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CT and MRI of the Lower Gastrointestinal Tract

1 What is shown in Figure 27-1 ? A topogram from a computed tomographic colonography (CTC), an examination tailored to evaluate for colorectal polyps and masses. 2 What is the adenoma-carcinoma sequence? The adenoma-carcinoma sequence refers to a series of genetic mutations whereby small adenomatous colon polyps (<5 mm) transform into large adenomatous polyps (>1 cm), noninvasive carcinomas, and then invasive carcinomas. This entire process takes, on average,…

Fluoroscopy of the Lower Gastrointestinal Tract

1 Identify the parts of the colon (numbers 1 through 8) labeled in Figure 26-1 . For the answer, see the figure legend. 2 What are haustra? The longitudinal muscle layer of the colon is divided into three thick bands, termed the taeniae coli . There is a paucity of longitudinal muscle between the three tenial bands. Haustra are sacculations of colon protruding between the three…

CT and MRI of the Upper Gastrointestinal Tract

1 What are the general indications for routine computed tomography (CT) and magnetic resonance imaging (MRI) of the upper gastrointestinal (GI) tract? General indications for routine abdominopelvic CT or MRI evaluation of the upper GI tract include: Assessment of patients with clinical symptoms or signs potentially related to GI tract pathology for detection and characterization of the underlying etiologies. Staging, pretreatment planning, response assessment, and restaging…

Fluoroscopy of the Upper Gastrointestinal Tract

1 What organs are studied during an upper gastrointestinal (GI) series? The esophagus, stomach, and duodenum are studied. The radiologist evaluates the morphology and motility of these organs. 2 What organs are studied during a pharyngoesophagogram? The radiologist evaluates the motility of the oral cavity, pharynx, and esophagus, and the morphology of the pharynx, esophagus, and gastric cardia. The radiologist records the fluoroscopic images of oral,…

Abdominal Radiography

1 What is a “flat plate” of the abdomen? Flat plate is a historical term that refers to a past method of radiography when radiographs were recorded on flat plates of glass coated with an emulsion sensitive to x-rays. This examination also has been termed a plain abdominal radiograph, plain film of the abdomen, abdominal plain film, and KUB. KUB refers to the kidney, ureters, and…

Tubes, Lines, Catheters, and Other Devices

1 What is the radiographic appearance of an endotracheal tube (ETT), and where is it optimally placed? An ETT usually appears as a faintly radiopaque tube with a thin, densely radiopaque line along its length, and its position should be determined relative to the carina, which if not seen on a chest radiograph can be approximated by following the course of the mainstem bronchi medially at…

Imaging of Pleural Disease

1 Describe the normal pleural anatomy and physiologic features. The pleural space is a potential space that contains 2 to 10 mL of pleural fluid between the visceral and parietal pleural layers that essentially represents interstitial fluid from the parietal pleura (an ultrafiltrate of plasma). The pleural space is contiguous with the interlobar fissures of the lungs. The pleura is a thin, serous layer that covers the…

Imaging of Mediastinal Disease

1 Describe the anatomy of the mediastinum. The mediastinum is located centrally within the thorax between the pleural cavities laterally, the sternum anteriorly, the spine posteriorly, the thoracic inlet superiorly, and the diaphragm inferiorly. It is usually divided into anterior, middle, and posterior compartments to help categorize tumors and diseases by their site of origin and location. Processes that arise in these different compartments are generally…

Special Procedures

24.1 Introduction Special procedures are defined by the following characteristics: ▪ Unique beam configuration, accessories, or radiation delivery device settings compared to other treatments such as 3D conformal radiation therapy (3D CRT) or intensity-modulated radiation therapy (IMRT) ▪ Relative number of patients treated is small ▪ Not widely offered in all clinics because of the relative effort to implement a special procedure compared to the number…

Intraoperative Radiotherapy (IORT)

23.1 Introduction The goal of intraoperative radiotherapy (IORT) is to deliver a single high dose of radiation at the time of surgery to enhance tumor control. IORT is typically useful in cases where a complete surgical resection will be difficult. For example, a locally invasive tumor might surround a nerve or blood vessel that cannot be resected, or a tumor may invade into a bone that…

Prostate Seed Implant

22.1 Introduction Prostate brachytherapy is one of several treatment techniques available for patients with localized disease. Prostate brachytherapy is currently practiced using two different techniques: (1) prostate seed implant (PSI) using low dose rate (LDR) sources and (2) high dose rate (HDR) brachytherapy. Because prostate HDR is one variation of interstitial implants, it is grouped with other interstitial implants in Chapter 20 . Like other technologies…

Interstitial Brachytherapy

21.1 Introduction Interstitial brachytherapy has a long tradition, starting with radium needles being implanted in superficial tumors in the 1930s. The implant systems developed at the time, Manchester and Quimby, still guide the needle placement patterns used in implants today. Though radium needles where initially used for interstitial implants, other radioactive nuclei were developed over time. Table 8.1 in Chapter 8 contains a list of the…

Intracavitary Brachytherapy

20.1 Introduction Intracavitary brachytherapy can be performed using low dose rate (LDR), pulsed dose rate (PDR), or high dose rate (HDR) sources. LDR implants expose the patient care team to more radiation than HDR and require longer hospitalization of the patient and more resources dedicated to source storage and radiation safety measures. There is also an increased risk of error, for example, by selecting the incorrect…

Respiratory Motion Management for External Beam Radiotherapy

19.1 Introduction One of the primary goals in radiation therapy is to maximize the dose to the target while minimizing the dose to healthy tissue. For targets that exhibit significant motion (>5 to 10 mm) during the respiratory cycle this creates a challenge. If a target is 3 cm in diameter (volume = 14.1 cm 3 ) and moves ±10 mm in one direction and ±5 mm in the other directions,…

Clinical Aspects of Image Guidance and Localization in Radiotherapy

18.1 Introduction Image-guided radiotherapy (IGRT) is well established; however it is important to note that there has never been a prospective randomized trial to examine its value. There are, however, a number of retrospective series examining the impact of IGRT as outlined in recent papers. The potential impact of IGRT can be appreciated by considering a recent study that linked biochemical failures in prostate cancer patients…

SRS and SBRT

17.1 Introduction Stereotactic radiosurgery (SRS) was originally defined as fulfilling all of the following conditions: 1. Single-fraction treatment 2. High dose per fraction (>5 Gy) 3. Target with diameter of <3.5 cm in the brain 4. Delivery accuracy of <1 mm as defined by the Winston-Lutz test 5. No planning target volume (PTV) or internal target volume (ITV) margins are used; clinical target volume (CTV) margins may be used…

IMRT and VMAT

16.1 Introduction Intensity-modulated radiotherapy (IMRT) provides exceptional control over the delivery of dose. Figure 16.1 shows an example of a 7-field IMRT plan for a patient with T3 oropharyngeal carcinoma of the head and neck. This case illustrates the ability to sculpt dose around nearby organs at risk (in this case the cord and parotid) while irradiating the gross tumor volume and at-risk nodal regions to…

The Use of Electrons for External Beam Radiotherapy

15.1 Introduction Electron beams have been used in radiotherapy since the 1940s but did not gain widespread use until the 1970s with the commercial development of linear accelerators (linacs). Electrons lose energy as they traverse a medium through various elastic and inelastic collisions with atomic electrons and the nucleus. Inelastic collisions with the nucleus result in a radiative loss of a photon, called bremsstrahlung production. The…