TwinTree Insert

20-04 Spatial Encoding Leads to MR Imaging

n radiology, the times of conventional imaging ended in September 1971 when the world's first axial x-ray computer assisted tomograph (CT or CAT) was in­stal­led in England.

In the same month, on 2 September 1971, Paul C. Lauterbur, a professor of che­­mis­­try at the State University of New York at Stony Brook (Figure 20-24), recorded in his laboratory notebook the idea of applying magnetic field gradients in all three di­­men­­si­ons to create NMR images — and had his invention certified (Figure 20-25); yet, he was never able to patent it — the president, administrators and lawyers of the uni­ver­si­ty did not believe that the technique would have any future.

Figure 20-24:
Paul C. Lauterbur (1929-2007).

Figure 20-25:
First page of Lauterbur's laboratory note­book de­scribing his idea of "Spatially re­solv­ed nuclear mag­netic resonance ex­pe­ri­ments," signed and witnessed on 3 Sep­tem­ber 1971.

Lauterbur once stated [⇒ Dawson 2013]:

"European scientists, physicians, governments and industries moved more con­fi­dent­ly and thoughtfully into this new area than did their American counterparts."

Already in the 1950s and 1960s Lauterbur had established his fame in the com­mu­ni­ty of nuclear magnetic resonance scientists by showing carbon and si­li­con spec­tra which led to many pub­li­ca­tions on various classes of organic che­mi­cals [⇒ Lauterbur 1957].

However, all experiments before Lauterbur's invention of 1971 had been one-di­men­sio­nal and lacked spatial information. Nobody could determine ex­act­ly where the NMR sig­nal originated within the sample. Lau­ter­bur's idea chan­ged this.

Lauterbur called his imaging me­thod zeugmatography, combining the Greek words "zeugma" (ζεῦγμα = the bridge or the yoke that holds two animals together in front of a car­ri­a­ge) and "graphein" (γράφειν = to write, to depict) to describe the join­ing of chemical and spatial in­for­ma­tion. This term was later re­pla­ced by (N)MR imaging or MRI. A graphic depiction from 1978 of what would become the first whole-body MR apparatus at his laboratory is shown on Figure 03-01.

He published the first images of two tubes of water in March 1973 in Na­tu­re (Fi­gu­re 20-26) [⇒ Lauterbur 1973]. Later in the year the pic­tu­re of a living animal, a clam, fol­low­ed and in 1974 the image of the tho­ra­cic cavity of a mouse [⇒ Lau­ter­bur 1974].

Figure 20-26:
Lauterbur’s first published MR images ac­quir­ed at the State University of New York at Stony Brook (from Nature 1973; 242: 190-191; reprinted with per­mission).

Many of today's innovations were thought of and developed in Lauterbur's la­bo­ra­to­ry in the late 1970s and 1980s, from radio-frequency coil design, mag­­ne­­ti­­za­­tion trans­fer, 3D-, as well as chemical shift imaging, heart and lung imaging, using elements dif­fe­rent from hy­dro­gen, to NMR microscopy and contrast agents, oblique and cur­ved slice re­con­struc­tions, and flow imaging [⇒ Bernardo 1982; ⇒ Frank 1976; ⇒ Lai 1980; ⇒ Lau­ter­bur 1974; 1975; 1976; 1977; 1978; ⇒ Muller 1983; ⇒ Rinck 1984; ⇒ Simon 1981].

Some early ex­amp­les are shown in Figure 20-27.

Figure 20-27:
Early examples of “zeugmatography”.
Top: Follow-up of the growth of an implanted tumor in a mouse for a period of 38 days. Each image was resonstructed from 12 projection, the slice thickness was about 3 cm.
 Later, most images in Lauterbur's laboratory were acquired in three dimensions. These images were made in 1982. 3D-imaging with commercial systems became only possible some 10 years later.
Bottom left: Coronal images from a 3D human brain study.
Bottom right: Transverse images from a 3D study of a dog's heart, synchronized with the ECG, 400 ms after the R-wave.

Field gradients had been used before, though only in one dimension and with­­out imag­ing in the mind of the researchers.

Figure 20-28: Erwin Louis Hahn (1921-2016).

They are an essential feature of the study of molecular diffusion in liquids by the spin-echo method developed by Erwin L. Hahn in 1950 (Figure 20-28) [⇒ Hahn 1950]; his group also used a gradient approach to cre­ate a storage memory [⇒ Anderson 1955].

Figure 20-29: Robert Gabillard (1926-2012).

In 1951, Robert Gabillard from Lille in France had imposed one-dimensional gra­di­ents on samples [⇒ Gabillard 1951; 1952].

Figure 20-30: Herman Y. Carr (1924-2008).

Herman Y. Carr and Edward M. Purcell de­scrib­ed the use of gradients in the de­ter­mi­na­tion of diffusion in 1954 [⇒ Carr 1954].