Jacob H. Miller, Presenter: Nothing to Disclose

Theodore T. Miller MD, Abstract Co-Author: Nothing to Disclose

Ronald Steven Adler MD, PhD, Abstract Co-Author: Nothing to Disclose

The purpose is to determine whether radiography, CT scanning, MR imaging, or sonography is the most sensitive for detecting calcium hydroxyapatite in a soft tissue phantom.

Powdered calcium hydroxyapatite (Spectrum Co.) was mixed with water to form slurry concentrations of 60%, 40%, 20%, 10%, 5%, 1%, .5%, .25%, .1%, and .05%. The slurries were injected into two different gelatin carriers which had been poured into two ice cube trays: one pure gelatin (Knox, Inc), and the other gelatin with Metamucil.  The two gelatin ice cube tray phantoms underwent radiography using 46 KVp and 1.25 mAs. CT scan was performed on a 16 detector unit (Phillips, Inc.) using 1mm thick slices at 1mm intervals. MR imaging was performed on a 1.5 T unit (GE, Inc.) using an 8 channel coil; gradient echo and fast spin echo proton density sequences were performed using 3 mm thick images without an inter slice gap. Sonography was performed on an IU 22 unit (Phillips, Inc.) using a linear (“hockey stick”) 15-7 MHz transducer. Three pairs of musculoskeletal radiologists with subspecialty expertise in each of the modalities independently reviewed the images on a PACS station, and identified the lowest concentration gelatin cube in which calcium was visible.  

The radiologists who reviewed the radiographs and CT images and the radiologists who reviewed the MR images were able to identify calcium down to 5% in both pure gelatin and gelatin/Metamucil. The radiologists who reviewed the sonographic images were able to identify calcium in the gelatin down to .1% and in the gelatin/Metamucil down to .5%. Posterior acoustic shadowing of the calcium was present in the 60%, 40%, and 20% concentrations, and was absent in concentrations of 10% or lower.

Sonography is the most sensitive modality for detecting calcium hydroxyapatite. Posterior acoustic shadowing occurrs at concentrations of 20% and higher.

Sonography is the most sensitive modality for detecting calcific tendonitis. Acoustic shadowing is a function of calcium concentration, not the calcium state (eg, soft or hard).

Miller, J, Miller, T, Adler, R, Sensitivity of Imaging Modalities for Detecting Calcium Hydroxyapatite in a Soft Tissue Phantom.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8007524.html