Kenneth Nichols PhD, Presenter: Royalties, Syntermed, Inc

Maria Bernadette Tomas MD, Abstract Co-Author: Nothing to Disclose

Fritzgerald Leveque, Abstract Co-Author: Nothing to Disclose

Christopher J. Palestro MD, Abstract Co-Author: Nothing to Disclose

Publications differ on the best means of acquiring & processing 123I-MIBG data, including use of low energy high resolution (LEHR) or medium energy (MED) collimators & iterative reconstruction (IR) or filtered backprojection (FB) of SPECT data. Clinical data acquisitions often are lengthy, making repeated acquisitions with different collimators impractical, so we designed phantom studies to evaluate the optimal means of performing these studies. 

11 SPECT & 9 planar simulations were acquired. 0.5-3.0 mCi 123I was added to background of a 6,200-mL water bath containing a 500-mL saline bag simulating liver, & two 1-cc volumes simulating an intense central lesion & a 2nd less intense peripheral lesion. True lesion contrast ranged from 0-85%. Activities & acquisition times were adjusted to simulate typical clinical data. Commercially available collimators were used. Quantified lesion image contrast was assessed by tabulating counts in manually drawn regions of interest encompassing simulated lesions, liver & background volumes on planar & transaxial images. An experienced nuclear physician blinded to phantom configurations used 5-point grading scales for confidence of visual lesion detection & image quality.

Total counts were significantly higher for LEHR than MED planar (1.2±0.8 versus 0.8±0.5x106 counts, p = 0.004) & SPECT acquisitions (3.3±1.6 versus 2.3±1.2 x106 counts, p < 0.0001). Lesion contrast was similar for LEHR & MED planar images (16±3% versus 15±4%, p = 0.45) but different among SPECT methods (ANOVA p < 0.0001). All methods underestimated true simulated lesion contrast of 67±34% (ANOVA p < 0.001). LEHR IR SPECT contrast was highest & MED FB SPECT contrast lowest (42±17% versus 17±10%, p < 0.0001). Confidence of visual lesion detection was similar for planar LEHR & MED phantoms (2.6±1.7 versus 2.3±1.7, p = 0.06), as was image quality (2.0±0.9 versus 1.9±0.6, p = 0.35). Confidence differences were significant for SPECT detection of the 2nd lesion (ANOVA p = 0.001), with LEHR IR highest & MED FB lowest (3.7±0.7 versus 2.3±1.5, p = 0.001). Sensitivity was higher for LEHR IR than MED FB, but not significantly (94.4% versus 85.0%, p = 0.21). 

The combination of LEHR IR SPECT produced higher contrast, confidence & image quality than MED FB SPECT.

123I-MIBG imaging should be performed with LEHR collimators, with SPECT iteratively reconstructed to maximize image quality & interpretation confidence.

Nichols, K, Tomas, M, Leveque, F, Palestro, C, Phantom Simulations to Optimize I-123-MIBG Protocols.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14007326.html