Nuclear Medicine Resources Manual

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CHAPTER 5. GUIDELINES FOR GENERAL IMAGING

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5.6.4.8. Reporting

In addition to patient demographics, the report should include the

following information:

(a) The indication for the study.

(b) Procedure:

(1) Radiopharmaceutical:

—Dose;

—Method of administration (intravenous).

(2) Acquisition:

—Duration of acquisition (e.g. 1 hour);

—Frame rate (e.g. 60 s/frame);

—Projections acquired (e.g. anterior or lateral projections).

(3) Display (e.g. static or cine).

(4) Findings:

—Onset (e.g. early or late, correspondence including gastric

activity);

—Location;

—Characteristics;

—Size and shape (e.g. focal or diffuse);

—Movement (if any).

(5) Study limitations and confounding factors.

(6) Interpretation (e.g. positive, negative or indeterminate).

5.6.4.9. Sources of errors

The sources of error that arise in Meckel’s diverticulum scintigraphy are

as follows:

(a) Procedures that may cause interference:

(1) False negative results can be due to:

—Barium enema (attenuation);

—Upper gastrointestinal contrast studies;

—Perchlorate (uptake blockage);

—Recent in vivo RBC labelling (stannous effect).

(2) False positive results can be due to:

—Laxatives or endoscopy causing bowel irritation (non-specific

uptake).

(b) Anatomical/physiological causes of errors:

(1) False negative results:

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—Too small amount of gastric mucosa in a Meckel diverticulum;

—Ischaemia or necrosis of diverticulum;

—Obscured by urinary tract activity, e.g. in the bladder.

(2) False positive results:

—Urinary tract activity;

—Gastric secretion into the small bowel;

—Lesions with increased blood pool;

—Ulceration;

—Inflammation;

—Irritation;

—Tumour;

—Intussusception;

—Gastric activity secreted into small bowel.

BIBLIOGRAPHY TO SECTION 5.6.4

FORD, P.V., et al., Procedure guideline for gastrointestinal bleeding and Meckel’s diver-

ticulum scintigraphy, J. Nucl. Med. 40 (1999) 1226–1232.

SFAKIANAKIS, G.N., CONWAY, J.J., Detection of ectopic gastric mucosa in Meckel’s

diverticulum and other aberrations by scintigraphy: Indications and methods – A 10-

year experience, J. Nucl. Med. 22 (1981) 732–738.

5.6.5. Gastric emptying and motility

5.6.5.1. Principle

Radionuclide studies of gastric emptying and motility are the most physi-

ological procedures available for evaluating gastric motor function. These

studies are non-invasive, use a labelled physiological meal (solid or liquid) and

are quantitative. Serial testing can determine the effectiveness of therapy.

5.6.5.2. Clinical indications

Clinical indications relating to gastric emptying and motility are:

(a) Post-prandial:

—Nausea and vomiting;

—Upper abdominal discomfort and bloating;

—Chronic aspiration.

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(b) Suspected gastroparesis.

(d) Gastroesophageal reflux.

(e) Following response to therapy for previously documented motility distur-

bances.

5.6.5.3. Radiopharmaceuticals

The composition of radiolabelled meals varies widely. An important

consideration is that normal emptying rates must be established for any specific

meal, patient position, imaging protocol and environment. The radiolabel

stability in gastric fluids for any solid meal should be established.

Meals are most often labelled with

99m

Tc-SC and may include:

(a) Solids. Prior to cooking the meal, the radiotracer is added to:

—Eggs (scrambled, whole, egg whites or hard boiled);

— Beef stew;

—Liver paté.

(b) Liquids. Almost any liquid can be used, but liquid emptying alone is not

as sensitive as solids or semi-solids for the detection of delayed gastric

emptying:

—Orange juice;

—Water;

—Milk.

Non-absorbable liquids or solids can be labelled with either

99m

Tc (7.4–

14.8 MBq (0.2–0.4 mCi)) or

111

In (3.7–7.4 MBq (0.1–0.2 mCi)).

5.6.5.4. Patient preparation

Patient preparation for radionuclide studies of gastric emptying and

motility require that:

(a) No food or drink should be taken for a minimum of 8 hours prior to

imaging. It is preferable that the patient has been fasting since midnight;

then administer the radiolabelled meal in the morning.

(b) The patient should be advised of the logistical demands of the procedure

(e.g. the meal to be used, the time required for imaging and the position

that he/she will be required to maintain throughout the study). Diabetics

need to be instructed to bring insulin with them. The dose of insulin is to

be adjusted at the time of the meal. If the patient cannot tolerate the

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293

standard solid or liquid meal protocols, the procedure should not be

carried out.

their menstrual cycle to avoid the effects of hormonal variation on

gastrointestinal motility.

5.6.5.5. Information pertinent to performing the procedure

The following information is relevant to this procedure:

(a) Related diseases and conditions:

—Hiatal hernia;

—Gastroesophageal reflux.

(b) Previous interventions:

—Indications (e.g. cisapride, metoclopramide, domperidone or erythro-

mycin usage);

—Surgery.

5.6.5.6. Clinical contraindications

The following are clinical contraindications to this procedure:

(a) Allergy to the meal;

(b) Fasting in diabetic patients resulting in hypoglycaemia.

5.6.5.7. Procedure

Ingestion of the radiolabelled test meal should be completed as quickly as

possible, optimally within 10 min. The technologist should record how long it

took to ingest the meal, and if any portion of it was not eaten. The method

should be standardized as to patient positioning and environmental conditions

such as ambient noise and lighting or other factors affecting patient comfort.

The normal values should be based on this standard methodology.

Images are obtained in a format of at least 64 ¥ 64 pixels using a general

purpose collimator. Recommended photopeak settings are 20% at 140 keV for

99m

Tc. For

111

In, 20% energy windows should be established around both the

172 and 246 keV photopeaks. If

111

In is used, a medium energy collimator must

be employed for image acquisition. Dual isotope imaging can be performed,

which allows for simultaneous evaluation of solid and liquid gastric emptying

phases, provided both type of meals are labelled with different radionuclides.

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Planar images with the distal oesophagus, stomach and proximal small

bowel included in the FOV should be obtained immediately following

ingestion of the meal.

Images are optimally obtained for at least 90 min, although a longer

period (2–3 hours) is suggested for meals with larger volume or higher caloric

content. Anterior and posterior views allow calculation of a geometric mean/

square root of the product of the counts in the ROI and more consistently

represent the amount of tracer in the stomach, independent of the effect of

fundus and antrum motility. This can be performed sequentially with the

patient on a rotatable stool using a single head camera or, preferably, simulta

neously with a double head camera. Alternatively, the study can be acquired in

the LAO view with a single head camera, in which case no mathematical

compensation for attenuation is required.

Continuous data collection with a framing rate of 30–60 s is recom-

mended. If data acquisition is interrupted at intervals, the emptying half-time is

not as accurately determined and phase lag information may be unavailable.

Intermittent data acquisition may be more suitable than continuous data for

imaging patients in the upright position.

Images may be obtained standing, sitting or in the supine position, but the

position should not change during the study. Normal values must be established

for the position used (i.e. there should be separate normal values for upright or

supine).

(a) Interventions

Metoclopramide or other prokinetic drugs can be used diagnostically in

conjunction with gastric emptying studies to evaluate the effectiveness of a

particular therapy.

(b) Processing

The steps involved in processing data are:

(1) An ROI is drawn around the area of tracer activity in the stomach in the

anterior and posterior views (or in the LAO view). A cine-display may be

helpful to confirm the stomach outline and to determine the extent of

patient motion so that the ROI may be appropriately adjusted. Alterna

tively, if continuous imaging is used, the stomach contour may be

identified with initial images combined with later images in the study,

after the radiolabelled meal has distributed within the stomach. Using

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295

initial or late images exclusively may under-represent the extent of the

fundus and antrum.

(2) Data points must be corrected for radioactive decay.

(3) A time–activity curve obtained from the geometric mean or attenuation

corrected counts of ROI activity should then be displayed.

(4) Measurements of gastric emptying may be derived and reported in

several ways. Normal values should be available for the specific protocol

being used. The half-emptying time reported should be accompanied by a

brief description of what the value represents or how it was obtained.

Values may be obtained by:

—Direct determination of the time taken to evacuate half the peak

counts;

—A least squares fit of the emptying data to derive a half-emptying time

at 50% of the peak counts;

— Comparison with a graphic display of normal values plotted as a

percentage against time.

(5) In addition, rate of emptying and per cent emptying at the end of the

study may be reported together with other information that can be

obtained from gastric motility studies, including:

—Regional motility (e.g. antral contraction frequency and amplitude);

—Response to medical interventions;

—Effect of varying meal composition on emptying.

Normal values for the specific meal and environment used should be

established before results can be reported. The shape of the curve varies

according to the labelled meal: solids exhibit an initial ‘lag phase’ with further

almost lineal downslope, while liquids present an exponential downslope with

no ‘lag phase’.

Display of images in a cine-format demonstrate better gastric anatomy

and findings such as oesophageal reflux, overlap of small bowel with gastric

ROI, and possible movement of gastric contents outside the ROI.

Previous surgical procedures and current medications should be

considered during the interpretation of findings.

(d) Reporting

The report should include details about the following:

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—The type of meal, imaging protocol and techniques for data analysis

should be outlined.

—The gastric emptying data reported should be compared with normal

values.

—The study should be compared with previous studies, if available. If the

previous study protocol differed from the current procedure (e.g. type of

meal and patient position), the differences should be reported.

—Any medications being taken that may alter gastric emptying should be

documented.

(e) Quality control

The ingested meal must be controlled for caloric content (amount of

carbohydrates, fat and protein), volume and temperature.

(f) Sources of error

Errors can arise for the following reasons:

—Food in the airways or the small bowel. (Before a liquid meal is adminis-

tered to an infant or to a patient with severe neurological impairment

through a feeding tube, an abdominal radiograph should be obtained to

ensure that the meal is placed in the stomach and not in the airways or the

small bowel.)

—Poor labelling of the food.

—Non-standard meal.

—Marked variations in the environment such as noise, lighting or

temperature during imaging.

—Emotional fluctuations such as fear of the procedure, anxiety about

results or anger after a long waiting time.

—Nausea caused by a meal that may be unfamiliar to the patient.

—Food eaten by the patient immediately prior to the study.

—Slow transit of the ingested meal from the mouth or oesophagus into the

stomach.

—Gastroesophageal reflux.

—Overlap of small bowel activity with the stomach ROI.

—Excessive time for patient to ingest the meal.

—Lack of attenuation correction particularly in obese patients.

—Failure to recognize that patient has not eaten the entire meal.

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297

BIBLIOGRAPHY TO SECTION 5.6.5

DONOHOE, K.J., et al., Procedure guideline for gastric emptying and motility, J. Nucl.

Med. 40 (1999) 1236–1239.

5.6.6. Oesophageal studies

5.6.6.1. Principle

By using radionuclide techniques, the function of the oesophagus and the

gastro-oesophageal junction, and the presence and severity of gastro-

oesophageal reflux, can be studied. The main advantages of the procedure are

that it is non-invasive, is physiological and can be modified to reproduce the

circumstances in which the patient’s symptoms occur.

5.6.6.2. Clinical indications

(a) Adults

Oesophageal motility disorders usually present with dysphagia or chest

pain (often mimicking ischaemic cardiac disease). The following symptoms and

conditions often occur in combination:

—Reflux oesophagitis;

—Hiatus hernia;

—Oropharyngeal dysfunction;

—Primary and secondary achalasia;

—Diffuse oesophageal spasm;

—Oesophageal atresia and stricture;

—Connective tissue disorders;

—Other systemic, neurological and myopathic disorders.

(b) Children

Gastro-oesophageal reflux (GOR), especially in infants, is one of the

commonest problems studied in the child presenting with recurrent pneumonia

or lower respiratory tract symptoms. GOR can also present in more subtle ways

such as:

—Abnormal vomiting;

—Failure to thrive;

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—Episodes of apnoea;

—Haematemesis.

5.6.6.3. Radiopharmaceuticals

Many different radiolabelled compounds, foods and liquids have been

used, but the most commonly employed is

99m

Tc-SC or DTPA mixed with water

or milk. Krypton-81m (half-life of 13.3 s) in an aqueous solution allows for

repeated studies to be done in a short period.

The volume of tracer swallowed ranges between 5 and 20 mL, and the

administered activity of

99m

Tc ranges between 37 and 74 MBq (1–2 mCi).

For infants, 8–12 MBq (0.2–0.3 mCi) of

99m

Tc colloid are diluted to 2 mL

in saline and 3 mL of milk, following which the preparation is added to an

empty bottle for the next feed.

5.6.6.4. Equipment

A low energy medium resolution collimator and a standard FOV camera

are adequate. In order to evaluate the dynamics of oesophageal transit,

dynamic studies using an image matrix of 64

¥ 64 pixels are required.

5.6.6.5. Patient preparation

No special preparation is required. Patients are usually studied in a

fasting state:

—Infants under 6 months are kept fasting for 3 hours.

—Infants between 6 and 12 months are kept fasting for 4–6 hours.

—Infants over 1 year are kept fasting for 6 hours.

—In older children, the intake of some liquids during the fasting period (but

no solid food) can still be allowed.

For infants, an empty bottle (for administering the radioactivity) as well

as a bottle containing the next feed should be brought to the nuclear medicine

department.

5.6.6.6. Procedure

For the study of deglutition the patient is usually in the supine or an erect

position. When a search is made for GOR, the supine position is required.

Data acquisition is usually done in the anterior projection, with frame rates of

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299

1–20 per second for the first 1–2 min, followed by a frame rate of 6 per minute

for a further period of 20–30 min.

During the deglutition phase of the study, care should be taken to include

both the mouth and the stomach in the FOV. In infants, the rest of the feed is

administered after completion of the deglutition study. Breast feeding is

allowed.

Since GOR, especially in infants, can be secondary to delayed gastric

emptying, early and late images of the stomach at 2 hours and preferably also at

6 hours should be obtained.

Visual assessment of oesophageal transit is usually done before quanti-

tative analysis is performed. A cine-display of the images is helpful to identify

subtle retrograde motion or retention of the tracer. A useful additional method

of display is to condense each dynamic image into a single column of pixels (y

axis), with time expressed on the x axis. The resulting image of composite

vertical lines is often useful to recognize subtle abnormalities.

Using ROIs over the lower oesophagus and stomach, the amount of

reflux and the rate of gastric emptying can be quantitated.

5.6.6.7. Interpretation

The steps listed below should be taken:

—Note the activity, positioning and time frames used for the study.

—Evaluate oesophageal transit.

—Note any evidence of reflux.

—Calculate rate of gastric emptying.

5.7. NUCLEAR MEDICINE IMAGING STUDIES IN ENDOCRINOLOGY

5.7.1. Thyroid scintigraphy

5.7.1.1. Principle

Thyroid scintigraphy is based on iodide physiology involving the

following: iodine ingestion, trapping and concentration in the thyroid,

oxidation and organification to produce iodotyrosines, and a coupling process

to form thyroid hormones. In thyroid imaging, the radioiodine is readily taken

up by the thyroid gland, where it is trapped and concentrated from the plasma,

and then undergoes the organification process. Similarly, the pertechnetate ion

is also trapped and concentrated by the thyroid gland but it does not undergo