Daily cone-beam CT (CBCT) imaging, built directly into the Akesis Gemini 360, lets the treatment team see the exact position and shape of a patient's anatomy immediately before every session. Because organs and tumors shift slightly day to day from bladder filling, bowel gas, or weight changes, this onboard imaging allows the radiation plan to be verified — or adjusted — before each dose is delivered, rather than relying on a single scan taken weeks earlier.
Why Does Radiation Therapy Need Imaging Every Day, Not Just at Planning?
A traditional radiotherapy plan is built from one CT scan taken days or weeks before treatment starts. Between that planning scan and each daily session, soft tissue can move by a centimeter or more. Without a way to check that positioning in real time, the treatment team has to add extra margin around the target to make sure the tumor stays covered — which also means more healthy tissue sits inside the radiation field. Onboard CBCT imaging removes much of that guesswork by capturing a fresh 3D image of the anatomy right on the treatment table, immediately before beam delivery.
How Does the Akesis Gemini 360's Imaging Actually Work?
The Gemini 360 pairs onboard CBCT imaging with the LINAC itself, so the imaging and treatment happen on the same machine, in the same position, without moving the patient between scanning and treatment. The team compares the day's CBCT image to the original planning scan, checks that the target and nearby organs line up with the plan, and makes positioning corrections before treatment begins. When anatomy has shifted enough to matter, the plan can be re-optimized that same session — the basis of the adaptive radiotherapy approach used at 5D Cancer Services. More detail on how each session flows from imaging to delivery is on the how it works page.
What Does the Research Say About Image-Guided Radiotherapy?
Image guidance is not a new concept in radiation oncology — it's been studied for over a decade, primarily in prostate cancer treatment, where daily organ movement is well documented. A widely cited study published in the *International Journal of Radiation Oncology, Biology, Physics* (Zelefsky et al.) found that patients treated with daily image-guided setup verification experienced meaningfully lower rates of gastrointestinal and genitourinary toxicity compared to patients treated without it, largely because tighter, more accurate targeting allowed for smaller treatment margins. That principle — image first, then treat — is what onboard CBCT imaging is designed to deliver on every visit, not just at the start of a course of care.
Planning-Scan-Only vs. Daily Onboard Imaging
| Factor | Planning scan only | Daily onboard CBCT imaging |
|---|---|---|
| Anatomy check frequency | Once, before treatment starts | Immediately before every session |
| Accounts for daily organ movement | No | Yes |
| Typical margin around target | Larger, to compensate for uncertainty | Can be smaller with verified positioning |
| Ability to adjust plan same-day | Not typically | Yes, when imaging shows a meaningful shift |
Which Conditions Benefit Most From Daily Imaging?
Organs that move or fill and empty naturally benefit the most from onboard imaging verification. This is especially relevant for prostate and gynecologic malignancies, where bladder and rectal filling can shift the target from day to day. Full imaging capabilities, including how CBCT integrates with dose painting and multi-target therapy, are outlined on the imaging page.
What Should Patients in Southern Utah Take Away From This?
Imaging isn't a separate step bolted onto treatment — at 5D Cancer Services in St. George, it happens on the same machine, in the same visit, as part of every session. For patients weighing radiation therapy options, understanding that the plan is checked and can be adjusted daily — not just set once at the start — is a meaningful part of what adaptive radiotherapy is built to offer. Patients can review frequently asked questions or contact the St. George office to ask how imaging fits into their specific treatment plan.