Ct scan

It is ___mm for CT; however, the spatial resolution for nuclear medicine, US, and MRI is ____, ____, ___ mm, respectively

2mm for ct 0.1, 0.25, 2 mm

when is a specific diagnosis of chronic pancreatitis made on ct?

A specific diagnosis of chronic pancreatitis can be made on CT if pancreatic calcification and pancreatic ductal dilatation are seen

describe brain hemorrhage on ct

Brain Hemorrhage recent, contains hemoglobin which is relatively dense on CT because of its protein content as the hematoma ages, the hemoglobin is removed and the hematoma becomes lower in density Bleeding can be epidural, sudural, intraparenchymanl

what kind of brain trauma can be demonstrated on CT?

Brain Trauma- CT can provide direct information regarding brain injury contusions or hematomas of the brain (blood clots) as well as hematomas outside the brain, such as epidur

modality assessment of trauma in the acute phase, acute hemorrhage, and detection of calcification

CT

what is the modality of choice for the pancreas?

CT

which is faster ct or MRI?

CT

Ct is the most sensitive technique for assessment of what?

CT also remains the most sensitive technique for assessment of hypoxic ischemia damage to the neonatal brain caused by asphyxia at birth or nonaccidental injury

what can CT be paired with?

CT is paired with PET scan or SPECT scan to produce PET/CT or SPECT/CT which provide more information about the patient's medical condition In addition, CT can be used to assist in radiation treatment planning.

what is the modality of choice for he chest?

CT is the modality of choice for chest (screening CT for smokers to detect early lung cancer)

cerebral contusions

Cerebral Contusions - these injuries to the brain classically cause a mixture of edema and hemorrhage, manifested on CT as mixed low-density and high- density in the affected area these most frequently affect the anterior portion of the temporal or frontal lobe

what are Cerebral Infarctions

Cerebral Infarctions initially produces edema in the area of the ischemic brain, later followed by necrosis or cystic change the result is a low-density change occurs in the affected brain often extending to the cortical surface and obliterating the normal gray-white distinction On the image: MCA infarction In the first 24-hours of infarct, MRI is more sensitive to infarction

Data Acquisition slice by slice- Volume data acquisition-

Data Acquisition A. Slice by slice: Conventional CT scans: It takes pictures of slices of the body (like slices of bread). These slices are a few millimeters apart. B. Volume data acquisition: The newer spiral (also called helical), the x-ray tube rotates around the patient and traces a spiral-helical path to scan an entire volume of tissue during a single breath hold. The CT scan takes continuous pictures of the body in a rapid spiral motion, so that there are no gaps in the pictures collected

Spine Ct. imaging what plane is it always done in? what does it detect?

Spine CT Imaging is almost always done in the transverse plane. If its performed to detect for fracture, contrast is not needed If it is performed to detect for disc herniation, a contrast is needed Because of its contrast resolution, CT differentiates between the disk and adjacent ligamentum flavum, thecal sac, intraspinal fat and bone.

what are the goals and advantages of CT?

The goal of CT is to overcome the limitations of radiography by achieving the following: Minimizing the problem of superimposition. Improving the contrast of the image. Finding a way to record very small differences in tissue contrast. CT provides excellent contrast resolution which is the ability of an imaging system to demonstrate small changes in tissue contrast

describe the location of the gantry compared to the patient

During a CT scan, the patient lies on a bed that slowly moves through the gantry while the x-ray tube rotates around the patient, shooting fan-shaped, narrow beams of x-rays through the edge of the selected body slice.

each time the Xray source completes a full rotation what does the CT computer DO?

Each time the x-ray source completes one full rotation, the CT computer uses sophisticated mathematical techniques to construct a 2D image slice of the patient.

Calcifications are less frequently seen in islet cell tumors than in ductal adenocarcinoma T or F

False Calcifications are more frequently seen in islet cell tumors than in ductal adenocarcinoma

are ct images 2d or 3d?

Image slices can either be displayed individually or stacked together by the computer to generate a 3D image of the patient Once the data from the different views have been collected, the process of image digital reconstruction begins. The computer takes the information acquired from the different views and converts this into a numerical representation known as a digital image.

although CT is known to be more sensitive than ultrasound, it is only used when ultrasound has been inconclusive or when more detailed localization and characterization of lesions is required

Liver CT scan

what is the most common benign intracranial tumor

Meningioma - most common benign intracranial tumor It arises from dura adjacent to the inner table of the skull meningioma, which is typically vascular, and thus readily increases its density following administration of IV contrast.

this is the most common primary mass within the orbit

Orbital Hemangioma

parotid gland ct

Parotid Gland CT Scan Parotid gland tumors are the most frequent salivary gland tumors most tumors are benign, well-defined, and enhance readily CT can be helpful in planning surgery, because these should be completely removed

Cerebral Glioblastoma

- the most common primary malignant tumor of the brain arising within brain substance the prognosis is poor, with few surviving more than one year typically has a mixture of low-density enhancing areas and mass effect on CT Intracerebral tumors, such as glioblastoma, do not have a normal blood-brain barrier, and this allows the passage of contrast into the tumor. Thus these tumors show increased density or enhancement. Similarly, the wall of a cerebral abscess shows enhancement

pheochromocytomas and tumors producing Cushing's and Conn's syndromes that are larger than ___ cm. are consistently demonstrated on CT

1

Basic Components of a CT Scanner

1- The gantry aperture refers to the opening in which the patient is positioned during the scanning procedure it must be capable of being tilted to accommodate all types of patients and clinical examinations The gantry and patient couch are often referred to as the scanner 2- the x-ray tube which generates x-rays 3- the detector that captures x rays, detector electronics 4 -the computer and its associated processors, the image display device, image storage, recording devices, and the system control console are located in the operator's room.

The thickness of the tissue represented in each image slice can vary depending on the CT machine used, but usually ranges from ____ ____ millimeters.

1-10mm

what are the other names for pencil ionization chamber method

The pencil ionization chamber method or CT dose index or (CTDI) method

why must Radiation Dose be known ?

The radiation dose must be known if one is to estimate the patient's potential risk from the radiation and weigh this risk against the benefits received by the patient undergoing the CT scanner procedure.

CT with Contrast how is it used?

The rationale for using IV contrast stems from the fact that iodine provides further attenuation of the x-ray beam (it obstructs the x ray passage towards the film and thereby allows structures containing the contrast medium to appear denser on CT, thus allowing them to be more apparent. In particular, normal structures that have a rich vascular supply, such as blood vessels, choroid plexus and dura, appear denser following contrast.

name the limitations of CT

The spatial resolution, line pairs millimeter, (the degree of blurring present in an image) of CT is notably poorer compared with radiography spatial resolution is a measure of the ability to discriminate objects of varying density a small distance apart against a uniform background It is 2 mm for CT; however, the spatial resolution for nuclear medicine, US, and MRI is 0.1, 0.25, 2 mm, respectively The radiation dose in CT is generally higher for similar anatomic regions. In CT, it is difficult to image anatomic regions in which soft tissues are surrounded by large amounts of bone, such as the posterior fossa, spinal cord, pituitary and the interpetrous space. The imaging process may create artifacts that obscure diagnosis The presence of metallic objects on the patient produces streak artifacts on CT images. Limitations in slice-by-slice: longer examination times because of the stop-start action necessary for patient breathing, table indexing and cable unwinding. Omission of certain portions of the anatomy, because of patient respiration phase may not always be consistent form scan to scan.

describe competid tomography

The term "computed tomography", or CT, refers to a computerized x-ray imaging procedure in which a narrow beam of x-ray is aimed at a patient and quickly rotated around the body, producing signals that are processed by the machine's computer to generate cross-sectional images—or "slices"—of the body. These slices are called tomographic images and contain more detailed information than conventional x-rays. Once a number of successive slices are collected by the machine's computer, they can be digitally "stacked" together to form a three-dimensional image of the patient that allows for easier identification and location of basic structures as well as possible tumors or abnormalities.

how are tumors manifested. by?

Tumors intracranial tumors may be manifested by headaches, seizures, neurologic dysfunction by providing direct anatomic information about the brain, CT allows for the detection of intracerebral and extracerebral cranial tumors

when a full slice its complete what happens to the motorized bed ?

When a full slice is completed, the image is stored and the motorized bed is moved forward incrementally into the gantry The x-ray scanning process is then repeated to produce another image slice. This process continues until the desired number of slices is collected.

Chest and Mediastinum CT Scan can nearly all mediastinal abnormalities detected chest radiograph or suspected clinically can be confirmed with ct? what did ct replace? what is it most likely used for ? name some limitations

almost all mediastinal abnormalities detected on chest radiograph or suspected clinically can be confirmed with CT conventional tomography it is most commonly used for the detection of lymphadenopathy in patients with suspected bronchogenic carcinoma, lymphoma, or other malignancies although highly sensitive, some limitations of CT and MRI exist, including the detection of tumors within normal-sized nodes, enlarged hyperplastic nodes without tumor, and undetected enlarged nodes

describe the Ct control console

an integrated console consists of a floating keyboard, an operating panel and a video display monitor. The integrated console controls the entire system, including turning the scanner on and off, and also enables a number of different functions to be carried out.

the enhancement of vascular structures in the mediastinum with intravenous contrast medium makes it easy to differentiate an ____ of the aorta from other mediastinal masses

aneurysm

adrenal metastases most commonly seen with ___ and ___carcinomas are readily demonstrated on CT

bronchogenic and breast

best method for screening patients following blunt abdominal trauma or the presence of splenic injury

ct

As the x-rays transmitted through that slice of the patient, they leave the patient and are picked up by special digital x-ray detectors (instead of film) which are located directly opposite the x-ray source and then transmitted to a computer

describe the process of the X-rays being transmitted through a slice of the patient

The radiation dose in CT is generally lower for similar anatomic regions. t or f

false higher

Unlike a conventional x-ray—which uses a fixed x-ray tube—a CT scanner uses a motorized x-ray source that rotates around the circular opening of a donut-shaped structure called a_______

gantry

in adrenal hyperplasia how do the present ?

in adrenal hyperplasia the adrenals may appear normal in size or slightly enlarged

why is ct better for visualizing the pancreas than ultrasound ?

in general, the success rate for delineating the entire pancreas is much higher with CT than ultrasound because bowel gas often obscures part or even the entire pancreas

Abdomen CT Scan remains radiology standard for investigating the abdomen but requires pt transfer and what type of delay?

inevitable delay (bowel preparation)

The ionization chamber method is the easiest and probably most accurate of any of the commonly used methods.

ionization chamber

The_____method is the easiest and probably most accurate of any of the commonly used methods.

ionization chamber

Epidural hematoma

is when bleeding occurs between the tough outer membrane covering the brain (dura mater), and the skull They typically occur when a skull fracture tears an underlying blood vessel. EDHs are about half as common as a subdural hematomas and usually occur in young adult

because of their hypervascularity they may be identified with rapid scanning following the injection of contrast agent, particularly using the new volumetric acquisition methods

islet cell tumors

Limitations in slice-by-slice

longer examination times because of the stop-start action necessary for patient breathing, table indexing and cable unwinding.

when a patient presents with acute pancreatitis is imaging necessary to diagnose? when should imaging be used?

no acute pancreatitis is a clinical diagnosis and usually neither CT nor ultrasound is necessary imaging should only be used in patients with suspected complications

what are the main methods used to. evaluate. the kidney?

renal ultrasound and excretory urography continue to be the main methods used for investigating the kidney in most cases, ultrasound can distinguish a cystic form a solid mass

what types of pathology. can be evaluated when visualizing the retroperitoneum on Ct?

retroperitoneal fibrosis and retroperitoneal hemorrhage can also be evaluated on CT

are islet cell tumors large or small? why are they less difficult to diagnose? how do. they appear on us?

small They are less difficult to diagnose because of their hypervascular nature The tumors appear as hyperdense masses on contrast-enhanced CT

name the advantages of Ct over ultrasound?

the advantage of CT over ultrasound is that CT is not limited by the wounds, drains, ostomies, bandages, and bowel gas associated with paralytic ileus, which are commonly present in the postoperative patient

in addition to the assessment of mediastinal lymphadenopathy, CT is also successful in patients with proved or suspected bronchogenic carcinoma in determining the extent of invasion of what parts. of the body?

the chest wall, mediastinum, and diaphragm and the presence of extrathoracic metastases in the liver and adrenal glands

what is the main role of ct in the pelvis?

the main role of CT in the pelvis is in staging the extent of tumor involvement and documenting any change that may occur following treatment

Adrenal Glands CT Scan Imaging CT has made it possible to delineate normal adrenal glands easily and reliably, except when ?

the patient is extremely thin

Hepatoma on CT Scan what is very important in. the detection of focal masses. tin the liver?

the proper use of intravenous contrast is important in the detection of focal masses in the liver, particularly in the identification of hepatoma in the cirrhotic liver

renal CT is often performed however, because it can provide additional information regarding the extent of the disease and the relationship to normal structures in the retroperitoneum, the main indication for imaging is for the detection of lymphomatous or metastatic lymph nodes what is the retroperitoneum obscured by in ultrasound ?

the retroperitoneum is often obscured on ultrasound because of bowel gas, fat and bony structures CT is therefore the superior and obvious method of choice

Cerebral Abscess

the typical abscess within the brain produces a doughnut-shaped lesion, with a low-density center and a rim enhances readily

Subarachnoid Hemorrhage when does it most frequently occur? % of accuracy without contrast ? what happens if the ct os negative?

this most frequently occurs as a result of a ruptured aneurysm CT without contrast is approximately 85% accurate in demonstrating subarachnoid hemorrhage when performed within 24 hours of the event if the CT is negative, a lumbar puncture is performed, because the latter may be positive for 7-10 days after the event

T or F whereas focal masses can be seen in the spleen on both CT and ultrasound, the results of spleen assessment in patients with lymphoma has unfortunately been poor for both methods

true

Occasionally, calculi may appear as filling defects in the renal pelvis, mimicking ___ or ____in pyelography in these patients CT, may be useful to differentiate it from a tumor

tumors or blood clots

Acute Subdural Hematoma

typically produce a high-density collection situated between the skull and adjacent brain the collection follows the contour of the brain and is associated with a variable amount of mass effect chronic subdural hematoma appears as a low density

when Is Ct useful when evaluating the kidney?

when a solid lesion is identified, CT is useful for preoperative staging CT is also useful in detecting local recurrence following nephrectomy

why is Ct the method when necessary for acute pancreatitis ?

when acute pancreatitis, CT is the method of choice mainly because of the high incidence of associated paralytic ileus in these patients, which obscures visualization by ultrasound

when there tis a clinical and biochemical evidence of adrenal biofunction what modality is the only one necessary?

when there is clinical and biochemical evidence of hyperfunction, CT is usually the only imaging method necessary