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Technegas Functional Lung Imaging

Technegas is an ultra-fine dispersion of Technetium-labelled carbon, produced by heating Technetium-99m in a carbon crucible for a few seconds at 2,750 degrees Celsius1. The resultant gas-like Technegas, thus produced in a Technegas generator, is a dispersion of nanosized (average size 30-60nm) pure carbon platelets of hexagonal shape fully encapsulating Technetium metal crystals2. The small size and hydrophobic properties together confirm ideal characteristics for gas-like behaviour and alveoli deposition into the lungs2-3. Technegas penetrates to the sub-segmental areas of the lung and is trapped by surfactant in the alveolar walls4.

Once inhaled by the patient suspected of having a pulmonary embolism (PE), the patient is then imaged under a gamma camera in the ventilation part of a ventilation/perfusion single-photon emission computed tomography (V/Q SPECT) scan3. Generated into a mobile generator, Technegas, used in the ventilation part of the V/Q scan, is cost-effective, simple to perform and accurate5. With the uptake in SPECT imaging, V/Q SPECT results with Technegas can be argued to be superior to planar imaging and computed tomography (CT) when comparing sensitivity, accuracy and negative predictive value6-7.

Of significant interest, when compared to CT, is the low radiation dose imparted by V/Q SPECT imaging8. This is important in all patients but particularly in young women with proliferating breast tissue9.

Lung scintigraphy has a superior sensitivity combined with adequate specificity and low rate of non-diagnostic tests. The low radiation dose, the possibility to quantify the degree of embolism and to use the test for follow-up of treatment of embolism and its feasibility in very sick patients, contribute to the priority of lung scintigraphy over Computed Tomographic Pulmonary Angiography ” 10

Table 1: Diagnostic ability of CT, planar V/Q scintigraphy, V/Q SPECT and hybrid V/Q SPECT/CT to detect PE6-7
(adapted from Reinartz et al, 2004 et Hess et al, 2016)

With the advent of SPECT and SPECT/CT technology, significant improvements in ventilation-perfusion imaging have been made, not only in our ability to resolve subtle heterogeneity in ventilation and perfusion distributions but also in providing relative quantification of ventilation and perfusion11 “

Table 2: Functional and quantitative lung imaging. Images and 3D quantification provided by

As a result of these technical improvements, advanced quantitative V/Q SPECT/CT with Technegas could be used as a tool for pre-operative evaluation, monitoring disease progression and following-up treatment response12-13 in a range of conditions whereas functional imaging of alveolar spaces are required, including for:

Pulmonary embolism
Chronic Thromboembolic Pulmonary Hypertension
Chronic Obstructive Pulmonary Disease
Pre-operative quantification of lung function
Radiotherapy treatment planning

To learn more about Technegas clinical capabilities, visit our clinical page


Benefits of Technegas V/Q SPECT

      Diagnostic accuracy: 

Sensitivity, specificity and accuracy at least equivalent to CTPAgiving the clinician interpretative confidence in diagnosing PE event at subsegmental levels6,14.

     3D images:

The gas-like behaviour of Technegas coupled with the ideal energy of Tc-99m gives excellent penetration to peripheral areas3,15. Images may be acquired in multiple projections facilitating image interpretation16 .

      Low radiation burden to the patient:

V/Q SPECT with Technegas has 27 to 36 times less radiation dose to the patient breast as compared with CTPA8.


     Quick and simple:

Rapid and easy administration of Technegas15 (3-4 breaths only) allowing accurate and quick decisions even in case of lung obstructive disease16.

     Minimal exclusion criteria:

Technegas may be administered to almost all patients including patients with renal impairment17, iodinated contrast allergy17 and chronic lung obstruction disease18. Technegas should be also favoured in young women of child-bearing age8,16 and in pregnant women8-9.


Because Technegas is easy to breath, it aids patients’ comfort and compliance.



Useful documents

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  1. Fawdry RM, et al. Initial experience with Technegas – a new ventilation agent. Australas Radiol 1988; 32(2): 232-238
  2. Senden TJ, et al. The physical and chemical nature of Technegas. J Nucl Med 1997; 38: 1327-1333
  3. Roach PJ, Schembri GP and Bailey DL. V/Q scanning using SPECT and SPECT/CT. J Nucl Med 2013; 54: 1588-1596
  4. Mortensen J and Gutte H. SPECT/CT and pulmonary embolism. Eur J Nucl Med Mol Imaging 2014; 41(Suppl1): 81-90
  5. Roach PJ, Bailey DL, Harris BE. Enhancing lung scintigraphy with single-photon emission computed tomography. Semin Nucl Med 2008; 38: 441–449
  6. Reinartz P, et al. Tomographic imaging in the diagnosis of pulmonary embolism: A comparison between V/Q lung scintigraphy in SPECT technique and multislice spiral CT. J Nucl Med 2004; 45: 1501-1508
  7. Hess S, et al. State-of-the-Art Imaging in Pulmonary Embolism: Ventilation/Perfusion Single-Photon Emission Computed Tomography versus Computed Tomography Angiography — Controversies, Results, and Recommendations from a Systematic Review. Semin Thromb Hemost 2016; 42: 833–845
  8. Isidoro J, et al. Radiation dose comparison between V/P-SPECT and CT-angiography in the diagnosis of pulmonary embolism. Phys Med 2017; 41: 93-96
  9. Bajc et al. V/P SPECT as a diagnostic tool for pregnant women with suspected pulmonary embolism. Eur J Nucl Mol Imaging 2015; 42: 1325-1330
  10. Bajc et al. Comparison of ventilation/perfusion scintigraphy and helical CT for diagnosis of pulmonary embolism; strategy using clinical data and ancillary findings. Clin Physiol Funct Imaging 2002; 22(6): 392-397
  11. Elojeimy S, et al. Overview of the novel and improved pulmonary ventilation-perfusion imaging applications in the era of SPECT/CT. AJR Am J Roentgenol 2016; 207(6): 1307-1315
  12. Inmai T, et al. Clinical evaluation of 99mTc-Technegas SPECT in thoracoscopic lung volume reduction surgery in patients with pulmonary emphysema. Ann Nucl Med 2000; 14(4): 263-269
  13. Hsu K, et al. Endoscopic lung volume reduction in COPD: improvements in gas transfer capacity are associated with improvements in ventilation and perfusion matching. J Bronchology Interv Pulmonol 2018; 25(1): 48-53
  14. Grüning T, et al. Three-year experience with VQ SPECT for diagnosing pulmonary embolism: diagnostic performance. Clin Imaging 2014; 38(6): 831-835
  15. Bajc M and Jonson B. Ventilation/perfusion SPECT for diagnosis of pulmonary embolism and other diseases. Int J Mol Imaging 2011; 682949
  16. Hess S and Madsen PH. Radionuclide diagnosis of pulmonary embolism. Adv Exp Med Biol 2017; 906: 49-65
  17. Miles S, et al. A comparison of single-photon emission CT lung scintigraphy and CT pulmonary angiography for the diagnosis of pulmonary embolism. Chest 2009; 136: 1546-1553
  18. Nasr A, Lindqvist A and Bajc M. Ventilation defect typical for COPD is frequent among patients suspected for pulmonary embolism but does not prevent the diagnosis of PE by V/P SPECT. EC Pulmonology and Respiratory Medicine 2017; 4(3): 85-91
  19. Sánchez-Crespo A, et al. A technique for lung ventilation-perfusion SPECT in neonates and infants. Nucl Med Commun 2008; 29(2): 173-177



Pending market authorisation – not yet available for use

Ultralute is a revolutionary innovation that allows Nuclear Medicine departments to increase the productivity of their Tc-99m generator. It does this by allowing you to elute any amount of activity in approximately 2ml. By increasing the concentration of Tc-99m from an elution, the decay profile and the growth of Tc-99m from a Mo-99m/Tc 99m generator can be better utilised.