Nuclear Medicine Resources Manual

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CHAPTER 5. GUIDELINES FOR GENERAL IMAGING

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(3) Hybridization and washing procedure. The membrane containing the

denatured DNAs should be prehybridized in a solution for at least two

hours. The most commonly used solution is composed of SSC, SDS and

bovine lacto transfer technique optimizer (BLOTTO). After prehybridi

zation the membrane is hybridized with radiolabelled single stranded

DNA fragments with sequences complementary to those being sought.

The probes should be boiled prior to addition to the hybridization

solution in order to be single stranded. The hybridizations are usually

carried out at 37°C for oligoprobes and at 60°C for regular cloned

molecules or PCR products. The resulting double stranded DNA bearing

the radiolabel is then, if present, detected by autoradiography.

The stringency of the assay is mediated mainly by the concentration

of the SSC in the washing procedure and also the temperature used.

(c ) In situ hybridization

The previous sections describe techniques in which DNA removed from

clinical samples is separated and placed on nylon membranes and then probed

for target sequences. In some cases, it is preferable to apply these labelled

probes directly to cells and tissues to localize the source of the signal. This

technique is known as in situ hybridization. Using this method the cells are

previously digested with proteinase K while DNA within the native tissues is

denatured by heating, followed by application of a labelled probe that binds to

the complementary sequence of interest. Following several washing steps, a

detection method is used to localize the signal indicating areas in which the

probe has bound to the tissue. When radioactive probes are used, the tissue

sections on microscope slides are dipped in a silver emulsion similar to an X ray

film. These slides are kept in the dark for a period of time (from days to weeks)

after which the emulsion is developed in a fashion similar to developing a film.

BIBLIOGRAPHY TO SECTION 5.13

AVILA, H.A., et al., Polymerase chain reaction amplification of Tryp cruzi kinetoplast

minicircle DNA isolated from whole blood lysate: Diagnosis of chronic Chagas’ disease,

Mol. Biochem. Parasitol. 48 (1991) 211–222.

AZIZ, D.C., Use and Interpretation of Laboratory Tests in Oncology, 3rd edn,

Speciality Laboratories, Valencia, CA (1998) 212.

5.13. MOLECULAR METHODS

431

BRAMWELL, N.H., BURNS, B.F., The effects of fixative type fixation time on the

quantity and quality of extractable DNA for hybridization studies on lymphoid tissue,

Exp. Hematol. 16 (1988) 730–732.

BRITTO, C., CARDOSO, A.C., WINCKER, P., MOREL, C.M., A simple protocol for

the physical cleavage of Trypanosoma cruzi kinetoplast DNA present in blood samples

and its use in polymerase chain reaction (PCR) based diagnosis of chronic Chagas’

disease, Mem. Inst. Oswaldo Cruz 88 (1993) 171–172.

DARRON, R.B., BRYAN, J.T., CRAMER, H., FIFE, K.H., Analysis of human papillo-

mavirus types in exophytic Condylomata acuminata by hybrid capture and Southern

blot techniques, J. Clin. Microbiol. 31 (1993) 2667–2673.

FERENCYZ, A., Viral testing for genital human papillomavirus infections: Recent

progress and clinical potential, Int. J. Gynecol. Cancer 5 (1995) 321–328.

FEY, M.F., PILKINGTON, S.P., SUMMERS, C., WAINSCOAT, J.S., Molecular

diagnosis of haematological disorders using DNA from stored bone marrow slides, Br. J.

Haematol. 67 (1987) 489–492.

GLOVER, D.M. (Ed.), DNA Cloning — A Practical Approach, IRL Press, Oxford and

Washington, DC (1985).

HOLLSTEIN, P., SCHAUBLE, B., Tumours associated with p53 germline mutations: A

synopsis of 91 families, Am. J. Pathol. 150 (1997) 1–13.

MULLIS, K.B., et al., Specific enzymatic amplification of DNA in vitro: The polymerase

chain reaction, Cold Spring Harbor Symp. Quant. Biol. 51 (1986) 263–273.

MULLIS, K.B., FALOONA, F.A., Specific synthesis of DNA in vitro via a polymerase-

catalyzed chain reaction, Methods Enzymol. 155 (1987) 335–350.

OOSTRA, B.A., JACKY, P.B., BROWN, W.T., ROUSSEAU, F., Guidelines for the

diagnosis of Fragile X syndrome, J. Med. Genet. 30 (1993) 410–413.

PIMENTEL, M.M.G., Fragile X syndrome: Molecular diagnosis, J. Bras. Patol. 34 (1999)

94–98.

ROUSSEAU, F., et al., Direct diagnosis by DNA analysis of the Fragile X syndrome of

mental retardation, N. Engl. J. Med. 325 (1991) 673–1681.

RUPP, G.M., LOCKER, J., Purification and analysis of RNA from paraffin-embedded

tissues, Biotechniques 6 (1988) 56–60.

SAIKI, R.K., et al., Enzymatic amplification of b-globin genomic sequences and

restriction site analysis for diagnosis of sickle cell anemia, Science 230 (1985) 1350–1354.

CHAPTER 5. GUIDELINES FOR GENERAL IMAGING

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SAIKI, R.K., GELFAND, D.H., Introducing AmpliTaq DNA polymerase, Amplifica-

tions 1 (1989) 4–6.

SAMBROOK, J., FRITSCH, E.F., MANIATIS, T., Molecular Cloning — A Laboratory

Manual, 2nd edn, Cold Spring Harbor Laboratory Press, Woodbury, NY (1989).

VERKERK, A.J.M.H., et al., Identification of a gene (FMR-1) containing a CGG

repeat coincident with a breakpoint cluster region exhibiting length variation in Fragile

X syndrome, Cell 65 (1991) 905–914.

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Chapter 6

RADIONUCLIDE THERAPY

6.1. SETTING UP A UNIT

6.1.1. Introduction

The therapeutic use of radionuclides may be a potential radiation risk for

both family members and individuals close to the patient, as well as health

workers and the environment. Radionuclides must be used in strict accordance

with safety measures and any special instructions, and all precautions must be

taken to avoid unnecessary exposure to radiation. This chapter summarizes the

steps to be taken before commencing therapy procedures.

6.1.2. Licensing

The administration of therapeutic doses of radionuclides must be under

the responsibility of a physician who is licensed under national regulations to

administer radioactive materials to humans. Radioactive material for diagnosis

or therapy should only be used and stored at medical institutions which have

purpose designed facilities. Technical staff, physicists and nurses may also be

subject to licensing.

Licensing requirements vary from country to country and may even

include minimum design and construction requirements for the facility. Local

requirements must be established at the start of a project.

6.1.3. Facility design and construction

The general principles for the design of nuclear medicine units are

discussed in Chapter 3, and further information regarding therapy units is

provided in Section 6.2.

When designing therapy units, it is important to bear in mind the

following:

(a) Patients must be housed in a separate room, with dedicated bathroom

and toilet.

(b) Access to the treatment room must be controllable.

the eventuality of pregnant patients in adjacent rooms.

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It is both easier and less costly to design a unit correctly from the start

than to modify it later. Close cooperation between the nuclear medicine staff

and architects and builders is vital. If an existing space is to be modified, it may

be necessary to determine experimentally the adequacy of walls and floors as

radiation shields.

If any building work is to be performed, a regular inspection of work in

progress is advisable to ensure adherence to agreed plans and specifications. In

particular, it should be noted that:

—Brick walls often have inadequate mortar joints, which can be a shielding

problem.

—Flooring should be free of open joints and sealed to the walls, a fact often

forgotten by builders.

6.1.4. Responsibilities

The physician administering the therapeutic radionuclide dose is

ultimately responsible for taking every precaution to avoid unnecessary

radiation to staff, other patients, visitors and the general public.

Before commencing therapy, agreement should be reached on medical

and radiation safety protocols. This chapter is intended to provide assistance in

determining these protocols.

6.1.5. Records

A record keeping system must be in place before treatment commences.

In addition to normal medical records, a logbook should be kept, listing the

patient’s name, the radiopharmaceutical and radioactive quantities adminis

tered, and the administration date.

6.1.6. Training

Radionuclide therapy may involve staff outside the nuclear medicine

department, especially nurses and medical staff. A little effort devoted to famil

iarization and training in the medical and safety aspects of radionuclide therapy

can avoid potentially serious problems later.

6.2. SAFETY PRINCIPLES

435

6.2. RADIONUCLIDE THERAPY — SAFETY PRINCIPLES

6.2.1. General principles

Radionuclide therapy presents relatively few hazards to staff and

patients, but there are a number of common principles of radiation safety that

have to be observed. This section will consider the requirements for patient

accommodation (design requirements including shielding), as well as radiation

safety procedures necessary for safe practice.

For safety purposes, each therapy can be divided into different stages,

with specific safety issues that may need to be considered (Table 6.1).

All of the above may not be necessary for every type of therapy. The

specific radiation safety issue for each of the common therapies is discussed

later in this section.

6.2.2. Discharge limits

Patients may be discharged only when the remaining activity is less than

that prescribed by the local regulatory authority. This can be estimated using a

simple ratio of dose rates at a standard distance referenced to the dose rate

immediately following dose administration, or by measurement of a dose rate

alone. In the absence of local regulations, the limits in Table 6.2 (NRC Guide

8.39, see Bibliography to Section 6.2) can be used.

TABLE 6.1. SAFETY ISSUES

Stage Typical issues

Pre-therapy Possible pregnancy, including advice to patient by physician, and

pregnancy testing

Day of therapy Physician’s guidelines, administration protocol, advice to nursing

staff and preparation of patient room (if an inpatient)

During therapy Nursing care, control of radioactive waste including urine, faeces,

syringes, swabs and other items that may be contaminated, control

of visitors, and monitoring of both patient and the local

environment

Discharge Discharge limits and information given to the patient

Post-discharge Advice on future pregnancies

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On discharge, patients must be given information regarding contact with

children and adults, toilet use, etc., for the period following discharge. This

information is often modified to take into account the specific circumstances of

each patient.

6.2.3. Design of therapy areas

There are two types of therapy areas – inpatient areas and areas where

outpatient therapies are administered. The factors to be considered are:

—Types of radiation emitted (photon or particle, or mixed);

—The potential for contamination and the degree of the hazard;

—The type of waste products generated – human excreta, biological waste

and general waste – and the way they should be handled;

—The role of nursing and medical staff in the care of the patient (high or

low level of care).

General building requirements have been discussed in Section 6.1.

Normally, the only difference between therapy areas is in the degree of any

shielding required and the issues involved in integrating inpatient areas into a

ward, such as access control and toilet facilities.

(a) Inpatient therapy areas

It is necessary to designate a single bedroom in the ward that meets the

general radiation protection requirements. These include:

TABLE 6.2. RADIOACTIVE PATIENT DISCHARGE LIMITS

Radionuclide

Activity remaining

(GBq (mCi))

Dose rate at 1 m

(mGy/hour) (mrad/hour)

I-131 1.2 (33) 0.07 (7)

P-32 No practical limit Not applicable

Re-186 28 (770) 0.15 (15)

Re-188 29 (790) 0.2 (20)

Sm-153 26 (700) 0.3 (30)

Sr-89 No practical limit Not applicable

Y- 90 No practical limit Not applicable

6.2. SAFETY PRINCIPLES

437

—A non-porous, easily decontaminated floor and wall surfaces with coved

junctions to make cleaning easier;

—A minimum of projections, to prevent dust collection;

—A dedicated shower and toilet, the toilet draining directly to the main

sewer or to a system of radiation waste disposal, depending on local

regulatory requirements;

—A physical barrier to entry: a simple door may be sufficient;

—Moveable lead shields to minimize nursing exposure;

—The possible installation of a remote patient monitoring system (video);

—Door signs prohibiting entry by pregnant women, children and other

persons without permission, giving a time limit for approved visitors,

prohibiting removal of anything from the room without clearance, and

requiring use of protective clothing in the room;

—A place to keep supplies of disposable gloves and gowns, and possibly

overshoes, outside the room;

—Storage within the room for collection and temporary storage of waste.

Patient comfort should be catered for by radio, music, television and/or

videotape facilities as well as a comfortable (but easily decontaminated) chair.

Disposable sheets, blankets and eating utensils should be provided.

(b) Outpatient therapy areas

Outpatient areas are usually part of the nuclear medicine department,

located at some distance from imaging equipment and public areas; the

construction requirements for these are the same as for imaging rooms and the

radiopharmacy. A floor drain is advisable in case of spillage of the therapy

radiopharmaceutical. A trolley or folding steel bench is useful to hold the items

used in the therapy.

6.2.4. General inpatient therapy guidelines

Most inpatient therapies involve

131

I, as reflected in the guidelines given

below. If radiopharmaceuticals with a low risk of contamination are involved,

the guidelines may be suitably modified.

6.2.5. Guidelines for ward staff

The entrance to the radionuclide therapy room must be clearly labelled

with:

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—A radiation warning sign;

—A sign prohibiting entry by pregnant women and children;

—A notice giving the visiting time limit;

—A notice, if necessary, to require use of protective clothing;

—A notice to the effect that nothing should be removed from the room

until it has been declared free of radioactive contamination.

No member of staff should enter the therapy room without wearing a

radiation monitor. Where digital dosimeters are in use, a record of the dose and

the name of the staff member should be kept with the monitors outside the

treatment suites. A record of all doses should be maintained.

Only essential nursing procedures may be performed during the

treatment period. No blood samples, urine or faecal samples should be

collected without nuclear medicine approval.

There must be no rubbish disposal from the room during the course of

treatment.

Persons entering the room should put on plastic aprons, gloves and shoes.

As the barrier is crossed on leaving the room, this protective clothing must be

removed and placed in the disposal bag provided. (Note: This protective

clothing only protects against radioactive contamination but NOT against a

radiation hazard within the room.)

6.2.6. Guidelines relating to the patient

The following guidelines apply:

(a) The patient must be aware of the basic regulations listed below before the

administration of a radionuclide. Before therapy, the patient should be

given a booklet of common questions and answers.

(b) Any patient who is very ill and is considered incapable of a reasonable

level of self-caring should NOT be given a therapy dose.

tration of therapy.

(d) Patients should be offered disposable hospital nightwear and towels to

prevent their own becoming contaminated. If they wish to wear their own

clothes, they must be advised on what should be done with garments on

discharge.

(e) Patients may only use dedicated toilets, showers and washing facilities.

(f) Meals must be supplied on disposable plates, and eaten with disposable

cutlery.

6.2. SAFETY PRINCIPLES

439

(g) Adult patients should normally be supplied with an electric kettle, plus

coffee powder, tea bags, sugar and milk. Ideally, there should be a refrig

erator to keep milk fresh, and to store cold drinks if required. This

encourages the patient to drink freely and reduces the radiation exposure

to nursing staff.

(h) Patients should use disposable tissues rather than handkerchiefs, since

nasal mucosa tends to have a high radioactive content.

(i) Should sheets and/or pillow covers require changing, used linen should be

placed in a bag and left within the suite. Under no condition should it be

sent to the laundry until checked for contamination. Disposable linen

may be preferred.

(j) Rubbish must be kept within the suite until dealt with by a physicist. This

may involve storage prior to incineration in a licensed incinerator or

storage until complete decay of the contamination.

Patients should only leave the therapy room for the purpose of a scan or

in an emergency, in which case protective clothing (i.e. plastic aprons, shoes and

gloves) must be worn. Unless an emergency precludes this, protective clothing

should be put on upon leaving the room and removed on re-entry to the suite.

When the patient is ready for discharge, all the patient’s belongings must be

checked for radioactive contamination and stored or washed separately as

necessary. Any other belongings that may have become contaminated must be

stored for a suitable length of time to allow the radioactivity to decay. The

patient should be given a discharge card listing the radionuclide and activity

administered, the activity on discharge and any necessary precautions.

6.2.7. Contamination

With any radionuclide therapy, there is a high potential for contami-

nation. Decontamination procedures are covered in Chapter 8. It is, however,

strongly advisable to keep a small decontamination kit in or near the therapy

area (inpatient or outpatient) for immediate access if required.

6.2.8. Radioiodine therapy

(a) Pre-therapy

It is imperative that a doctor explain to female patients that therapy

cannot be given to pregnant patients. If there is any chance that a patient may

have become pregnant by the time the therapy administration is to commence,

she must report this to a nuclear medicine doctor or technologist.