TDF Calc vs Spine Physics
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
TDF Calc
This app calculates the biologically effective dose (BED) for radiation therapy fractionation regimens. It allows for comparisons of different treatment schedules and helps determine dose per fraction based on desired treatment duration.
- Linear-quadratic (LQ) method implementation
- Biologically effective dose (BED) calculation
- External beam radiation therapy (EBRT) fractionation
- Low dose rate (LDR) brachytherapy
- Permanent implant brachytherapy
- Dose per fraction calculation
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TDFCalc is an application which implements the linear-quadratic (LQ) method for comparing the biologically effective dose (BED) of external beam radiation therapy (EBRT) fractionation regimens as well as low dose rate (LDR) and permanent implant brachytherapy treatments. It calculates BED for a given alpha/beta ratio as a function of the dose per fraction and number of fractions for EBRT, and initial dose rate for brachytherapy. For a predetermined BED, the app solves the quadratic equation to calculate dose per fraction as a function of the number of fractions desired. This enables quick comparison of modified fractionation regimens (e.g. hypofractionation or compensating for missing treatment fractions) vs a conventional and/or originally intended regimen.
Spine Physics
This app visualizes how obesity affects the body, using a teeter-totter analogy for the spine to explain the importance of maintaining a healthy abdominal girth. It serves as an educational tool for patients, drawing on a surgeon's perspective.
- Obesity impact visualization
- Spine teeter-totter analogy
- Abdominal girth importance
- Surgeon's educational tool
- General health information
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Spine Physics visualizes the effects of obesity on the body. The analogy of the spine to a teeter totter shows the importance of keeping the abdominal girth small and light. As a surgeon, I draw this all the time for my patients to educate them. ***Disclaimer*** No advice: This app (“App)” provides only information, is not medical or treatment advice and may not be treated as such by the user. As such, this App may not be relied upon for the purposes of medical diagnosis or as a recommendation for medical care or treatment. The information on this App is not a substitute for professional medical advice, diagnosis or treatment. All content, including text, graphics, images and information, contained on or available through this App is for general information purposes only Professional Medical Advice and Assistance: You are strongly encouraged to confirm any information obtained from or through this App with your physician or another professional healthcare provider and to review all information regarding any medical condition or treatment with your physician or other a professional healthcare provider. No Reliance: YOU MUST NEVER RELY ON ANY INFORMATION OBTAINED USING THIS APP FOR ANY DIAGNOSIS OR RECOMMENDATION FOR MEDICAL TREATMENT. YOU MUST NEVER RELY ON THE INFORMATION RECEIVED FROM THIS APP AS ALTERNATIVE TO MEDICAL ADVICE FROM YOUR PHYSICIAN OR OTHER PROFESSIONAL HEALTHCARE PROVIDER. YOU MUST NEVER DISREGARD PROFESSIONAL MEDICAL ADVICE OR DELAY SEEKING MEDICAL TREATMENT AS RESULT OF ANY INFORMATION YOU HAVE SEEN ON OR ACCESSED THROUGH THIS APP. IF YOU HAVE ANY SPECIFIC QUESTIONS ABOUT ANY MEDICAL MATTER YOU SHOULD CONSULT YOUR PHYSICIAN OR OTHER PROFESSIONAL HEALTHCARE PROVIDER. IF YOU THINK YOU MAY BE SUFFERING FROM ANY MEDICAL CONDITION YOU SHOULD SEEK IMMEDIATE MEDICAL ATTENTION. No Warranty: The information provided by this App is provided “as is” without any representations or warranties, express or implied. This App makes no representations or warranties in relation to the medical or other information in this App.
Screenshots
Verdict
The clearest difference is update cadence: Spine Physics at every 2 days against TDF Calc's every 67 months. TDF Calc's advantage is iOS requirement (13.2 vs 15.0). On price, rating, ratings volume and ads there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. Neither carries in-app purchases, so what you see is what you pay.
On the App Store both sit at effectively the same score — 5.0 for TDF Calc against 5.0 for Spine Physics. Both are backed by a comparable volume of ratings — 1 and 1 respectively.
TDF Calc ships an update every 67 months, Spine Physics every 2 days. The most recent releases landed on June 5, 2026 and September 10, 2026 respectively.
| Parameter | TDF Calc | Spine Physics |
|---|---|---|
| Price | Free | Free |
| Rating | 5.0 (1 ratings) | 5.0 (1 ratings) |
| Positive reviews | 100.0% of reviews | — |
| Number of ratings | 1 | 1 |
| Update frequency | Every 67 months | Every 2 days — better |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Free | Free |
| Devices | iPhone, iPod | iPhone, iPod |
| Requires iOS | 13.2 — better | 15.0 |
| Further details — not scored | ||
| Size | 2 MB | 10 MB |
| Age rating | 4+ | 12+ |
| Developer | Eye Physics | Jonathan Nakhla |
Customer experience
TDF Calc
Spine Physics
In-app purchases
TDF Calc
No in-app purchases
Spine Physics
No in-app purchases









