Scanner Generation

The terms first-generation through fourth-generation scanners are used to represent the developments in technology that relate the configuration of the x-ray tube to the detectors. The first-generation scanners, which are no longer in use, had a thin x-ray beam pass linearly over the patient in a 180° arc, followed by a single detector on the opposite side.2 Scanning time was very lengthy. Second-generation scanners used multiple detectors and a fan-shaped x-ray beam that continued to pass linearly across the patient before rotating. Scan times improved but were still very long.

Third-generation scanners represented a significant advance in technology, and scan times were greatly reduced. This design incorporates a fan-shaped beam and a detector array, and both move in a circle within the gantry. With the use of a rotating detector, all of the readings that make up a view can be recorded at the same time.1 Third-generation scanners are the most common conventional models in use today.

Fourth-generation scanners have a detector array that is fixed and positioned in a complete circle within the gantry. The x-ray tube produces a fan-shaped beam that rotates around the patient. Scan times are theoretically shorter than with third-generation scanners, but few fourth-generation scanners have been installed. 2

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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