Charles W. Coffey

Approaches to Optimization of Dose in Radiation Therapy of Cervix Carcinoma

A treatment planning approach to radiation therapy for carcinoma of the cervix which attempts to maximize tumor dose and minimize the effect on normal tissue must include additonal dose reference points besides the standard ones (Manchester points A and B, mg-hrs.) A variety of loading configurations can be used to treat the tumor volume to a specified dose. In order to avoid inappropriate loading arrangements, dose at the tumor and at the vault must be carried to required therapeutic levels.

A clinical trial for advanced cervico-vaginal pelvic carcinomas using californium CF-252 fast neutron therapy: Report of early responses☆

Abstract This report summarizes clinical experiences with Californium (Cf) 252 for the radiotherapy of advanced cervicovaginal carcinomas at the University of Kentucky Medical Center from November 1976 to April 1979. Fifty-nine patients were treated with Cf-252 during this period. After pilot studies, a treatment schedule was developed which appeared to offer improved local control and clearance of these tumors in ∼90% of treated patients. However, a longer follow-up period is essential to determine whether local tumor control is sustained or whether local tumor recurrence remains as great a problem as for patients who receive conventional radio-nuclide therapy. Ultimate long term survival and outcome will depend upon the frequency of control of local-regional disease and the frequency of appearance of more disseminated and metastatic disease. Cf-252 neutron brachytherapy was combined with 4500–5500 rad of Cobalt 60 or linear accelerator external beam fractionated radiotherapy for 4–6 weeks. Neutron treated patients whose disease was in appropriate clinical stages were also treated with combined radiotherapy-surgery without problems. Stage dependent regression was noted; low stage tumors responded distinctly better and more rapidly than higher stage tumors. All histological patterns responded, and no unusual severe or unanticipated early side effects or toxic tissue reactions were observed.

X-ray beam characteristics of the Varian Clinac 6-100 linear accelerator.

Beam characteristics and dosimetry measurements of the 6 MV x-ray beam from a Varian Associates Clinac 6-100 linear accelerator are presented. Percentage depth dose tables are given as a function of field size for square fields. Tissue-maximum ratios and scatter-maximum ratios are tabulated as a function of depth and field size. Investigation of surface dose and depth of maximum dose reveal a dependence on field size. Other beam parameters measured are presented include field flatness, symmetry, SSD dependence, and penumbra. Treatment planning parameters including field size output factors and wedge factors are discussed.

Enhancement of radiation effect on mouse intestinal crypt survival by timing of 5-fluorouracil administration.

There is a marked dependence of mouse crypt survival on the sequence of combined drug-radiation treatment and on the time lapse between irradiation and drug administration. When 5-fluorouracil is administered 6 hours after irradiation or later (up to 18 hours postirradiation), crypt survival drops significantly.

Five-year cure of cervical cancer treated using californium-252 neutron brachytherapy

FEMALE PELVIC CARCINOMA IS ONE OF THE COMMON malignancies seen at the University of Kentucky Medical Center and often presents in an advanced stage. In 1976, we began to test californium-252 neutron brachytherapy (NT) for its efficacy for control of primary and recurrent advanced uterine, cervix, and vaginal cancers. The first protocol used was 5000–5500 rad of whole pelvis irradiation followed by 1–2 Cf-252 insertions using a single tandem placed in the utero-cervico-vaginal region. Of 27 patients with primary carcinomas treated, 10 are alive and well 5 years later (37%) Two of two recurrent tumors were locally controlled but failed later. These patients had advanced cervical, vaginal, or endometrial carcinomas. In 1977, a transitional year, treatment of only unfavorable stages and presentations with NT was initiated. Similar results were obtained with NT as compared to conventional photon therapy (PT). Further improvement in treatment results can be anticipated as NT brachytherapy is used for advanced cancer therapy by more effective treatment schedules and radiation doses. Cf-252 can be used as a radium substitute and achieved similar rates of tumor control and 5-year survivals.

Dosimetric evaluation of a variable energy superficial X-ray machine with applications for endocavitary radiotherapy techniques.

This investigation presents the beam characteristics of a newly-marketed variable energy superficial X ray machine for radiotherapy. The X ray system hardware, including a high voltage generator, and console software allow for nine independent operator-selected X ray beams from 10-150 kVp. Filament current values are also independently variable; 1.0-13.0 mA for 90-150 kVp, and 1.0-30.0 mA for 10-90 kVp. The HVLs, effective energies, and radiation outputs for the nine combinations of kVp and mA are presented. In addition, percentage depth dose and beam uniformity results are presented as a function of cone size. Radiation output stability and reproducibility results are included. Discussion of adaptation of this X ray system to the Papillon technique for the treatment of rectal cancers is presented.

Method for localizing and calculating vaginal dose in brachytherapy.

Contrast agents in the vagina are being used to determine the position of vaginal surfaces relative to applicators in an effort to assess dose at these sites. Computer treatment planning allows consideration of dose at many more sites than was formerly possible, but dose prescription to critical tumor volumes then becomes of greater importance. Vaginal reference dose points VR, VL, VA, and VP are proposed. With dose specification determined at these points, the problem of low vaginal dose from overly wide vaginal ovoid geometries and related difficulties can be avoided. Attention to central vaginal doses can reduce the probability of central pelvic recurrence in the vagina. We have found the VR, VL doses were much larger than VA, VP doses in standard loaded implant configurations.

A slice geometry phantom for cross sectional tomographic imagers

This investigation presents the design and fabrication of a magnetic resonance imaging (MRI) test phantom for determining slice thickness, slice adjacency, slice offset, and slice angulation. This test phantom is a three-dimensional conic section of MRI image producing material; proper orientation allows analysis in each of the major imaging planes. The phantom design (geometrical configuration) incorporates both theoretical and quantitative methodologies. The necessary mathematical analyses are both simple and rapid. In addition, this phantom has been successfully used to assess the image slice parameters for computed tomography (CT) scanners and single photon emission computed tomography (SPECT) imaging systems. Slice profile parameter results, full width at half maximum (FWHM), from this phantom design are compared with conventional methods.

A cumulative normal distribution model for simulation of electron beam profiles.

Abstract A mathematical model for the electron beam profile has been developed using parameters of the cumulative normal distribution. The central feature of this model involved the derivation of an expression for penumbra width, w , as a function of depth and energy. The value of w was used in a derived analytical function to find σ, the parameter that uniquely defines the shape of the cumulative normal distribution. There was excellent agreement with measured beam profiles produced by a Varian Clinac 18 electron linear accelerator, thereby allowing us to use this model to generate isodose curves of considerable accuracy.

Tandem-vaginal cylinder applicator for radiation therapy of uterine adenocarcinoma

Preoperative radiotherapy for stage II adenocarcinoma of the endometrium was studied in 74 patients using the University of Kentucky tandem-vaginal cylinder applicator. The intrauterine tandem and vaginal cylinder were inserted and loaded at the same time or sequentially. Forty to 45 Gy of fractionated whole pelvis photon radiotherapy was combined with the single intracavitary insertion which gave 20 Gy to a parauterine isodose at 2 cm and to the vaginal surface. Treatment with this system gave a 5 year survival rate of 88% with a 4% complication rate for stage II corpus adenocarcinomas.