**6. Contaminations by physiological secretions**

External contamination by physiological or pathological body secretions or excretions can cause positive radioiodine uptake and this mimics metastatic involvement of differentiated thyroid cancer.(Bakheet, Hammami et al. 2000) Sweat, breast milk, urine, vomitus and nasal, tracheobronchial, lacrimal, salivary secretions and faeces contain radioiodine and their contamination on the hair, skin or clothes can be misinterpreted as metastasis of thyroid cancer.(Shapiro, Rufini et al. 2000) Any focus of radioiodine uptake that cannot be explained by physiological or pathological causation must also be suspected as arising from contamination by secretions. Fortunately, the contaminations are usually easily recognized by their pattern and acquiring images after removing the contamination with decontaminating procedures and with taking the stained clothes off. However, unusual patterns of contamination might occur and suspecting uptake lesions as contamination would be difficult.

Physiologic and False Positive Pathologic Uptakes on Radioiodine Whole Body Scan 19

Fig. 25. Contamination at the skin of the right upper arm. There was also noted intense tracer accumulation in the rectum and moderate tracer accumulation in the descending

anterior posterior

Fig. 26. Vanishing contaminations after cleansing the right forearm, both thighs and right foot. There was also noted intense tracer accumulation in the thyroid bed area and colon

Physiologic

Residual thyroid tissue thyroid bed Active radioiodine uptake by

Sites of uptake Mechamism of radioiodine uptake

expression of the NIS

expression of the NIS

expression of the NIS

expression of the NIS *\*controversial* 

Active radioiodine uptake by the

Active radioiodine uptake by the

Active radioiodine uptake by the

and moderate tracer accumulation in the liver.

Lingual thyroid mediatinal thyroid Intratracheal thyroid Paracardiac thyroid Intraheaptic thyroid

Salivary gland Parotid and submandibular salivary glands

Ocular and periocular area

Ectopic normal thyroid tissues

Lacrimal sac/nasolacrimal duct Lacrimal gland\*

colon and the liver.

Patients' peculiar physical characteristics or odd habits produce extraordinary contamination patterns. Uptake in the scalp or a wig has been reported in patient with excessive sweating, and contamination of a wig was reported in patient with a bizarre habit of styling hair with sputum.(Bakheet, Hammami et al. 2000) False positive scans due to contamination can be kept to a minimum by careful preparation of patients, such as image acquisition in a clean gown after taking a shower.

Contaminations are almost always superficial, (Carlisle, Lu et al. 2003), therefore, the use of lateral and/or oblique views to give a third dimension to the scan may help to identify the contamination. Furthermore, the SPECT image alone or the SPECT image fused with the anatomical image, which provides detailed information about the anatomic location of the radiotracer uptake sites, can be the best way to correctly determine that contamination is the reason for the uptakes.

Fig. 23. Cases with contaminations at the hair and scalp. A case with unilateral hair contamination by saliva and cases with uni- or bilateral scalp contamination by excessive perspiration are demonstrated.

Fig. 24. Contamination at the right posterior chest wall by excessive perspiration. There was also noted intense tracer accumulation in the thyroid bed (by remnant tissue of the thyroid and edema of the cervical soft tissue).

Patients' peculiar physical characteristics or odd habits produce extraordinary contamination patterns. Uptake in the scalp or a wig has been reported in patient with excessive sweating, and contamination of a wig was reported in patient with a bizarre habit of styling hair with sputum.(Bakheet, Hammami et al. 2000) False positive scans due to contamination can be kept to a minimum by careful preparation of patients, such as image

Contaminations are almost always superficial, (Carlisle, Lu et al. 2003), therefore, the use of lateral and/or oblique views to give a third dimension to the scan may help to identify the contamination. Furthermore, the SPECT image alone or the SPECT image fused with the anatomical image, which provides detailed information about the anatomic location of the radiotracer uptake sites, can be the best way to correctly determine that contamination is the

Fig. 23. Cases with contaminations at the hair and scalp. A case with unilateral hair contamination by saliva and cases with uni- or bilateral scalp contamination by excessive

Fig. 24. Contamination at the right posterior chest wall by excessive perspiration. There was also noted intense tracer accumulation in the thyroid bed (by remnant tissue of the thyroid

posterior

anterior

right lateral left lateral

acquisition in a clean gown after taking a shower.

reason for the uptakes.

perspiration are demonstrated.

and edema of the cervical soft tissue).

Fig. 25. Contamination at the skin of the right upper arm. There was also noted intense tracer accumulation in the rectum and moderate tracer accumulation in the descending colon and the liver.

Fig. 26. Vanishing contaminations after cleansing the right forearm, both thighs and right foot. There was also noted intense tracer accumulation in the thyroid bed area and colon and moderate tracer accumulation in the liver.


Physiologic and False Positive Pathologic Uptakes on Radioiodine Whole Body Scan 21

Contaminations

Table 4. Causes of radioiodine uptake not related to thyroid cancer on the radioiodine whole

Fig. 27. Schematic presentation for the locations of physiologic uptake and possible

contamination sources the radioiodine whole body scans.

Pleural and pericardial effusions

Skin of any part of the body, hair,

Gastric adenocarcinoma Salivary adenocarcinoma Lung adenocarcinoma Fibroadenoma Meningioma Nurilemoma Teratoma

Tracheostomy site

wig, cloth, etc

Non-thyroidal neoplasm

Tear

Saliva Sweat Vomitus Breast milk Urine Feces

body scan.

Trauma Biopsy site

Sites of uptake Mechamism of radioiodine uptake

Active radioiodine uptake by the NIS of the tumor and/or incresed blood flow and enhanced capillary permeability in the tumor

Increased perfusion and vasodilation, and enhanced capillary permeability

Contamination by physiological or pathological body secretions or

by the tissue trauma

excretions


By nasal secretion Nose "hot nose" Focal accumulated nasal secretion

Choroid plexus Brain Active radioiodine uptake by the

Breast Breast, especially lactating Active radioiodine uptake by the

Pathologic

Fungal infection (eg, aspergilloma)

tissue Struma ovarii Active radioiodine uptake by the

By excreted or swallowed saiva

By excreted urine

Gastric mucosa

By excreted gastric secretion

Metabolism of radioiodinated proteins

Heterotopic thyroid

Inflammations associated with/without infection

Thymic uptake Thymus

Oral cavity Oesophagus

Achalasia

Renal pelvis Ureter

Stomach

Liver Biliary tract Gall bladder Bowels

Urinary bladder

Oesophageal diverticulum Oesophageal stricture or scarring

Urinary tract diverticulum Urinary tract fistula Renal cyst\*

Gastric duplication cyst Meckel's diverticulum Barrett esophagus

Oesophageal uptake Bowel uptake

Colon Diffuse and/or focal (any part of

colon)

Pericarditis Skin burn Dental disease Arthritis Cholecystitis Folliculitis Paranasal sinusitis Dacryocystitis Bronchiectasis

Sites of uptake Mechamism of radioiodine uptake

glands

with radioiodine

expression of the NIS

expression of the NIS

Gastroesophagel reflux

expression of the NIS

expression of the NIS

by the inflammation

thyroglobulin.

Hassal's bodies

*mechanism* 

Focal accumulated saliva with radioiodine activity from the salivary

Accumulated urine radioiodine activity excreted by the kidneys *\* Active radioiodine uptake by the expression of the NIS can be another* 

Expression of the NIS in thymic tissues and/or iodine concentration by

Active radioiodine uptake by the

Translocation of excreted gastric secretion into the bowel

Transport of radioiodine into the intestine from the mesenteric circulation and biliary excretion of the metabolites of radioiodinated

Increased perfusion and vasodilation, and enhanced capillary permeability

Metabolism of radioiodinated thyroid hormones or thyroglobulin and their excretion into the gall bladder and bowels via the biliary tract


Table 4. Causes of radioiodine uptake not related to thyroid cancer on the radioiodine whole body scan.

Fig. 27. Schematic presentation for the locations of physiologic uptake and possible contamination sources the radioiodine whole body scans.

Physiologic and False Positive Pathologic Uptakes on Radioiodine Whole Body Scan 23

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