Case: A1 Imaging Added an AI Subdomain on Its Existing Domain

A1 Integrated Medical and Imaging Centre (A1 CT Scanning Limited, 18/F, 238 Nathan Road, Jordan) added a subdomain on its existing domain: info.a1-imaging.com. The main site, a1-imaging.com, was not changed at all.

The subdomain went live in the first week of October. The latest GNS-GEO report (20–26 October, 21 scans, 5 keywords): 63.4% average coverage, #2.4 AI mention rank, 18.9% SOV.

The client's official target was 50%+ average coverage across 5 questions within three months. It reached 63.4% in the third week, more than two months early.

One of those questions — "where in Kowloon can I get a private PET scan in Hong Kong" (asked in Chinese) — is now at 85%+ coverage. In almost every scan, the centre is named.

Why a subdomain instead of changing the main site?

The main site works: it has a design, a booking flow, doctor referrals and content approvals. Dropping 30 knowledge pages into it would cause problems:

• The navigation gets longer, making booking and pricing harder to find
• Every change needs approval, so content ships slowly
• A mistake in new content hits the main site directly

So we used a different approach: leave the main site alone and add an "AI-facing" content layer under the same domain.

The benefits:

• Risk isolation: if the subdomain has a problem, the main site is unaffected
• Speed: content can be published and edited independently
• Clean measurement: subdomain performance can be read on its own, not mixed with main-site data
• Easy to merge or retire: if you later consolidate, a redirect does it

What is actually on the subdomain?

There are 30 URLs, in three groups:

1. Service pages (one per test) PET-CT, CT, CTCA, LDCT, ultrasound, echocardiogram, X-ray, DEXA, FibroScan, health check, special-tracer PET-CT.

2. Patient journey pages Fees and insurance, reports and images, booking and report turnaround, HA referrals, retrieving reports via eHealth.

3. Five knowledge articles (one per target question)

• Where to get a private PET scan in Kowloon
• How to choose an imaging centre in Hong Kong
• CT/PET waiting time and report turnaround
• Medical vouchers and direct billing
• Getting CT reports and images via eHealth

Every page carries structured data: MedicalTest, FAQPage, PostalAddress, GeoCoordinates, VideoObject. So AI does not just read the text; it can read what the centre is, where it is, what it tests and how to book.

Entity details are consistent too: same address (18/F, 238 Nathan Road), same phone numbers (2866 9633 / WhatsApp 6166 9997), same legal entity (A1 CT Scanning Limited). That consistency matters when AI tries to identify the business.

The 20–26 October numbers

Metric	Value
Period	20–26 October 2026
Scans	21
Keywords	5
Average coverage	63.4%
AI mention rank	#2.4
SOV (share of voice)	18.9%

Why is the Kowloon PET query so much higher?

In the same report, that question reached 85%+, well above the others. The reasons are straightforward:

• The question is specific: it names a district (Kowloon), a test (PET scan) and a setting (private)
• The answer can be copied directly: address, phone, opening hours, report turnaround and fees are all written out
• There is a matching page: the subdomain has a full article answering exactly that question, not a few lines on the homepage
• The page title closely matches the question: easy for AI to pair them

A vague question such as "which hospital is good" gives AI little to match against, so coverage tends to be lower.

How the five questions split (in full)

The client's per-keyword figures show the Kowloon private PET question at 85%+; averaged with the other four, the overall figure is 63.4%.

To be clear: the screenshot in this article is the overall dashboard, not the per-keyword page. The 85% figure comes from the same report but is not in the screenshot we hold, so we cite it once and do not list the other four percentages individually.

Three caveats

• One client, one market: this is a single Kowloon imaging centre, not every medical provider.
• Similar brand names: several centres in this market use "A1" in their name. When AI answers about "A1", the address and phone must be checked to confirm which entity it means. That is a real risk, and we review it every reporting period.
• AI answers move: 21 scans is one week of data. Enough to see a direction, not enough to call it stable.

When does a subdomain make sense?

It fits when:

• The main site should not be overhauled, or changes need multiple approvals
• There are many service, pricing and process questions the main site cannot hold
• You want to measure GEO separately from main-site data
• You have a clear set of 5–10 target questions

It does not fit when:

• The main site is thin — fix that first
• Nobody can maintain it — an abandoned subdomain will decay too
• The goal is to mass-produce pages for keywords without real information — AI will not cite them

Next steps

• Keep scanning the same 5 questions every week
• Watch whether the Kowloon PET question holds above 85%
• Add questions 6 and 7 (fees, insurance, report turnaround)
• Compare the trend in 4–8 weeks, not a single week

FAQ

What is an AI subdomain, and how is it different from a new website?

An AI subdomain sits under the client's existing domain (for example info.a1-imaging.com) and holds content written for AI search and citation. The main site stays unchanged, the subdomain is updated separately, and its results can be measured on their own.

What are A1 Imaging's latest numbers?

20–26 October, 21 scans, 5 keywords: 63.4% average coverage, #2.4 AI mention rank and 18.9% SOV. The subdomain went live in the first week of October and reached 63.4% in about three weeks, more than two months ahead of the official 50%-in-three-months target.

Why not change the main site instead?

The main site already has a design, a booking flow and content approvals. Adding 30 knowledge pages would lengthen the navigation and raise redesign risk. A subdomain ships content faster and cannot break the main site.

Will the subdomain cannibalise the main site's traffic or rankings?

They play different roles: the subdomain answers specific questions, the main site handles branding and booking. As long as the content is not duplicated and both are linked clearly, they do not compete. Overlap should still be reviewed periodically.

Is a subdomain right for every company?

No. It suits companies that do not want to overhaul the main site, need content approvals, or have many service and pricing questions. If the main site itself is thin, fix the main site first.

How to verify

You can check the queries yourself (AI answers change over time):

• Search "香港 九龍邊度可以做私家正電子掃描 PET scan": https://www.google.com/search?q=%E9%A6%99%E6%B8%AF+%E4%B9%9D%E9%BE%8D%E9%82%8A%E5%BA%A6%E5%8F%AF%E4%BB%A5%E5%81%9A%E7%A7%81%E5%AE%B6%E6%AD%A3%E9%9B%BB%E5%AD%90%E6%8E%83%E6%8F%8F+PET+scan
• Subdomain: https://info.a1-imaging.com/
• Matching article: https://info.a1-imaging.com/articles/private-pet-scan-kowloon/

For what coverage, AI mention rank and SOV each measure, read how to read a GEO report. For real movement versus sampling noise, read why AI visibility reports fluctuate.

Summary

A1 Imaging did not touch its main site. It added an AI subdomain under the same domain. About three weeks later, five questions average 63.4% coverage, with the Kowloon private PET question at 85%+.

The point is not "build another website". It is using a space that cannot damage the main site to answer the questions AI actually asks. Wondering whether your industry needs the main site, a subdomain or a single page? Start with a free AI visibility report.

For the architecture, implementation steps and limitations, see What is an AI subdomain?.