radiology exam #4

study of choice for detecting & staging intracranial & spinal cord abnormalities

MRI because of its superior contrast & soft tissue resolution

study of first choice in acute head trauma

unenhanced CT. the search for findings should initially focus on finding mass effect or blood

linear skull fractures

important mainly for the intracranial abnormalities that may have occurred at the time of the fracture

depressed skull fractures

can be associated with underlying brain injury and may require elevation of the fragment

basilar skull fractures

more serious and can be associated w CSF leaks

blow out fractures of the orbit result from a direct blow and may present with

- orbital emphysema

- fracture through floor or medial wall of orbit

- entrapment of fat and/or extraocular muscles in the fracture

four type of intracranial hemorrhages that may be associated with trauma

- epidural hematoma

- intracerebral hemorrhage

- subdural hematoma

- subarachnoid hemorrhage

epidural hematomas

- hemorrhage into the potential space btwn the dura mater & the inner table of the skull

- usu due to injuries to the middle meningeal artery or vein from blunt head trauma

- almost all (95%) have an associated skull fracture

- when acute, appear as a hyperintense collection of blood in a lenticular shape

subdural hematomas

- MC result from deceleration injuries or falls

- acute portend the presence of more severe brain injury

- crescent shaped bands of blood, may cross suture lines & enter interhemispheric fissure

- do not cross the midline

traumatic intracerebral hematomas

- frequently from shearing injuries

- present as petechial or larger hemorrhages in the frontal or temporal lobes

- may be assoc w increased intracranial pressure & brain herniation

brain herniation types

- subfalcine

- transtentorial

- foramen magnum/tonsillar

- sphenoid

- extracranial

diffuse axonal injury

- serious consequence of trauma

- corpus callosum MC affected

- CT findings similar to ICH following head trauma

- MRI is study of choice in identification

increased intracranial pressure is due to either

increased volume of the brain (cerebral edema) or increased size of the ventricles (hydrocephalus)

major categories of cerebral edema

vasogenic and cytotoxic

vasogenic edema

- represents extracellular accumulation of fluid

- type that occurs w malignancy & infxn

- affects the white matter more

cytotoxic edema

- represents cellular edema

- due to cell death

- affects both gray and white matter

- assoc w cerebral ischemia

T or F: is MRI more sensitive to the early diagnosis of stroke than CT

true

strokes

- acute loss of neuro fxn when blood supply to area of brain is lost/compromised

- usu due to embolic (MC) or thrombotic events

- divided into ischemic (MC) & hemorrhagic (poorer prognosis)

- HTN is frequently assoc

intracerebral hemorrhage on nonenhanced CT scans

will display as increased density. after about 2 mos, only small hypodensity may remain

berry aneurysms

- usu formed from congenital weakening in arterial wall

- when ruptures, blood typ enters subarach space appearing in basilar cisterns & sulci

- can be detected on either CTA or MRA

hydrocephalus represents an increased volume of CSF in the ventricular system and may be due to

- overproduction of CSF (rare)

- under absorption of CSF at level of the arachnoid villi (communicating)

- obstruction of the outflow of CSF from ventricles (noncommunicating)

normal pressure hydrocephalus

- form of communicating hydrocephalus

- triad of sx: gait, dementia, urinary incontinence

- may be improved by insertion of a ventricular shunt

cerebral atrophy

- a loss of both gray & white matter

- may resemble hydrocephalus, except CSF dynamics are normal in atrophy

- produces proportionate enlargement of both the ventricles & the sulci

glioblastoma multiforme

- highly malignant glioma that occurs MC in frontal & temporal loves

- produces a v aggressive infiltrating, partially enhancing, sometimes necrotic mass

- may cross the corpus callosum to the opposite cerebral hemisphere

metastases to th ebrain

- well defined round masses near the gray white junction

- usually multiple, hypodense or isodense on nonenhanced CT that can enhance w contrast

- can provoke vasogenic edema out of prop to size of the mass

- lung, breast, melanoma most frequent sources

meningiomas

- usu occur in middle aged women in a parasagittal location

- tend to be slow growing w excellent prognosis if surgically excised

- on CT, can be dense w/o contrast bc of calc within the tumor. may enhance dramatically

vestibular schwannomas

- occur MC along course of CN 8 within internal auditory canal at cerebellopontine angle

- best identified on MRI, where they homogenously enhance

multiple sclerosis

- MC demyelinating disease

- characterized by a relapsing & remitting course

- predilection for the periventricular area, corpus callosum, & optic nerves

- best seen on MRI, shows discrete globular foci w high intensity (white) on T2 weighted images

transient tachypnea of the newborn

- MC cause of resp distress in the newborn

- MC in infants born v c section or precipitous delivery

- lungs are usually hyperinflated w streaky perihilar linear densities

- fluid in the fissures and or laminar pleural effusions

neonatal respiratory distress syndrome

- a disease of premature infants

- typ diffuse ground glass or finely granular in a bilateral & sym distribution w air bronchograms

- lungs are frequently hypoaerated

meconium aspiration syndrome

- common cause of NRDS in full term/postmature infants

- lungs are hyperinflated w diffuse "ropey" densities

- may be patchy areas of atelectasis along w emphysema from air trapping

chronic lung disease of infancy

- a consequence of early acute lung disease, freq NRDS

- infants w this have a supplemental O2 dependence

- lungs usu hyperaerated and sponge like in appearance

- lungs contain both coarse linear densities from atelectasis

- atelectasis intermixed w lucent foci from hyperexpanded areas of air trapping

complications of treatment of resp distress in the newborn are usu from barotrauma (air leaks) and include

- pulmonary interstitial emphysema

- pneumomediastinum

- pneumothorax

- pneumopericardium

reactive airways disease/bronchiolitis

- general term for group of dz in peds featuring wheezing, SOB, & coughing

- may be peribronchial thickening and hyperaeration on chest radiographs

asthma

- a clinical diagnosis

- CXR can help in determining the cause or complications of an asthmatic episode

- pneumonia is an example of an attack cause

- pneumothorax & atelectasis are complications of an attack

neonatal pneumonia

- neonates may only have a fever

- bacterial produces lobar consolidation or round pneumonia w pleural effusion in some

- viral shows interstitial opacities or patchy areas of consolidation (bronchopneumonia)

adenoids

- can grow until about 6 and involute through adulthood

- enlarged adenoids show marked narrowing or obliteration of airway on lateral neck x ray

- tonsil and adenoids frequently enlarge together

acute bacterial epiglottitis

- can be a life threatening medical emergency

- the epiglottis should not normally be thumb sized in appearance

- occurs at and older age (3-6) than croup (6 mo to 3 yrs)

croup key imaging findings seen on lateral soft tissue neck x ray

- distension of the hypopharynx

- distension of the laryngeal ventricle

- haziness and/or narrowing of the subglottic trachea

foreign body ingestions

- most occur btwn 6 mos to 6 yrs, majority pass spontaneously

- impact at several diff anatomic landmarks where the esophagus naturally narrows

- disk batteries & magnets pose particular hazards & should generally be removed

the cardiothoracic ratio may reach up to _____ in infants and still be normal

65%

in a child, the thymus gland may overlap portions of the heart and sometimes mimic

cardiomegaly

growth plate fractures

- common in childhood

- salter-harris commonly used method to describe

fractures pointing to child abuse

- metaphyseal corner fractures

- rib fractures

- certain head injuries

- x ray eval key in diagnosing child abuse

necrotizing enterocolitis

- MC GI medial and/or surg emergency occurring in neonates, esp premature infants

- may be dilated loops of bowel, thickened bowel walls, pneumatosis intestinalis, & portal venous gas

esophageal atresia

- may occur w or w/o tracheoesophageal fistula

- MC form is blind ending esophagus w fistulous connection btwn trachea & distal esophageal remnant

tracheoesophageal fistula may be associated with other congenital anomalies such as(VACTERL)

- vertebral anomalies

- anal atresia

- cardiac abnormalities

- TEF and/or esophageal atresia

- renal agenesis or dysplagia

- limb defects

arterial access facilitates many other image guided arterial interventions such as

embolization for active bleeding and angioplasty for arterial stenosis

central venous access

- used for venous intervention, pharmacotherapy, or hemodialysis

- tunneled catheters are used for long term hemodialysis or pharmacotherapy (chemo)

pts who have a life-threatening, massive pulm embolism are at a high risk for developing a bleeding complication if

they receive systemic IV thrombolytic medication, may benefit from catheter directed thrombectomy/thrombolysis

IVC filters may be placed when

- pts w pulm embolus when anticoag is contraindicated

- when progression of thromboembolic dz occurs despite anticoag use

- chronic, recurrent PE when anticoag thx has failed

image guided biopsy is indicated for

the minimally invasive sampling of a lesion previously identified on an imaging study or when the pathology of a lesion is in question

transjugular intrahepatic portosystemic shunt

- minimally invasive procedure for lowering the poral pressure with portal hepatic venous shunt

- used most often to control recurrent variceal bleeding refractory to endoscopic and med tx

- used to control abdominal ascites secondary to cirrhosis

percutaneous nephrostomy (PCN)/nephroureterectomy (PCNU) tubes

- can alleviate hydronephrosis 2nd to renal/ ureteral stones, malignancy, or inflammation

- can also be used for urinary diversion & preop access to urinary collecting system

aneurysm repair

- either open surg repair or endovascular with covered stent placement (endograft)

- endograft forms a new endoluminal channel through which blood flows

- endograft excludes flow through aneurysm itself and prevents rupture

indications for EVAR

- thoracic or abd aneurysm asymp >=5.5 cm in men, >=5cm in women or growth rate >1 cm/yr or >0.5 cm in 6 mos

- symptomatic thoracic or abd aneurysm regardless of size

- thoracic or abdominal aneurysm w known or impending rupture

MRI uses a very strong magnetic field to influence the electromagnetic activity of

hydrogen nuclei, also called protons

protons

- each have a charge and possess a spin

- the constant mvt of protons gen a small mag field, causing proton to be a mini magnet

- when placed in powerful magnetic field of MRI scanner, they all align with this field

radiofrequency pulse

transmitted by a transmitter coil, displaces the protons from the original alignment w the external magnetic field of the scanner

when the RF pulse of an MRI is turned off

- the displaced protons relax & realign w main magnetic field

- produce an radiofrequency (echo) as they realign

- receiver coils receive the echo given off by the protons

- a computer reconstructs the information from the echo to generate an image

main magnet in an MRI scanner

usually a superconducting magnet that is cooled to extremely low temps in order to carry the electrical current

pulse sequences

- consist of a set of imaging parameters that determine the way a tissue will appear

- 2 main pulses sequences are called SE and GRE

T1 and T2

- are both time constants

- T1 is the longitudinal relaxation time

- T2 is the transverse relaxation time

TR

the repetition time btwn two RF pulses. a short TR creates a T1 weight image

TE

the echo time btwn a pulse and its resultant echo. a long TE creates a T2 weighted image

fat is T1 and T2 _____, water is T1 ____ and T2 _____

bright, dark, bright

suppression

- a feature of MRI that will cancel out or elim signal from certain tissues

- most often used for fat

- although normally T1 bright, fat will be dark on T1 weighted, fat suppressed images

- fat suppression is useful for tissue charac after administration of gadolinium

gadolinium

- MC IV contrast agent used in clinical MR imaging

- its effect is to shorten the T1 relaxation time of H nuclei yielding a brighter signal

- tumors and inflammation enhance after admin and become more conspicuous

ferromagnetic objects

- must be kept outside of the MRI scanning room, could become airborne

- pts who may have metallic FBs in eyes must 1st have orbital x ray to determine if present

pregnancy and MRI

MRI can be performed at any stage if risk to benefit is deemed appropriate due to lack of ionizing radiation, but gadolinium is contraindicated

nephrogenic systemic fibrosis

- debilitating fibrotic dz that can occur in pts w renal insuff who receive IV gadolinium

- negligible risk w newer group II gadolinium agents are typ safe for pts w CKD