PET Lung Ventilation/Perfusion Imaging Using 68Ga Aerosol (Galligas) and 68Ga-Labeled Macroaggregated Albumin

Abstract

Pulmonary imaging using ventilation/perfusion (V/P) single-photon emission tomography (V/P scan) with Tc-99m-labeled radiotracers is a well-established diagnostic tool for clinically suspected pulmonary embolism (PE). Ga-68 aerosol (Galligas) and Ga-68-labeled macroaggregated albumin (MAA) are potential tracers for positron emission tomography (PET) lung V/P imaging and could display an advantage over conventional V/P scans in terms of sensitivity and specificity. After radiochemical and animal studies, the clinical applicability of Ga-68 aerosol (Galligas) and Ga-68-labeled MAA was investigated in an exploratory study in patients with clinical suspicion of PE. PET scans were acquired using a 16-slice Gemini TF positron emission tomography/computed tomography (PET/CT) scanner. The acquisition protocol included low-dose computed tomography (CT) for attenuation correction (AC). Dosimetry calculations and continuative phantom measurements were performed. Structural analyses showed no modification of the particles due to the labeling process. In addition, in vitro experiments showed stability of Ga-68 MAA in various media. As expected, Ga-68-labeled human serum albumin microspheres (HSAM) were completely retained in the lung of the animals. In clinical use, PET lung ventilation and perfusion imaging using Ga-68 aerosol (Galligas) and Ga-68-labeled MAA was successful in all cases. In one case a clinically suspected PE could be detected and verified. The administered activity of Ga-68 aerosol (Galligas) and Ga-68-labeled MAA may be reduced by more than 50%, resulting in comparable radiation exposure to conventional V/P scans. In conclusion, Ga-68 aerosol (Galligas) and Ga-68-labeled MAA are efficient substitutes for clinical use and could be an interesting alternative with high accuracy for lung V/P imaging with Tc-99m-labeled radiotracers, especially in times of Mo-99 shortages and increasing use and spread of PET/CT scanners and Ga-68 generators, respectively.

Lyophilized Kit for the Preparation of the PET Perfusion Agent [68Ga]-MAA

“…MAA was first successfully labeled with 68 Ga in 1989 [4] but never used, probably due to unreliability of the existing 68 Ge/ 68 Ga generators and low availability of PET imaging cameras. Revived interest has been shown recently [5, 6], and the first PET lung perfusion studies in humans have been performed [7, 8]. …”

Detection of Pulmonary Embolism with Gallium-68 Macroaggregated Albumin Perfusion PET/CT: An Experimental Study in Rabbits

“…In approximately an hour, both ventilation and perfusion studies were completed. Previously, ventilation studies have been published with 68 Ga (Galligas) [21][22][23]. Although the imaging time is short with Galligas, it may be necessary to wait between perfusion and ventilation studies, and this delay can prolong the total diagnosis time.…”

A Feasibility Study of Single-inhalation, Single-energy Xenon-enhanced CT for High-resolution Imaging of Regional Lung Ventilation in Humans

“…By comparison, advantages of the XeCT method demonstrated in the present study include higher resolution, volumetric imaging, improved quantitation, shorter study time, and lack of aerosol deposition artifacts in the airways. Notably, newer radiolabeled gases or aerosols for use with nuclear medicine ventilation imaging such as Ga-68 aerosol (Galligas) (26,27), an ultrafine dispersion of 99m Tc-labeled carbon (Technegas) (28,29), and radioactive Xe-133 gas (30) can reduce airway deposition artifacts, but are not currently approved for clinical use in the United States.…”