Ventilation–Perfusion SPECT with ^99mTc-DTPA Versus Technegas: A Head-to-Head Study in Obstructive and Nonobstructive Disease

Abstract

Lung scintigraphy is primarily used to diagnose pulmonary embolism. Ventilation imaging is often performed using 99m Tc-DTPA or Technegas, an ultrafine dispersion of 99m Tc-labeled carbon. Despite the common use of these radioaerosols, they have not been compared in an intraindividual study, and not with ventilation-perfusion (V/P) SPECT. The aim of the present head-tohead study was to systematically investigate differences in ventilation studies performed with 99m Tc-diethylenetriaminepentaacetate (DTPA) and Technegas. Methods: Sixty-three patients, 28 without and 35 with obstructive lung disease, were examined with V/P SPECT using both 99m Tc-DTPA and Technegas. V/P SPECT images were randomized and assessed independently by 2 masked physicians according to a predefined scoring system. A paired comparison was performed using the Wilcoxon signed-rank test. Results: In both obstructive and nonobstructive disease, the overall unevenness of radiotracer deposition and the degree of central deposition were more pronounced in 99m Tc-DTPA than Technegas studies. Because of better peripheral penetration, the extent of reverse mismatch was less when Technegas was used. Additionally, in obstructive disease, the degree of focal deposition in distal airways was more pronounced with 99m Tc-DTPA. Mismatched perfusion defects were more frequently found with Technegas in obstructive disease. Conclusion: This intraindividual comparative study shows that Technegas is the preferred radioaerosol, particularly in obstructive disease.Key Words: pulmonary embolism; ventilation-perfusion singlephoton emission computed tomography (V/P SPECT); COPD; 99m Tc-DTPA; Technegas Lung scintigraphy allows imaging of ventilation and perfusion distribution and assessment of regional lung function in lung disease (1). Lung scintigraphy is used primarily to identify pulmonary embolism (PE), although other diseases such as pneumonia, heart failure, and obstructive lung disease may be identified (1-5). Ventilationperfusion (V/P) SPECT improves the diagnostic accuracy for PE (6-9). V/P SPECT performed according to the state of the art also simplifies recognition of ventilation and perfusion patterns typical of other cardiopulmonary diseases (10).Perfusion scintigraphy is most commonly achieved by microembolization with 99m Tc-labeled macroaggregates of human albumin (MAA). For ventilation studies, the inert gas 81m Kr and the aerosols 99m Tc-diethylenetriaminepentaacetate (DTPA) and an ultrafine dispersion of 99m Tc-labeled carbon (Technegas; Cyclomedica Ltd.) are currently recommended (11). 81m Kr is of limited use because of its high cost and short half-life.Previously, 133 Xe was also used for ventilation studies, but this is no longer recommended according to the guidelines of the European Association of Nuclear Medicine (11).How aerosol droplets or particles are distributed and deposited within airways and alveoli depends on their aerodynamic properties, particularly their mass median aerodynamic diameter (11). Even with the best liquid aerosol gen...

Ventilation Perfusion Single Photon Emission Tomography (V/Q SPECT) in the Diagnosis of Pulmonary Embolism

“…The term pseudogas has been used to describe the agent, a reflection of the fact that its behaviour during inspiration is close to that of a true gas. The superiority of Technegas to conventional DTPA aerosols has been demonstrated in COPD (Jögi et al 2010). There is limited central deposition except in severe COPD.…”

Quantitative Ventilation/Perfusion Tomography: the Foremost Technique for Pulmonary Embolism Diagnosis

“…V/P SPECT is sufficiently sensitive as a method to identify the functional changes in COPD. In comparison with DTPA aerosols, Technegas penetrates the lung periphery better (Jögi et al, 2010), which is especially important in COPD (exemplified in Fig 3). Technegas ventilation imaging has been shown to visualise the early changes of COPD before they can be observed with high resolution CT (HRCT) (Yokoe et al, 2006).…”

“…Technegas significantly reduces problems of central airway deposition and peripheral hotspots. Patients routinely admitted for V/P SPECT and a group of patients with known COPD were recently studied with both 99mTc-DTPA and Technegas showing superiority of the latter (Jögi et al, 2010). Unevenness of radiotracer deposition and degree of central deposition were significantly reduced with Technegas, particularly in the obstructive patients (Fig 3).…”

68Ga PET/CT Ventilation–Perfusion Imaging for Pulmonary Embolism: A Pilot Study with Comparison to Conventional Scintigraphy

“…First, V/Q images were characterized as normal, abnormal, or nondiagnostic. Second, 3 qualitative parameters were used as previously defined by Jogi et al (3) to assess image quality: unevenness of radioaerosol distribution, deposition of radioaerosol in major and intermediate conducting airways (i.e., central deposition), and focal peripheral deposition in more distal airways. Each of these parameters was scored from 0 (none or normal) to 10 (very high).…”

“…V/Q imaging has improved in the past 3 decades because of major advances in image acquisition, reconstruction, and analysis techniques. The use of 99m Tc-labeled carbon nanoparticles (Technegas; Cyclopharm) has improved the assessment of ventilation because of favorable imaging characteristics and small particle size, resulting in better peripheral distribution than is obtained with other aerosol techniques (2,3).…”