# Using Radioactive Antibodies to Find Tumors Inside the Body

> A 1973 method for finding cancer tumors by injecting patients with radioactive antibodies that attach to tumor-specific proteins, allowing doctors to scan for their location.

- **Patent:** US 3927193
- **Original title:** Localization of tumors by radiolabelled antibodies
- **Owner:** F Hoffmann La Roche AG
- **Granted:** 1975
- **Status:** Public domain (expired)
- **Times cited:** 66
- **Field:** biotech, pharmaceutical

## What it does

The patent describes a diagnostic technique where a patient is injected with an antibody that has been tagged with a radioactive isotope. This antibody is specifically designed to bind to carcinoembryonic antigen, a protein often found in high levels near certain tumors. Once the antibody attaches to the tumor, the radioactive tag emits gamma rays. A photoscanning device then detects these rays to map exactly where the tumor is located within the body.

## What it does NOT cover

- Does not cover the use of antibodies for treating or killing tumor cells.
- Does not cover scanning methods that use non-radioactive markers like fluorescent dyes.
- Does not cover antibodies that target proteins other than carcinoembryonic antigen.
- Does not cover isotopes with a half-life significantly longer than 8 days.

## The clever bit

The invention cleverly repurposed the immune system's natural ability to recognize specific proteins to act as a delivery vehicle for radioactive tracers, effectively turning the tumor itself into a beacon for medical scanners.

## Real-world examples

1. Radioimmunoscintigraphy
2. Early cancer diagnostic imaging
3. Targeted diagnostic nuclear medicine

## Why it matters

This patent represents an early milestone in the field of radioimmunodetection. It helped establish the concept of using the body's immune system components as 'homing devices' to deliver diagnostic signals directly to diseased tissue, a principle that eventually evolved into modern PET and SPECT imaging techniques.

## Frequently asked questions

### What does Using Radioactive Antibodies to Find Tumors Inside the Body cover?

A 1973 method for finding cancer tumors by injecting patients with radioactive antibodies that attach to tumor-specific proteins, allowing doctors to scan for their location.

### Who owns patent US 3927193?

F Hoffmann La Roche AG owns this patent, granted in 1975.

### When does this patent expire?

This patent has expired and is now in the public domain — anyone can use the invention freely.

### What is patent US 3927193 cited by?

This patent has been cited by 66 later patents that build on its ideas.

### What problem does this patent solve?

This patent represents an early milestone in the field of radioimmunodetection. It helped establish the concept of using the body's immune system components as 'homing devices' to deliver diagnostic signals directly to diseased tissue, a principle that eventually evolved into modern PET and SPECT imaging techniques.

### What does this patent NOT cover?

Does not cover the use of antibodies for treating or killing tumor cells.

**Full plain-English explainer:** https://patentbrief.org/patent/us/3927193/ivermectin

**Original patent:** https://patents.google.com/patent/US3927193

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_Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._