A single breath hold of 20 seconds can enable more precise measurements of maximum standardized uptake value (SUVmax), especially in the lower lung field and for small tumors--which may be affected by respiratory motion--according to research published in this month’s Journal of Nuclear Medicine.

“Although the fusion of PET and CT images significantly improves both sensitivity and specificity in the detection of diseases, image misregistration may occur in the chest and abdomen because of motion artifacts caused by respiration,” the authors noted.

A research team at the Hamamatsu University School of Medicine in Hamamatsu, Japan, compared 18F-FDG uptake between a single 20-second acquisition of deep-inspiration breath-hold PET/CT and PET/CT for lung cancer.

They noted that although the CT scan is acquired in a few seconds, capturing the chest at a single phase of a single respiratory cycle, the emission PET scan is acquired over many minutes and averages many respiratory cycles.

“As a result, the two datasets frequently do not overlie each other,” they wrote. “Additionally, respiratory motion blurs PET images, degrades contrast, overestimates tumor volume, and increases variability in SUV.”

Their method to mitigate this issue is for patients to hold their breath in deep inspiration for 20 seconds during a single PET scan. The duration of breath hold was determined by the results of a phantom study conducted earlier by the research team.

The cohort for the study consisted of 47 (37 men) consecutive lung cancer patients with a mean age of 68 years.

“On the basis of the phantom study, patients with lung tumors smaller than 13 mm were excluded,” they noted. “We also excluded lung tumors showing weak 18F-FDG uptake (SUVmax