European Nuclear Medicine Guide
Functioning respiratory cilia is the basis of normal mucociliary clearance. Through the trapping of inhaled particulate matter, coordinated motility of the ciliae to the oropharynx followed by swallowing this mechanism acts as a mechanical barrier.
This process can be investigated by measuring the speed of mucociliary clearance in the nose by following the movement of a 99mTc-nanocolloid droplet across the nasal mucosa for a specific duration of time. The speed of movement of the radioactive droplet is calculated by measuring the displacement of radioactivity, corrected for small head movements.
The investigation of mucociliary clearance can also be performed by means of inhalation of radioactive aerosols and measuring the alveolar clearance. In the trachea, the normal speed is ~4-5 mm/min in healthy non-smoking adults.
Apart from smoking, aging, and asthma/COPD, mucociliary clearance is decreased in cases of abnormal hyper viscous mucus (e.g. cystic fibrosis), abnormal ciliary ultrastructure (e.g. primary ciliary dyskinesia: Kartagener syndrome, a group of rare autosomal recessive diseases with an incidence of less than 1/20.000), and a wide range of chemical, mechanical, and inflammatory mediators. This test assesses the functioning of the mucociliary transport mechanism in the nose. It is similar to the saccharin test, in which a saccharin particle is placed in the nasal cavity, and the time to tasting saccharine is noted. The latter test clearly requires extensive patient cooperation. The nuclear medicine test is more objective.
If delayed or absent mucociliary transport is measured, this test must be supplemented by microscopy of ciliar motility and electron microscopy for the detection of dynein arm deficiency in the ciliae of a more invasive nasal mucosal biopsy.
The suggested activities to administer is 2 MBq, deposited on the nasal floor.
No recommendations are available for paediatric nuclear medicine.
The effective dose per inhaled activity is 4.9 µSv/MBq [3].
The effective dose for an inhalation of 40 MBq is: 0.2 mSv.
The administered activity is 2 MBq, deposited on the nasal floor. The ED, ranges from 48 µSv (70 kg adult) to 152 µSv (5-year-old).
Caveat
“Effective Dose” is a protection quantity that provides a dose value related to the probability of health detriment to an adult reference person due to stochastic effects from exposure to low doses of ionizing radiation. It should not be used to quantify the radiation risk for a single individual associated with a particular nuclear medicine examination. It is used to characterize a certain examination in comparison to alternatives, but it should be emphasized that if the actual risk to a certain patient population is to be assessed, it is mandatory to apply risk factors (per mSv) that are appropriate for the gender, the age distribution and the disease state of that population."
Healthy non-smokers have a nasal mucociliary average transport speed of 6 mm/min with a range of 2.3-12.0 mm/min. It should be emphasized, that this test has a good sensitivity (up to 100%). In primary ciliary dyskinesia, little or no mucociliary transport is measured in either nostril (average 0.2 mm/min, range 0-0.7 mm/min), provided the patient has been properly instructed and has not sniffed during the investigation. However, the specificity of this test is low (approximately 55%). Numerous disorders can ultimately result in greatly reduced or absent mucociliary transport (drug use, viral/bacterial infections, or anatomical abnormalities).
If there is no transport of the activity, consider repeating the test 1 to 2 weeks later while any local drugs are stopped. If the outcome of the test remains the same, this is considered definitive.
At least 2 days beforehand, the patient should not use any local drugs, particularly decongestants, that can influence the function of the ciliary epithelium. Sympathomimetic drugs must be avoided. Local corticosteroid sprays may continue to be used. If a local sympathomimetic drug such as oxymetazoline is used chronically (>14 days in a row), it must be stopped 14 days prior to the test to allow the rebound swelling of the nasal mucosa to recover.
No EANM guidelines are available at this time.
Confirm that any drugs that could affect the results of the investigation have been adequately suspended.
Tell the patient, prior to drawing up the active droplet, to breathe through their mouth during the imaging and not to sniff before or during the investigation.
Especially in children, it is worthwhile showing the pipette beforehand, since once fixed to the camera, the sight of it might cause distress accompanied by tears and sniffing, potentially rendering the investigation inconclusive.
Using tape, fix a point source to the tip of the nose and to the mastoid (behind the ear at the level of the meatus) or in front of the trachus in order to correct for movement but also as an anatomical reference. The patient sits with their head left or right laterally against the gamma camera, and the head is fixed in positioned, preferably with a head support (e.g. a modified eye measurement head support). The patient is positioned in such a way, so that the reference markers are aligned horizontally. Spread the naris using the nasal speculum and inspect the nasal cavity. Using the pipette, a droplet of 99mTc-nanocolloid is deposited on the nasal floor, 1cm behind the frontal section of the concha inferior (inferior turbinate) or naris.
Dynamically acquire 40 frames of 30 sec in a 128x128 or 64x64 matrix for 20 min.
To calculate the transport speed, the pixel size of the gamma camera used must be known. The displacement of the maximum counts of the deposit is measured in pixels/minute and corrected for movement of the head. Head movement is inferred from the displacement of the maximum number of counts of the point sources on the tip of the nose and mastoid. The transport speed is expressed in mm/min.
Repeat the investigation for the other nostril if no nasal mucociliary transport is observed; in all other cases, check with the nuclear medicine physician if the investigation should be repeated for the other nostril for other reasons. Before repetition of the investigation, ask the patient to blow his or her nose thoroughly to remove remnant radioactivity.