Douglas Arthur Kieper BS, Presenter: Vice President, Dilon Technologies LLC

Marcela Bohm-Velez MD, Abstract Co-Author: Nothing to Disclose

The purpose of this prospective trial was to evaluate the clinical factors impacting tracer delivery and breast tissue distribution in patients undergoing MBI examinations.

Patients scheduled for MBI were imaged using a Dilon 6800 Gamma Camera following the SNM Practice Guidelines for Breast Scintigraphy (2010). Patients were randomized into three groups to receive a 185, 370, or 555 MBq dose. A “straight stick” single-syringe injection technique was used and the activity in each syringe was measured before and after injection. Imaging was conducted within 10 minutes of injection and an image photon density (PD) in counts/cm2/MBq was calculated for each image. A bilateral PD value was calculated for each patient and then plotted against dose delivered, patient weight and age along with breast size and tissue density. Delayed imaging was conducted to determine tracer washout.

44 patients were enrolled in the study. On average, only 76% of the patient dose was delivered, 24% remaining in the syringe after injection. There was a linear relationship between the injected dose and PD for each patient, but a broad range of PD of within the population (+/- 36%) with a strong correlation between patient weight and PD. Correlations between PD and patient age, breast tissue density and breast size were poor. The effective half-life of MIBI in the breast tissue was calculated to be 134 minutes.

These data suggest that there are at least three critical areas that need to be addressed by low-dose protocols. First, the injection technique needs to be improved and validated by checking the post-injection syringe for undelivered dose. Second, the use of a patient weight adjusted dose model may be useful. Third, the patient throughput should be designed to minimize injection-to-imaging time. Patient factors such as age, breast size and tissue density do not significantly influence tracer uptake.

Low-dose MBI is a recent advancement in breast imaging needing robust clinical protocols. This work investigates patient and clinical variables that need to be addressed in their development.

Kieper, D, Bohm-Velez, M, Low-dose Molecular Breast Imaging: Factors to Consider When Establishing a Clinical Protocol.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13012353.html