What Maryland's law actually requires
Maryland has become the first U.S. state to require mammography providers to tell patients when they have breast arterial calcification, or BAC — calcium buildup in the walls of breast arteries that shows up as a routine, incidental finding on a mammogram taken for cancer screening. House Bill 1364 was introduced in February 2026, passed both chambers of the Maryland legislature unanimously, and took effect October 1, 2026.
The mechanism mirrors the FDA's existing breast-density notification requirement: providers must tell patients, in their results letter, when BAC is present, describe it as a common finding that may indicate increased cardiovascular disease risk, and encourage them to discuss it with a physician. The law does not mandate a specific follow-up test or treatment — it mandates that the information reaches the patient at all. As Maryland House Speaker Joseline Pena-Melnyk put it, the bill exists to "provide that needed uniformity" to a finding that, until now, different radiologists and practices have handled inconsistently.
That inconsistency is the real story. BAC has been visible on mammograms for decades. What changed is that lawmakers decided noticing it isn't good enough — it has to be captured and communicated every time.
Why BAC is a real cardiac signal, not a footnote
BAC is a form of medial arterial calcification distinct from the calcifications radiologists look for as signs of breast cancer, and a growing body of evidence ties it to cardiovascular outcomes. A multicenter retrospective cohort study led by Nitesh Nerlekar and colleagues, published in JACC: Cardiovascular Imaging in 2026, followed 21,514 women aged 40 and older with no known cardiovascular disease across sites in the United States and Australia. BAC was identified in 22.7% of women overall, rising sharply with age — from about 8% in women under 50 to 61% in women over 70.
Over a mean follow-up of 4.7 years, the cohort accrued 828 major adverse cardiovascular events. Each 10-percentile increase in age-adjusted BAC was associated with a 17% relative increase in that risk (adjusted hazard ratio 1.17), independent of conventional cardiovascular risk factors. Adding BAC to a standard risk model improved its discriminative accuracy (the C-statistic rose from 0.67 to 0.71), with the biggest benefit in reclassifying women who otherwise looked low- or intermediate-risk.
In other words: a scan that nearly a quarter of women already get for cancer screening is quietly carrying a second, measurable cardiac risk signal — one most of those women have never been told about.
The gap the law is trying to close
Radiologists are not unaware of BAC. The problem is that awareness has never reliably translated into consistent reporting. A survey of 598 American College of Radiology members, published in Academic Radiology, found that 87% include BAC in at least some mammogram reports — but only 41% report it "always" or "most of the time." A separate survey of 378 radiologists by the European Society of Breast Imaging, published in European Radiology, found 80.7% aware of the BAC–cardiovascular link, yet only 61.9% routinely documented it in the report and just 45.5% ever told the patient directly.
That 40-point-plus gap between "I know this matters" and "I write it down every time" is exactly what a legal mandate is built to close — and exactly why some radiologists pushed back on Maryland's bill. Critics quoted in trade press raised a fair concern: there is still no single standardized method for quantifying BAC and no agreed clinical pathway for what happens after a patient is told, which risks inconsistent, anxiety-inducing follow-up even after notification becomes mandatory.
Both things can be true. The mandate forces capture; it doesn't, by itself, standardize the method. That second half of the problem — making a judgment call reproducible across every radiologist, every shift, every study — is a workflow and tooling question, not a legislative one.
The same pattern, a different modality
Mammography is not the only modality where a clinically significant signal is sitting in images acquired for an unrelated reason. Chest and abdominal CT carry the same structural problem: an incidental lung nodule's malignancy risk, an incidental renal mass that needs a defined follow-up pathway, or vertebral bone density visible on a routine chest CT are all opportunistic data that only becomes clinically useful if the report captures it consistently.
| Incidental finding | Modality | What it flags | 2026 status |
|---|---|---|---|
| Breast arterial calcification | Mammography | Cardiovascular event risk (MACE) | Legally mandated patient notification (Maryland, Oct 2026) |
| Lung nodule | Chest CT | Lung cancer risk | Best-practice risk scoring; no capture mandate |
| Renal mass | Abdominal CT | Malignancy risk, follow-up imaging need | Best-practice follow-up guidelines; no capture mandate |
| Vertebral bone density | Chest/abdominal CT | Osteoporosis and fracture risk | Opportunistic-screening research; no capture mandate |
Breast arterial calcification is simply the first of these to cross from "something a careful radiologist might mention" into "something the law says must be in the report." The underlying argument for the rest — that opportunistic findings are only as good as the report that captures them — doesn't need a statute to be true. Maryland just made it official for one finding, on one modality.
Where structured AI drafting fits
Notably, the Nerlekar study didn't rely on radiologists eyeballing each mammogram for calcification — BAC was quantified using an AI detection model, applied the same way to every scan in the cohort. That's the operational lesson behind mandates like Maryland's: a reporting requirement that depends on individual attentiveness — "did this radiologist happen to notice and write it down this time" — will keep producing the 40-point awareness-to-reporting gap the surveys above describe, no matter how many statutes get passed. A structured reporting process that checks for the same defined set of findings on every single study, every time, is what makes a mandate like this operationally durable rather than aspirational. That is the premise xAID's foundation-model approach to CT reporting is built on: drafts are structured to flag defined incidental findings consistently, with in-house radiologist review on every preliminary before the report reaches the client's reading radiologist ready-to-sign.
Frequently asked questions
What does Maryland's new mammography law require?
Maryland's HB 1364, effective October 1, 2026, requires mammography providers to notify patients in their results letter when breast arterial calcification (BAC) is detected, describing it as a common finding that may indicate increased cardiovascular disease risk and encouraging patients to discuss it with a physician. Maryland is the first U.S. state with this requirement. The law does not mandate any specific additional test or treatment.
What is breast arterial calcification and why does it matter for heart disease risk?
Breast arterial calcification (BAC) is calcium buildup in the walls of breast arteries that is visible as an incidental finding on routine mammograms. A 2026 multicenter study of 21,514 women published in JACC: Cardiovascular Imaging found BAC in 22.7% of women screened, rising from 8% under age 50 to 61% over age 70, and found that each 10-percentile increase in age-adjusted BAC was associated with a 17% relative increase in major adverse cardiovascular events, independent of conventional risk factors.
Why wasn't BAC already being reported consistently before this law?
Surveys show a gap between awareness and consistent reporting. An American College of Radiology survey of 598 radiologists found 87% include BAC in at least some mammogram reports, but only 41% report it always or most of the time. A European Society of Breast Imaging survey of 378 radiologists found 80.7% were aware BAC signals cardiovascular risk, yet only 61.9% routinely documented it and just 45.5% told patients directly.
What does the Maryland law suggest about the future of incidental findings in radiology?
It signals that opportunistic capture of clinically significant incidental findings — a marker visible on a scan already being done for another reason — is moving from a best-practice discussion to a legal expectation. The same pattern applies to CT: incidental lung nodules, renal masses, and vertebral bone density only become actionable if the structured report captures them on every study, not only when a radiologist happens to notice.
Source: Radiology Business; bill details via AuntMinnie and Radiology Business; clinical data from Nerlekar et al., JACC: Cardiovascular Imaging (2026), as summarized by Diagnostic Imaging; reporting-gap surveys from Brown et al., Academic Radiology (2022), and Trimboli et al., European Radiology (2021). Figures are rounded as reported.