▪ Gallbladder Anatomy The gallbladder is an ovoid cystic organ along the undersurface of the liver at the interlobar fissure, between the right and the left lobes of the liver. Although the size and shape of the gallbladder vary with the fasting state, it is approximately 10 cm long and 3 to 5 cm in diameter. The normal capacity of the gallbladder is approximately 50 mL.…
▪ Introduction Diffuse liver processes range from incidental signal and/or enhancement derangements, such as steatosis or transient hepatic intensity differences (THIDs), to serious, and potentially end-stage parenchymal disorders, such as cirrhosis and Budd-Chiari Syndrome (BCS). Segmental, or geographic lesions typically fall into one of two categories—(abnormal) signal or enhancement lesions. Diffuse liver disorders stratify into either: 1) primarily signal, 2) fundamental morphology, or 3) imaging occult…
▪ Introduction Magnetic resonance imaging (MRI) is the most comprehensive and definitive noninvasive modality for evaluating the liver. A combination of enhancement characteristics and exquisite tissue contrast allows for the characterization of liver lesions. Unique artifacts—such as susceptibility and chemical shift—allow for sensitive detection of hepatic iron and lipid deposition, respectively. Common indications for liver MRI include liver lesion characterization, hepatic steatosis quantification and surveillance, liver…
▪ Magnetic Resonance Imaging: What is the Objective? Magnetic resonance imaging (MRI) exploits the inherent magnetism of the protons that constitute the human body in a creative way—through manipulation with radiofrequency (Rf) energy in the presence of a strong magnetic field. This manipulation induces the protons to emit energy, which is detected and reconstructed into an image. The human body—not ostensibly magnetic—is effectively magnetized by a…
In this chapter entities such as disk disease and the osseous structures of the spinal canal will be discussed again, as well as postoperative spine changes. The appearances of the bones in the setting of some systemic diseases are additional descriptions in this chapter as are the incidentally encountered abnormalities in the axial skeleton and ribs when evaluation of chest-abdomen-pelvis imaging is performed. Metallic implants and…
Introduction The advent of increasing numbers of rows of detectors has expanded the utility for CT technology. Multidetector CT (MDCT) has the ability to produce near-isotropic voxel images that allow multiplanar reformations and faster data acquisition. This technique is particularly valuable in the setting of trauma, for which conventional radiographs can be difficult to obtain because patients may be unable to comply with positioning requirements. Volume-rendered…
Anatomy The true (lesser) pelvis is divided from the false (greater) pelvis by an oblique plane extending across the pelvic brim from the sacral promontory to the symphysis pubis. The true pelvis contains the rectum, bladder, pelvic ureters, and prostate and seminal vesicles in males, or vagina, uterus, and ovaries in females. The false pelvis is open anteriorly and is bounded laterally by the iliac fossae.…
Basic Principles CT complements endoscopy and barium examination of the gastrointestinal (GI) tract by demonstration of intramural and extraintestinal components of GI disease, including disease in the mesentery, peritoneal cavity, lymph nodes, and liver. CT is used to diagnose the presence of GI disease, evaluate its nature and extent, and demonstrate complications such as abscess, phlegmon, fistula, and perforation. CT is excellent for determining the extent…
The adrenal glands are the primary focus of diagnostic attention in three clinical circumstances. A patient may be referred for imaging because a clinical diagnosis of adrenal hormone hyperfunction has been made. CT is then used to identify and characterize the lesion. The adrenal glands are commonly imaged to detect suspected metastatic disease, especially when the primary tumor, such as lung carcinoma, commonly metastasizes to the…
Kidneys Anatomy of the Retroperitoneal Space A detailed understanding of the retroperitoneal fascial planes and compartments is a prerequisite for accurate interpretation of abdominal CT. The retroperitoneum is the anatomic compartment between the posterior parietal peritoneum and the transversalis fascia extending from the diaphragm to the pelvic brim. It is divided into three distinct compartments—anterior pararenal, perirenal, and posterior pararenal spaces—by the anterior renal fascia and…
With high-resolution multidetector CT and dynamic multiphase postcontrast protocols, an increasing number of splenic lesions are being detected. These require characterization by combination of imaging findings with clinical data. Many spleen lesions are nonspecific in appearance. At a minimum, splenic lesions should be characterized as benign or potentially malignant. Anatomy The spleen occupies a relatively constant position in the left upper quadrant of the abdomen. It…
Multidetector CT is the imaging method of choice for evaluation of pancreatitis and competes with magnetic resonance imaging (MRI) for detection and staging of pancreatic tumors. Rapid CT acquisition times allow high-resolution multiphase scanning of the entire pancreas within a single breath hold in most instances. CT Technique CT evaluation of pancreatitis is usually performed as a routine abdomen scan with extension of CT scanning of…
Biliary Tree Primary imaging of the biliary tree depends increasingly on CT, ultrasonography, magnetic resonance imaging, and magnetic resonance cholangiopancreatography, and with diminishing reliance on invasive endoscopic retrograde cholangiopancreatography. Multidetector CT (MDCT) with thin sections and multiplanar reformats can clearly demonstrate the normal anatomy, anatomic variants, stones, tumors, and inflammatory disease of the biliary system. Anatomy The bile ducts arise as biliary capillaries between hepatocytes. Bile…
Anatomy In 2000 the Terminology Committee of the International Hepato-Pancreato-Biliary Association refined the accepted terminology of hepatic anatomy and liver resections. The international classification system divides the liver into eight independent segments (Couinaud [pronounced “kwee-NO”] segments) ( Fig. 11.1 , Tables 11.1 and 11.2 ). Each segment is a self-contained unit that can be surgically resected without damaging the remainder of the liver. Each segment has…
Multidetector CT (MDCT) is the imaging method of choice for the diagnosis of intra-abdominal injury following blunt abdominal trauma. Treatment is directed by characterization of the precise nature of the injury, or by the reliable demonstration of the absence of significant injury. CT is particularly valuable when physical examination of the abdomen is equivocal or unreliable, such as with head trauma or impairment of consciousness caused…
Peritoneal Cavity Anatomy The various recesses and spaces of the peritoneal cavity are easiest to recognize on CT when ascites is present. Identifying the precise compartment that an abnormality is in goes a long way toward identifying the nature of the abnormality and deciding on a plan for intervention. The peritoneum is a thin membrane that produces serous fluid, which lubricates the abdominal and pelvic cavity.…
Despite marked advances in limiting image times for magnetic resonance imaging, CT remains the primary modality for most indications for imaging the abdomen and pelvis. The technology of multidetector CT (MDCT) scanners continues to advance, with progressive increases in the number of detectors, now exceeding 128 detector rows, and progressive decrease in acquisition times. Concern is now focused on CT radiation dose and overuse as thin-slice…
Technical Considerations In general, the pleura and chest wall are adequately evaluated with routine thoracic CT techniques. Contrast medium infusion is helpful in showing pleural thickening and in allowing its differentiation from pleural fluid. Soft-tissue window settings and bone windows are most suitable for evaluating pleural abnormalities, the chest wall, and the diaphragm. It should be kept in mind that the diaphragm and posterior pleural space…
On CT, normal lung varies in appearance, depending on the window settings used. With a window mean of –600 to –700 Hounsfield units (HU) and a width of 1000 to 1500 HU, the lungs appear dark, but not as black as the air visible in the trachea or bronchi. This slight difference in attenuation between lung parenchyma and air should be sought in choosing an appropriate…
CT is helpful in the diagnosis of endobronchial lesions, hilar and parahilar masses, and hilar vascular lesions. Technique In most patients the hila are adequately assessed with spiral CT with a 5-mm slice thickness (it takes about 15 contiguous 5-mm slices to image the hila), but thinner slices are optimal in identifying some findings such as bronchial abnormalities, small lymph nodes, and hilar vessels. Scans with…