Reza Forghani MD, PhD, Presenter: Nothing to Disclose

Michael Roskies MD, Abstract Co-Author: Nothing to Disclose

Michael Hier MD, Abstract Co-Author: Nothing to Disclose

Alex Mlynarek, Abstract Co-Author: Nothing to Disclose

Mark Levental MD, Abstract Co-Author: Nothing to Disclose

Accurate pre-operative localization of parathyroid adenomas (PAs) is essential for successful minimally invasive surgery, and is typically based on two concordant studies. 4-dimensional MDCT is increasingly used for localization of PAs. There are also isolated reports of dual-energy CT (DECT) for localization of PAs but no systematic evaluation of this technique. DECT has the potential to increase accuracy of PTA detection by enabling more accurate iodine content evaluation and to eliminate the need for an unenhanced scan, reducing radiation exposure. In this study, we evaluated the utility of multiphasic DECT for PA localization in a group of patients having discrepant or unidentified PAs.

20 patients with primary hyperparathyroidism having either discrepant or unlocalized PAs underwent a multiphasic DECT in a 64-slice scanner (GE Discovery CT750HD). Scans were obtained at 25, 55, and 85 sec after injection of 80 mL of iopamidol at 3.5 mL/sec. DECT scans were reconstructed as 70 keV monochromatic images and source images transferred to a dedicated workstation for reconstruction of virtual monochromatic images. The scans were prospectively reviewed by 2 attending head and neck radiologists. The final results were compared with localization during minimally invasive surgery and histopathologic confirmation.

Out of 20 patients, 11 had negative and 9 discordant standard imaging. DECT identified PAs in 8 of 11 and 7 of 9 patients, respectively. Of the 15 PAs, 7 were prospectively identified as PA candidates but characterized as atypical, based on absence of rapid arterial phase enhancement and early washout and/or presence of internal low attenuation areas. 7 patients have so far undergone surgery, and DECT correctly localized the PA in 6 of 7 patients, for a total of 7 PAs (one patient had bilateral PAs).

3-phase DECT without an unenhanced scan can accurately localize PAs in a significant proportion of unlocalized or discrepant cases. Although perfusion characteristics are important, a high proportion of PAs lacked typical perfusion characteristics in this patient population but were identifiable based on other features.

Multiphasic DECT without an unenhanced scan can accurately localize a significant number of PAs not localized by conventional imaging enabling successful minimally invasive surgery with reduced surgical exploration and associated patient morbidity.

Forghani, R, Roskies, M, Hier, M, Mlynarek, A, Levental, M, Dual-energy Multiphasic CT Scan for Localization of Discrepant or Unlocalized Parathyroid Adenomas.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14016925.html