PET/CT with intravenous contrast can be used for PET attenuation correction in cancer patients

PurposeIf the CT scan of a combined PET/CT study is performed as a full diagnostic quality CT scan including intravenous (IV) contrast agent, the quality of the joint PET/CT procedure is improved and a separate diagnostic CT scan can be avoided. CT with IV contrast can be used for PET attenuation correction, but this may result in a bias in the attenuation factors. The clinical significance of this bias has not been established. Our aim was to perform a prospective clinical study where each patient had CT performed with and without IV contrast agent to establish whether PET/CT with IV contrast can be used for PET attenuation without reducing the clinical value of the PET scan.MethodsA uniform phantom study was used to document that the PET acquisition itself is not significantly influenced by the presence of IV contrast medium. Then, 19 patients referred to PET/CT with IV contrast underwent CT scans without, and then with contrast agent, followed by an 18F-fluorodeoxyglucose whole-body PET scan. The CT examinations were performed with identical parameters on a GE Discovery LS scanner. The PET data were reconstructed with attenuation correction based on the two CT data sets. A global comparison of standard uptake value (SUV) was performed, and SUVs in tumour, in non-tumour tissue and in the subclavian vein were calculated. Clinical evaluation of the number and location of lesions on all PET/CT scans was performed twice, blinded and in a different random order, by two independent nuclear medicine specialists.ResultsIn all patients, the measured global SUV of PET images based on CT with IV contrast agent was higher than the global activity using non-contrast correction. The overall increase in the mean SUV (for two different conversion tables tested) was 4.5±2.3% and 1.6±0.5%, respectively. In 11/19 patients, focal uptake was identified corresponding to malignant tumours. Eight out of 11 tumours showed an increased SUVmax (2.9±3.1%) on the PET images reconstructed using IV contrast. The clinical evaluation performed by the two specialists comparing contrast and non-contrast CT attenuated PET images showed weighted kappa values of 0.92 (doctor A) and 0.82 (doctor B). No contrast-introduced artefacts were found.ConclusionThis study demonstrates that CT scans with IV contrast agent can be used for attenuation correction of the PET data in combined modality PET/CT scanning, without changing the clinical diagnostic interpretation.

[1]  G. Muehllehner,et al.  Positron emission tomography , 2006, Physics in medicine and biology.

[2]  Gerald Antoch,et al.  Whole-body positron emission tomography-CT: optimized CT using oral and IV contrast materials. , 2002, AJR. American journal of roentgenology.

[3]  J. Debatin,et al.  Effect of oral contrast agents on computed tomography-based positron emission tomography attenuation correction in dual-modality positron emission tomography/computed tomography imaging. , 2003, Investigative radiology.

[4]  J. Keyes SUV: standard uptake or silly useless value? , 1995, Journal of nuclear medicine : official publication, Society of Nuclear Medicine.

[5]  Andrew M. Keenan,et al.  Clinical Molecular Anatomic Imaging , 2005 .

[6]  A.H.R. Lonn Evaluation of method to minimize the effect of X-ray contrast in PET-CT attenuation correction , 2003, 2003 IEEE Nuclear Science Symposium. Conference Record (IEEE Cat. No.03CH37515).

[7]  J. H. Hubbell,et al.  Review of photon interaction cross section data in the medical and biological context. , 1999, Physics in medicine and biology.

[8]  A. Buck,et al.  PET attenuation coefficients from CT images: experimental evaluation of the transformation of CT into PET 511-keV attenuation coefficients , 2002, European Journal of Nuclear Medicine and Molecular Imaging.

[9]  Valerie Treyer,et al.  CT vs 68Ge attenuation correction in a combined PET/CT system: evaluation of the effect of lowering the CT tube current , 2002, European Journal of Nuclear Medicine and Molecular Imaging.

[10]  R. Wahl,et al.  Initial experience with oral contrast in PET/CT: phantom and clinical studies. , 2003, Journal of nuclear medicine : official publication, Society of Nuclear Medicine.

[11]  Richard L Wahl,et al.  Applications of positron emission tomography/computed tomography image fusion in clinical positron emission tomography-clinical use, interpretation methods, diagnostic improvements. , 2003, Seminars in nuclear medicine.

[12]  Paul Kinahan,et al.  Attenuation correction for a combined 3D PET/CT scanner. , 1998, Medical physics.

[13]  Thomas Beyer,et al.  Acquisition protocol considerations for combined PET/CT imaging. , 2004, Journal of nuclear medicine : official publication, Society of Nuclear Medicine.

[14]  Jeffrey Bisker,et al.  Principles and Practice of Positron Emission Tomography. , 2003 .

[15]  Gerald Antoch,et al.  Focal tracer uptake: a potential artifact in contrast-enhanced dual-modality PET/CT scans. , 2002, Journal of nuclear medicine : official publication, Society of Nuclear Medicine.

[16]  Yuji Nakamoto,et al.  Effects of nonionic intravenous contrast agents at PET/CT imaging: phantom and canine studies. , 2003, Radiology.

[17]  Douglas G. Altman,et al.  Practical statistics for medical research , 1990 .

[18]  Søren Holm,et al.  Estimation of the noise contributions from blank, transmission and emission scans in PET , 1995 .

[19]  G. V. von Schulthess,et al.  Staging of non-small-cell lung cancer with integrated positron-emission tomography and computed tomography. , 2003, The New England journal of medicine.

[20]  Thomas Beyer,et al.  To enhance or not to enhance? 18F-FDG and CT contrast agents in dual-modality 18F-FDG PET/CT. , 2004, Journal of nuclear medicine : official publication, Society of Nuclear Medicine.

[21]  David W. Townsend,et al.  Positron Emission Tomography , 1985, Other Conferences.