The S&P/ASX 200 Index (ASX: XJO) has given back its early gains and is on course to end the week in the red. In afternoon trade, the benchmark is down 0.25% to 8,568.2 points.

Four ASX shares that are falling more than most today are listed below. Here's why they are dropping:

Imricor Medical Systems Inc (ASX: IMR)

The Imricor Medical Systems share price is down almost 4% to $1.27. This medical technology company's shares have come under pressure this week. This is despite news that it has received regulatory approval for its 3D MRI mapping system NorthStar in Europe. Investors appear more disappointed that its approval process in the United States has been delayed. The company's chair and CEO, Steve Wedan, remains positive. He said: "We continue to march towards commercialising Imricor's groundbreaking technology across the globe. In Europe the regulatory approvals are now in place, the commercial launch is fully underway, and the sales team are growing and progressing the pipeline."

Ora Banda Mining Ltd (ASX: OBM)

The Ora Banda share price is down almost 11% to 64.7 cents. This gold miner's shares are falling today following the release of a production update and its guidance for FY 2026. Ora Banda advised that gold produced for the quarter totalled 21.9k ounces. This was lower than expected due to the impacts of a slower than planned ramp up of the mill and mining delays at Riverina Underground. Looking ahead, management is guiding to production of 140k ounces to 155k ounces in FY 2026. Managing director, Luke Creagh, said: "Despite the previously announced challenges in the June quarter, the operations and OBM team are set up well going into FY26. This has set a strong platform as FY26 commences our next phase of growth, with production anticipated to increase over 60% to between 140 and 155 thousand ounces."

Ventia Services Group Ltd (ASX: VNT)

The Ventia Services share price is down over 2% to $5.10. This is despite the essential infrastructure services provider announcing an additional fibre upgrade works contract from the NBN. The contract is expected to deliver additional revenue of approximately $280 million to Ventia over the next 3.5 years. Though, it is worth noting that NBN also awarded a $360 million contract to rival Service Stream Ltd (ASX: SSM). It is possible the market was betting on Ventia winning both.

Vulcan Energy Resources Ltd (ASX: VUL)

The Vulcan Energy share price is down 10% to $3.59. This has been driven by the completion of a strategic institutional placement this morning. The lithium developer is raising approximately $53.6 million at a 15% discount of $3.40 per new share. Management notes that proceeds from the placement will be used to maintain and de-risk the execution of critical path scope for development of the Phase One Lionheart Project.