divided into four groups according to the different treatment regimens they received: Group I, moderate dose radiotherapy alone; Group II, high dose radiotherapy alone; Group III, radiotherapy plus vincristine and cytoxan; and Group IV, radiotherapy plus vincristine, Adriamycin, cytoxan and actinomycin. The problem of local recurrence appears to be solved with combined chemotherapy and radiation therapy with only one of 36 patients having a recurrence at the primary site in Groups III and IV. Multimodal therapy is the preferred treatment to obtain control of the primary lesion by radiation therapy while preserving good function. However, the major cause of failure remains distant metastases, 19 of 36 (53%) in Groups III and IV. In addition, 4 of 10 patients who have survived over 5 years have developed osteogenic sarcoma.

Antineoplastic Agents↗

PubMed1979

Single dose whole pelvis megavoltage irradiation for palliative control of hematuria or ureteral obstruction.

Of 7 patients with bladder carcinoma whose medical condition or disease status prevented an operation 5 had intractable vesical hemorrhage and 2 had progressive azotemia caused by ureteral obstruction. These patients were treated with pelvic irradiation of 1,000 rad single doses. Four patients received 3 doses 3 to 4 weeks apart and 1 patient received 2 doses at a 4-week interval. Prompt cessation of bleeding occurred in all patients and renal function improved in the 2 patients with ureteral obstruction.

Aged↗

PubMed1979

Parameningeal rhabdomyosarcoma.

The records of 27 patients with rhabdomyosarcoma involving the parameningeal area (nasopharynx, paranasal sinus, and middle ear) treated from 1961 to 1976 were reviewed. Due to the location of the primary tumor, radiation and chemotherapy were used but surgery was limited to simple biopsy. In the literature, spread of tumor from these primary sites to the meninges has been as high as 26-35%. In this series, meningeal disease developed in only 2 of the 27 patients (7%).

Adolescent↗

PubMed1979

Skeletal effects of megavoltage irradiation in survivors of Wilms' tumor.

The skeletal effects of megavoltage irradiation (60Co) in 25 long term survivors of Wilms' tumor are described. In general, the changes seen with megavoltage irradiation are as frequent but not as severe as those previously reported after orthovoltage irradiation. Vertebral body changes generally occur within 5 years after irradiation. Scoliosis and/or kyphosis do not usually develop until after five years postirradiation. Kyphotic curves tend to progress after the adolescent growth spurt while scoliotic curves do not. Other bony and nonosseous changes are detailed.

Bone and Bones↗

PubMed1978

Integrated therapy for invasive bladder carcinoma. Experience with 108 patients.

One hundred eight patients with invasive bladder carcinoma, clinically staged T3, who underwent preoperative irradiation followed by radical cystectomy and ileal conduit urinary diversion without pelvic lymphadenectomy at this Center between January 1, 1969, and December 30, 1975, were reviewed. Sixty-two patients are alive and free of disease twelve to ninety-six months after treatment. The incidence of recurrent pelvic disease is 8%. With protracted radiotherapy (5,000 rads TD/five weeks), pelvic lymphadenectomy is not necessary and has the benefit of distinguishing high-risk population who may benefit from adjuvant therapy.

Adult↗

PubMed1977

Radiotherapy of choroidal metastases: breast cancer as primary site.

Forty-two cases of metastatic breast cancer to the choroid treated by radiation therapy were reviewed. Fifteen patients (36%) had bilateral and 27 patients (64%) had unilateral choroidal involvement. In 12 patients (29%) the choroid was the first site of dissemination. The median survival period after choroidal metastases was 10 months. Most patients were treated with Co60 in doses of 2500 rads tumor dose (TD) in ten fractions, 2500 rads, (TD) in five fractions and 3000 rads (TD) in ten fractions. An early group of patients had orthovoltage therapy. Good visual responses were obtained with each of the above treatment programs. Radiation treatment in the range of 2500-3000 rads TD in a short course is recommended for palliation of metastatic breast cancer to the choroid.

Breast Neoplasms↗

PubMed1976

Carcinoma of the prostate. Its treatment by a combination of radioactive gold-grain implant and external irradiation.

Out of 67 patients treated with radiotherapy from 1967 to August 1972, a small group of 17 patients were treated by a combination of radioactive gold grain implant plus external Cobalt-60 teletherapy. The average dose from the implant was 4000 rads, which was supplemented with external irradiation to a total dose of 8000 rads TD. Because of the small number of patients and the short follow-up, no definite conclusions can be drawn at this time. The technique used permits the delivery of a higher total tumor dose of about 8000 rads with relatively low complication rate.

Gold Radioisotopes↗

PubMed1976

Effects of irradiation on the eye.

From 1954 through 1971, 47 patients with malignant tumors of the nasal cavity and paranasal sinuses were treated with an entire eye included in the tumor dose volume. All patients were treated with megavoltage radiation and received approximately 6,000 rads in 30 fractions in six weeks. Two thirds of the patients treated by irradiation alone had no problems with vision or difficulties related to treatment of the eye. When 5-fluorouracil (5-FU) was used in conjunction with high-dose radiotherapy, loss of vision was much more frequent and all patients had either visual loss or major clinical difficulties.

Blindness↗

PubMedDate not supplied

Intracoronary radiation for patients with refractory in-stent restenosis: an analysis from the WRIST-Crossover Trial. Washington Radiation for In-stent Restenosis Trial.

BACKGROUND: In-stent restenosis (ISR) is a limitation of intracoronary stent implantation. In animal models and clinical trials, ionizing radiation has been shown to decrease in-stent neointimal formation. METHODS AND MATERIALS: In the Washington Radiation for In-stent Restenosis Trial (WRIST), patients with in-stent restenosis were first treated with conventional catheter-based techniques and then randomized to gamma irradiation (l92Ir, 15 Gy at 2 mm from the source) or placebo. Patients randomized to placebo that developed recurrent ISR and presented with anginal symptoms were crossed-over to active therapy. We compared the clinical and angiographic outcomes of 39 patients in the crossover group with 65 patients treated primarily with radiation. The primary clinical endpoints were mortality, morbidity, and repeat target lesion revascularization (TLR) at 6 months. RESULTS: Procedural success was 100%. In-hospital and 30-day complications were minimal. At 6 months, the rate for any multiple adverse cardiac events (MACE: death, MI, or TLR) was 25.6% in the crossover group vs. 29.2% in the primary treatment group (p = 0.86). Three patients in the crossover group and four in the primary treatment group died (p = NS). There were no Q-wave myocardial infarction. Ten (9.6%) of the patients presented with late thrombosis and total occlusion: 6.2% (4/65) in the primary treatment group vs. 15.4% (6/39) in the crossover group (p = 0.13). CONCLUSIONS: Patients who fail conventional catheter-based intervention without radiation can be treated with 192Ir with results similar to those who initially receive brachytherapy. This is of specific importance with respect to patients initially assigned to the placebo arm of randomized clinical trials.

Brachytherapy↗

PubMedDate not supplied

Modulation of protein expression and activity by radiation: relevance to intracoronary radiation for the prevention of restenosis.

Restenosis is a common complication of percutaneous transluminal coronary angioplasty. Recent studies have demonstrated a striking reduction in the neointimal hyperplasia characteristic of restenosis following intracoronary radiation (IR), but the mechanisms by which radiation reduces neointima formation following balloon overstretch injury are not elucidated fully. In addition to direct antimitotic effects mediated via oxygen free radicals, ionizing radiation can induce the expression of numerous genes and thereby mediate indirect effects. Additionally, IR prevents restenosis at the cost of decreased healing and increased thrombosis, and we suggest that these adverse reactions can be modulated by adjunct pharmacology or gene-based strategies. This review discusses several genes and proteins modulated by radiation in the context of arterial injury, and their possible therapeutic relevance.

Animals↗

PubMedDate not supplied

Differential remodeling after balloon overstretch injury and either beta- or gamma-intracoronary radiation of porcine coronary arteries.

BACKGROUND: Restenosis is a consequence of both neointimal hyperplasia and vessel remodeling. Prior studies have shown that intracoronary radiation (IR) prevents neointima accumulation, but its contribution to vessel remodeling is unknown. The purpose of this study was to evaluate the effect of IR on differential vascular remodeling after balloon angioplasty in porcine coronary arteries. METHODS: A total of 20 juvenile swine (30 coronary arteries) were subjected to overstretch balloon injury (BI) followed by IR with either beta- or gamma-radiation ((90)Y or (192)Ir). After 2 weeks following treatment, serial tissue sections were perfusion fixed and stained by hematoxylin and eosin (H&E), Verhoeff von Giesson (VVG), or Masson Trichrome. Adventitial area (AA), lumen area (LA), vessel area (VA), intimal area (IA), and IA corrected for medial fracture length (IA/FL) were quantified by digital image analysis. The vessel circumference was divided into two regions containing (1) the undisrupted region (UReg) with the undisrupted arc of media and internal elastic lamina (IEL) and (2) the disrupted region (DReg) with the disrupted arc between the medial tears. Quantitative regional analysis was performed by (1) measuring the IEL to define the UReg, (2) calculating the area of the UReg with the perimeter value derived from measurement of the IEL, and (3) calculating the DReg as follows: LA+IA-UReg. Immunohistochemical smooth muscle cell alpha-actin and Masson Trichrome were quantified by digital image analysis. RESULTS: The IA/FL was significantly smaller following treatment with (90)Y or (192)Ir vs. control (P<.01). A smaller AA was obtained following IR with both beta- and gamma-sources vs. control (P<.01). The UReg calculation was smaller in the irradiated arteries as compared to control (beta: 2.3+/-0.4 mm(2), gamma: 2.1+/-0.5 mm(2), P<.01 vs. control; control: 3.6+/-0.7 mm(2)). In contrast, the DReg was increased following IR, as demonstrated by the FL and the calculated area of the injured segment (control: 2.7+/-0.5 mm(2); beta: 5.5+/-1.1 mm(2), gamma: 5.5+/-1.1 mm(2), P<.01 vs. control). Adventitial alpha-actin positive cell density (CD) was decreased after IR; however, the collagen density was similar. In contrast, the neointimal collagen density in the injured segment was significantly decreased following IR. CONCLUSION: We consider that the global arterial remodeling after IR is a heterogeneous process that includes the absence of retraction in an UReg and a positive remodeling in the DReg as shown in the porcine coronary model. These changes in adventitia and neointima appear to contribute to differential vascular remodeling caused by IR in injured vessels.

Angioplasty, Balloon, Coronary↗

PubMedDate not supplied

Intracoronary radiation with gamma wire inhibits recurrent in-stent restenosis.

To study the safety and efficacy of intracoronary gamma radiation delivered via a new high-activity (192)Ir source wire for the treatment of in-stent restenosis. In-stent restenosis results from neointimal tissue proliferation especially in its diffused form and presents a therapeutic challenge. Gamma radiation has been shown to decrease neointima formation within stents in animal models and in initial clinical trials. A total of 26 patients with in-stent restenosis underwent successful intervention and was treated with open-label (192)Ir using a high-activity line source. The specific activity of the source wire was 372+/-51 mCi, and the dwell time was 10.8+/-1.9 min. Primary endpoints were freedom from death, myocardial infraction (MI), and repeat target lesion revascularization (TLR) at 6 months. Secondary endpoints included angiographic restenosis and intravascular ultrasound (IVUS) neointimal hyperplasia. Procedural success was high (96.2%), and in-hospital and 30-day complications were low with no deaths, MI, or requirement for repeat revascularization. At 6 months, event-free survival was 85%: one patient required repeat PTCA, one underwent bypass surgery, and two had an MI. Baseline lesion length measured 15.77 mm. Follow-up angiography was available in 21/25 (84%) patients. The binary restenosis rates were 19.0% (4/21) in-stent and 23.8% (5/21) in-lesion. Follow-up IVUS was available in 20/25 patients. There was no increase in intimal hyperplasia from postintervention to follow-up (3.11.8 vs. 3.41.8 mm(2); P=.32). Eight patients had a reduction of neointimal intimal tissue at follow-up. These results indicate that intracoronary gamma radiation with the Angiorad source wire is safe and effective in preventing in-stent restenosis.

Adult↗

PubMedDate not supplied

Intravascular radiation accelerates atherosclerotic lesion formation of hypercholesteremic rabbits.

OBJECTIVES: The purpose of the present study is to evaluate the effect of intravascular radiation (IR) on the arterial wall of uninjured vessels in the hypercholesteremic rabbit model. METHODS: Aortas of 24 New Zealand white rabbits were treated with either intravascular 192-Ir gamma-radiation (15 Gy at 2 mm from the center of the source) or were exposed to the source catheter without radiation (sham controls). Following the radiation treatment, the animals were fed a 2% cholesterol diet until euthanasia at 2 (n=8) or 6 (n=16) weeks. Arteries were analyzed using light and scanning electron microscopy (SEM); transforming growth factor beta (TGF-beta) 1, a promoter of connective tissue deposition, was also monitored. RESULTS: At 2 weeks, SEM analysis showed well-aligned endothelial cells in nonradiated segments, whereas irradiated arteries consistently contained adherent and subendothelial macrophages with focal areas of endothelial disruption. Further radiated segments at 2 weeks showed a 7-fold increase in active TGF beta-1 over nonradiated segments. At 6 weeks, there was a significant increase in plaque and vessel wall area relative to control arteries, however, no differences were noted in the density of actin-positive smooth muscle cells (SMCs) or macrophages. Similarly, no differences were noted in cell proliferation between groups as evidenced by the marker bromodeoxyuridine (BrdU). In contrast, nonirradiated segments frequently contained cellular areas with extracellular lipid. CONCLUSION: Exposure of previously uninjured vessels to IR and hypercholesterolemia is associated with increased plaque burden and leads to more advanced plaque types. Special care should be taken to minimize radiation exposure in normal vascular segments in hypercholesterolemic patients undergoing radiation therapy.

Animals↗

PubMedDate not supplied

Supplemental oxygen does not synergize with intracoronary radiation for the prevention of restenosis in porcine coronary arteries.

PURPOSE: Recurrence of obstructive coronary arterial lesions (restenosis) after angioplasty remains a significant clinical problem. Ionizing radiation, at doses >10 Gy administered locally to the angioplasty site, has been shown to inhibit restenosis in porcine coronary arteries, but lower doses are ineffective. Methods that will allow delivery of lower doses of radiation while retaining the antirestenotic efficacy observed at the higher doses are desirable. Hypoxic cells are known to be radioresistant; accordingly, we hypothesized that increasing blood oxygenation through the use of the TherOx Aqueous Oxygen system would lower the doses of endovascular radiation required for the prevention of restenosis. MATERIALS AND METHODS: Five swine were studied as follows: balloon injury + oxygen alone was performed in two swine. Each swine had a balloon overstretch injury in two arteries, left anterior descending (LAD) and either right coronary artery (RCA) or left circumflex (LCX) artery (three arteries total). Balloon injury + oxygen followed by intracoronary irradiation was performed in a further three swine (six arteries). Controls consisted of arteries treated with 0, 5, or 15 Gy of 192Ir alone. RESULTS: Arteries treated with the TherOx Aqueous Oxygen system alone were indistinguishable from arteries treated without oxygenation except for a larger adventitial area (5.29 +/- 0.20 vs. 2.77 +/- 0.28 mm2; p < 0.05). Arteries treated with the TherOx Aqueous Oxygen system along with 5 Gy of 192Ir exhibited a greater injury-corrected intimal area than arteries treated with radiation alone (0.76 +/- 0.18 vs. 0.33 +/- 0.08 mm2; p < 0.05). Neither thrombosis rate nor thrombus area was significantly different in arteries receiving the TherOx Aqueous Oxygen as compared with controls. CONCLUSIONS: The TherOx Aqueous Oxygen system is safe in the context of balloon overstretch injury, but decreases the antirestenotic efficacy of 5 Gy of 192Ir. These findings suggest that hypoxia does not seem to be a major contributor to the dose of radiation required for suppression of neointima, at least when using noncentered gamma radiation delivery systems.

Animals↗

PubMedDate not supplied

Quantitative measurement of improvement in sitting balance in children with spastic cerebral palsy after selective posterior rhizotomy.

Severe muscular spasticity encountered frequently in patients with spastic cerebral palsy not only affects patient locomotor function but also causes musculoskeletal complications. Significant reduction of spasticity over pelvis and lower limbs after selective posterior rhizotomy (SPR) results in improvement of trunk stability, locomotor function, and function of upper limbs also. The purpose of this study was to investigate the difference of sitting balance before and after SPR using a quantitative measurement in sitting stability represented as dispersion index provided by the Chattecx Balance System. Seventeen children with spastic cerebral palsy, ten boys and seven girls, with a mean age of 5.06 yr, underwent SPR. Their sitting stability under static and dynamic, visual and nonvisual testing conditions was assessed before SPR and three mo after SPR. Their sitting balance showed significant improvement at postoperative evaluation except for the static-nonvisual testing condition. Dispersion index under the dynamic testing condition was significantly higher than under the static testing condition, which implies that dynamic sitting balance was worse than static sitting balance in these patients. There was no statistical difference of sitting performance between visual and nonvisual condition both preoperatively and postoperatively. Quantitative measurement of dispersion index provided by the Chattecx Balance System offers an objective evidence of improvement in sitting balance for children after SPR.

Cerebral Palsy↗

PubMedDate not supplied

Electrophysiologic evaluation of autonomic function in cerebral palsy.

The presence of clinical autonomic dysfunction in patients with neurologic diseases, such as multiple sclerosis, Parkinson's disease, and cerebrovascular accident, has become increasingly recognized in the past decade. Very few autonomic tests have been done on pediatric patients thus far. The purpose of this study was to investigate the autonomic function in patients with cerebral palsy using two noninvasive tests: sympathetic skin response (SSR) and R-R interval variation (RRIV). Twenty-four patients with cerebral palsy and 24 control subjects between the ages of 4 and 12 yr were enrolled in this study. There was no significant difference of mean latency, amplitude, or amplitude ratio of SSR between the two groups under electric stimulus, startling stimulus, and deep breathing conditions. No significant difference in frequency of absent response and asymmetric response was also noted. Mean heart rate under relaxed sitting condition was significantly higher in the study group. Significant negative correlation between heart rate and age was noted in the control group but was not present in the study group. Also, there was no statistical difference of mean RRIV between the two groups. No objective evidence of autonomic disturbance in patients with cerebral palsy was found in this study.

Age Factors↗

PubMedDate not supplied

Effects of surface spinal cord stimulation on spasticity and quantitative assessment of muscle tone in hemiplegic patients.

Spasticity after a stroke interferes with the normal function of a limb. Electric stimulation has been used in a variety of ways to decrease spasticity. The purposes of this study were (1) to quantify the effectiveness of electric stimulation on decreasing ankle spasticity and (2) to develop a quantitative assessment of muscle tone, which could be replicated in the clinic. Ten patients with hemiparesis resulting from ischemic stroke participated in the study according to the selection criteria. Their mean age was 57 yr, with a mean stroke interval of 12.5 months. Patients received electric stimulation for 45 min through surface electrodes applied to the skin in the 12th thoracic and 1st lumbar areas. All patients received five electric stimulation treatment sessions. The electrical pulses were amplitude modulated frequency beat with a carry frequency of 2500 Hz and a stimulation frequency of 20 Hz. The stimulation intensity was adjusted to each patient to produce a sensory stimulation. The pre- and posttreatment evaluation included surface electromyography activity during passive ankle dorsiflexion, passive ankle dorsiflexion resistance at different angular velocities, as measured by an isokinetic machine and the modified Ashworth scale. Our results indicate that the surface spinal cord stimulation with middle frequency modulated to low frequency for sensory stimulation on the skin of 12th thoracic and first lumbar area is effective in reducing calf muscle spasticity of hemiplegic patients. The isokinetic torque measures for spasticity are a sensitive tool to document the effects of the treatment.

Adult↗

PubMedDate not supplied

Functional electrical stimulation on chronic and acute hemiplegic shoulder subluxation.

OBJECTIVE: The present study investigated and assessed the effectiveness of a functional electrical stimulation (FES) program in the management of acute and chronic shoulder subluxation. DESIGN: By their postonset duration, hemiplegic subjects with subluxation participating in the study were placed into a short-duration group and a long-duration group. Subjects in each group were further assigned randomly to either a control subgroup or an experimental subgroup. The experimental subgroups of both short and long duration received FES therapy in which supraspinatus and posterior deltoid were induced to contract repetitively up to 6 hr/day for 6 wk. The duration of the FES session and muscle contraction/relaxation ratio were progressively increased as performance improved. RESULTS: The experimental subgroup of short duration showed significant improvements in reducing subluxation as indicated by x-ray compared with the control subgroup of short duration after the first FES treatment. The same effect was not shown for the experimental subgroup of long duration. The second FES treatment program only resulted in an insignificant change of shoulder subluxation for both the short- and long-duration subgroups. CONCLUSIONS: The present study suggests that hemiplegic subjects with short postonset duration are effectively trained for shoulder subluxation by the first FES treatment program. The same FES showed not to be effective when applied to the subjects with subluxation of > 1 yr.

Acute Disease↗