title: Does chemotherapy influence the quantification of SUV when contrast-enhanced CT is used in PET/CT in lymphoma?
abstract: OBJECTIVE
  In patients with lymphoma, we investigated the impact of contrast-enhanced CT on PET attenuation correction in lesions and normal tissues, particularly when PET/CT was performed after chemotherapy.
  
  
  METHODS
  Fifty patients (51+/-18 years) with Hodgkin's disease (n=17) or non-Hodgkin lymphomas (n=33) were studied before and after chemotherapy. PET/CT scans were performed 60 min after injection of FDG. Iopamiron 300 (iopamidol, 1.5 cc/kg) was injected immediately afterwards, followed 50 s later by a second craniocaudal CT (CT+). PET images were successively reconstructed using the unenhanced CT (PET-) and the CT+ (PET+) for attenuation correction, using iterative reconstruction (4 iterations, 8 subsets, 5 mm post-filtering). HU(mean), SUV(max) and SUV(mean) were measured before and after chemotherapy in ten non-tumoural ROIs [aorta, femur, kidney, lung, iliopsoas muscle, occipital cortex, T12 vertebra, liver, spleen and inferior vena cava (IVC)] and in tumoural lymphadenopathies or malignant tissues (n=397 and 51 VOIs respectively before and after chemotherapy) using a 3D-thresholding method (identical threshold for PET- and PET+). ROIs were defined on the PET- and automatically applied on the unenhanced CT (CT-), the CT+ and the PET+.
  
  
  RESULTS
  In the non-tumoural tissues, HU(mean) increased significantly in the CT+ compared with the CT- in the vessels and the highly vascularised organs, and slight increases were observed in the occipital cortex (+11%), the iliopsoas muscle (+6%) and the femur (+3%). SUV(max) increased significantly in the PET+ compared with the PET- in the aorta (+14%), the liver (+10%), the spleen (+10%) and the IVC (+12%). SUV(mean) increased significantly in the PET+ compared with the PET- in the aorta (+15%), the kidney (+13%), the liver (+11%), the spleen (10%) and the IVC (+12%). In the lesions, HU(mean) was not significantly different before and after chemotherapy, whatever the normal region considered. SUV(max) increased significantly after treatment in the T12 vertebra (+12%). SUV(mean) increased significantly after treatment in the T12 vertebra (+13%) and in the liver (+12%). HU(mean) increased significantly in the CT+ compared with the CT- in the lesions (+55%) before chemotherapy. SUV(max) and SUV(mean) increased significantly in the PET+ compared with the PET- in the lesions (+4%) only before chemotherapy. No significant difference was seen in measurements (HU(mean), SUV(max) and SUV(mean)) after chemotherapy.
  
  
  CONCLUSIONS
  Our study demonstrates that use of enhanced CT for attenuation correction has a negligible effect on quantification at staging and after chemotherapy. A "single-shot" enhanced PET/CT may thus be performed in the evaluation of patients with lymphoma at staging, during treatment and at follow-up.
authors: Department of Nuclear Medicine, Henri Becquerel Centre and Rouen University Hospital, 1 rue d'Amiens, Rouen, France. pierre.vera@rouen.fnclcc.fr
authors: Pierre
authors: P
authors: Vera
authors: Matthieu John
authors: MJ
authors: Ouvrier
authors: Sébastien
authors: S
authors: Hapdey
authors: Marc
authors: M
authors: Thillays
authors: Anne Sophie
authors: AS
authors: Pesquet
authors: Brigitte
authors: B
authors: Diologent
authors: Françoise
authors: F
authors: Callonec
authors: Anne
authors: A
authors: Hitzel
authors: Agathe
authors: A
authors: Edet-Sanson
authors: Jean François
authors: JF
authors: Ménard
authors: Fabrice
authors: F
authors: Jardin
authors: Hervé
authors: H
authors: Tilly
mesh_terms: D000970:Antineoplastic Agents / Q000008:administration & dosage*; D016477:Artifacts; D003287:Contrast Media; D005260:Female; D006801:Humans; D008223:Lymphoma / Q000000981:diagnostic imaging* / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D000970:Antineoplastic Agents; D003287:Contrast Media
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