Historical Perspective on Nanoparticles in Imaging from 1895 to 2000 - Nanotechnology for Biomedical Imaging and Diagnostics - page 3

Barium sulfate
for X-ray, 1909

PEGylated
nanoparticles,
1982

Magnetic
nanoparticles,
1986

Microbubbles,
Gramiak &
Shah 1968

Liposomes,
Bangham 1961

KI for X-ray,
Heuser 1919

Near-infrared
nanoparticles,
1996

131 I-labeled
liposomes,
Gregoriadis
1971

Targeted
nanoparticles,
Torchillin
1979

Quantum dots,
Efros 1982

198 Au colloid in
humans, 1948

1900 Nanoparticles in imaging 2000

Gamma
camera,
Anger 1958

PET,
Ter-Pogossian &
Phelps 1974

MRI, 1979

X-ray,
1895

Optoacoustic/
photoacoustic
imaging,
Oraevsky &
Kruger 1994

Geiger-
Müller tube,
1928

NIR optical
tomography,
1980s

Optical angiography
with ICG,
Flower 1974

SPECT,
Edwards &
Kuhl 1963

Ultrasound,
Howry &
Holmes
1950

PET prototype,
Brownell 1953

figure 1.2 Timeline of the most important events in the development of nanoparticles for
imaging and diagnostics covering the period from the twentieth century. The upper part corre-
sponds to nanoparticles, and the lower part to the development of imaging modalities. ( See
insert for color representation of the figure.) .)

1.2 X-ray and first contrast agents (1895-1930s)

The history of medical imaging started on November 8, 1895, when a 50-year-old
Wilhelm conrad röntgen—a physicist from the University of Würzburg in germany—
observed a greenish glow from a recently invented crookes tube. a new form of
radiation, which röntgen called an “X-ray,” freely penetrated through biological
tissue but was absorbed by dense material such as bones. recorded on radiation-
sensitive photographic plates, a well-recognized X-ray image was made. This entirely
noninvasive imaging technique quickly spread across the world after its demonstration
to the public in 1896. a review of major medical colleges across the United States
conducted by the American X-Ray Journal (fig. 1.3 shows the cover of this journal)
in 1899 revealed more than 80 institutions where X-ray machines were available for
patients [1], a remarkable rate given that it was just 4 years after X-ray discovery. With
X-ray imaging, bone fractures, kidney stones, and metallic objects such as bullets and
needles could be reliably located. With further refinement, physicians could even rec-
ognize and visualize certain organs. However, imaging inside the organs was impos-
sible since the low and uniform density of soft tissue composed of transparent to
X-rays water and organic media provided little contrast within the tissue.
To address this shortcoming, W. cannon from Harvard Medical School began
developing “contrast agents,” biocompatible compounds that could absorb X-rays. In
1905, he discovered that high-density metal salts such as bismuth-based compounds
provided the desired contrast in the intestines: “The animals thus fed with food mixed
with bismuth subnitrate were exposed to the X-rays and, without disturbing the