Whole-body imaging of oncologic patients using high-resolution 16-channel PET-CT: Evaluation of an optimized iv-contrast enhanced MDCT protocol in 205 patients

Abstract

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Objectives: Whole-body PET-CT using a 16-channel spiral CT component requires adaptation of standard imaging protocols used for stand-alone multi-detector row CT (MDCT) examinations. The purpose of this study was to evaluate a modified iv-contrast enhanced whole-body MDCT imaging protocol for high-resolution PET-CT.

Methods: 205 patients with different malignant tumors were enrolled into a prospective study. All patients underwent whole-body 18 F-FDG PET-CT on a hybrid scanner equipped with a 16-slice CT component (Biograph Sensation 16, Siemens). Contrast enhanced MDCT (16x1.5 mm, 120 kVp, 160 mAseff, Care Dose) was also used for attenuation correction of the PET scan. A bolus of 120 ml of non-ionic CM (300 mg/mL iodine)@ 3 ml/sec via an antecubital vein (standardized scan delay 70 sec; 50 ml saline chaser bolus) was administered. PET was acquired immediately after the CT scan (18F-FDG@4 MBq/kg bw). MDCT data sets were analyzed by two radiologists determining scan range and duration, occurrence of CM-induced artifacts, and mean CT densities [HU] of jugular (jv) and subclavian (scv), superior (vcs) and inferior (vci) caval, portal (pv), and bilateral external iliac (eiv) veins, bilateral pulmonary (ap) and external iliac arteries, descending thoracic (dta) and abdominal (aa) aorta, all cardiac chambers, as well as right (rl) and left liver (ll) lobe, spleen, adrenal glands and kidneys using a ROI-method (e-soft® workstation, Siemens).

Results: All whole-body PET-CT examinations revealed no contrast media-related image artifacts. Mean scan duration was 15.3±2.8 sec. Homogeneous contrast enhancement was found in the mediastinal veins (right vs. left jv 171±34 vs. 171±35 HU, right vs. left scv 127±50/127±41 HU; svc 153±36 HU) and arteries (pa right/left 145±26/151±26 HU, dta 143±27 HU), as well as the cardiac chambers (e.g. ra 149±25 HU). Abdominal vessels (e.g. ivc 138±24, pv 159±25, aa 149±25 HU) and parenchymal organs (rl 106±21, ll 109±20, spleen 113±17, rk 166±29, lk 166±27 HU) revealed sufficient and homogenous contrast enhancement in all cases. Highest observed density was 232 HU in right scv, 237 HU in left scv and 217 HU in vcs.

Conclusions: The chosen whole-body PET-CT protocol allowed for craniocaudal MDCT scanning with excellent parenchymal and vessel contrast and simultaneously avoided high-contrast artifacts in mediastinal veins.