The Origin of Nuclear Medicine: How Measuring Blood Flow Started Everything

1. The Problem: Measuring Flow Without “Breaking” Physiology

In 1924, a young student assistant named Hermann Blumgart stood in Walter Cannon’s physiology laboratory at Harvard, grappling with a fundamental silence in medical science. While it was understood that tissue viability depended entirely on the heart’s output and the velocity of blood, no one actually knew how fast human blood moved. To the medical establishment, the circulatory system was a closed loop; measuring its speed seemed to require a degree of “violence to the system” that was unacceptable in a clinical setting.

Historically, the only widely cited data point available was over two centuries old, derived from a method that would have horrified Blumgart’s colleagues at Boston City Hospital.

“Stephan Hales in 1717 had computed blood velocity in the aorta of a horse to be 1734.9 ft/hour, but with a method (aortic excision) frowned upon for Harvard’s patients.”

Blumgart spent a year in England searching for a better way, only to find that every attempt involved “tampering with blood vessels”—an act considered physiologically forbidden. He returned to Harvard in 1926 with a radical realization: if he could not touch the blood without disturbing the very flow he wished to measure, he would have to find a way to make the blood speak from a distance.

2. The Workaround: From Cancer Therapy to Physiological Clarity

The solution arrived not from cardiology, but from the high-stakes world of early radiation physics. Blumgart learned of William Duane, closely associated with Marie Curie’s era of radioactivity work, who had developed a “radium-radon extraction cow.” This device was designed to protect the primary radium source while “milking” it for radon gas for therapeutic use.

Blumgart observed that Duane could detect and quantify radiation externally, from outside the patient’s body. This was his “Aha!” moment. In an era before modern radiological protection culture—when biological effect was often discussed in terms like “Threshold Erythema”—Blumgart saw radiation not as a threat, but as a tool for physiological clarity.

Concept Spotlight: The Physiological Tag

Blumgart’s core logic was to inject a detectable amount of radon into a peripheral vein—the only “violence” to the system—and then use sensors to measure its arrival time at the heart and then a peripheral artery. This enabled remote measurement—quantifying circulation (transit) time and inferring faster vs slower flow without disturbing physiology.

The theory was elegant, but the transition from a theoretical “tag” to a functioning medical test required navigating a gauntlet of 1920s engineering hurdles.

3. Engineering Reality: Solving the “Little Problems”

Discovery in the 1920s was a visceral, DIY endeavor. Before the era of government grants, Blumgart had to become a chemist, a glassblower, and a scavenger to secure his materials.

The Problem-Solver’s Log

Securing the material was only half the battle. To charge his “hot wire,” Blumgart needed a power source that would have terrified a modern safety officer.

4. Building the Homemade Lab: The 2,200-Volt Solution

Blumgart’s laboratory was a testament to the pioneer spirit. To generate the necessary 2,200 volts of direct current, he constructed a massive homemade battery consisting of 1,200 small test tubes. Long before modern health physics programs, the room could become contaminated with escaped radon gas—an occupational reality Blumgart largely accepted as part of the work. To reduce electrocution risk while operating the high-voltage rig, he devised a “broomstick on-off switch” to keep himself at a safer distance.

Preparing a single bolus for injection was a meticulous, multi-step bench protocol:

• Ionization: Charge the sharpened platinum wire with 2,200V to attract the radon gas.
• Pressure Adjustment: Use a specially designed Hg (mercury) manometer to monitor and adjust air pressure.
• Acid Bath: Insert the radon-clad electrode into a fine tube of Hydrochloric Acid (HCl).
• Neutralization: Carefully bring the solution to blood-safe pH using Sodium Hydroxide (NaOH).
• Preparation: Withdraw the resulting 0.1 ml of radon-in-saline into a tuberculin syringe.
• Injection Control: Use a three-way stopcock to ensure the bolus was injected at the exact pressure required to match venous flow.

Once the tracer bolus was standardized, Blumgart faced his final challenge: building a device sensitive enough to detect the “tag” as it passed through the heart.

5. Inventing the Detector: Collaboration, Shielding, and Signal

Detection became the main bottleneck. Existing electroscopes were inadequate because they could not be effectively shielded from the background radiation of the room. Following advice from C.T.R. Wilson, Blumgart experimented with cloud chambers for arm-to-arm measurements, but eventually turned to radiation physicist Otto Yens.

Before Geiger-type instruments became standardized and widely available, Yens built a custom detection chamber from scratch. The primary challenge was the weight of protection. While an arm-to-heart detector could be heavily shielded with lead, that approach became too cumbersome for other anatomical sites. This drove the creation of a “small shielded Geiger chamber” designed for portability.

To succeed, Yens’ detector had to meet three rigorous requirements:

• Selective Shielding: Thick enough lead to block background “noise” but light enough for clinical use.
• Anatomical Portability: The ability to be moved between the arm and the chest.
• Automatic Registration: A mechanism to record the exact “time-of-arrival” to the fraction of a second.

6. Clinical Validation: Normals → Disease States

This was no mere laboratory curiosity. Blumgart validated his “Physiological Tag” with the rigor of a master clinician, establishing a baseline with 62 normal controls. He then applied the method to patients suffering from thyrotoxicosis, myxedema, anemias, and carcinomas—mapping measurable circulatory differences across disease states.

Between 1926 and 1931, Blumgart published extensively on circulatory velocity, including a multi-part series in the Journal of Clinical Investigation. In 1927, he co-authored an article with Soma Weiss containing a conclusion that has since become a cornerstone of the field.

“2. Because of the simplicity of the procedure... the method is well suited to its determination in man.”

This “Famous Second Conclusion” became aphoristic, cited in announcements of new nuclear medicine diagnostic techniques for decades. Even so, the discipline itself took time to crystallize; only later—especially in the postwar nuclear era—did the medical community formally name the field Blumgart had already helped pioneer.

7. Modern Translation: Why This Matters to You in Clinic

• Stress testing arrival-time thinking: Just as Blumgart measured arrival at the heart, modern transit times in first-pass studies or bolus tracking rely on time-of-arrival logic to initiate imaging.
• Injection technique still matters: Blumgart used a three-way stopcock to match venous flow pressure. Today, a bad bolus (interstitial or slow) can still invalidate quantitative work by distorting the input function.
• Detector placement parallels: The portability problem Yens solved is the ancestor of modern detector positioning strategy—maximize sensitivity while managing background.
• QC mindset: Blumgart’s fight against background radiation is why we care about background checks and daily QC. If your detector environment isn’t “clean,” the tag gets lost in the noise.

8. Summary: The Discovery Mindset

Hermann Blumgart’s journey reveals the true, messy, and brilliant process of scientific discovery:

• Cross-disciplinary vision: Breakthroughs happen when we stop looking at a problem through a single lens. Blumgart solved a cardiology mystery by borrowing tools from early radiation physics.
• The “hacker” ethos: Before big-budget science, innovation required building what didn’t exist, from 1,200-tube batteries to broomstick switches.
• Physiological integrity: True discovery requires solving the “real problems”—such as venous pressure and pH balance—so measurement does not change the thing being measured.

By daring to look beyond the “physiologically forbidden,” Hermann Blumgart helped introduce a new physics to medicine, a new instrumentation to physics, and a new radiopharmacology to science.

References

Primary sources first; secondary sources for historical context.

1. Blumgart, H. L., & Weiss, S. (1927). Studies on the Velocity of Blood Flow: I. The method utilized. Journal of Clinical Investigation, 4(1), 1–13.
2. Blumgart, H. L., & Yens, O. C. (1927). Studies on the Velocity of Blood Flow: II. The velocity of blood flow in normal resting individuals. Journal of Clinical Investigation, 4(1), 15–31.
3. Hales, S. (1733). Statical Essays: Containing Haemastaticks. London: W. Innys and R. Manby.
4. Duane, W. (1915). On the extraction and purification of radium emanation. Physical Review, 5(4), 311.
5. Curie, M. (1910). Treatise on Radioactivity.
6. Brucer, M. (1990). A Chronology of Nuclear Medicine. Heritage Publications.
7. Journal of Clinical Investigation (1926–1931). The Blumgart & Weiss series on circulatory velocity (multi-part series).

Takeaways

• Measurement should not change physiology.
• “Normals” define the abnormal.
• Signal matters only when background is controlled.
• Innovation requires a builder mindset.