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Note 3 - Investments and Agreements (Details Textual) - USD ($) |  |  |  |  | 3 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Feb. 02, 2026 | Feb. 18, 2025 | Jan. 08, 2025 | Jan. 08, 2024 | Mar. 31, 2026 | Mar. 31, 2025 | Dec. 31, 2025 | Aug. 13, 2024 | Mar. 31, 2024
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items] |  |  |  |  |  |  |  |  |  |
Common stock, par value |  |  |  |  |  | $ 0.001 |  | $ 0.001 |  |
Other income from a related party |  |  |  |  |  | $ 0 | $ 1,400,000 |  |  |
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% |
Stock issued during period, shares |  |  | 3,379,377 |  |  |  |  |  |  |
Stock purchase price per share |  |  | $ 3.02 |  |  |  |  |  |  |
Proceeds from issuance of common stock |  |  | $ 10,200,000 |  |  |  |  |  |  |
2024 At-the-Market (ATM) Agreement [Member] | Common Stock [Member] |  |  |  |  |  |  |  |  |  |
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items] |  |  |  |  |  |  |  |  |  |
Stock issued during period, shares | [1] |  |  |  |  |  | 3,379,377 |  |  |
Maximum amount of securities offer and sell |  |  |  |  |  |  |  |  | $ 250,000,000 |
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% |  |  |  |  |
Lantheus Investment Agreement | Option Agreement [Member] |  |  |  |  |  |  |  |  |  |
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items] |  |  |  |  |  |  |  |  |  |
Percent of outstanding shares |  |  |  |  |  |  |  |  |  | 19.90%
Other income from a related party |  |  |  | $ 1,400,000 |  |  |  |  |  |
One-time payment received for rights granted |  |  |  |  | $ 28,000,000 |  |  |  |  |
Repayment provisions |  |  |  |  | $ 0 |  |  |  |  |
Piper Sandler & Co. and UBS Securities LLC [Member] | Underwriting Agreement [Member] | Two Thousand Twenty Six Pre-funded Warrants [Member] |  |  |  |  |  |  |  |  |  |
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items] |  |  |  |  |  |  |  |  |  |
Warrants to purchase shares of common stock |  | 6,598,046 |  |  |  |  |  |  |  |
Warrant exercise price per share |  | $ 3.789 |  |  |  |  |  |  |  |
Shares and warrants, price difference per share |  | $ 0.001 |  |  |  |  |  |  |  |
Gross proceeds from public offering |  | $ 175,000,000 |  |  |  |  |  |  |  |
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% |  |  |  |  |  |  |  |
Piper Sandler & Co. and UBS Securities LLC [Member] | Two Thousand Twenty Six Offering [Member] | Underwriting Agreement [Member] |  |  |  |  |  |  |  |  |  |
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items] |  |  |  |  |  |  |  |  |  |
Stock issued during period, shares |  | 39,576,088 |  |  |  |  |  |  |  |
Sale of stock, price per share |  | $ 3.79 |  |  |  |  |  |  |  |
[1] | 1. See Note 3, Investments and Agreements, for additional information.

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