History of radiation therapy timeline

Cell Cycle Stage

The cell cycle is the series of distinct phases leading to duplication of DNA and, ultimately, cell division. The cell cycle is of interest because the radiosensitivity of a cell is dependent upon its stage in the cell cycle.

G1: First growth phase

The cell is performing normal functions and growing.

S: Synthesis phase

During the S phase, the cell replicates its DNA. S phase is the least radiosensitive phase of the cell cycle because the cell contains two copies of its DNA.

G2: Second growth phase

The cell is again performing normal functions and continues to grow.

M: Mitosis phase

The cell divides into two cells in a process called mitosis. Mitosis is the most radiosensitive phase both because mitosis is sensitive to disruption and because the cell is well oxygenated during this phase.

1.2.1 The Discovery of X-Rays and Radioactivity

By the end of the nineteenth century, “Newtonian” physics had explained nearly all the phenomena involving mass, speed, electricity, and heat. However, some questions remained unanswered, notably the origin of the luminescence phenomena observed either in glass vacuum tubes subjected to a high voltage (e.g., the Crookes tubes—Fig. 1.2) or on certain ores [4]. In both cases, one of the major questions was their inducibility vis-à-vis the sunlight. The German physicist Wilhelm Conrad Roentgen addressed the first challenge by putting some opaque boxes on the Crookes tube, while the Frenchman Henri Becquerel focused on the second one by studying light emitted by uranium ores in the darkness. The two series of experiments became legendary and led to two Nobel prizes in physics [4].

In November 1895, Wilhelm Conrad Röntgen (Roentgen) (1845–1923) detected electromagnetic radiation of a sub-nanometer wavele

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