Procedures in radiography

Published on 01/04/2015 by admin

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Chapter 6 Procedures in radiography

Karen Dunmall

KEY POINTS

All patients follow a standardised pathway through the imaging department, coming in to contact with the same key areas regardless of their examination.

Patient privacy and comfort should be ensured at all times.

Mobile radiography provides a diagnostic service for patients who are unable to attend the X-ray department.

Mobile radiography introduces radiation safety issues which should be addressed during all examinations.

The use of contrast media enhances areas that may not be visualised during conventional examinations.

Contrast media are either barium or iodine based.

Some contrast media can cause undesirable side- effects in patients and all patients should be observed after the introduction of the contrast medium to ensure swift action in the event of a reaction.

INTRODUCTION

Radiology is an integral department within the hospital in that many inpatients are required to have at least one radiological examination in some form or another during their hospital stay. There are many other sources of referral for imaging examinations, ranging from outpatient clinics to accident and emergency departments (Table 6.1).

Table 6.1 Referral sources and input in a diagnostic imaging department

Referring source	Diagnostic imaging input
Medical/surgical	Departmental appendicular and axial skeletal radiography
	Departmental chest and abdominal radiography
	Mammography
	Dental
	Mobile ward radiography
	Departmental and theatre based fluoroscopic examinations
	Non ionic iodinated contrast studies
	Theatre based appendicular and axial skeletal radiography
	CT, MRI, US, RNI
Outpatients/GPs	Departmental appendicular and axial skeletal radiography
• Orthopaedic	Departmental chest and abdominal radiography
• ENT	Mammography
• Gynaecology	Dental
• Obstetrics	Departmental fluoroscopic examinations
• Oncology	Non ionic iodinated contrast studies
• Paediatric	CT, MRI, US, RNI
• Care of the elderly
Accident and emergency	Departmental appendicular and axial skeletal radiography
	Departmental chest and abdominal radiography
	Mobile resuscitation unit radiography
	CT, MRI, US

CT, computed tomography; MRI, magnetic resonance imaging; RNI, radionuclide imaging; US, ultrasound

PATIENT PATHWAYS THROUGH THE IMAGING DEPARTMENT

(Figs 6.1 and 6.2)

Figure 6.1 A patient’s pathway through a diagnostic imaging department for routine appendicular, axial, chest and abdominal radiography.

Figure 6.2 Pathway for appointed special examinations; for example barium enema.

RECEPTION DESK

This is most likely to be the first contact point that a patient or carer has with a diagnostic imaging department. It has been documented that patients should be given good quality information with regards to their care and be sufficiently informed before any medical examination takes place. It is therefore essential that the information process begins well. The reception team must be able to converse with the patients to ascertain their personal details; however, they must also be aware that there is the potential to be overheard by others. In some departments there is a line indicated by a stripe on the floor, indicating that only one patient should be at the desk at one time, whereas in other departments there may be a separate cubicle in which to ask personal details (Fig. 6.3). There are various notices informing patients of the no-smoking policy and zero tolerance of aggressive behaviour.

Figure 6.3 Reception desk with separate cubicle.

The patient will usually be directed to a sub-waiting area close to the X-ray room where their examination is to be carried out. In Figure 6.4 it can be seen that chairs have wipeable upholstery to reduce the risk of cross-infection. The chairs are also ranging in height and style to suit patients with mobility problems. A waiting area should be light and airy and have a selection of reading materials. The inclusion of wipeable toys may also be preferable in areas dealing with small children. It is important that if there is a delay due to unforeseen circumstances, the patients are aware of the time delay; this can often defuse difficult situations.

Figure 6.4 Waiting area.

CHANGING CUBICLE

A changing cubicle should contain a bench or chair to sit on. There should be a supply of gowns to accommodate both male and female statures. The door should be lockable but with safety locks in case of emergencies and patients should not be placed in a cubicle for long periods of time.Some hospitals provide baskets/lockers for the patient’s clothes in order to reduce the risk of theft and also free up cubicles for a more rapid throughput of patients.

For certain examinations (e.g. barium enemas) where patients may need to access a toilet promptly after the examination, a cubicle with toilet and shower facilities should be used. An emergency cord is also essential in case a patient feels unwell (Fig. 6.5).

Figure 6.5 Changing facilities with emergency cords highlighted.

GENERAL X-RAY ROOM

In the X-ray room it is important to remember that to a member of the public, old or young, this room containing lots of big pieces of machinery may look rather frightening. Therefore, it is important to make the patient comfortable and at ease by giving instructions in simple non-jargon terms. For example, to most people a bed or couch is what you lie on, not a table, so be aware of potential confusion. Following the examination the patient should be asked to wait until the image is checked and then given information on when and how to get the results. Table 6.2 shows patient preparation and aftercare for some typical departmental examinations.

Table 6.2 Patient preparation and aftercare for some typical departmental examinations

FLUOROSCOPY ROOM

The impression of this type of room is very similar to that of a general radiography room, but more high-tech. It is essential that the patient receives succinct instruction of what to do and is told in advance of any table or X-ray tube movements.

The patient is likely to spend more time in this room than in a general room. It will also be necessary for the patient to wait for any effects that the drugs or the examination may have had to wear off; for example the administration of a muscle relaxant (e.g. Buscopan or glucagon) may give blurred vision and therefore driving is not recommended until adequate vision has returned.

PATIENT SHOWER CUBICLE

In some examinations the end product of the examination might involve emptying the bladder whilst on the X-ray table or the leaking of contrast during the procedure. In either case patients usually feel as though they require a shower before getting dressed to remove traces of contrast medium. For this reason a shower cubicle may be provided in close proximity to the toilets and cubicles.

MOBILE RADIOGRAPHY

The imaging of a patient using equipment other than the static department-based equipment is commonly known as mobile or portable radiography. However, the term portable only relates to equipment that can be carried. Mobile radiography can be divided into two distinct types:

1) Mobile plain-film radiography using mobile X-ray equipment (Fig. 6.6).

2) Mobile fluoroscopy using a mobile image intensifier (Fig. 6.7).

Figure 6.6 A mobile X-ray machine.

Figure 6.7 A mobile image intensifier.

PATIENT TYPES AND LOCATIONS FOR MOBILE RADIOGRAPHY

The patients who require mobile radiography are usually unable to come to the diagnostic imaging department due either to their condition or to the operating theatre environment required for the surgical procedure they are undergoing. The following areas within a hospital are likely to contain patients requiring mobile radiography:

1 Intensive therapy unit (ITU)

2 Coronary care unit (CCU)

3 High dependency unit (HDU)

4 Special care baby units (SCBU)

5 Neonatal intensive care units (NICU)

6 Isolation wards

7 Recovery wards

8 Resuscitation/major trauma units

9 Minor operating departments

10 Operating theatres (orthopaedic/general surgical)

The most common mobile procedures are:

• plain film imaging of the chest (in areas 1–8, above)

• a plain film trauma series (cervical spine, chest, pelvis) and other appendicular/axial skeleton plain film imaging (resuscitation/major trauma units)

CONSIDERATIONS SPECIFIC TO MOBILE RADIOGRAPHY

There are four issues which must be considered when undertaking imaging outside the static department and which involve patients who may be unconscious or unable to cooperate:

1 Patient identification.

2 Radiation protection.

3 Health and safety.

4 Infection control.

PATIENT IDENTIFICATION

The request form for mobile plain film and fluoroscopy must be completed to the same standard as required for a department-based study. If the patient is to be anaesthetised then the identification and pregnancy status should ideally be determined before anaesthetic is administered; however, in the case of patients who are anaesthetised, the anaesthetist should check and confirm the information required. In cases of patients who are unconscious or unable to confirm their ID, the following should be used:

1 A wrist band.

2 Nurse/carer verification.

When needing to establish pregnancy status for the above types of patient, the referrer must complete the last menstrual period (LMP) details on the request card.

The identification of the image requires the patient’s name, date of birth, sex and hospital number (according to the departmental protocol). Images acquired from mobile procedures should also include:

a) Time of examination (if not automatically recorded on image).

b) Source–object distance (SID, see p. 109).

c) Exposure values.

d) Patient position, e.g. erect/supine, anteroposterior.

e) Anatomical marker.

The adaptation of the technique, especially SID and exposure factors, can mask changes in patient condition varying with time or operator.

RADIATION PROTECTION [IR(ME)R]

When carrying out mobile imaging procedures using ionising radiation it is essential to establish a temporary controlled area and to ensure that there are sufficient numbers of lead equivalent aprons for all individuals who require one.

Wards and units

Radiation protection and safety can be achieved by using warning cones and placards in the vicinity of the mobile examination and also by using a verbal warning when imaging is occurring. It is difficult to restrict access to a whole ward which contains patients other than the one undergoing the examination. In this instance, the inverse square law is utilised to reduce the dose to individuals who cannot leave the area. All staff, patients and visitors should be asked to move as far away as possible from the patient under examination, but if this is not possible then lead-equivalent shielding should be used to afford protection. If a staff member or carer is required to give physical support to the patient they must wear a lead-equivalent apron and the details of exposure must be recorded in conjunction with the name of the ‘holder’. The issue of immobilising patients is most pertinent in SCBU/NICU where the named nurse of several babies may be called upon to hold them in the case of serial imaging over the course of ventilation.

Theatre environment

Within an operating theatre it is possible to contain the area within the walls of a room. Only persons whose presence is absolutely essential remain in the theatre and there should be local rules to cover this. All essential people must wear lead-equivalent aprons during the time when radiation is being produced. The image intensifier should be operated using the pulsing mode whenever possible and stringent collimation should be applied. Lastly, the image intensifier should be positioned correctly before ‘screening’ begins, fluoroscopy should not be used to locate the area under examination. Monitoring of the theatre environment should be carried out on a routine basis using personal and area dose recorders. The image intensifier must be key operated to maintain the security of the unit.

HEALTH AND SAFETY

The health and safety issues of mobile radiography relate to:

• manual handling

• electrical safety

• trip hazards.

INFECTION CONTROL AND OPERATING THEATRE DRESS CODE

The mobile machines should be regularly cleaned to prevent cross-infection between wards, in the same way as equipment is cleaned following an infectious patient in the department.

In operating theatres and sterile environments there should be disposable sterile covers available for the X-ray tube head and intensifier sections of the mobile intensifier. The dress code in operating theatres serves two purposes:

1 Maintenance of hygiene and infection control.

2 Identification of staff.

Maintenance of hygiene and infection control

Microorganisms can be found on the skin, hair and clothing of everyone, without causing obvious infections to that individual. For the purpose of prevention of cross-infection, anyone entering an operating theatre is required to wear special clothing and head covering (Fig. 6.8).

• Mask – this is optional for staff members not directly involved in the surgical procedure.

• Footwear – outdoor shoes must be exchanged for theatre footwear and stored separately. There is a need to be aware of hand hygiene when changing shoes.

• Headwear – disposable theatre caps are designed to cover hair and facial hair to reduce skin/hair particles being shed.

• Clothing – theatre clothing must only be worn whilst in the theatre environment and not during visits to other departments.

• Green drapes are also placed over the patient. Care must be taken not to de-sterilise the area by touching the sterile drapes.

Figure 6.8 Professional dressed for theatre.

USE OF CONTRAST MEDIUM

The contrast of an image is the difference in optical density between different tissues of the body. Body tissues attenuate the beam to different degrees dependent on many variables related to the number of electrons in the path of the incident X-ray photons. The number of electrons in the object is dependent on:

• the proton number of the tissue

• the thickness of the object being studied

• the density of the object being studied.

There is a naturally occurring contrast between bone and soft tissue due to the difference in proton numbers (bone Z = 13.8, soft tissue Z = 7.4); hence the outlines of the structures can be visualised. However, if the two organs have similar densities and proton numbers then it is not possible to distinguish them on a plain image; for example blood vessels within soft tissue organs.

The contrast of the blood vessel or the lumen of hollow structures can be increased by the introduction of a liquid with a higher average proton number, e.g. iodine or barium.

CONTRAST MEDIA TYPES

There are two main types of positive contrast agent:

1 Barium based.

2 Iodine based.

BARIUM SULPHATE SOLUTION

A suspension of large insoluble particles, which have good coating properties, is utilised in the visualisation of the lining of the gastrointestinal (GI) tract. Barium is used because it has a high proton number (Z = 56), is relatively cheap and inert. However, if barium sulphate permeates outside the GI tract it can be irritating to peritoneal membranes or cause pulmonary oedema in the lungs. Therefore, in cases of suspicion of perforation or aspiration, a water-soluble iodinated contrast is recommended.

Examples of barium sulphate used in diagnostic examinations

• Barium swallow: Baritop G 150% w/v 100 ml

• Barium meal: E-Z HD 250% w/v 135 ml + CO₂

• Barium follow-through: Baritop G 100% w/v 300 ml

• Small bowel enema: E-Z Paque 150 ml (+ gastrografin)

• Barium enema: Polibar 125% w/v 500 ml (+air)

IODINE BASED CONTRAST MEDIA

These are differentiated into ionic and non-ionic media containing iodine in solution.

Ionic contrast media

Ionic compounds dissociate into charged particles when the contrast enters into a solution (e.g. blood). An ionic contrast agent has an osmolarity approximately five times that of human plasma. The high osmolarity is associated with unwanted side-effects.

Examples of ionic contrast media

• Conray 280

• Conray 325

• Conray 420

The number refers to the iodine concentration in mg ml⁻¹

Non-ionic contrast media

Non-ionic contrast media do not dissociate into discharged particles when introduced into a solution. These media have low osmolarity and are more expensive than ionic contrast media. Non-ionic dimer contrast media tend to be reserved for patients undergoing vascular investigations and those at risk of reactions.

Examples of non-ionic contrast media

• Niopam 150, 200, 300, 340, 370 monomer

• Omnipaque 140, 180, 240, 300, 350 monomer

• Isovist 240, 300 dimer

Iodised oils

These are used infrequently in radiography, where water-soluble agents are contraindicated or when viscosity is required. Examinations include lymphoscintigraphy and sialography. This agent is not easily absorbed and in some circumstances it carries a risk of oil emboli. It is made of poppy seed oil.

Examples of iodised oils

• Lipiodol

• Myodil

Water-soluble iodine based contrast agents

These are used for imaging the GI tract and are characterised by an aniseed taste. They are recommended for use where there is a suspected leakage into pleural or peritoneal cavities.

Examples or water-soluble iodine based contrast media

• Gastrografin 370 mg ml⁻¹

• Gastromiro 300 mg ml⁻¹

CONTRAST MEDIA USAGE

ANGIOGRAPHY

This is defined as the investigation of blood vessels and can be divided into arteriography, venography and digital subtraction angiography.

• Arteriography: Contrast medium is introduced via a catheter into an artery, which then follows the natural flow of blood into the periphery of the body or organ.

• Venography: Conversely, contrast medium is introduced intravenously (IV) and follows the normal flow of blood returning to the heart.

• Digital subtraction angiography: A specialised type of angiography which utilises the computer hardware to subtract a precontrast image from a postcontrast image to leave the contrast filled vessels free from overlying structures.

INTRAVENOUS UROGRAPHY (IVU)

The rapid elimination properties of contrast media mean that the kidneys excrete it. Following an intravenous injection of contrast media into the median cubital vein a series of images of the urinary tract can be obtained.

BILIARY TRACT

The gall bladder can be visualised by the ingestion of contrast medium, which concentrates in the liver and collects in the gall bladder.

In percutaneous transhepatic cholangiography (PTC) the ducts are cannulated via a needle which passes through the skin and liver. In ERCP, the ducts are cannulated via the ampulla of Vater in the duodenum.

GASTROINTESTINAL TRACT

The upper GI tract is visualised by the ingestion of contrast media. The large colon is visualised by contrast medium introduced via the rectum.

OTHER EXAMINATIONS

There are a wide variety of examinations where contrast media can be used, e.g. in joint visualisation, salivary glands.

CONTRAST MEDIA SAFETY

There are many characteristics of contrast media that are responsible for causing reactions:

• Dose dependent adverse reactions due to the physiochemical effects of the contrast medium, e.g. osmolarity or electrical charge. Reaction is seen as heat, pain, vasodilation, cardiac depression or hypotension.

• Some reactions are almost independent of dose and concentration. These present as nausea and vomiting or allergy-like hypersensitivity reactions such as urticaria, bronchospasm or laryngospasm.

• Viscosity may cause pain due to the force needed to inject the contrast medium through a needle or catheter.

• The higher the osmolarity the more water is drawn into the solution from the tissues. The higher the osmotic pressure the poorer the tolerance, which is directly linked to heat and discomfort.

• Chemotoxicity. This refers to the mechanism responsible for causing toxic effects, such as histamine release. It is thought that some contrast media can cause histamine release from mast cells causing allergy-like reactions.

For clinical purposes reactions are divided into three categories:

1 Minor – flushing, nausea, vomiting, pruritus, mild rash, arm pain.

2 Moderate – more severe urticaria, facial oedema, hypotension, bronchospasm.

3 Severe – hyposensitive shock, laryngeal oedema, convulsions, respiratory and cardiac arrest.

EXAMINATION PREPARATION

For all examinations carried out in the diagnostic imaging department, preparation before the patient enters the room is essential. In the general X-ray room this may involve getting a cassette ready, selection of exposure factors and ensuring any positioning aids required are ready for use. In the fluoroscopy room preparation will be as for a general room but, in addition to this, the contrast medium will need preparation, as will the patient. A trolley may need to be set up for the examination and this should be sterile with all equipment laid out ready for use.

PREGNANCY CHECKS

For all radiographic examinations it is essential that a pregnancy check be carried out for all patients of reproductive age undergoing examinations of the abdominal area. These checks are divided into high dose and low dose examination checks, depending on the region and examination.

LOW DOSE EXAMINATIONS

Plain film abdomen, pelvis, lumbar/sacral spine may be undertaken within 28 days of the patient’s LMP if the patient verifies that there is no possibility of pregnancy, also known as the ‘28-day rule’.

HIGH DOSE EXAMINATIONS

These examinations are defined as procedures that carry a potential fetal dose greater than 10 mGy (e.g. abdominal/pelvic CT, barium enema; see p. 84 for SI units commonly used in radiography). For these examinations patients should be booked an appointment within the first 10 days of the menstrual cycle, known as the ‘10-day rule’. However, the average length of the patient’s menstrual cycle should be ascertained, as 10 days is an arbitrary figure for a 28-day cycle; 7 days is more applicable for a 21 day cycle (Fig. 6.9).

Figure 6.9 Flow diagram to demonstrate the process involved in the 28-day and 10-day rules.

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