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Biomedical subjects

O A Mendiondo

Publications and source records attributed to O A Mendiondo.

17 recordsLinked to original sources
PubMed1997

A precision repeat localization head frame for fractionated stereotactic radiotherapy.

An immobilization device was constructed for Fractionated Stereotactic Radiotherapy (FSRT) based on registration of the teeth and facial bones in a single thermoplastic mask system, along with a custom hardened foam pillow for posterior head immobilization relative to the mask. The unit interfaces mechanically with all of our current radiosurgery equipment and can be used with any standard stereotactic planning system. After initial trials to design a reproducible radiographic localization test, we performed a series of daily AP and Lateral port films on 3 patients over five isocenters. Seventy-nine films were reviewed and the maximum deviation in anatomical projection in both sagittal and coronal planes was less than 2 mm, with over 60% of films showing no distinguishable deviations from initial port films. Ninety-three percent of the test films showed a repositioning accuracy of less than 1 mm for all tested structures. We have developed an accurate, non-invasive means of repeat head immobilization that, when properly constructed, can facilitate precise fractionated stereotactic radiation therapy with patient comfort, ease of construction and long term stability.

Humans↗
PubMed1991

A rapid-afterloading vaginal cylinder for 137Cs brachytherapy.

A small diameter, single-step afterloading vaginal cylinder has been developed for 137Cs brachytherapy of the vaginal cuff and walls. The Lucite cylinder has an interior slot of rectangular cross section running along its length and opening to the outside of the patient. A single rectangular Lucite insert, containing preselected sources, fits into the slot. Two short sources in the tip form a T with the sources along the vaginal canal and provide a high, uniform dose rate across the spherical tip of the applicator. A catalog of 30 precalculated loadings provides surface dose rates at the tip which vary from 140 to 230 cGy/hr for standard source strengths, as well as a variety of dose rate profiles along the vaginal wall. The applicator is tapered at the base for comfortable and secure placement, and the single-step insertion reduces both patient discomfort and personnel radiation exposure for this procedure.

Brachytherapy↗
PubMed1983

Complications associated with preoperative radiation therapy and Iodine-125 brachytherapy for localized prostatic carcinoma.

Twenty-five consecutive patients with localized adenocarcinoma of the prostate treated with 1,050 rad preoperative radiation therapy and Iodine-125 seed brachytherapy arreviewed. Significant long-term postoperative complications included radiation cystitis (12%), radiation proctitis (4%), genital and leg edema (12%), stress incontinence (8%), total incontinence (4%), and impotence (26%). Complications occurred in 75 per cent of patients who received additional postoperative radiation. Improved staging with CT scan, lymphangiography, and Chiba needle biopsy of any possibly abnormal lymph nodes provided excellent preoperative staging with only 1 patient (6%) upstaged at surgery to Stage D1.

Adenocarcinoma↗
PubMed1983

A simple device for loading radioactive seeds into absorbable sutures.

Radioactive I-125 seeds that are loaded into absorbable sutures are convenient for permanent or removable interstitial-implantation. A simple device for loading radioactive seeds into commercially available sutures is described. This loader permits fast placement of seeds in the suture with minimal exposure to the involved personnel. Variable spacing is accomplished either by absorbable spacers or by minor manipulation of the loaded suture.

Brachytherapy↗
PubMed1983

Radioprotection combined with hypoxic sensitization during radiotherapy of a solid murine tumor.

EMT6 tumors were transplanted intramuscularly in the right hind leg of female BALB/c mice and irradiated when they reached a diameter of 6-7 mm. Each mouse received an intraperitoneal injection of WR-2721, misonidazole, or both prior to irradiation, and the dose needed to control half of the tumors at 30 days (TCD50/30) was recorded. WR-2721 offered slight tumor protection, with a dose-modifying factor (DMF) of 1.04-1.15 for radioprotector doses of 150-500 mg/kg. Pretreatment with misonidazole at doses of 300-900 mg/kg yielded tumor sensitization with a DMF of 0.71-0.92. Pretreatment with both WR-2721 and misonidazole gave overall tumor sensitization with a DMF of 0.78-0.97. Possible combinations of sensitizers and protectors, while providing overall tumor sensitization, do not seem to improve the therapeutic ratio over what could be obtained from a sensitizer or protector alone.

Amifostine↗
PubMed1983

Nasopharyngeal carcinoma in the second decade of life.

The clinical findings and treatment results in 27 patients, 11 to 20 years of age, with nasopharyngeal carcinoma were retrospectively reviewed. The histological diagnosis was lymphoepithelioma in 18 patients and undifferentiated carcinoma in nine patients. Seven patients (26%) presented with T4 lesions, 24 patients (89%) with clinically positive cervical nodes, and two patients (7%) with distant metastases. All patients received radiation therapy to the primary site; chemotherapy was employed as an adjuvant in six patients. Overall survival was 64% at five years and 57% at 10 years. Local control of the primary tumor and regional lymph nodes was 85%. Distant metastases were more frequent in patients with advanced primary disease and were associated wtih extremely poor prognoses. A moderate dose of radiotherapy is the recommended treatment for primary tumors and neck nodes. More effective adjuvant chemotherapy is suggested as a possible way to improve therapeutic results.

Adolescent↗
PubMed1982

Toxicity and radiation protective effect of WR-77913 in BALB/c mice.

The toxicity and radiation protective effect obtained by intraperitoneal injection of WR-77913 have been investigated in BALB/c mice. The toxic LD50/30 was 3574 mg/kg. When WR-77913 was given 30 min before whole body irradiation adequate protection was observed against bone marrow and gut death. Dose modifying factors of 1.91 and 1.76 for bone marrow and 1.95 and 1.80 for gut death were obtained with drug doses roughly equivalent to one half and one quarter of the maximum tolerable doses (MTD). No protective effect was observed against central nervous system injury. Preliminary experiments with the EMT6 tumor show limited tumor protection with a dose of WR-77913 equivalent to 70 per cent of the MTD. Because of its low toxicity, adequate bone marrow and gut protection at doses equivalent to one quarter MTD and limited protection of the EMT6 tumor, WR-77913 deserves further investigation to determine its value in multiple drug dose regimens and its capability to protect other normal tissues.

Amifostine↗
PubMed1979

Proton radiation as boost therapy for localized prostatic carcinoma.

A 160-MeV proton beam has been modified to irradiate patients with localized tumors by using convention treatment schedules. This proton beam has the physical advantage of megavoltage x-rays of reducing the radiation dose to normal tissues adjacent to the tumor volume. A perineal proton technique used as boost therapy (2,000 to 2,500 rads) was evaluated in the definitive irradiation of 17 patients with localized prostatic carcinoma. This technique allows repeated daily treatment of the carefully defined target volume with a precision of +/- 2 mm. Total dose to the prostatic tumor, but not to the posterior rectum, has been increased by 500 to 700 rads. After 12 to 27 months of observation, no noteworthy rectal reaction has developed in a patient, easily managed urethral strictures have developed in two patients, and all but one are locally controlled.

Adenocarcinoma↗
PubMed1976

Postoperative radiotherapy in carcinomas of the rectum and distal sigmoid colon.

Twenty-seven patients with Stage B and C carcinomas of the rectum and lower sigmoid received radiotherapy following radical surgery. Local control ratios for Stages B2, B3, and C (modified Duke's) were 7/9, 2/6, and 4/12, respectively. Nine of these 13 patients are alive with no evidence of disease 4-54 mo. after treatment; the other 4 died of unrelated causes. One died of complications attributable to irradiation 6 mo. after treatment; no tumor was found at autopsy. These results suggest that postoperative irradiation plays a significant role in Stage B lesions, but prognosis for Stage C disease does not appear to be altered.

Adenocarcinoma↗
PubMedDate not supplied

Sodium hydrogen-S-(3-amino-2-hydroxypropyl) phosphorothioate (WR-77913): toxicity and bone marrow radioprotection.

Experiments have been carried out to compare the toxicity and radioprotective effect of sodium hydrogen-S-(3-amino-2-hydroxypropyl) phosphorothioate (WR-77913) with those of S-2-(3-aminopropylamino)ethyl phosphorothioic acid (WR-2721). The drugs were given intraperitoneally to 12 week-old female BALB/c mice 30 minutes before whole body irradiation. Lethality at 30 days was the endpoint used. The drug LD50/30 was 678 mg/kg for WR-2721 and 3574 mg/kg for WR-77913. The LD50/30 for WR-77913 combined with 500 mg/kg of WR-2721 was 3328 mg/kg. The LD50/30 for misonidazole was 380 mg/kg when given in combination with 500 mg/kg of WR-2721 and 801 mg/kg when combined with 2200 mg/kg of WR-77913. Protection of bone marrow by WR-77913 and WR-2721 was comparable at doses close to the maximum tolerable dose (MTD, drug dose lethal to 10% of the animals at 30 days), but WR-77913 gave better protection at 35% of the MTD. These characteristics of low toxicity, non-additive toxicity with WR-2721, less toxicity in combination with misonidazole and adequate bone marrow protection at 25% of the MTD, make WR-77913 a protector worthy of further investigation.

Amifostine↗
PubMedDate not supplied

A comparison of air-cavity inhomogeneity effects for cobalt-60, 6-, and 10-MV x-ray beams.

The inclusion of air-filled spaces in treatment fields creates a potential dosimetric problem due to the loss of charged particle equilibrium near the air-tissue interface. We have used a simulated larynx phantom and a small buildup/extrapolation chamber to compare the magnitude and spatial extent of underdosing and overdosing at the distal surface for two linear accelerators (10- and 6-MV x-rays) and a cobalt-60 machine. Surface doses were compared to doses measured in a similar but homogeneous phantom to give observed/expected ratios (O/E), which were greater than 1.0 for large field sizes and less than 1.0 for small field sizes on all machines. The minimum field sizes which produce no surface underdosing for a simulated 2-cm-diam larynx are roughly 7 X 7 cm for 10-MV x-rays, 6 X 6 cm for 6-MV x-rays, and 5 X 5 cm for cobalt-60. In addition, the depth over which underdosing occurs is seen to increase with increasing energy.

Air↗