Dual-modality PET/CT imaging: the effect of respiratory motion on combined image quality in clinical oncology

Abstract

To reduce potential mis-registration from differences in the breathing pattern between two complementary PET and CT data sets, patients are generally allowed to breathe quietly during a dual-modality scan using a combined PET/CT tomograph. Frequently, however, local mis-registration between the CT and the PET is observed. We have evaluated the appearance, magnitude, and frequency of respiration-induced artefacts in CT images of dual-modality PET/CT studies of 62 patients. Combined PET/CT scans during normal respiration were acquired in 43 subjects using single- or dual-slice CT. Nineteen patients were scanned with a special breathing protocol (limited breath-hold technique) on a single-slice PET/CT tomograph. All subjects were injected with approximately 370 MBq of FDG, and PET/CT scanning commenced 1 h post injection. The CT images were reconstructed and, after appropriate scaling, used for on-line attenuation correction of the PET emission data. We found that respiration artefacts can occur in the majority of cases if no respiration protocol is used. When applying the limited breath-hold technique, the frequency of severe artefacts in the area of the diaphragm was reduced by half, and the spatial extent of respiration-induced artefacts was reduced by at least 40% compared with the acquisition protocols without any breathing instructions. In conclusion, special breathing protocols are effective and should be used for CT scans as part of combined imaging protocols using a dual-modality PET/CT tomograph. The results of this study can also be applied to multi-slice CT to potentially reduce further breathing artefacts in PET/CT imaging and to improve overall image quality.

Motion artifacts occurring at the lung/diaphragm interface using 4D CT attenuation correction of 4D PET scans

“…( 11 , 13 , 14 ) It has been reported that using CT data acquired at deep inspiration can produce severe artifacts, ( 15 ) and also that CT protocols using normal expiration breath‐hold or partial breath‐hold acquisition can reduce artifacts in this region. ( 15 , 16 ) Others have proposed that errors due to attenuation correction can be reduced by using a Cine‐CT to produce an averaged (or max) image dataset for correction purposes. ( 17 – 20 ) …”

PET/CT imaging: Effect of respiratory motion on apparent myocardial uptake

“…This can produce a mis-registration between the CT data used to perform attenuation correction and the PET emission data which is acquired over many respiratory cycles. There have been several studies showing that this effect can cause artifacts in PET/CT reconstructions in oncology -especially at borders between the lung and soft tissue, such as the liver-lung interface [1][2][3][4][5][6]. Because the heart also has a lung-soft tissue interface, it would seem likely that there would be similar artifacts in apparent myocardial activity uptake when performing cardiac PET/CT studies.…”

Phased Versus Midventilation Attenuation-Corrected Respiration-Correlated PET for Patients with Non-Small Cell Lung Cancer

“…The image of a certain slice is thus recorded in fractions of a second, and a moving tumor will likely not be imaged at its average position, given the average duration of a full respiration cycle (4 s) (5). A PET scan, on the other hand, will take 2-5 min per bed position, resulting in a distortion of the combined PET/CT image (6,7). Furthermore, respiratory motion could lead to blurring of the PET image and consequently to uncertainties in tumor size, position, and shape of the tumor and an underestimation of the measured standardized uptake value (SUV) (8,9).…”