Conformation therapy using a computer controlled telecobalt unit for advanced cervical carcinoma.

This retrospective analysis evaluates the results of conformation radiotherapy for patients with advanced cervical carcinoma. Between January 1980 and September 1987, 16 patients with high common iliac/para-aortic node metastases from advanced carcinoma of the uterine cervix were treated using conformation radiotherapy. A large area from L1/L2 to the pelvis, with an average length of 23 cm, was treated to a total tumour dose of 5000-5500 cGy, with a daily tumour dose of 180-200 cGy in 28-30 daily fractions, using a computer controlled tracking cobalt unit (CCTCU). Before external beam irradiation, 11 patients underwent laparotomy/hysterectomy, seven were given chemotherapy and eight received brachytherapy. The preliminary results are encouraging. The actuarial 1-year, 3-year and 5-year survival rates after treatment were 81%, 44% and 37%, respectively. The locoregional control rate was 62.5%. None of the patients relapsed in the para-aortic nodes. All patients tolerated the large area of tracking irradiation therapy very well. None had any severe acute or delayed radiation complications. Use of the conformation radiotherapy technique to include the pelvic and para-aortic nodes has been shown to be an effective form of radiotherapy with minimal morbidity.

Dosimetric intercomparison in the British Institute of Radiology fractionation study of 3F/week versus 5F/week in radiotherapy of laryngo-pharynx cancer.

A dose intercomparison was carried out by the National Physical Laboratory between the seven radiotherapy centres which contributed the largest number of patients to the British Institute of Radiology fractionation study of three fractions per week versus five fractions per week in clinical cancer treatment. Six of the centres showed remarkable agreement within the acceptable limits of error of the measurements. In one centre there appeared to be a physical dose discrepancy of 2.8% which was materially less than could be detected clinically.

Treatment of medulloblastoma using a computer-controlled tracking cobalt unit.

Radiation therapy of the length of the spinal column presents various clinical and physical problems. The completed plan may be complicated to set up, be time-consuming and require daily variation to achieve reasonable dose homogeneity. A case of medulloblastoma is used to illustrate the steps in producing a plan for dynamic treatment using a computer-controlled tracking cobalt unit. After definition by computed tomography, the target is considered in segments in order to develop a plan which keeps the spinal cord constantly positioned at the beam isocentre. The main computer is used to develop the patient treatment file and information is transferred to a second computer which controls and monitors the safe functioning of the cobalt unit. The cranial fields are treated separately in a conventional way. Good and consistent control of the dose distribution is achieved along the entire target volume. This technique is a marked improvement over all existing methods of treating the spinal axis.

Five years hospital experience with the Amersham caesium 137 manual afterloading system.

The Amersham caesium 137 manual afterloading system for treatment of cancer of the uterine cervix and endometrium has been in use at the Royal Free Hospital for more than five years. The system uses permanently loaded flexible source pencils in combination with standard packs of disposable plastic applicators. Both sources and applicators have proved trouble-free in use. The sources are transported in special containers designed and built at the Royal Free Hospital and are inserted and removed on the ward by nursing staff. A set of sources is used in theatre for rectal and bladder dose measurements when the applicators are inserted. Staff radiation doses are low. The system is mainly used to produce pear-shaped dose distributions similar to those of the Manchester system, but simple cylindrical distributions are possible using symmetrically loaded source pencils.

Conformation therapy at the Royal Free Hospital. A progress report on the tracking cobalt project.

A computer-controlled tracking cobalt unit (CCTCU) was commissioned for treating patients in January 1980. The system has proved to be reliable and acceptable in routine use for conventional and conformation therapy. The system comprises a modified TEM MS90 Mobaltron, a Hewlett-Packard System 1000 Model 30 mini-computer and user programmes. Tracking techniques are suitable for the treatment of tumours of the oesophagus, thyroid, bronchus, chains of lymph nodes or medulloblastoma. Tumours 85 cm long can be treated at the isocentre. The high dose volume may be considerably reduced when tracking techniques are used instead of conventional techniques. The major obstacle to the routine use of conformation therapy is treatment planning. Work in progress is designed to produce a computerized planning system linking a CT scanner and the CCTCU. It is expected that the system will produce both a plan optimized in 3-D and the necessary control data in machine readable form within an hour of a patient being scanned. The present planning system is based on a Rad-8 planning system and an Alderson phantom to verify the dose distribution in 3-D. An outline of the tracking technique is given. The computer control system is described briefly, with its methods of use for treating patients. Brief reverence is made to work at other centres using conformation therapy.

The influence of surface rugosity on haemolysis occurring in tubing.

Haemolysis was measured in three tubes of the same chemical composition but differing surface texture. It was found that during the first hour of pumping the increase in haemolysis in both human transfusion blood and fresh cattle blood was greatest in the roughest tubes. When pumping of blood was continued for longer periods the rate of further haemolysis increase was equal in all tubes.

Conformation therapy using the tracking cobalt unit.

A description is given of the principles and application of the tracking technique using an automated cobalt teletherapy unit. The technique is a combination of moving table and arcing techniques which is used to shape the irradiated volume to match the tumour volume in three dimensions. The method has the additional advantage that corrections can be made for variations in dose rate along the tumour axis resulting from changes in body outline and the presence of inhomogeneities. An outline of the treatment planning procedure and the way the machine executes the planned treatment is given. Isodose distributions ar presented for two cases for which the technique was employed. The first of these illustrates the treatment of an oesophageal tumour, showing how the technique can be used to compensate for an irregularly shaped tumour in a part of the body having a large variation in cross section. The second shows how the technique copes with a tumour having a regular shape but having an awkward orientation in the body. Brief reference is made to work at other centres using moving table and three-dimensional shaping techniques which employ synchronous shielding.