Intra oral digital x ray
In dentistry two major types of x rays used to film the mouth - intra oral x-rays and extra oral x rays. Intra oral x-rays involve placing the x-ray film inside the mouth and extra oral x-rays place the x-ray film outside the mouth. The amount of radiation is reduced by around 80% using this technique. These x-rays allow the dentist to identify dental problems that cannot be identified with the naked eyes. Intra oral digital xrays help the dentist take a close look at the tooth roots, study the condition of the developing tooth, scrutinize general tooth health, identify caries and check the strength of the bony region adjoining the tooth.
Various types of intra oral x-rays are bite-wing x-rays, periapical x-rays and occlusal x-rays. X-ray films are substituted with electronic pad or sensors and the pictures are filmed. The x-rays fall on the pad in a similar fashion as they fall on the film and the pad or sensor transfers the image directly to the computer and a print out is taken unlike developing the x-ray film in a dark room. The main benefit of these x-rays is that they help comparison of current images to previous images without any difficulty and over the computer itself.
Esophagram is a test whereby the patient is administered a barium sulfate compound that enables the radiologist to study the function and appearance of the esophagus. A series of x rays of the esophagus is taken after the patient has swallowed the barium. The barium solution coats and outlines the walls of the esophagus. This enables the radiologist to assess the process of swallowing. Hence it is also called barium swallow. An Esophagram is done when the patient complains of pain or difficulty in swallowing. It is also done to assess the reasons for blood stained vomit and when abdominal pain and weight loss occurs or diagnosing cases of Barrett's esophagus. The Esophagram helps the radiologist to detect narrowing, stricture, obstruction or irritation of the esophagus. It helps to study complications such as ulcers, polyps and tumors. It also helps to assess hiatal hernia.
The patient is advised not to eat or drink for 8 to 10 hours prior to the examination. The patient is asked not to smoke or chew gum at least 6 hours prior to the procedure. A patient is given a cup of barium sulfate to swallow. A radiologist watches and evaluates the swallowing process with fluoroscopy. The barium swallowed coats the lining of the esophagus, and x rays are taken to track the pathway to the stomach. The patient is placed in various positions throughout the exam so that structures are optimally demonstrated on the x rays.
The problem is that it can miss small abnormalities in the esophagus such as small erosions and ulcers. This test is not very effective for diagnosing gastro esophageal reflux associated with GERD. Pregnant mothers are advised not to undergo this procedure as the risk of radiation affects the fetus.
CBCT, also known as C-arm CT, Cone Beam Volume CT or flat panel CY is a medical imaging technique, like a conventional CT scan. It provides fast and accurate visualization of bony anatomical structures in three dimensions. It is essentially X-ray computed Tomography where the X rays are divergent, forming a cone. Unlike traditional dental x-rays that are flat images, CBCT scan can provide multiple images of the teeth, soft tissues, bone and nerve pathways. The image quality is better due to reduced scatter radiation. These images help compile exact 3D images of various angles of the face and jaw. It also allows the dentist to zoom into specific maxillofacial structures with alternate angles for clearer evaluation.
CBCT is important in planning and diagnosis in implant dentistry and interventional radiology among other things. In dentistry, it is used in oral surgery, endodontics and orthodontics.
CBCT is an important tool in image-guided radiation therapy for patient positioning and verification. Nearly 600 distinct images can be captured by rotating the CBCT scanner around the patient's head. In interventional radiology, a single 200 degree rotation over the region of interest provides volumetric data. The scanning software collects the data and reconstructs it, producing a digital volume composed of three dimensional voxels of anatomical data that can be manipulated and visualized with specialized software.
CBCT offers invaluable information in planning and assessment of surgical implants. A dental cone beam scan is the preferred method for pre surgical assessment of dental implant sites. Since CBCT is a 3D rendition, there are several structures that can be viewed with this facility, which are not available with conventional 2D radiology. CBCT offers an undistorted view of the dentition. That is why it is used for accurately visualizing both erupted and non erupted teeth. It is also used in tooth root orientation and anomalous structures.
Use of CBCT in Interventional Radiology (IR)
The scanner is mounted on a C arm in the IR suite offering real time imaging. Since this can be done on a stationary patient, it eliminates the time spent to transfer a patient from the Angiography suite to a conventional computed Tomography scanner. It also facilitates many applications of CBCT during IR procedures. Both primary and supplementary form of imaging can be done with CBCT. For fluoroscopy and soft tissues, it can be very helpful during complex procedures to reduce patient's radiation exposure.
Clinical applications of CBCT
In hepatocellular carcinoma, CBCT contrast confirms that the proper artery is selected to deliver the therapy. For benign prostatic hypertrophy BPH, CBCT provides soft tissue details needed to visualize prostatic enhancement, identify duplicated prostatic arteries and avoid non target embolization. During abscess drainage, CBCT confirms needle tip location after placement under ultrasound and confirms drain placement by revealing contrast injection into the desired location.
For adenoma adrenal vein sampling, contrast enhanced CBCT shows perfusion of the adrenal gland to confirm catheter placement for obtaining a satisfactory sample. During stent placement, CBCT improves the visualization of intracranial and extracranial stents. CBCT guides needle placement and allows diagnostic accuracy, sensitivity and specificity in lung nodules. After correction of vascular anomalies, CBCT sensitively detects small infarcts in tissue during the procedure to prevent further shunting.
Although it is a compact, faster and safer version of the regular CT, dental CBCT delivers more radiation than conventional dental X rays. Even properly shielded CBCT exposes patients to radiation many times more than 2D digital dental x rays. However, improved outcomes at lowered cost and time saving, reduced morbidity and reduced need for exploratory procedures and other such benefits of CBCT continue to make it popular with practitioners.
Bibliography / Reference
Collection of Pages - Last revised Date: February 19, 2019