Accurate contiguous sections without breath-holding on chest CT: value of respiratory gating and ultrafast CT.

OBJECTIVE To image truly contiguous CT sections without breath-holding, we developed a respiratory-gating device combined with ultrafast CT. The purpose of this study was to evaluate the utility of this system, especially focusing on the contiguity of the images. SUBJECTS AND METHODS In 37 patients, we obtained respiratory-gated scans and breath-hold scans with 6-mm collimation and 6-mm incrementation (19 patients) and with 3-mm collimation and 3-mm incrementation (18 patients). We compared these two sets of images with respect to quality and contiguity. In nine patients who could not hold their breath because of dyspnea or infancy, we obtained only respiratory-gated scans with 3-mm collimation and 3-mm incrementation. Our respiratory-gating device was composed of a commercial ECG and respiratory monitor, a triggering device, an original amplifier, and an original switching unit. It was designed to control the scan timing of an ultrafast CT scanner at a user-selected level of the respiratory curve obtained with transthoracic impedance plethysmography. RESULTS The respiratory-gated images were equal in quality to the breath-hold images in 31 of the 37 patients who had both sets of images. In 15 of 19 patients who had 6-mm-thick sections and in 11 of 18 patients who had 3-mm-thick sections, satisfactory contiguous images of bronchi and pulmonary vessels were obtained. Additionally, in seven of the nine patients who could not hold their breath, satisfactory contiguous sections were obtained. CONCLUSION The respiratory gating system combined with ultrafast CT can provide contiguous CT scans without breath-holding or patients' cooperation. The procedure could improve the diagnostic accuracy of CT, especially in severely ill patients, infants, and senile patients.