**3.2. Contrast medium**

From the early days of medical application of X-rays, practitioners noticed the need of soft tissue and blood vessels imaging. Thus, many experiments were conducted in order to alter the absorption characteristic (atomic number) of the tissue in relation to their adjacent structures (soft tissue effective atomic number ≈ 7.4). Thus, negative contrast media (air) and positive contrast media were developed for gastrointestinal tract in 1910, for oral and rectal administration

**Figure 3.** (A) Radiologist using a fluoroscope during an examination; and (B) red goggles.

**8.** Medical imaging: radiographic imaging is used to extract patients' anatomical and physiological data in order to diagnose a clinical condition. Image formation consists of the

**2.** As X-rays penetrate through the body tissues, it become modified and each part of

**3.** A suitable image receptor receives the signal and creates radiograph with different

Interventional radiology is a newly emerged branch from radiology using fluoroscopic guidance to perform complex procedure noninvasively. Nowadays, many imaging modalities are used in the field of image-guided interventions. These imaging technologies include, in addition to planar fluoroscopy, CT, MRI, and ultrasound. The image-guided intervention techniques expanded rapidly due to its numerous advantages including local anesthesia and

Fluoroscopy, or real-time imaging, is an imaging technique that produces dynamic images at low tube current range from 0.5 to 5.0 mA for longtime intervals, resulting in dynamic images with lesser image quality. The fluoroscopy played a fundamental role in emergence of interventional radiology since its introduction by Thomas Edison (1847–1931) in May, 1896, just an year after the discovery of X-rays. The early fluoroscope composed of fluorescent screen (zinc-cadmium sulfide) placed over the patient's body between the patient and radiologist (**Figure 3**) at complete darkness, and the radiologist looked directly at the screen. Dark adaptation was required from 10 to 30 minutes by wearing red goggles to enhance viewing.

From the early days of medical application of X-rays, practitioners noticed the need of soft tissue and blood vessels imaging. Thus, many experiments were conducted in order to alter the absorption characteristic (atomic number) of the tissue in relation to their adjacent structures (soft tissue effective atomic number ≈ 7.4). Thus, negative contrast media (air) and positive contrast media were developed for gastrointestinal tract in 1910, for oral and rectal administration

**1.** X-ray passes through the patient during imaging procedures.

the beam is attenuated in a degree that depends on:

levels of gray scales according to the tissue attenuation.

low rate of mortality and morbidity (short stay at hospital).

following stages:

**a.** the tissue type;

36 Medical Imaging and Image-Guided Interventions

**b.** the intensity of the beam; and

**c.** thickness of the tissue.

**3. Image-guided interventions**

**3.1. Fluoroscopy**

**3.2. Contrast medium**

exclusively (barium sulfate (BaSO<sup>4</sup> ), with effective atomic number 56), and gastrografin (Diatrizoate Meglumine and Diatrizoate Sodium Solution, effective atomic number 53), which is an iodinated soluble contrast medium, was developed in 1954. For cardiovascular system, urografin (amidotrizoate meglumine; sodium amidotrizoate (C11H9 I 3 N2 O4 )) was developed [2].

Afterward, the clinical experiments on cardiac catheterization and angiography progressed extensively, and in 1956, Forssman and Cournand received the Nobel Prize in physiology and medicine for their efforts in development of cardiac catheterization [3].

The image-guided intervention was started as a diagnostic technique, but due to the development of recent imaging technology such as CT angiography and magnetic resonance angiography (MRA), it becomes a pure therapeutic technique. Image-guided intervention is performed usually under fluoroscopic guidance. However due to the development of other imaging modalities such as CT, MRI, and ultrasound, these techniques are progressing with some drawbacks that include radiation risk in CT imaging, metallic surgical tools as a limitation for MRI application in interventional procedures, and ultrasound poor image quality [4]. In addition to that, a combination of fluoroscopy with endoscopy provided also excellent approach to treat many clinical conditions.
