Note 5 - Stockholders' Equity (Details) - Options outstanding and exercisable, by exercise range (USD $)	3 Months Ended
	Jul. 31, 2013
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding at July 31, 2013	262,167
Options Outstanding, Weighted-Average Remaining Contractual Life	7 years 36 days
Options Outstanding, Weighted-Average Exercise Price (in Dollars per share)	$ 4.64
Options Exercisable at July 31, 2013	136,917
Options Exercisable, Weighted- Average Exercise Price (in Dollars per share)	$ 4.42
$3.01 - $4.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding at July 31, 2013	125,250
Options Outstanding, Weighted-Average Remaining Contractual Life	5 years 87 days
Options Outstanding, Weighted-Average Exercise Price (in Dollars per share)	$ 3.57
Options Exercisable at July 31, 2013	80,333
Options Exercisable, Weighted- Average Exercise Price (in Dollars per share)	$ 3.69
$4.01 - $5.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding at July 31, 2013	24,167
Options Outstanding, Weighted-Average Remaining Contractual Life	8 years 295 days
Options Outstanding, Weighted-Average Exercise Price (in Dollars per share)	$ 4.35
Options Exercisable at July 31, 2013	7,500
Options Exercisable, Weighted- Average Exercise Price (in Dollars per share)	$ 4.35
$5.01 - $6.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding at July 31, 2013	115,000
Options Outstanding, Weighted-Average Remaining Contractual Life	8 years 266 days
Options Outstanding, Weighted-Average Exercise Price (in Dollars per share)	$ 5.54
Options Exercisable at July 31, 2013	38,333
Options Exercisable, Weighted- Average Exercise Price (in Dollars per share)	$ 5.21
$7.01 - $8.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding at July 31, 2013	10,750
Options Outstanding, Weighted-Average Remaining Contractual Life	5 years 40 days
Options Outstanding, Weighted-Average Exercise Price (in Dollars per share)	$ 7.05
Options Exercisable at July 31, 2013	10,750
Options Exercisable, Weighted- Average Exercise Price (in Dollars per share)	$ 7.05