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Biomedical subjects

L J Verhey

Publications and source records attributed to L J Verhey.

At least 37 records · Page 2Linked to original sources
PubMed1996

Gamma knife radiosurgery in children.

52 pediatric patients were treated with radiosurgery at the University of California, San Francisco. Arteriovenous malformations were treated in 27 patients. Complete obliteration was noted in 4 of 12 patients imaged more than 2 years after radiosurgery. Arteriovenous malformation rebleed was noted in 1 patient. Symptomatic T2 changes were noted in 2 patients. Among 29 neoplasms treated in 25 patients, local control was noted in 5 of 7 low-grade gliomas, 5 of 14 high-grade gliomas, 4 of 5 craniopharyngiomas and 3 of 3 sarcomas. Three patients treated for neoplasms developed necrosis after radiosurgery.

Adolescent↗
PubMed1995

Advanced prostate cancer: the results of a randomized comparative trial of high dose irradiation boosting with conformal protons compared with conventional dose irradiation using photons alone.

PURPOSE: Following a thorough Phase I/II study, we evaluated by a Phase III trial high versus conventional dose external beam irradiation as mono-therapy for patients with Stage T3-T4 prostate cancer. Patient outcome following standard dose radiotherapy or following a 12.5% increase in total dose to 75.6 Cobalt Gray Equivalent (CGE) using a conformal perineal proton boost was compared for local tumor control, disease-free survival, and overall survival. METHODS AND MATERIALS: Stage T3-T4, Nx, N0-2, M0 patients received 50.4 Gy by four-field photons and were randomized to receive either an additional 25.2 CGE by conformal protons (arm 1--the high dose arm, 103 patients, total dose 75.6 CGE) or an additional 16.8 Gy by photons (arm 2--the conventional dose arm, 99 patients, total dose 67.2 Gy). Actuarial overall survival (OS), disease-specific survival (DSS), total recurrence-free survival (TRFS), (clinically free, prostate specific antigen (PSA) less than 4ng/ml and a negative prostate rebiopsy, done in 38 patients without evidence of disease) and local control (digital rectal exam and rebiopsy negative) were evaluated. RESULTS: The protocol completion rate was 90% for arm 1 and 97% for arm 2. With a median follow-up of 61 months (range 3 to 139 months) 135 patients are alive and 67 have died, 20 from causes other than prostate cancer. We found no significant differences in OS, DSS, TRFS or local control between the two arms. Among those completing randomized treatment (93 in arm 1 and 96 in arm 2), the local control at 5 and 8 years for arm 1 is 92% and 77%, respectively and is 80% and 60%, respectively for arm 2 (p = .089) and there are no significant differences in OS, DSS, and TRFS. The local control for the 57 patients with poorly differentiated (Gleason 4 or 5 of 5) tumors at 5 and 8 years for arm 1 is 94% and 84% and is 64% and 19% on arm 2 (p = 0.0014). In patients whose digital rectal exam had normalized following treatment and underwent prostate rebiopsy there was a lower positive rebiopsy rate for arm 1 versus arm 2 patients (28 vs. 45%) and also for those with well and moderately differentiated tumors versus poorly differentiated tumors (32 and 50%). These differences were not statistically significant. Grade 1 and 2 rectal bleeding is higher (32 vs. 12%, p = 0.002) as may be urethral stricture (19 vs. 8%, p = 0.07) in the arm 1 versus arm 2. CONCLUSIONS: An increase in prostate tumor dose by external beam of 12.5% to 75.6 CGE by a conformal proton boost compared to a conventional dose of 67.2 Gy by a photon boost significantly improved local control only in patients with poorly differentiated tumors. It has increased late radiation sequelae, and as yet, has not increased overall survival, disease-specific survival, or total recurrence-free survival in any subgroup. These results have led us to test by a subsequent Phase III trial the potential beneficial effect on local control and disease-specific survival of a 12.5% increase in total dose relative to conventional dose in patients with T1, T2a, and T2b tumors.

Aged↗
PubMed1995

Optimization of leaf positions when shaping a radiation field with a multileaf collimator.

Computer-controlled multileaf collimators are receiving increasing acceptance for clinical use in radiation therapy due to their efficiency in shaping radiation fields. Because of the physical leaf width of the multileaf collimator, a smooth field contour prescribed by a physician is approximated by a staircase-shaped field boundary. The point of intersection with the prescribed field contour determines the error of the approximation and may affect the outcome of the treatment. This article provides analytically optimized solutions for leaf positioning based on two different geometric object functions.

Humans↗
PubMed1994

A robust method of multileaf collimator (MLC) leaf-configuration verification.

Presents a novel and robust method for leaf-position verification with a multileaf collimator (MLC). On the portal image associated with an MLC-generated treatment field, all true treatment-held-edge lines are either parallel or perpendicular to each other. This unique feature of an MLC treatment field has been fully exploited by the authors' method. Employing a Hough-type transformation as an edge-line-orientation detector and a chamfer-matching method, the authors can find the best matching parameters (including translation, rotation and scaling) adaptively between a prescribed MLC leaf configuration and the actual treatment-held edges generated by the MLC system. This works even if the portal image is partially corrupted by noise or covered by compact bony structures. Comparing these parameters with clinically accepted tolerances, the authors can make a "go-or-no-go" decision quickly.

Algorithms↗
PubMed1992

Water calorimeter dosimetry for 160 MeV protons.

The absorbed dose to water from a 160 MeV proton beam as determined by a flexible, temperature regulated, sealed glass core, water calorimeter was compared to that determined from ionization chambers used in accordance with AAPM Report 16. The ratios of these doses as obtained from two experiments done over four months apart, are 0.992 +/- 0.004 and 0.990 +/- 0.004. As there are no radiation dependent parameters required for the water calorimeter, these data add to the growing body of evidence which supports the use of the calorimeter as a reliable absorbed dose standard. They also support the use of 60Co-calibrated ionization chambers used in accordance with AAPM Report 16 for the dosimetry of proton beams.

Calorimetry↗
PubMed1991

Biopsy after external beam radiation therapy for adenocarcinoma of the prostate: correlation with original histological grade and current prostate specific antigen levels.

We obtained post-irradiation biopsies in 37 men with initially stage T3 prostatic adenocarcinoma treated by external beam radiotherapy. Eligibility for post-irradiation biopsy included no clinical local failure, interval since treatment of 24 months or more and no endocrine therapy. Of the 37 patients 23 (62%) had negative biopsies while 14 (38%) had positive biopsies. Of 23 patients whose original cancer was well or moderately differentiated 18 (78%) had negative biopsies, compared to only 5 of 14 (36%) of those with poorly differentiated cancer (p less than 0.03). Among 19 patients whose current serum prostate specific antigen (PSA) value is less than 2.5 ng./ml. 15 (79%) had negative biopsies, compared to only 4 of 14 (29%) with a PSA level of greater than 2.5 ng./ml. (p less than 0.02). These results strongly suggest that there is a low probability of positive post-irradiation biopsy regardless of its significance in men with a normal prostate by palpation and a normal serum PSA value. However, short followup since biopsy precludes analysis of the predictive value of post-irradiation biopsy on long-term local and distant disease status.

Adenocarcinoma↗
PubMed1989

Conservative treatment of uveal melanoma: local recurrence after proton beam therapy.

Twenty-three of 1006 (2.3%) uveal melanoma patients treated with proton beam therapy at the Harvard Cyclotron Laboratory between July 1975 and December 31, 1986 received additional treatment for documented (15 patients) or suspected (eight patients) tumor growth in the irradiated eye. Growth within the initially irradiated volume was documented at Massachusetts Eye and Ear Infirmary in 12 patients. Documented growth occurred in nine of 665 (1.4%) patients with small and intermediate size tumors, at times after treatment ranging from 6 to 48 months (median 16 months), and in three of 341 (.9%) patients with large tumors at 7, 11, and 12 months after treatment. Melanoma growing totally outside the treated volume was also documented in three additional patients at 7, 9, and 45 months; two of these were thought to be "ring melanomas". Eight patients had the treated eye removed elsewhere for suspected tumor growth. The additional treatment in these 23 patients was conservative in nine patients (repeat proton irradiation in five and laser photocoagulation in four). Thirteen underwent immediate enucleation and one had orbital exenteration. Ultimately, 17 of the 23 eyes (74%) were removed. Estimated probability of local control of the melanoma within the irradiated eye at 60 months was 96.3 +/- 1.5%. Dose distributions to the 12 patients with documented local failure within the irradiated volume were analyzed. Ten tumors recurred marginally in an area receiving less than the prescribed dose of 70 CGE (CGE = Cobalt Gray Equivalents = proton Gy X RBE 1.1), whereas only two recurred in the volume receiving full dose. Based on these data, it appears that a dose of 70 CGE in five fractions is associated with very high rates of local control in human uveal melanoma. It is reasonable to consider initiating studies using a lower total dose or a more protracted course, to determine if some of the observed complications are dose-related.

Adult↗
PubMed1984

Relative biological effectiveness of modulated proton beams in various murine tissues.

The relative biological effectiveness (RBE) of proton beams produced by Harvard University 160 MeV synchrocyclotron was studied in various murine tissues. Reference radiation was Cobalt-60 gamma-rays from a teletherapy unit at the Massachusetts General Hospital. Animals were C3Hf/Sed mice derived from our defined flora mouse colony. Test tissues are: lens, lung, testes and tail vertebrae. The RBE of the third generation isotransplants of a spontaneous mouse mammary carcinoma was also investigated. The proton and Cobalt-60 irradiations were carried out simultaneously by 2 teams. The dose response curves obtained for testes weight loss and growth stunting of tail vertebrae indicated that the RBE for our protons was independent of radiation dose in the range of 0.4 to 16 Gy. This finding was identical to our previous studies of the murine fibrosarcoma, skin and small intestine. The RBE values for lens and lung tissues were obtained by determining radiation dose to result in a complete cataract in half the irradiated eyes in 210 days and a 50% mortality in 180 days respectively. We have studied proton RBE in 7 normal tissues and 2 tumors including previously reported results. The RBE values for these tissues were found to fall between 1.09 and 1.32. No significant differences in the proton RBE were found between the several normal and tumor tissues studied.

Animals↗
PubMed1983

Protons or megavoltage X-rays as boost therapy for patients irradiated for localized prostatic carcinoma. An early phase I/II comparison.

A total of 180 patients with carcinoma of the prostate limited to the pelvis were treated with one of two external beam irradiation techniques between 1972 and 1979. One hundred and sixteen patients were treated with conventional pelvic megavoltage x-ray therapy. Sixty-four patients were treated with combined pelvic x-ray therapy plus a perineal proton beam boost to a carefully defined prostatic tumor volume. A 160 MeV proton beam has been modified to irradiate patients with localized tumors by using conventional treatment schedules. This proton beam has the physical advantage over megavoltage x-rays of reducing the dose to normal tissues adjacent to the tumor volume. By using the proton beam boost we have delivered an increased prostatic tumor dose of 500 to 700 cGy without increasing treatment morbidity at all. The two groups are actuarially analyzed for patient survival, disease-free survival and local recurrence-free survival, and thus far, no significant differences have been noted. Because of the minimal complications observed in the proton group despite a 10% increase in dose, a randomized clinical trial comparing these two treatment techniques is studied.

Clinical Trials as Topic↗
PubMed1983

Determination of the radioprotective effects of topical applications of MEA, WR-2721, and N-acetylcysteine on murine skin.

Topical applications of MEA (beta-mercaptoethylamine or cysteamine), WR-2721 [S-2-(3-aminopropylamino)-ethylphosphorothioic acid], and N-acetylcysteine (NAC) were tested for their ability to protect the normal skin of the hind legs of mice against acute and late damage from single doses of 137Cs radiation. No significant protection was observed with either WR-2721 or NAC. MEA was shown to offer significant protection against acute skin damage in both buffered and unbuffered forms, but no significant protection against late contraction. The use of topical MEA on unanesthetized animals breathing carbogen (95% O2, 5% CO2) appears to give an enhanced level of radioprotection over that shown for anesthetized, air-breathing animals.

Acetylcysteine↗
PubMed1982

Precise positioning of patients for radiation therapy.

We have developed a number of immobilization schemes which permit precise daily positioning of patients for radiation therapy. Pretreatment and post-treatment radiographs have been taken with the patient in the treatment position and analyzed to determine the amount of intratreatment movement. Studies of patients in the supine, seated and decubitus positions indicate mean movements of less than 1 mm with a standard deviation of less than 1mm. Patients immobilized in the seated position with a bite block and a mask have a mean movement of about 0.5 mm +/- 0.3 mm (s.d.), and patients immobilized in the supine position with their necks hyperextended for submental therapy evidence a mean movement of about 1.4 mm +/- 0.9 mm (s.d.). With the exception of those used for the decubitus position, the immobilization devices are simply fabricated out of thermoplastic casting materials readily available from orthopedic supply houses. A study of day-to-day reproducibility of patient position using laser alignment and pretreatment radiographs for final verification of position indicates that the initial laser alignment can be used to position a patient within 2.2 mm +/- 1.4 mm (s.d.) of the intended position. These results indicate that rigid immobilization devices can improve the precision of radiotherapy, which would be advantageous with respect to both tumor and normal tissue coverage in certain situations.

Casts, Surgical↗
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↗