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Background, Basis of Presentation and Liquidity (Details Narrative) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 6 Months Ended 8 Months Ended
Jan. 10, 2022
Dec. 23, 2020
Dec. 04, 2020
Sep. 18, 2020
Apr. 08, 2019
Oct. 31, 2022
Oct. 31, 2021
Oct. 31, 2022
Oct. 31, 2021
Jul. 31, 2021
Apr. 30, 2022
Nov. 20, 2020
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                        
Net loss           $ 4,844 $ 5,171 $ 10,696 $ 8,250      
Cash in operations               11,001 $ 10,375      
Accumulated deficit           264,466   264,466     $ 253,770  
Cash           10,300   10,300        
Short-term investments           $ 35,900   $ 35,900        
Number of common stock shares sold         1,542,000              
2020 ATM Facility [Member]                        
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                        
Proceeds from initial public offering $ 25,000                      
Proceeds from issuance or sale of equity, net of issuance costs $ 75,000                      
2020 ATM Facility [Member] | Alliance Global Partners [Member]                        
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                        
Offering amount capacity                       $ 100,000
Proceeds from initial public offering     $ 50,000                  
Number of common stock shares sold                   17,179,883    
Proceeds from issuance or sale of equity, net of issuance costs                   $ 50,000    
Combined purchase price per share                   $ 2.91    
Payment of sales commission                   $ 1,600    
Stock Purchase Agreement [Member] | Aspire Capital Fund, LLC [Member]                        
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]                        
Number of common stock shares sold               3,722,251        
Proceeds from issuance or sale of equity, net of issuance costs               $ 11,800        
Combined purchase price per share           $ 3.17   $ 3.17        
Aggregate purchase of common stock.       $ 12,500                
Percentage of outstanding common stock   19.99%   19.99%                
Shares can be issued based upon outstanding percentage       3,722,251                
Additional sales of common stock shares sold   9,864,706                    
Proceeds from issuance or sale of equity, net of issuance costs               $ 700