E. R. Hering

Progress in the use of iodine therapy for tumours of the eye.

Developments in a new system of brachytherapy for tumours of the eye are reported. This involves the use of 125I sources with special screens and filters to avoid irradiation of vital structures and to produce a homogeneous radiation field. Methods for the treatment of tumours of the lids, conjunctiva, retina, choroid and lachrymal gland have been developed. Sixteen out of 20 treatments appear to have been successful. This system would seem to be a material advance on those previously reported.

Malignant melanoma of the eyelid and palpebral conjunctiva treated with iodine-125 brachytherapy

OBJECTIVE To evaluate the results on malignant melanomas of the eyelid and palpebral conjunctiva treated with iodine-125 (125I) brachytherapy with shielding of the eye. DESIGN Noncomparative case series. PARTICIPANTS Fourteen patients treated with 125I brachytherapy at an ocular oncology referral center from 1974 through 1996, all of whom had had previous debulking, incomplete resection, or recurrence after surgery. INTERVENTION A stainless steel pericorneal ring eyeshield was attached to the extraocular muscles, over which a lid was fitted to protect the cornea without touching it. Iodine-125 seeds in polythene tubes were inserted into the eyelid and attached to the lid margin for a single plane implant. In five cases additional seeds were glued on to the shield as well for a volume implant. A median dose of 37 Gy (range, 17.3-67.6 Gy) was given over the course of 113 hours (range, 47-190 hours) to the outer surface of target volume. MAIN OUTCOME MEASURES Local control is regarded as freedom from recurrence in those without measurable disease and complete clinical regression in those with measurable disease. Morbidity is assessed in terms of function and cosmesis. Survival is given from the time of the implant. RESULTS There was local control in 13 patients maintained from 11 to 227 months (median, 39 months). There were two recurrences at 8 and 13 months in the first patient who received 17.3 Gy. Late complications consisted of mild eyelid telangiectasia, mild eyelid atrophy, and loss of eyelashes in most patients. Five patients, four of whom had upper eyelid tumors, experienced a dry eye, which was managed with tear supplements, and one of these patients developed a cataract. A corneal ulcer developed in one eye, which later perforated after treatment of a subsequent bulbar melanoma and was exenterated. Another eye was enucleated after treatment for a subsequent melanoma in the fornix. Cosmesis was acceptable to patient and doctor in the other 12 patients. Vision was maintained in seven patients, reduced in two, and not recorded in the remaining three patients. Three patients died of hematogenous metastases at 44, 62, and 79 months after implant, one of bronchial carcinoma at 46 months and one of an astrocytoma at 39 months. All patients were clear of local disease. The remainder survived for a median of 45 months (range, 18-227 months). CONCLUSIONS Iodine-125 brachytherapy can be used as an alternative to wide excision or exenteration of these tumors. There was good local control, reasonable maintenance of vision, and good cosmesis.

Postenucleation orbits in retinoblastoma: treatment with 125I brachytherapy

PURPOSE Children with retinoblastoma that extends into or through the choroid, sclera, or optic nerve are at risk of developing orbital disease, as well as metastases. Previously, these enucleated orbits were treated with external beam radiotherapy in addition to chemotherapy. 125I brachytherapy for tumors in and around the eye was pioneered by Sealy in Cape Town, South Africa, in 1974. In 1983, he developed a technique to irradiate the contents of the orbit while limiting the dose to the bony orbit and eyelids. METHODS AND MATERIALS Six nylon tubes containing 125I seeds were implanted through the eyelids around the periphery of the orbit. Each contained a metal gutter that screens the outer part of the seeds from the bony orbit. A seventh unscreened tube was placed in the center, and a metal disc with 125I seeds on its posterior surface was secured beneath the eyelids. Between 1983 and 2000, 57 orbits were treated in 56 children with retinoblastoma. Thirty-six were treated prophylactically and 21, with tumor at the resection line of the nerve, extrascleral tumor, or metastases, were treated therapeutically. They received a median dose of 34 Gy in 70 h; 30 also received chemotherapy. Children with tumor at the resection line of the nerve also received treatment to the craniospinal axis. RESULTS The median follow-up of the 35 patients treated prophylactically was 35 months (range 0-187). Seven patients died, 6 of metastases, at a median of 10 months (range 4-29) after the implant. Eight of the 13 patients with microscopic extraocular tumor survived a median of 29 months (range 5-156). None of the 8 patients presenting with orbital tumor or metastases survived. No orbital recurrences developed in any of the patients. Cosmesis was considerably improved compared with previous forms of irradiation. CONCLUSION Orbital brachytherapy is an effective method of irradiating the orbit to prevent recurrent tumor, the treatment time is short, and the cosmesis is much more acceptable than with other forms of irradiation. No facial atrophy or second nonocular tumors have occurred.

Radiation dose from a linear slit scanning X-ray machine with full-body imaging capabilities

Doses for a range of examinations and views using digital X-ray equipment with full-body linear slit scanning capabilities (Statscan) have been compared with those from other published studies. Entrance doses (free-in-air) were measured using a dosimeter, and effective doses were generated using a Monte Carlo simulator. Doses delivered by the linear slit scanning system were significantly lower than those from conventional X-ray equipment. Effective doses were between 9 and 75% of the United Nations Scientific Committee Report on the Effects of Ionising Radiation doses for standard examinations. This dose reduction can be explained by the properties of linear slit scanning technology, including low scatter, beam geometry, the use of a digital detector and the use of higher than usual tube voltages.

The treatment of cancer of the uvula and soft palate with interstitial radioactive wire implants

A new method of implantation of the soft palate with radioactive wires is described. Experience with 25 patients is reported and the results analyzed. This method of treatment appears to be highly effective and avoids radiation complications.

Paediatric dose measurement in a full-body digital radiography unit

BackgroundIonizing radiation has a detrimental effect on the human body, particularly in children. Thus it is important to minimize the dose. Linear slit-scanning X-ray units offer the possibility of dose reductions. In order to further develop linear slit-scanning radiography, the dose needs to be accurately calculated for various examinations.ObjectiveTo measure the entrance dose (free-in-air) and calculate the effective doses for various radiological examinations in children on Lodox Statscan and Shimadzu radiography units.Materials and methodsEntrance doses (free-in-air) were measured using a dose meter and ionization chamber on the Statscan and Shimadzu units at two South African hospitals. The entrance doses were measured for a number of common examinations and were used to compute the effective dose using a Monte Carlo program.ResultsThe standard deviation of the entrance doses was in the range 0–0.6%. The effective dose from the Statscan unit was well below that from the Shimadzu unit as well as that found in other radiological studies from around the world in children. The one exception was chest examination where the dose was similar to that in other studies worldwide due to the use of Chest AP projection compared to Chest PA used in the comparitive studies.ConclusionLinear slit-scanning systems help reduce the dose in radiological examinations in children.

A comparison of the biological effect of iodine 125 and tantalum 182 gamma rays using vicia faba roots

Seeds containing iodine 125 as supplied by Lawrence Soft Ray Corporation have now been used at this hospital to treat a variety of patients with tumours which would have been treated with applicators or moulds loaded with 182Ta or 226Ra if the seeds had not been available. Iodine seeds have also been extensively used at other hospitals, e.g. Kim and Hilaris (1975), Hilaris (1976), and Charyulu et al. (1976). The advantages of 125I over 182Ta have already been outlined earlier (Sealy et al., 1976; Hering et al., 1977). However, whereas the radiobiological effectiveness (RBE) of the 182Ta radiation relative to 250 kV X rays is well known, there is at present no such information available for 125I. By considering the LET spectrum of the X rays of 125I, Kim and Hilaris (1975) have predicted an RBE of the seeds for human tumours higher than one and less than 1.5. Some radiobiological studies are needed to test this prediction and this has led to some preliminary investigations on vicia faba as outlined below.

Localized whole eye radiotherapy for retinoblastoma using a 125I applicator, “claws”

PURPOSE To treat children with retinoblastoma, who require whole eye radiotherapy, with a specially designed (125)I applicator that irradiates the eye while sparing the surrounding tissues. METHODS AND MATERIALS Under general anesthesia, a pericorneal ring is attached to the 4 extraocular muscles, and 4 appendages, each loaded with (125)I seeds, are inserted beneath the conjunctiva in-between each pair of muscles and attached anteriorly to the ring. Twenty-nine eyes were treated. Eighteen received a median dose of 28 Gy during 91 hours and 11 received 40 Gy during 122 hours, when the relative biologic effectiveness was taken as 1 instead of 1.5. Six had received prior chemotherapy. RESULTS Twenty-four eyes were followed up for 2-157 months (median 29). Although 22 eyes responded, local control was achieved in 13 patients, 3 of whom required additional treatment for new tumors; a further 3 required additional treatment for tumor recurrence as well as new tumors. One of these eyes was enucleated for neovascular glaucoma. All 6 Group I-III eyes and 6 of 18 Group V eyes were retained for 2-157 months (median 39), with good vision in 10 eyes. Three developed cataracts 7, 8, and 12 years later, 1 of which has been removed. CONCLUSIONS This is a new way of irradiating the whole eye with a minimal dose to the surrounding tissues. The treatment time is only 5 days. It is effective in Groups I-III, but only 33% of Group V eyes retained vision. No late cosmetic defects occurred.

OER and RBE for 125I and 192Ir at low dose rateon mammalian cells

The oxygen enhancement ratio (OER) for 125I and 192Ir as well as the relative biological effectiveness (RBE) at low dose rates (40-80 cGy h-1) were determined for B16 melanoma cells in culture. The OER was found to be 2.1 +/- 0.03 for 125I and 2.7 +/- 0.04 for 192Ir. The RBE for 125I relative to 192Ir was determined as 1.8 +/- 0.03 under aerated conditions and as 2.4 +/- 0.03 under hypoxia.

The use of screened low energy radiation sources for moulds

It is well-known that large squamous carcinomas in the mouth have a low cure rate with conventional radiation treatment. Attempts may be made to improve this situation by implantation of sources or treatment with an intra-oral cone, but as these may be difficult to control applicators are often preferred. The conventional oral radium applicator is uncomfortable for the patient to wear and is associated with considerable exposure to staff. In addition, the high energy γ rays are difficult to screen and radiation tolerance under these circumstances may be reached, not by the tumour and its immediate structures, but by normal tissues in the neighbourhood. Maximum screening of associated normal tissues can be achieved by using 125Iodine, a radioisotope which emits X and γ rays of 27–35 keV. This is available in seeds which are useful for the manufacture of small or large applicators (Sealy et al., 1976) and which are acceptable to patients because of their light and elegant form.