All components of inventory are valued at the lower of cost (first-in, first-out) or market.  We adjust inventory to market value when the net realizable value is lower than the carrying cost of the inventory.  Market value is determined based on estimated sales activity and margins.  We estimate a reserve for obsolete inventory based on management’s judgment of probable future commercial use, which is based on an analysis of current inventory levels, estimated future sales and production rates, and estimated shelf lives.

The components of inventory as of September 30, 2016 and December 31, 2015 are as follows:

During the nine month-period ended September 30, 2015, we wrote off $120,000 of materials related to production issues.  During the nine-month periods ended September 30, 2016 and 2015, the Company used $45,000 and $184,000, respectively, of Lymphoseek inventory for clinical study and product development purposes.