CT TEACHING MANUAL PDF

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CT Teaching Manual 3rd edition. Home ยท CT Teaching 44MB Size Report. DOWNLOAD PDF Teaching atlas of mammography 3rd Edition. Read more. This is the first English-language edition of an introduc- tory computed tomographic (CT) manual previously published in Germany. Its stated goals include. OVERVIEW. The text CT Teaching Manual: A Systematic Approach to. CT Reading was written for medical students, technologists, interns, and residents, or.


Ct Teaching Manual Pdf

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CT Teaching Manual: A Systematic Approach to CT Reading, 4th ed. By Mattias Hofer. New York, NY: Thieme Medical, pp., $ softcover (ISBN. HOFER - CT Teaching Manual - A Systematic Approach to CT Reading, 2nd Ed. - Ebook download as PDF File .pdf), Text File .txt) or read book online. Thieme is an award-winning international medical and science publisher serving health professionals and students for more than years.

In patients with suspected renal dysfunction base- line blood urea nitrogen and creatinine levels should be obtained see below. It is important to note whether prior CT images are available for comparison. Information about prior surgery and radiation therapy in the anatomic region to be examined by CT is also important. Careful consideration of the pertinent radiologic findings on the current study in context with prior results and the patients clinical history allow the radiologistto render a meaning- fuldifferentialdiagnosis.

Renal Function With the exception of few such as stone protocol, fracture assessment most CT exams require the Lv. Since contrast agents are excreted by the kidneys and may cause changes in renal hemodynamics and tubular toxicity [8], the physician should evaluate the patient's renal function by measuring the plasma creatinine prior to CT. If results suggest renal dysfunction, contrast agents should only be given in a very narrow range of indications [9, 10].

Furthermore, the use of low osmolality iodinated contrast is associated with a lower risk of renal toxicity and should be considered under this circumstance. Adequate patient hydration is also an important adjunct measure.

Diabetic patients on metformin therapy, an oral anti- hyperglycemic medication,must be given special attention [8, 9J. In these patients, contrast agents may cause lactic acidosis especially when there is coexisting renal dysfunction. Therefore it isrecommended towithholdmetforminon thedayofthe examand the following 48hoursand toreinstate therapyafter repeatserum creatinine measurement hasconfirmed stable renal function. Until recently, incases wherecontrast agentswas absolutelynecessary for a dialysis patient, the CT examination wasscheduled so that dialysisfollowed immediately.

Recentreports, however, show that there is no need for urgent dialysis [11]. However, residual renal function in a dialysis patient can suffer from circulating contrast.

Otherwise thereseemto be no other complications if thecontrast agentcirculates foradayortwountil thenext dialysis. Creatinine levels can be checked quickly and are inexpensive; Inordertosave time you may wantto havethe resultavailable on the requisition for the exam for immediate review by the radiolo- gist when prescribing the examprotocol. Hyperthyroidism Examining for hyperthyroidism is costly and time-consuming. Laboratory parameters and possibly scintigraphy may be necessary.

Inother cases,the information"noclinical evidence of hyperthyroidism" or even better, the documentation of thyroid function onthe requisi- tion is helpful.

Thus, the radiologist can be sure that testing has been done. Notethatreferencevalues Table Check with your laboratory about commonly used units and normal ranges if these are not included on the report.

The risk of thyrotoxicosis caused by the iodinated contrast agents can thus be avoided. If radioiodine therapy for hyperthyroidism orthyroidcancerisplanned,theLv.

Radioiodinetherapy may have to bedelayed for sometimeas a result. Nevertheless, previous reactions are a pointer to an increased risk and should be elicited by taking a careful medical history. Theseverity ofany reactiontocontrast agents inthe past is of great importance. If the patients give a history of itching or hives following prior contrast administration, premedication is advisable.

With a history of hypotension or cardiovascular collapse, contrast agents should not be given at all or only after thorough assessment of the clinical indication and appropriate premedication. Asageneral rule,patients whorequirepremedica- tion because of a previous reaction should be kept NPO 6 hours prior tothe examination.

This reduces risk ataspiration incase of severe anaphylactic reaction requiring intubation and ventilation for detailed information see pp. Premedication history of previous adverse reactions to contrast agents In cases of mild adverse reactions, premedi- cationisaccomplishedwiththree oraldosesofPrednisone, 50mg each, taken 13,8 and 1 hour before the examination. In addition, 50mgof intramuscularantihistamine drug e. Benadryl isgiven 1 hour before the exam.

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Side effects such as raised intraocular pressure or urinary retention may occur. In addition, drowsiness may occur for about 8 hours following administration of these drugssodriving must beavoidedforthisperiod.

Ifan outpatient CT examination is scheduled, the patient must be informed about potential drowsiness and the possibility of temporarily impaired vision; heor she should be accompanied on the way home. You will find checklists of all key words concerning medical historiesand suggestions for premedication on a practicalcard in the rearfoldout.

CT examination. Inorder tofacilitatethecorrect choice of In such cases water-soluble gastrografin would be used instead of a con- trast agent containing barium sulfate. Andfinally, where possible, CTofthe abdomen should be delayed for 3 days afteraconventio- nal barium examination has been carried out for example: Usual- ly, the digital projection radiograph scanogram Fig.

The sequence of diagnostic proce- dures for patients with abdomi- naldiseasesshouldthereforebe carefullyplanned. Naturally,the patientmust havethefeelingthat heorshe s: Many patients are relieved to know that they can communicate withtheradiographersinthecontrol room viaanintercom andthat the examination can be interrupted or terminated at any time if thereare unexpected problems. Patients with claustrophobia may feel morecomfortable if they close their eyes during the examina- tion; the close proximityof the gantry isthen less of a problem.

In very rarecases, a mildsedative may be helpful. Inthe helical technique it is. In Figures For the same reasonall clothing with - ,,: This can be accomplished by opacifying the intestinal lumen with an orally administered contrast agent. For example, withoutof contrast agent it is difficult to distinguish between the duodenum and the head of the pancreas inFig. Equally, other parts of theintestinal tract wouldalso bevery similar to neighboring structures.

After an oral contrast agent, both the duodenum and the pancreas can be well delineated Fig. In orderto acquire images of optimal quality, the patient shouldfast be NBM beforedrinking contrast agents. This oral con- trast agent should therefore not be used if abdominal surgery involving opening ofthe bowellumen isscheduled,suchasinpar- tial resections or anastomotic sutures, or if there is any risk of injury tothe bowel.

Neither shouldbarium sulfatebeused incases of a suspectedfistulaor aGITperforation. Awatersoluble contrast agent, such asgastrografin,is then employed; it can be resorbed bythebody after it spreads intothe abdominal cavity.

For an optimal assessment of the stomach walls, plain water is increasingly used as a hypodense contrast agent in combination with intravenous buscopan,which relaxes the muscularis [15, 16]. If the urinary bladder has been removed and an i1ial conduit constructed, the abdomen is examined first with an intravenous contrast agent which is excreted into the urinein theconduit but notwithinthenativeintestines.

If necessary,theintestines can be examined ina second scanafter oral contrast agents. However,if theentirecolon and especial- lytherectum need to beopacified with barium sulfate,a periodof at least min is necessary in a fasting patient. Thewater- solublecontrastagent gastrografinspreadssomewhat morerapid- ly.

For the peivic organs bladder, cervix, orovary , ml of contrast agent may be given rectally to insure that tumors are clearlydifferentiated fromthe lowerintestinal tract. Dosage Toachieve completeopacificationof theentireGIT, mlof a barium sulfate suspension are dissolved andthoroughly mixed with water ml. For adequate contrast of the entire GIT, ml of water-soluble gastrografin in mlof water are enough. If only theupper part of the GIT needs to be opacified, ml of either medium are sufficient.

Administration of Contrast Agents 21 enous Contrast Agents - - ease in the density of blood vessels not only demarcates --r oener from muscles and organs butalso provides informa- the rate of blood perfusion contrast agent uptake in: I helical CTisavailable,aseries ofliver images inthe early: Line - -: Checking that the canula is correctly sited in the vessel is very important.

Atrial injection ofsterilesaline at a high flow rateinto the veinshould be carriedoutbefore injecting contrast agents. The absence ofsubcutaneousswelling confirms properpositioning;the fact that the vein can accommodate theintendedflow canalso be confirmed. Dosage Dosage is calculated on the basis of b. Whentolerancetocontrast agentsandoptimal vessel contrast are balanced,adosageof,forexample,1. Inflow Phenomena Thestreaming artifact of enhanced and unenhanced blood results fromashort interval between the startof injectionandtheonset of dataacqulsltlon.

Since inflow is usuallyfrom oneside viatheaxil- lary, subclavian, and brachiocephalic veins 91 into the superior venacava 92 ,thereis an apparent filling defect withinthevena cava Figs.

Knowingabout suchinflow phenomena avoids a false positive diagnosis of venousthrombosis. Using too high concentrations of contrast agents inthis area could result in disturbing artifacts, especially with the helical technique Fig. More inflow phenomena will be described on the next pages. Theseveins may containblood which has afairly highconcentration ofcontrast agentsandthis blood mixes with unenhanced blood returningfrom the lower extremitiesand pelvic organs.

In the early post-contrast phase the vena cava 80 caudal to the level of the renal veins is hypodense relative to the adjacent aorta 89 asin Figures I Fig. If the renalveins donotempty intothe cava at the same levelor if a kidney has been removed, a unilateral enhancement may occur Fig.

Such differences in density should not be mistaken forthrom- bosis of the inferior cava ct. Administration of Contrast Agents 23 Flow Phenomena If wetrace theinferior vena cava cranially towardtherightatrium, additional flow phenomena become apparent asmoreveins empty into it.

Moments later such inhomogeneities are no longer evident inthelumen 80 anddensityleveis are identicai to those inthe aorta 89 Fig, Thisplaqueappearsalso in Figure The patient had well-developedosteophytes 64 on thevertebral bodies Inimages such as in Figure An SCTof thethoraxshould therefore beobtainedfrom caudal tocranial. Inthat way structures nearthe diaphragm are imaged first, and when cranial parts are scanned the contrast agents will have been spread after having passedthe pulmonary circulation.

This trick helps avoid the artifacts 3 shown in Figure Only high-risk patients need to be super- vised for morethan30minutes. Since suchpatientscanusuallybe recognized by taking a thorough medical history, they can be premedicated accordingiy see p. If, despiteprecautions, erythema develops afteran l. Remember that i. There is a period of latency, and these antagonists are therefore primarily eftective in preventing the symptoms from worsening.

Serious incidents pulmonaryedema,circulatoryshock,convulsions occur very rarely with the new contrast media; they require immediate intensive care. Be sure to document any incident in your report.

Radiologists pertorming future examinations will be forewarned about the patient's sensitivitytocontrast agents. Give aminophylline: Ifpoorly responsive: Epinephrine 1: In patients with a medical history of yperthyroidism consider blocking the thyroid gland before l.

Alternatively, carbimazole can be ed to block hormone synthesis.

Both treatments take approxi- ately 1 week to become fully effective. Effectiveness must be: The symptoms may include diarrhea, muscle weakness as well asfever, sweating,dehydration,anxiety and restlessness, or even tachyarrhythmia. The main problem is the long periodof latency beforethethyrotoxicosis crisisbecomes manifest. This effect mayappear 4 to6 weeks after theintravascularcontrastadministrationin some ofthese catients.

It canoccur after theadministration of either ionic, high-osmolality or nonionic, low-osmolalitycontrast.

It is usuallysett-limt-: Therefore, if systemic radioactive iodine therapy is part of planned -satmen, a pretherapy diagnostic study of the patient using iodinated radiographic contrast medium intravascular or oral may be - traindicated; consultation withthe ordering clinician prior tocontrast administration inthese patients isrecommended.

For instance,thedifferential diagnosis DO of cerebral bleeding versus infarction in patient with sudden onsetof neurologic deficits does not require the administrationof contrast medium. However, intravenous injection of contrast medium is necessary to detect an impaired blood-brain barrier BBB as found in tumors, metastases or inflammations. I Selection of the ImagePlane The desired image planes parallel to the orbitomeatal line are selected on the sagittal localizer image topogram Fig.

This isa readily reproducible line drawnfrom the supraorbital ridge to the external auditory meatus, allowing reliable comparison with follow-up CT examinations. The posterior fossa is scanned in thin sections mm to minimize beam hardening artifacts, and the supratentorial brain above the pyramids in thickersections 5 mm. The images are displayed as seen from below caudal view and consequently are laterally reversed, i.

This means that the examiner can choose between several acceptable approachesand is not restricted toa "oneand only" strategy.

However, staying with a consistent arrangement of theimages tobeinterpretedhastheadvantagethat fewerfindings areoverlooked, especiallybythenovice. The checklist belowjust contains recommendations that can serve as good guideline for thenovice. First,thesize of theventricles andextracerebral CSFspaceshasto be evaluated to exclude a life threatening space-occupying process rightaway. Hereby,the patient'sagehasto be considered because of age-related widening of the CSFspaces.

Any blurring of the grey-white matter junction as manifestation of cerebral edema should be lookedfor see below. If a pathologicchange is suspected,the adjacent sections should beinspectedtoavoid any misinterpretationduetoa partial volumeeffect see Fig. Always usethe legendson thefrontcover flapforthischapter. The listednumbersapplytoall headandneckimages.

Thesubsequent pages provide you with a survey of the normal anatomy, followed by normal variantsand themost frequent pathologic findings. Sylvianfissure, refer to p. Sign ofimpaired BBB? Osseous lesions: Ruleout fractures especially cranial base, midfacial bones- DO sutures Since the hardcopies are orientedsuch that the sections are viewed from caudal, all structures appear as if they were lelUrightreversed see p.

The small topogram shows you the corresponding posi- tion of each image. You shouldfirstcheckfor any swellings in the soft tissues whichmayindicatetrauma to the head.

Always examine the condition of the basilar artery 90 in scans close to the base of the skull andthe brainstem The viewis often limited by streaks of artifacts 3 radiating from thetemporal bones 55b.

When examining trauma patients. In the caudal slices you can recognize basai parts of the temporal lobe and the cerebellum Orbital structuresare usually viewed in another scanning plane see pp. In Figure Normal Anatomy Fig. The pituitary gland and stalk are seen between the upper border of the sphenoid sinus 73 and the clinoid process Of the dural sinuses, the sig- moid sinus can be readily identified.

The basilar artery 90 and the superior cerebellar arlery 95a lie anterior to the pons The cerebellar tentorium The inferior temporal horns ofthe lateral ventricles as well as the 4th ventricle can be identi- fied in Figure Fluid occurring in the normally air-filled mastoid cells 62 or in the frontal sinus 76 may indicate a fracture blood or an infection effusion. The cortex nextto thefrontal bone 55a often appears hyperdense compared to adjacent brain parenchyma, but this is an artifact due to beam-hardening effects of bone.

Note that the choroid plexus 1 23 in the lateral ventricle is enhanced after Lv. Even in plain scans it may appear hyperdense becauseofcalci- fications. You will soon have recog- nizedthat theeeTimageson thesepagesweretaken after l. The branches 94 of the middle cerebral artery 91 b are visible in the Sylvian fissure 1 Even the pericallosal artery Nevertheless, it is often difficult to distinguish be- tweenthe opticchiasm and the pituitary stalk because these structures havesimilar densities.

InFigure Check whether the contours of the lateral ventricles aresymme- tric. A midline shift could be an indirect sign of edema. Calcifications in the pineal gland and the choroid plexus are a common finding in adults, and are generally without any patho- logic significance. Due to partial volume effects, the upper parts of the tentorium often appear without clear margins so that it be- comes difficult to demarcate the cerebellar vermis and hemispheres from theoccipital lobe It is particularly important to carefully inspect the internal capsule 1 21 and the basal ganglia: Consult the number codes in the front foldout for the other structures not specifically mentioned on these pages.

Cranial CT Normal Anatomy 31 The position of the patient's headisnot always as straight asinour example. Even small inclinations may lead to remarkably asymmetric pictures of the ventricular system, though in reality it is perfectly normal.

You may see only a partial slice of the convex contoursof thelateral ventricles 1 This could give you the impression that they are not well defined Fig. By using our website you agree to our use of cookies.

Home Contact us Help Free delivery worldwide. Free delivery worldwide. Bestselling Series. Harry Potter. Popular Features. New in In very rare cases. In order to facilitate the correct choice of:. For the same reason all clothing with.. CT examination. In Figures Inthe helical technique it is. If the patient cannot comply.. For adequate contrast of the entire GIT.

If necessary. For the peivic organs bladder. This oral contrast agent should therefore not be used if abdominal surgery involving opening ofthe bowel lumen isscheduled. The watersolublecontrastagent gastrografinspreadssomewhat morerapidly. Dosage To achieve completeopacification of the entire GIT. After an oral contrast agent. Neither should barium sulfate be used in cases of a suspectedfistula or a GIT perforation.

If the urinary bladder has been removed and an i1ial conduit constructed. Awatersoluble contrast agent. In ord er to acquire images of optimal quality. If only the upper part of the GIT needs to be opacified. This can be accomplished by opacifying the intestinal lumen with an orally administered contrast agent. For an optimal assessment of the stomach walls. Checking that the canula is correctly sited in the vessel is very important.

Inflow Phenomena The streaming artifact of enhanced and unenhanced blood results from ashort interval between the start of injectionandtheonset of data acqulsltlon. Thesame holds. Since inflow is usually from oneside viatheaxillary. A trial injection of sterile saline at a high flow rate into the vein should be carriedoutbefore injecting contrast agents.

Dosage Dosage is calculated on the basis of b. More inflow phenomena will be described on the next pages. Vascular grafts. Administration of Contrast Agents 21 enous Contrast Agents. Knowing about such inflow phenomena avoids a false positive diagnosis of venousthrombosis. I helical CTis available. When tolerance tocontrast agents and optimal vessel contrast are balanced.

The absence ofsubcutaneous swelling confirms properpositioning. Using too high concentrations of contrast agents in this area could result in disturbing artifacts.: Such differences in density shou ld not be mistaken for thrombosis of the inferior cava ct. In the early post-contrast phase the vena cava 80 caudal to the level of the renal veins is hypodense relative to the adjacent aorta 89 as in Figures I Fig.

Theseveins may contain blood which has a fairly highconcentration of contrast agentsandthis blood mixes with unenhanced blood returning from the lower extremitiesand pelvic organs.

Administration of Contrast Agents 22 Application of Contrast Agents Flow phenomena can alsobe seen inthe inferior vena cava 80 atthe level ofthe renal veins If the renal veins donot empty into the cava at the same level or if a kidney has been removed.

In images such as in Figure The patient had well-developed osteophytes 64 on the vertebral bodies An SCT of thethorax should therefore be obtained from caudal to cranial. Inthat way structures near the diaphragm are imaged first. This plaqueappears also in Figure This trick helps avoid the artifacts 3 shown in Figure Moments later such inhomogeneities are no longer evident in the lumen 80 and density leveis are identicai to those in the aorta 89 Fig.

Administration of Contrast Agents 23 Flow Phenomena If we trace the inferior vena cava cranially toward therightatrium. There is a period of latency. Be sure to document any incident in your report. Remember that i. Give aminophylline: Since such patients canusually be recognized by taking a thoroug h medical history.

If unresponsive to inhalers. Serious incidents pulmonary edema. Epinephrine 1. Ephinephrine SC or 1M 1. Epinephrine 1: Only high-risk patients need to be supervised for morethan 30 minutes. If poorly responsive: Alpha agonist arteriolar and venousconstriction Epinephrine SC 1. Radiologists pertorming futu re exami nations will be forewarn ed about the patient's sensitivity to contrast agents.

O2saturation pulse oximeter. It is usually sett-limt: The symptoms may include diarrhea. It can occur after the administration of either ionic. This effect may appear 4 to 6 weeks after the intravascular contrast administration in some ofthese catients.

Both treatments take approxiately 1 week to become fully effective. Effectiveness must be: The main probl em is the long period of latency beforethethyrotoxicosis crisis becomes manifest. In patients with a medical history of yperthyroidism consider blocking the thyroid gland before l.

The images are displayed as seen from below caudal view and consequently are laterally reversed. Sylvian fissure. DO sutures. DO physiologic calcification choroid plexus. The checklist below just contains recommendations that can serve as good guideline for the novice.

Sign of impaired BBB? For instance. I Selection of the Image Plane The desired image planes parallel to the orbitomeatal line are selected on the sagittal localizer image topogram Fig. Osseous lesions: Rule out fractures especially cranial base.

An y blurring of the grey-white matter junction as manifestation of cerebral edema should be looked for see below. Cranial CT. Always usethe legends on thefront cover flap for this chapter.

If a pathologic change is suspected. Thesubsequent pages provide you with a survey of the normal anatomy.. The posterior fossa is scanned in thin sections mm to minimize beam hardening artifacts. This means that the exam iner can choose between several acceptable approaches and is not restricted to a "one and only" strategy.

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The listed numbers apply toall head and neck images. This is a readily reproducible line drawnfrom the supraorbital ridge to the external auditory meatus. The view is often limited by streaks of artifacts 3 radiating from thetemporal bones 55b.

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Since the hardcopies are oriented such that the sections are viewed from caudal. The small topogram shows you the corresponding position of each image. Always examine the condition of the basilar artery 90 in scans close to the base of the skull andthe brainstem In the caudal slices you can recognize basai parts of the temporal lobe and the cerebellum When examining trauma patients.

In Figure Orbital structuresare usually viewed in another scanning plane see pp. The inferior temporal horn s of the lateral ventricles as well as the 4th ventricle can be identified in Figure Fluid occurring in the normally air-filled mastoid cells 62 or in the frontal sinus 76 may indicate a fracture blood or an infection effusion. The basilar artery 90 and the superior cerebellar arlery 95a lie anterior to the pons Of the dural sinuses.

The pituitary gland and stalk are seen between the upper border of the sphenoid sinus 73 and the clinoid process The cerebellar tentorium Normal Anatomy 28 I As the series of slices continues dorsally. The cortex next to the frontal bone 55a often appears hyperdense compared to adjacent brain parench yma. Note that the choroid plexus 1 23 in the lateral ventricle is enhanced after Lv. The branches 94 of the middle cerebral artery 91 b are visible in the Sylvian fissure 1 Even the pericallosal artery Even in plain scans it may appear hyperdense becauseofcalcifications.

You will soon have recognizedthat the eeTimages on these pages weretaken after l. A midline shift could be an indirect sign of edema.

It is particularly important to carefully inspect the internal capsule 1 21 and the basal ganglia: Calcifications in the pineal gland and the choroid plexus are a common finding in adults. Check whether the contours of the lateral ventricles are symmetric. Consult the number codes in the front foldout for the other structures not specifically mentioned on these pages. In Figure Due to partial volume effects.

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In late stages they are well defined and show the same density as CSF see p. As residues of older infarctions. Even small inclinations may lead to remarkably asymmetric pictures of the ventricular system. You may see only a partial slice of the convex contours of the lateral ventricles 1 The paraventricular and supraventricular white matter must be checked for poorly circumscribed hypodense regions of edema due to cerebral infarction.

For evaluating the width of the SAS. Compare the images on pages 50 and 52 in this context. Cranial CT Normal Anatomy 31 The position of the patient's head is not always as straight asin our example. This could give you the impression that they are not well defined Fig. The phenomenon must not be confused with brain edema: Continue to check for bone metastases or fracture lines. After athorough evaluationof thecerebral soft-tissue window.

Only now is your evaluation of a cranial CT really complete. I Note: If you have difficulties. After these you will find themost common anatomic variations. You should differentiate this kind of lesion. The presence of CSF-filled sulci in adults is an important finding withwhich toexclude brainedema.

Test yourself! Exercise 1: Note from memory a systematic order for theevaluation of cranial CTs.

The number codes for all drawings arefound inthe legend in the front foldout. CM was infused intravenously before the examination of the orbits. Cranial CT Normal Anatomy of the Orbit Axial 33 The face and the orbits are usually studied in thin slices 2 mm using 2-mm collimation steps. In the petrous part of the temporal bone 55b.

For a more detailed evaluation of the semici rcular canals and the cochlea. Two parts of the mandible appear on the left side: The orientation of the scanning plane is comparable to that for CCTs see p.. If there is fluid or a soft-tissue mass.

Forthe detection of a tumor-related arrosionof bone or a fracture. The following pages therefore present each scan level in both windows. The printouts are usually presented in the view from caudal: The branches of both the facial and angular vessels 89 as well asthe basilar artery 90 therefore appear markedly hyperdense in the soft-tissue window Fig.

The accompanying drawing Fig. The carotid artery. For examples of such diseases. Even a slighttilt Fig. This is due to the similar densities of these structures. The medial wall of e nasolacrimal duct 1 52 is often so thin that it cannot be differentiated. At first sight the appearance of the clinoid process , etweenthe pituitary stalk and the carotid siphon 85a on the left side only, may be confusing in Figure Thegray shadeoftheoptic nerves 78 as they pass through the chiasm to the optic tracts , however, is verysimilar to that of thesurrounding CSF You should always check on thesymmetry of theextraocularmuscles 47 intheretrobulbar fatty tissue 2.

Figure The superior rectus muscle 47a appears at the roof of the orbit and immediately next to it lies the levator palpebrae muscle Examples of pathologic changes of the orbits or fractures of facial bones are found on pages 61 to Due to similardensities. A suspected fracture of the zygomatic arch may require addit ional scans in the. Inorder toacquire scans in the coronal. The patient should be in a prone position. As for the s chapter. The same problem occurs in axial scans of the face compare with Fig.

Hemorrhage into the paranasal sinuses or the detection of intracranial bubblesof air must beinterpreted as an indirect sign of a fracture. The short inferior oblique muscle You should always make sure that all paranasal sinuses are filled exclusively with air. It representsthemain channel for discharging secretions of the paranasal sinuses. If a case of chronic sinusitis is suspected. You will find the answeron p. J al bone. I pleura window: Without doubt. What specific aspects must you consider when administeri ng this kind of CM.

Before going on with the anatomy of the:.

All exercises are numbered: Test Yourself! Reterto the relevant pages only if you getstuck. If you havedifficulties answering this question MRI examinations.

Note precisely.: Are thereany consequences for your list? Inflammation of these air-filled sinuses leadsto characteristic effusion and swelling of the mucous membranes see Fig. The topogram Fig. The two petrosal bones 55b are therefore enlarged and imaged separately. To ensure optimal resolution.

Only then is it possible to differentiate small structures like the ossicles 61a-i: Note the pneumatization of the mastoid cells 62 and the usually thin walls of the outer auditory canal 63b.. Th ink about differential diagnoses involving effusion inthemiddle ear The cerebellar hemispheres The funnel-shaped depression in the posterior rim of the petrosal bone Fig.

Apart from the ossicles 61 a--i: Exercise NO. If the eT scan in Figure Thewidth ofthe ventricles andthesurface SAS increases continuously with age. Especially in middle-aged female patients you will sometimes find hyperostosis of the frontal bone 55a Steward-Morel-Syndrome without any pathologic significance. The space between it and the frontal bone 55a becomes quite large.

After evaluating thesoft tissues it is essential to examine the inner and outereSFspaces. This so-called frontally emphasized brain invoiution should not be mistaken for pathologiC atrophyof the brain or congenitai microcephalus.

The frontal bone 55a Is internally thickened on both sides. In some patients this physiologic decrease in cortex volume is especially obvious in thefrontal lobe Before making a diagnosis of cerebral edema or brain atrophy you should therefore always check on the age of the patient.

In cases of doubt. If not. In patients with a history of orbital tumor. The CT scan of the orbit in Figure In the plane of Figure Usually only the part of the septum located between the two anterior horns of the lateral ventricles Fig. Refresh your anatomic skills by naming all other structures in Figure Please review the normal scans in Figures Involuntary movements of the head can be kept at a minimum by soft padding.

By comparing this plane with the adjacent one below it Fig. If the head is tilted even slightly during the scan procedure. The exact position of the nose in an a. Oniy its roof will appear. In ventilated or unconscious patients an additional immobilization of the head with suitable bandings may be necessary. The computer therefore calculates a blurred. In this example the bones of the:.

Such artifacts would not appear in MR images of these levels. Many injured patients cannot be expec? C base caused the hyperdense partial volume effect. Please note the considerable beam hardening bone artifacts 3 overlapping the brain stem Contusions with subcutaneous hematomas 8 may. After complete resorption of a hematoma Fig.

Possible complications of such leakage or of a subarachnoid hemorrhagearedisturbed eSFcirculationcaused byobstruction of the pacchionian granulations. Cranial Pathology Intracranial Hemorrhage 54 After having discussed that partialvolume effects dueto asymmetricprojections i. In anemic patients the hematoma is less dense and may therefore appear isodense to normal brain. An hydrocephalus with increased intracranial pressure and transtentorial herniation of the brain may result.

A eeT obtained im mediately after skull trauma which does not show any pathologic changes is therefore not a good predictor since deiayed cerebral bleeding cannot be ruled out. A foilow-up scan should be obtained if the patient's condition deteriorates.

Type of bleeding Characteristics Subarachnoid bleeding Hyperdense blood in the subarachnoid space or the basal cisterna instead of hypodense eSF Fresh hematoma: Quite frequently this in turn causes obstruction of the contralateral foramen of Monro resulting in unilateral dilation of the lateral ventricle on the side opposite thebleeding Fig.

Bleeding Caused by a Contusion As a direct consequence of skull trauma. The characteristicsuseful in differential diagnosis of the various types of intracranial bleeding are listed in Table An acute hemorrhage 8 appears as a hyperdense mass which may be accompanied by surrounding edema and displacement of adjacent brain tissue.

Epidural and subdural hematomas can also lead to major displacement of brain tissue and to midline shifts. Acute edema is thereforenot presenl yet. In this case the 3rd ventricle is completely filled with clotted blood. Please note the edema surroun. The patient is in danger of transtentorial herniation if the ambient cistern is effaced Fig.. In such cases it is important to havea closer look at the width of the SAS overthe.

In the present case though. In contrast to an epidural hematoma. It is thereforenot as important. Hematomas with the propensity to expand. The only identifiable sign may be a small hyperdense area adjacent to the falx Subdural Hematoma Bleeding into thesubduralspace results from cerebral contusions. In adults a small subarachnoid hemorrhage alsocauses only a minor.

This kind of bleeding is notconfined by cranial sutures and may spread along the entire convexity of the hemisphere. At the timeofthisCTscan the bleeding was soslight that it had not yet caused anydisplacement of brain tissue.

CT Teaching Manual 3rd Edition

The hematoma initially appears asa long. The danger involved in a small. Subdural hematomas can also cause marked displacement of brain tissue Fig. It is difficultto determine whether the bilateral. Arterial hemorrhage lifts the dura from the inner surface of the cranium 55 and then appears as a biconvex. Cranial Pathology Intracranial Hemorrhage 57 Extradural Hematomas Bleedings into the extradural spaces are usually caused by dam age to the middle meningeal artery. Use the free space below the picture: Inthis case the distortion of the midline was caused by the right-sided.

Exercise 8: Space for your suggested answer: Predisposed areas are temporoparietal regions or sometimes the posterior cranial fossa. In small extradural hematomas 8 the biconvex shape is not distinct Fig. The hematoma does not extend beyond the sutures between the frontal 55a. It is important to distinguish between a closed skull fracture with an intact dura. An unequivocal sign of a compound skull fracture Fig.

In this case the infarction Is 2 weeks old and necrotic tissue has been mostly resorbed and replaced by CSF. Old emboli result in small. A CT scan shoulc be repeated if the initial scan does not show any pathologicchanges even though the patient is symptomatic and if symptoms de notresolve resolution of symptoms points to a transient ischemic attack.

Vascular occlusion develops in association with atherosclerotic changes of cerebral arteries or. Cranial Pathology Stroke 58 Apart from cardiovascular and malignant diseases. If the area of infarction corresponds to the distribution of a cerebral artery. In classical infarctions of branches of the middle cerebral artery.

Adiffuse pattern of defects calls forcolor flow Doppler imaging or carotid angiographyand an ecnocaroiocramto exclude atrial thrombus. In case of aTIA: Please remember that in a suspected stroke it might take up te 30 hours to distinguish clearly the accompanying edema as " hypodense lesion from unaffected brain tissue.

The unenhanced follow-up CT scan in Figure A further cause are blood clots from the left heart or thrombotic plaques from the carotid bifurcation which embolize into a cerebral vessel. Such areas are called lacunal infarcts Fig. In contrast to theTIA. Incaseof embolization. Athrombus occludes a cerebral artery. Smaller areas of infarction do not usually show any significant midline shift.

If the arterial walls are damaged. Did you also spot the second. CM the lesion in the left hem isphere 7 is clearly demarcated Fig. Even small areas in which the blood-brain barrier is disturbed become visible Fig. In the unenhanced image Fig. The post-CM image. The differential diagnosis of brain tumors is made much easier by the injection of i. After l. Large metastases sometimes cause surrounding edema which could be misinterpreted as infarct-related edema on unenhanced images if the metastasis appears isodense to the adjacent tissue.

They typically have a broad base on the wall of a paranasal sinus. Bacteria from the aortic valve caused this septic embolism in the leff occipital lobe. Such cysts are only of significance if they obstruct the infundibulum 0 of the maxillary sinus or the semilunar canal.

Swelling of the mucous membranes of the external auditory canal 63b is visible without the need for CM. Haller's cells ". Contrast medium Fig. In patients with chronic sinusitis. Aretention cyst. CM is the demonstration of inflammatory processes. Withprogressing abscess formation. Cranial Pathology Inflammatory Processes 60 Another example of the advantages of i.

All of these variations can obstruct the semilunar canal and cause chronic. Endocrine Ophthalmopathy Minimal discrete changes can be missed during the reporting of a CT scan: The disease will continue and affect the medial rectus muscie 47cl.

In this case it causes a minor proptosis. The first findin g is an increase in the volume of the inferior rectus muscle 47b. Every mass within the orbit should. In order not to miss tumor invasion into the walls of the orbit. There will etten be a typical temporal pattern of involvement. Myositis should be considered inthe differential diagnosis. For planning aresection. Originatingfromthe mucous membranes of the right maxillary sinus It is therefore useful to examine both the soft tissue and bone windows.

Thefollowingexample shows a tumor of the paranasal sinuses 7 in an axial Fig. Another important question is whether or not the head of the mandible 58a in Fig. Diagnosis of the fracture in Figure Involving the lateral wall of the orbit and the frontal process of the maxilla to the contralateral side. In this case. The axial images are obtained and printed as viewed from caudally so the right lobe of the thyroid is imaged to the left of the trachea.

Inspiral CT. Malignant and inflammatory processes can be depicted more accurately with the aid of CM. During neck imaging. For cervical CTs there is also no 'one and only' approach. Usually sections of the neck are obtained using a mm thickness. Whenever there is no contraindication. CT examinations of the neck are carried out afteri.In this case the left internal jugular vein was also removed and the lumen of the right one 86a is therefore larger than normal.. Always check for degenerative changes at the margins of the bodies of cervical vertebrae 50 orforherniated discswhichmight narrow the spinal canal containing the cervical cord A patient with more body Width requires an increase in the tube currentto achieve an adequateimage quality.

How can you differentiate between them in CT morphology? Without doubt.