Note 3 - Investments and Agreements (Details Textual) - USD ($)							1 Months Ended	3 Months Ended
		May 24, 2024	Apr. 11, 2024	Mar. 04, 2024	Jan. 17, 2024	Jan. 08, 2024	Dec. 31, 2023	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2024	Aug. 13, 2024	Dec. 14, 2023	Nov. 17, 2023
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Common stock, par value							$ 0.001			$ 0.001
Maximum amount of securities offer and sell												$ 200,000,000
January 2024 Pre-funded Warrants [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Warrants to purchase shares of common stock					3,008,694
Warrant exercise price per share					$ 3.69
Percentage of ownership considered for warrant exercise					4.99%
Maximum increase or decrease in ownership percentage					19.99%
2024 At-the-Market (ATM) Agreement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Agent commission fee as a percentage of gross sales price											3.00%
2024 At-the-Market (ATM) Agreement [Member] | Common Stock [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Maximum amount of securities offer and sell											$ 250,000,000
March 2024 Private Placement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Stock issued during period, shares				9,200,998
Stock purchase price per share				$ 9.5
Proceeds from issuance of common stock				$ 87,400,000
Placement agents cash fee, percentage				5.85%
Lantheus Investment Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Stock issued during period, shares						5,634,235
Investment agreement, contingent amount of gross proceeds raised						$ 50,000,000
Percent of outstanding shares						19.99%
Asset purchase price in cash						$ 8,000,000
Lantheus Investment Agreement | Common Stock [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Stock issued during period, shares	[1],[2]								5,634,235
Lantheus Investment Agreement | Option Agreement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percent of outstanding shares									19.90%
One-time payment received for rights granted						28,000,000
Repayment provisions						$ 0
Public Offering [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Stock issued during period, shares					13,207,521
Sale of stock, price per share					$ 3.7
Shares and warrants, price difference per share					$ 0.01
Gross proceeds from public offering					$ 69,000,000
Public Offering [Member] | Common Stock [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Stock issued during period, shares	[1],[2]								15,639,954
Over-Allotment Option [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Stock issued during period, shares					2,432,432
Registered Offering [Member] | Common Stock [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Stock issued during period, shares	[1],[2]							5,151,588
Oppenheimer & Co [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Stock issued during period, shares			3,535,246				123,882
Stock purchase price per share			$ 14				$ 3.03
Proceeds from issuance of common stock			$ 49,500,000				$ 400,000
Maximum amount of securities offer and sale													$ 50,000,000
BofA Securities, Inc [Member] | Underwriting Agreement [Member] | May 2024 Pre-funded Warrants [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Warrants to purchase shares of common stock		146,425
Warrant exercise price per share		$ 15.09
Percentage of ownership considered for warrant exercise		4.99%
Percentage of ownership considered for warrant exercise		9.99%
Maximum increase or decrease in ownership percentage		19.99%
BofA Securities, Inc [Member] | Registered Offering [Member] | Underwriting Agreement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Stock issued during period, shares		5,151,588
Sale of stock, price per share		$ 15.1
Shares and warrants, price difference per share		$ 0.01
Gross proceeds from public offering		$ 80,000,000

[1] Amounts for prior periods presented have been retroactively adjusted to reflect the 1-for-10 reverse stock split effected on June 14, 2024. See Note 1 for details.

[2] See Note 3, Investments and Agreements, for additional information.