Therapeutic applications of radioactive (131)iodine: Procedures and incidents with capsules.

BACKGROUND: Treatments for thyrotoxicosis and carcinoma thyroid are carried out by oral administration of radioactive iodine ((131)I) in the form of liquid or capsules. The liquid form of (131)I has higher risk factors such as vapourization, spillage and need for management of higher activity wastes. Use of (131)I in capsule form simplify procedures of handling compared to liquid form of (131)I. The guidelines of safe handling and quality assurance aspects for therapeutic use (131)I are well outlined by International Atomic Energy Agency (IAEA) reports. AIM: A few unusual incidents with I-131 capsules encountered in the past need to be highlighted from health physics point of view.
MATERIALS AND METHODS: In Royal Hospital, Oman, I-131 is imported in capsules, and the total activity handled/year steadily increased over 10 years. Discrete activities range from 185 MBq (5 mCi) up to 7.4 GBq (200 mCi). In four incidents deviations in standard operational procedures were recorded.
RESULTS: Nature of incidents is described as follows: (1) After assay of activity, the capsule was directly put in the lead container with missing of inner cap. (2) Patient poured water in the Perspex tube, when the capsule was handed over to her, making an emergency situation. (3) In 3 high activity capsules (2 nos 2.96 GBq, 1 no. 4.26 GBq), observed sticky behavior in capsule holder on the 2(nd) day post receipt, which were in order on the 1(st) day. (4) A capsule could not be swallowed by a patient, which was taken back from the mouth. Monitoring of patient later did not show residual ingested activity.
CONCLUSIONS: The report documents some of the unusual incidents for information to other centers engaged in such radioactive administrations.

INTRODUCTION

Radioactive iodine (131I) treatments for management of thyrotoxicosis and carcinoma thyroid started. Clinical applications of radioactive iodine for thyroid treatments are practiced for more than six decades, as one of the peaceful use of atomic energy with 131I, which is available in abundance as fission product from nuclear reactors. Guidelines of safe handling and quality assurance aspects are well outlined by IAEA reports.[12] Though the procedure of 131I for therapeutic applications are simple, because of the need for good infrastructure and safety requirements, only the facilities of 131I therapy wards and hospitalization of patients are restricted to a few major centers globally. Liquid form of 131I as an unsealed source in vials was in practice for long time, which is being changed by making 131I available in gelatin capsules encapsulation. The use of 131I in liquid form has higher risk factors such as vaporization, spillage and the need for management of higher activity wastes. A vacuum technique[3] indicated an easy way for administration of high activities without direct handling of activity by personnel. The details on calibration of capsules and experience on waste disposal were explained earlier.[45] There are no reports available about the practical aspects of handling and incidents related to use of 131I capsules in clinics. We reviewed our records, and highlight incidents relating to 131I capsules encountered at our hospital.

MATERIALS AND METHODS

The department has standard operating procedures at different steps of receipt, assay, identification, certification, administration; documentation and waste for clinical use of 131I [Table 1]. The total activity handled/year steadily increased over last 10 years. Capsules of discrete individual activities 185 MBq (5 mCi), 555 MBq (15 mCi), 3.7 GBq (100 mCi), 5.5 GBq (150 mCi), 7.4 GBq (200 mCi) are imported from GE Health Care, Amersham, UK. Experience on therapeutic applications and details of patients could be referred from our earlier reports.[67] Recently, a method for estimating residual radioactive 131I body burden was highlighted.[8] There were four unusual incidents relating to I-131 capsules and patient administrations.

Table 1

Sequence of receipt and administration of I-131 capsules

RESULTS

The details of individual incidents and their nature of their occurrence are outlined.

In one occasion, after assay of activity, the capsule was directly put in the lead container. This was done by the assaying technician by inverting the capsule holder and dropping capsule inside lead container, because of lack of knowledge. During administration time in the ward, some other technician found that when the Perspex guide tube is inserted into the lead pot, there was no locking inner cap to engage the tube. With a lead container, the capsule cannot be administered directly to the patient. Another guide empty tube was taken; a spare inner cap was screwed to it. This guide tube was fit on the annular hole of the lead container and with an inverted geometry, the capsule brought to inner cap position. Because the activity was present without shielding of pot, quickly it was handed over to the patient for swallowing. There was no excess personnel exposure noted during that service month, showing that this incident did not result in significant personnel exposure

Patient poured water in the Perspex tube (provided by suppliers of capsule) when the capsule was handed over to her, making an emergency situation. The administering physicist observed the patient pouring water into the Perspex tube. Before the capsule absorbed water, capsule was put back into the lead container along with Perspex tube. There was a glove box available in each isolation room. The capsule container was moved out in the glove box. The guide tube was removed, capsule was made free by a splinter stick, and immediately administered [Figure 1]. This operation was carried out in a stainless steel tray inside glove box, and there was localized contamination due to leaked water in the absorbent tissues on the stainless steel tray when capsule was released. The waste was handled separately and later disposed by delay and decay method. During this incident there was localized contamination near fume hood, which is overcome by delay and decay method

Figure 1

Water poured in the Perspex guide tube containing I-131 capsule, later capsule released and administered to patient

In another occasion (June 2012), 3 high activity capsules (2 nos. 2.96 GBq, 1 no. 4.255 GBq) were in order when it was assayed in calibrator on the 1st day. They showed sticky behavior on the inner wall of capsule holder on the 2nd day post receipt. For one patient, first 2 capsules (2 nos. 2.96 GBq) were administered by gently shaking the capsules by a splinter stick and making them free in the capsule holder. The third capsule (4.255 GBq), when checked after 2 days storage, for its status, showed more discoloration, adherent to the Perspex cap and appeared having release of activity outside the capsule, due to likely rapture. Figure 2 shows the capsule in sticking status with inner capsule holder. Figure 3 shows comparison of a decayed capsule showing normal appearance. Procedure was cancelled, and activity was not administered to the patient

Figure 2

4.26 GBq in stuck condition inside the inner capsule holder

Figure 3

Decayed capsule in good condition after 4 years storage

When the iodine capsule (600 MBq) was administered orally by the medical physicist, the patient did not swallow the capsule and kept stuck in the tongue. Though she accepted the procedure and signed consent, she has not revealed to the medical physicists that she has not swallowed any medication in capsule form anytime in the past. In these circumstances, the in charge medical physicist used the Perspex tube pressed against her tongue (in open mouth) and took out the capsule. The capsule was slightly deformed due to moisture but was taken out in full form. The external counting method[8] estimated an activity of 0.03 MBq confirming that the patient did not consume 131I. The procedure was abandoned.

DISCUSSION

This presentation records some of the incidents we experienced relating to radioactive iodine capsule administrations. Compared to administrations of liquid form of radioactive iodine, capsule administrations are fairly less complicated. IAEA report[1] described 8 incidents relating to mis-administrations of 131I during therapy procedures. Administration to wrong patients two, wrong doses four occasions, violating recommendations, and radiation safety lapse one occasion each. Proper identification of patients before administration; Checklist of procedures regarding confirming correct activity, correct communications among staff members, double checks carrying out independently, maintaining correct records; fool-proof inventory maintenance; maintaining alertness during work and no complacency attitudes are the key issues to be followed in therapeutic applications of nuclear medicine. So far, there are no reports about specific problems encountered in nuclear medicine departments, with capsule 131I. In this report, we brought separately incidents relating to deviations in regular guidelines; first one, the capsule directly put in the container, which necessitated alternative methods to overcome the problem. The second one, it is uncommon to put water and take the capsule. This happened due to misunderstanding of the procedure by the patient when she was instructed to take the capsule with water. When the patient is illiterate, we have to resort to fool-proof methods of explanation to avoid exigencies.

For the changes in the integrity of the capsule, there is neither a report in the literature nor a possibility for the manufacturer of long reputation (GE Health Care, UK) to have quality control problems. It is felt that there may be condensation happened inside the lead container, making deliquescent nature subjecting capsule to get partially soaked. The same day, it was also reported by another hospital in the city (Sultan Qaboos University Hospital) that similar sticking of capsule was experienced, and the manufacturer was reported about it. It was felt that this could have occurred because of transportation of the consignments from the airport in non-air-conditioned van where there may be likelihood of exposure of excess temperatures due to mid-summer climates.

It is recommended that suppliers should look into possible changes in physical form of capsules due to environmental changes, and unforeseen factors taking into consideration of such an occurrence. The fourth incident could have been avoided if the patient had expressed about her difficulty in taking medication in capsule form.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.