Vinay Ravi MD, Presenter: Nothing to Disclose

Marc A. Seltzer MD, Abstract Co-Author: Consultant, General Electric Company Consultant, Alliance Imaging, Inc

Stephanie P. Yen MD, Abstract Co-Author: Nothing to Disclose

A shallow breathing PET/CT study has become the standard of care imaging test for evaluating patients with lung cancer. We prospectively studied the benefit of performing a low dose breathhold chest CT (BHCT) at the end of every shallow breathing PET-CT study. The objectives were to determine whether primary tumor size measurements differ between BHCT and shallow breathing CT (SBCT), and whether BHCT detects additional pulmonary nodules not seen on SBCT.

50 consecutive pts referred for evaluation of a lung nodule or lung cancer were studied on a 16 channnel multidetector PET-CT system (GE Discovery ST). PET-CT indications were assisting in diagnosis (n=8), initial staging (n=11), and restaging (n=31). Following completion of the standard shallow breathing PET-CT study, a maximal inspiratory BHCT was performed (120 kVp, 40mAs, 2.5mm slice thickness). The PET-CT, SBCT and BHCT were reviewed by consensus of two radiologists.

In 6 of 50 pts (11%), the primary axial tumor size measured by SBCT vs BHCT differed by more than 2 mm (mean 5.3 mm, range 3-10 mm). In 11 of 50 pts (22%), 15 additional pulmonary nodules >2 mm size were identified on BHCT that were not seen on SBCT (10 in lower, 3 in middle, and in 2 upper lobe locations; mean size 4.2 mm, range 3-9mm). None of the additional BHCT detected nodules had visible FDG uptake.

A separate BHCT should be obtained as part of every shallow breathing PET-CT study in order to more accurately size the primary lesion and to detect additional small pulmonary nodules that may represent early lung metastases. The performance of a BHCT also allows one to more reliably compare BHCT pulmonary findings to those seen on prior and future BHCT studies that are often not associated with a PET-CT.

Breathhold CT adds important diagnostic information when added to a shallow breathing PET-CT in patients with suspected or known lung cancer.

Ravi, V, Seltzer, M, Yen, S, Diagnostic Value of Adding a Breath-hold CT to a Shallow Breathing PET-CT for More Complete Evaluation of Patients with Suspected or Known Lung Cancer.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6022199.html