Note 4 - Inventory (Tables)
 9 Months Ended
Jan. 31, 2014
Inventory Disclosure [Abstract]  
Schedule of Inventory, Current [Table Text Block]
   
January 31, 2014
   
April 30, 2013
 
Raw material
  $ 3,838     $ 3,077  
Work-in-process
    1,612       1,409  
Finished goods
    2,992       2,434  
      8,442       6,920  
Reserves
    (602 )     (682 )
    $ 7,840     $ 6,238