Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Mar. 31, 2019	Jun. 30, 2018
Current assets:
Cash and cash equivalents	$ 4,059	$ 2,600
Short-term investments (Note 3)	2,333	825
Accounts receivable, net	1,116	1,192
Inventory	533	494
Prepaid expenses and other current assets	390	335
Total current assets	8,431	5,446
Property and equipment, net	1,564	1,311
Restricted cash	181	181
Inventory, non-current	243	319
Other assets, net of accumulated amortization	160	198
Total assets	10,579	7,455
Current liabilities:
Accounts payable and accrued expenses	1,001	1,391
Accrued protocol expense	117	77
Accrued radioactive waste disposal	65	37
Accrued payroll and related taxes	38	155
Accrued vacation	134	175
Total current liabilities	1,355	1,835
Long-term liabilities:
Asset retirement obligation	613	590
Total liabilities	1,968	2,425
Commitments and contingencies (Note 8)
Shareholders' equity:
Preferred stock
Common stock, $.001 par value; 200,000,000 shares authorized; 67,338,047 and 56,331,147 shares issued and outstanding	67	56
Additional paid-in capital	91,941	84,322
Accumulated deficit	(83,397)	(79,348)
Total shareholders' equity	8,611	5,030
Total liabilities and shareholders' equity	10,579	7,455
Series B Preferred Stock [Member]
Shareholders' equity:
Preferred stock