Technegas is a suspension of structured graphite ellipsoids with diameter around 100nm and labelled with ^99mTc in a carrier gas of Argon.

Technegas is formed by the initiation evaporation of ^99mTc

Accounting for tracer preparation and loading, Technegas preparation time would be around 12 minutes, essentially unattended.

On inhalation, the structured ultra-fine dispersion of labelled carbon adheres to the walls of the alveoli. Penetration characteristics within the lung are gaslike and the radioactive concentration per litre of carrier argon allows single breath inhalation of diagnostic value.

The biological clearance of Technegas is effected by macrophage activity within the body immune system. This clearance is slow when compared with the physical half-life of the radioactive tracer. There is negligible difference between the physical half-life (6 hours) and the effective half-life of Technegas in the lungs.

No contra-indications exist for the use of Technegas.

No adverse reactions to Technegas have been reported since its introduction for medical use in June 1986.

The mass of carbon inhaled per study has been calculated as approximately 50µg.

In children and young persons of reproductive age, the perfusion study may be performed first, and if the study shows abnormality, then proceed to the ventilation study. The quality of Technegas images enables this protocol to be followed.

A radioactive dose between 400-800 MBq is recommended in a volume of 0.14ml. A radioactive concentration of at least 4000 MBq/ml is required.

The Technegas system allows for multiple simmer cycles to be performed.
Following the completion of each simmer cycle, 0.14 ml of tracer may be added
until desired radioactivity has been introduced into the system.

It is dependent upon individual department protocols. Normally a count rate between 1000 cps and 2500 cps is required. It has been estimated that a count rate of 2500 cps, in posterior view, is equivalent to a retained activity of 37 MBq.

This is primary a basic infection and contamination control manoeuvre designed to assist in good work practice. Attempts to cleanse the PAS will result in damage to the valves, failure of the filter medium and faulty delivery
of Technegas.

Technegas exhaled through the mouthpiece / valve assembly is trapped on a filter.

All residual, unused Technegas is trapped onto a replaceable exhaust filter before access to the chamber is possible.

Based on an infinite residence time for Technegas particles in the lung, parenchyma radiation exposure has been calculated to 4.5 mGy for 37 MBq inhaled activity.

Radiation surveys indicate the maximum radiation dose rate detected in the operator position as 10 µSv/h per 100 MBq of 99mTc injected into the system.

In addition to regular cleaning of the unit, the crucible contact and purge filter (not for TechnegasPlus) must be changed after every 50 burns. This is simple procedure to implement.

Apart from routine maintenance, programmed servicing of the Technegas system is required at six monthly intervals. Full-trained engineers are available for prompt attention should service be required.

The Technegas generator incorporates 15 feedback systems, which constantly monitor critical functions. These failsafe systems do not have manual override devices ensuring the safe generation of Technegas.

The Technegas generator has lead lining incorporated in various areas of the machine as well as acrylic viewing screen lead shielding in the drawer to protect the user when adding the ^99mTc Pertechnetate to the generator.