Ebook Atlas on X-ray and angiographic anatomy: Part 2

(BQ) Part 2 book “Atlas on X-ray and angiographic anatomy” has contents: Angiograms, productin of x-rays, digital subtractin angiography, computed and digital radiography, picture archiving and communicatins system, computed tomography contrast media.

7 CHAPTER Angiograms CEREBRAL CIRCULATION Normal Intracranial Arterial System Branches of the aortic arch: Brachiocephalic artery, the left common carotid artery, and left subclavian artery (Flow chart 7.1) The extracranial carotid arteries: The right common carotid artery usually arises from the bifurcation of the brachiocephalic artery The left common carotid artery arises from the aortic arch distal to the origin of brachiocephalic artery Both the right and left common carotid arteries bifurcate into the external and internal carotid arteries on either side at C4- C5 level Branches of the external carotid artery: Superior thyroidal artery, ascending pharyngeal artery, lingual artery, occipital artery, facial artery, posterior auricular artery, internal maxillary artery and superficial temporal artery The internal maxillary artery branches are superficial temporal artery, middle meningeal artery, accessory meningeal artery and anterior deep temporal artery The superior thyroid artery supplies the thyroid and larynx The ascending pharyngeal artery supplies the nasopharynx and tympanic cavity The lingual artery supplies the tongue, floor of the mouth and submandibular gland The occipital artery supplies the scalp and upper cervical musculature Facial artery branches supply the palate, pharynx, orbit, face and important anastomosis with other external carotid artery branches The superficial temporal artery and posterior auricular arteries supply the scalp, buccal region and ear structures The internal maxillary artery gives vascular supply to temporalis muscles, meninges, paranasal sinuses and mandible While traversing the foramen spinosum, the middle meningeal artery may supply a branch, through the petrous bone, to the facial nerve Internal carotid artery: The intracranial portions are petrous and cavernous portions Petrous portion of internal carotid artery: The ICA while passing through the carotid canal, gives of the Vidian artery which anastomoses with the basilar artery of posterior circulation Cavernous portion of internal carotid artery: It gives off the following branches— Meningohypophyseal trunk, inferolateral trunk, ophthalmic artery, posterior communicating artery, anterior choroidal artery, anterior and middle cerebral arteries The ophthalmic artery is the first branch of the supraclinoid portion of the ICA and thus serves as a demarcation between the intracavernous and subarachnoid segments of the ICA The posterior communicating artery (PCOM) connects the ICA with vertebrobasilar circulation 68 Atlas on X-ray and Angiographic Anatomy Flow chart 7.1: Cerebral circulation Flow chart 7.2: Internal carotid artery branches (P1 segment of ipsilateral posterior cerebral artery) The posterior communicating artery supplies the thalamus, hypothalamus and optic chiasm The anterior choroidal artery originates from ICA, it supplies the choroid plexus of lateral ventricle and anastomoses with lateral posterior choroidal artery The occlusion of anterior choroidal artery can cause hemiplegia, hemiparesis, homonymous hemianopia as its minute perforators supply the internal capsule, thalamus, basal ganglia (Flow chart 7.2) Circle of Willis: It is an important collateral system at the base of the brain surrounding the optic chiasm and pituitary stalk It comprises of—the basilar artery bifurcation (basilar tip), P1 segments of posterior cerebral artery proximal Angiograms segments, paired distal ICA’s, paired posterior communicating arteries (PCOM), paired proximal A1 segments of ACA’s and the anterior communicating artery (ACOM) This vascular ring is complete only in about 25 percent of cases (Fig 7.1) Perforating vessels arising from the circle of Willis include branches to the thalamus, limbic system, reticular activating system, cerebral peduncles, posterior limb of internal capsule and oculomotor nerve nucleus The recurrent artery of Heubner originates from the A1 segment to supply the anterior limb of internal capsule, portion of the globus pallidus and head of the caudate nucleus The anterior cerebral artery: The most proximal segment is the A1 segment, its origin at the terminal ICA to the anterior communicating artery (ACOM) A2 segment is the portion distal 69 to the ACOM and extends into the distal ACA The A2 segment supplies the head of the caudate nucleus, portions of the globus pallidus, anterior limb of the internal capsule, anterior two-thirds of medial cerebral cortex The main branches of the A2 segment are the orbitofrontal and frontopolar arteries The ACA bifurcates into the pericallosal and callosomarginal arteries (Figs 7.2 to 7.6) The middle cerebral artery: The most proximal segment is M1 segment It extends from ICA bifurcation to the insular cortex (island of Reil) M2 segment is the course of the artery in the insular cortex and sylvian fissure and it bifurcates into anterior and posterior cortical branches The branches of the anterior cortical M2 segment are lateral orbitofrontal, operculofrontal and central sulcus arteries The central sulcus arteries are called precentral (prerolandic) and central (rolandic) branches which supply motor and sensory cortical strips The branches of posterior cortical M2 segment are the anterior and posterior parietal, angular and posterior temporal arteries (Figs 7.2 to 7.6) The Vertebrobasilar Circulation Fig 7.1: Circle of Willis Abbreviations: ACA: Anterior cerebral artery; ACom: Anterior communicating artery; MCA: Middle cerebral artery; ICA: Internal carotid artery; PCom: Posterior communicating artery; PCA: Posterior cerebral artery; SCA: Superior- internal carotid artery; Basilar: Basilar artery; AICA: Anterior cerebral artery; VA: Vertebral artery; ASA: Anterior spinal artery Vertebral arteries: The vertebral arteries originate from the subclavian arteries One of the vertebral arteries may be dominant in size as compared to the other Each vertebral artery passes through the transverse foramen of C6 and passes superiorly through the transverse foramina of C5 to C1, then it courses posteriorly around the atlanto-occipital joint and ascends through the foramen magnum, penetrating the atlanto-occipital membrane and dura It gives off the posterior-inferior cerebellar artery and the anterior spinal arteries It then travels superiorly around the lateral aspect of medulla to join with the contralateral vertebral artery to form the basilar artery at pontomedullary junction The posterior inferior cerebellar artery (PICA) provides branches to the medulla, the occlusion of which can cause the lateral medullary syndrome or pyramidal tract ischemia Lateral medullary 70 Atlas on X-ray and Angiographic Anatomy Fig 7.2: Angiogram of right anterior cerebral circulation arterial phase—AP view Fig 7.3: Angiogram of right anterior cerebral circulation arterial phase—Lateral view Angiograms Fig 7.4: Angiogram of right anterior cerebral circulation arterial phase—Lateral view Fig 7.5: Angiogram right anterior cerebral circulation capillary phase—AP view 71 72 Atlas on X-ray and Angiographic Anatomy Fig 7.6: Angiogram of right anterior cerebral circulation capillary phase—Lateral view Fig 7.7: Angiogram of right anterior cerebral circulation venous phase—AP view Angiograms 73 Fig 7.8: Angiogram of right anterior cerebral circulation venous phase—Lateral view syndrome consists of ipsilateral Horner’s syndrome, facial sensory loss, pharyngeal/ laryngeal paralysis, contralateral pain and temperature sensory loss in the limbs and trunk Superior cerebellar artery provides vascular supply to the cerebellar peduncles, vermis, dentate nucleus, lateral pontine structures, spinothalamic tracts and sympathetic Anterior spinal arteries: It originates from the vertebral arteries distal to the posteroinferior cerebellar artery origin, they course inferomedially to join with their contralateral artery along the anterior cord Posterior cerebral arteries: Arise from the basilar artery at the level of pontomesencephalic junction, superior to the oculomotor nerve and tentorium The proximal PCA is divided into P1 and P2 segments at the junction of the PCA with the posterior communicating artery A filling defect is frequently seen at the transition between P1 and P2 during frontal vertebral artery angiograms due to the inflow of unopacified blood from the ipsilateral posterior communicating artery The proximal P2 segment gives rise to the posterior thalamoperforating and thalamogeniculate arteries which supply the posterior portions of the thalamus, geniculate bodies, choroid plexus of third and lateral ventricles, posterior limb of internal capsule, optic tract and small Basilar artery: The two vertebral arteries join together to form the basilar artery at the pontomedullary junction The basilar artery courses anterosuperiorly over the ventral pons It gives off small pontine perforating branches which supply the pyramidal tracts, medial lemnisci, red nuclei, respiratory centers and nuclei for cranial nerves (III, VI, XII) The basilar artery gives off the anterior inferior cerebellar artery and the superior cerebellar artery The labyrinthine artery is a branch of the anterior inferior cerebellar artery 74 Atlas on X-ray and Angiographic Anatomy branches to the cerebral peduncles The other branches of posterior cerebral artery are the splenial artery, anterior and posterior temporal branches, parietooccipital artery The distal PCA courses posteriorly around the brainstem in the ambient cistern, travelling more medially in the quadrigeminal plate cistern The distal calcarine cortical branches converge towards the midline but are separated by falx, on Townes projection vertebral angiogram (Figs 7.9 to 7.12) NORMAL INTRACRANIAL VENOUS SYSTEM Cerebral cortical veins: Multiple cortical veins drain towards the superior sagittal sinus The superficial middle cerebral vein which lies in the sylvian fissure may have anastomotic communication with the deep cerebral venous system, the facial veins and the extracranial pterygoid venous plexus Posteriorly the superficial middle cerebral vein communicates with the veins of Trolard and Labbe towards the ipsilateral transverse sinus The veins of Trolard and Labbe cross the subdural space to enter the dural sinuses Deep cerebral veins: These are the paired septal veins which run close to midline beside septum pellucidum The paired thalamostriate veins pass along the floor of the lateral ventricles between the body of caudate nucleus and thalamus The internal cerebral veins run posteriorly in the roof of third ventricle The paired basal veins of Rosenthal are formed by the confluence of deep middle and anterior cerebral veins on the ventral surface of brain The basal veins then coalese posteriorly with the internal cerebral veins to form the vein of Galen (Figs 7.7 and 7.8) This vein of Galen travels in the midline for about 1–2 cm under the splenium of corpus callosum, it then joins the inferior sagittal sinus in the posterior fossa to form the straight sinus at the junction of falx and tentorial incisura (Flow chart 7.3) The posterior fossa veins: These are the anterior pontomesencephalic veins, the precentral veins, superior and inferior vermian veins The anterior Fig 7.9: Angiogram of posterior cerebral circulation arterial phase—AP view Angiograms Fig 7.10: Angiogram of posterior cerebral circulation arterial phase—Lateral view Fig 7.11: Angiogram of posterior cerebral circulation capillary phase—AP view 75 76 Atlas on X-ray and Angiographic Anatomy Fig 7.12: Angiogram of posterior cerebral circulation capillary phase—Lateral view pontomesencephalic vein runs along the ventral surface of pons, it drains either into the basal vein of Rosenthal or posterior mesencephalic vein (Figs 7.13 and 7.14) The precentral veins run along the posteriorly in the roof of fourth ventricle and drains into the vein of Galen (Flow chart 7.4) Dural sinuses: The dura mater which envelops the central nervous system has two layers that form the reflections like the falx cerebri, tentorium and falx cerebelli The layers of dura separate to form venous drainage channels or dural sinuses for the brain Some of them anastomose with the veins of scalp through the emissary veins The main dural sinuses found are the superior sagittal sinus, inferior sagittal sinus, occipital sinuses, paired transverse sinuses and paired cavernous sinuses (Figs 7.7 and 7.8) The superior sagittal sinus travels along the superior margin of falx cerebri, it continues posteriorly and inferiorly in a cresenteric course to the junction point between the falx and tentorium containing the confluence of sinuses—The torcular Herophili near the occipital protuberance The inferior sagittal sinus is found within the lower edge of falx between the cerebral hemispheres It drains posteriorly to join with the vein of Galen forming the straight sinus The straight sinus drains posteriorly in midline into the torcular herophili The occipital sinuses are of variable size, are seen to course superomedially within the dura of the posterior fossa, just lateral to foramen magnum and drains towards the torcular herophili The paired transverse sinus follows a cresenteric course within the periphery of the tentorium, laterally and anteriorly from the torcula The transverse sinuses receive drainage from the inferior cerebral veins and vein of Labbe, it communicates with the cavernous sinuses via 132 Atlas on X-ray and Angiographic Anatomy Table 9.5 Knee joint Bones Ossification Tibial shaft 7th week of fetal life Fibular shaft 8th week of fetal life Patella years Epiphysis Appearance Fusion Proximal tibia At birth 20th year Tibial tubercle 5–10 years 20th year Proximal fibular 4th year 25th year Distal femur At birth 20th year Table 9.6: Foot Bones Ossification Calcaneus 6th month of fetal life Talus 6th month of fetal life Navicular 3–4 years Cuboid At birth Lateral cuneiform year Middle cuneiform years Medial cuneiform years Metatarsal shafts 8th–9th week of fetal life Phalangeal shafts 10th week of fetal life Epiphysis Appearance Fusion Metatarsals years 17–20 years Proximal phalangeal base years 17–20 years Middle phalangeal base years 17–20 years Distal phalangeal base years 17–20 years Posterior calcaneal years At puberty 10 C H A PT E R Production of X-rays X-rays are invisible, highly penetrating, electro­ magnetic radiations having wavelength of 0.11 Å and speed is same as that of light (3×108 m/ sec) They are considered as a form of modified electrons X-ray tube is a diode consisting of tungsten filament cathode and a rotating anode target of tungsten held in an evacuated glass Tungsten anode is inclined at an angle so that it works on line-focus principle X-rays are produced when the electron beam strikes the anode made of tungsten or molybdenum Tungsten (atomic number 74) is used as target material for X-ray production Molybdenum (atomic number 42) is used as the target in mammography Cathode is connected to the negative terminal and consists of small coil of wire made of tungsten (filament) Cathode generates the electrons from the electric circuit and focuses them into welldefined beam aimed at anode Anode is relatively large piece of metal that connects to positive end of electric circuit It converts electronic energy into X-rays and rapidly dissipates heat produced during this process Anode is made up of tungsten because it has high melting point, low rate of evaporation and maintains strength at high temperature (Fig 10.1) The electrons are produced by cathode filament by electric current, emitting photoelectrons The electrons coming from the filament cathode are then accelerated towards the target anode by a large electrical potential applied between the filament and target When the beam of electrons hits the target anode there is rapid deceleration of electrons leading to emission of X-rays and heat About one percent of the energy generated is emitted as X-rays The rest of the energy is released as heat The assembly of cathode and anode is enclosed by the envelope which is made of glass It provides support and electric insulation, keeps cathode and anode in air-tight enclosure and maintains vacuum in tube Housing is the outermost covering that encloses and supports the envelope It is filled with oil that provides electric insulation, allows heat dissipation and cooling Modern X-ray tubes are based on hot cathode tube principle invented by Coolidge in 1913 which enables excellent control of kVp (kilovolt peak) and mAs (milliampere second) kVp is responsible for penetration of X-ray beam, low kVp gives high contrast mAs is responsible for the film blackening The radiation intensity on the cathode side of the X-ray tube is higher than on the anode side and this principle is called as the anode Heel effect The heat generated in the tube is dissipated in three ways: conduction, convection and radiation Diagnostic X-ray machine uses voltage upto 150 kVp whereas machines used for radiotherapy use high voltage >  200 KVP 134 Atlas on X-ray and Angiographic Anatomy Fig 10.1: Line diagram shows production of X-rays Two different interactions give rise to X-rays An interaction with electron shell produce characteristic X-rays photons, while interaction with atomic nucleus produces Bremsstrahlung X-ray photons In diagnostic radiology about 85 percent of X-rays arise from Bremsstrahlung radiation and 15 percent from characteristic radiation X-ray filter made of aluminum absorbs low energy radiation and decreases unnecessary patient exposure and thus improves film contrast Grid is made of parallel lead lines with intervening radiolucent material It absorbs scattered radiation Cones and collimators restrict field size and decrease scatter Distance from X-ray tube (focus) to the X-ray film is called focus film distance (FFD) It is 100 cm for usual radiographs of extremities, abdomen and skull However, for standing radiograph of chest, it is 180 cm (6 ft) so as to reduce the magnification 11 C H A PT E R Digital Subtraction Angiography Digital subtraction angiography (DSA) is a type of fluoroscopy technique used in interventional radiology to clearly visualize blood vessels in a bony or dense soft tissue environment Images are produced using contrast medium by subtracting a precontrast image or the mask from later images, hence the term ‘digital subtraction angiography’ Digital subtraction angiography (DSA) is primarily used to image blood vessels It is useful in the diagnosis and treatment of: Arterial and venous occlusions, carotid artery stenosis, pulmonary embolisms, acute limb ischemia, and arterial stenosis, which is particularly useful for potential renal donors in detecting renal artery stenosis, cerebral aneurysms and arteriovenous malformations In addition to above applications others include carotid and peripheral arteriography, thoracic and abdominal aortography, pulmonary arteriography, and ventriculography Future applications may include intracerebral and coronary arteriography DSA provide low-risk out­ patient screening arteriography In DSA, a computer is used to subtract an initial image without contrast medium taken directly from the image intensifier from the angiographic images with contrast medium in the blood vessels The intravenous administration of contrast material permits safe outpatient screening for arterial disease The bone, softtissue and gas are removed leaving only the contrast-medium- filled blood vessels in the final subtracted arterial images DSA requires cooperative patient who can keep still and hold breath, because any type of movement can cause image degradation Abdominal examinations are performed after an intravenous injection of 20 mg hyoscine butyl bromide to prevent peristalsis in the gastrointestinal tract and thoracic examinations can be done with ECG-triggered gating to prevent cardiac pulsations Advantages of DSA are both volume and iodine concentration of the nonionic contrast medium used for each run, because of the high contrast resolution of the imaging system in DSA, reduction in the length of the procedure, reduction in the size of the catheters used from 6-8 Fr down to 3-5 Fr, reduction in the number of radiographic film used, reduction in the radiation dose to the patient and angiographic staff Disadvantage of DSA is the fact that the images it produces are inferior in the quality of their spatial resolution to those produced by conventional film angiography The magnitude of this difference in image quality has been reduced with technical improvements in DSA systems In intravenous DSA, the high contrast resolution of the imaging system allows nonionic contrast medium to be injected intravenously in order to produce arterial images in patients with no femoral pulse, large volume of contrast medium is injected rapidly by a pump injector 136 Atlas on X-ray and Angiographic Anatomy through a catheter positioned in the SVC or right atrium The contrast medium is diluted as it passes through the lungs and into the left side of the heart and systemic circulation, but the images are of good quality Complication of intravenous DSA are hemorrhage from puncture site, vascular thrombosis, peripheral embolization, aneurysm, local sepsis, injury to local structures, guidewire fracture, and vasovagal reaction, and vascular disorders For peripheral angiography carbon dioxide digital subtraction angiography can be used as an alternative or adjunct to iodinated contrast in vascular imaging and interventional procedures Its unique qualities make it useful in diagnostic as well as therapeutic procedures in arteries and veins Because of its endogenous gaseous attributes, it is nonallergic, does not affect the kidneys, and can be used in unlimited quantities Compared with iodinated contrast, the low viscosity of CO2 permits greater sensitivity for arterial hemorrhage and arteriovenous fistulas as well as it is more facile using microcatheters Certain simple principles must be used with CO2 as a contrast agent When used appropriately, CO2 is safe and can be useful when iodinated contrast is either not sufficient or is contraindicated 12 C H A PT E R Computed and Digital Radiography Computed Radiography Computed radiography (CR) uses similar equipment as conventional radiography except that in place of a film to create the image, an imaging plate (IP) made of photostimulable phosphor is used The imaging plate housed in a special cassette is placed under the body part or object to be examined and the X-ray exposure is made Thereafter, instead of taking an exposed film into a darkroom for developing in chemical tanks or an automatic film processor, the imaging plate is run through a special laser scanner, or CR reader, that reads and digitizes the image The digital image can then be viewed and enhanced using software that has functions very similar to other con­ ventional digital image-processing software, such as contrast, brightness, filtration and zoom The CR imaging plate (IP) contains photo­ stimulable storage phosphors, which store the radia­tion level received at each point in local electron energies When the plate is put through the scanner, the scanning laser beam causes the electrons to relax to lower energy levels, emitting light that is detected by a photomultiplier tube (Fig 12.1), which is then converted to an electronic signal The electronic signal is then converted to discrete (digital) values and placed into the image processor pixel map The signals generated by the photodetector as the plate is being scanned are amplified and digitized by an analog-to-digital converter (ADC) The spatial resolution of computed radiography is influenced by factors such as the phosphor plate thickness, the readout time and the diameter of the laser beam, which is typically about 100 μm Imaging plates can theoretically be reused thousands of times if they are handled carefully An image can be erased by simply exposing the plate to a room-level fluorescent light Most laser scanners automatically erase the image plate after laser scanning is complete The imaging plate can then be reused Reusable phosphor plates are environmentally safe A fundamental limitation of CR is the time required to read the latent image Since, the decay time of the phosphor luminescence is ~0.7 μs, typically the readout of a 3,000×3,000 pixel image can takeover half a minute to complete An improvement can be obtained by line scanning, where a full line of pixels is stimulated and read out simultaneously instead of single pixels This line-scanning approach requires a linear array of laser light sources, e.g laser diodes, as well as a linear array of photodetectors as wide as the imaging plate, and gives rise to readout times of less than 10 seconds Advantages Over Conventional Radiography • No silver-based film or chemicals are required to process film 138 Atlas on X-ray and Angiographic Anatomy Digital Radiography Fig 12.1: Schematic mechanism of CR system: Imaging plate-coated with photostimulable phosphor (PSP) exposed to X-rays and contains image data In CR reader, imaging plate is read using red laser beam, which is swept across the plate by a rotating polygonal mirror The light emitted by imaging plate is converted into electrical signal and used to form image • Reduced film storage costs because images can be stored digitally • Computed radiography often requires fewer retakes due to under or over exposure which results in lower overall radiation dose to the patient • Image acquisition is much faster image previews can be available in less than 15 seconds • By adjusting image brightness and/or contrast, a wide range of thicknesses may be examined in one exposure, unlike conventional film based radio­ graphy, which may require a different expo­sure or multiple film speeds in one exposure to cover wide thickness range in a component • Images can be enhanced digitally to aid in interpretation • Images can be stored on disk or transmitted for off-site review • Ever growing technology makes the CR more affordable than ever today With chemicals, dark-room storage and staff to organize them, you could own a CR for the same monthly cost while being environmentally conscious, depending upon the size of the radiographic operation Digital radiography (DR) is a form of X-ray imaging, where digital X-ray sensors are used instead of tra­ ditional photographic film (Fig 12.2) Advantages include time efficiency through bypassing chemical processing and the ability to digitally transfer and enhance images Also less radiation can be used to produce an image of similar contrast to conventional radio­graphy Digital radiography is essentially filmless X-ray image capture In place of X-ray film, a digital image capture device is used to record the X-ray image and make it available as a digital file that can be presented for interpretation The advantages of DR over film include immediate image preview and availability, a wider dynamic range which makes it more forgiving for over and under exposure as well as the ability to apply special image processing techniques that enhance overall display of the image DR has the potential to reduce costs associated with processing, managing and storing films The digital image capture devices include flat panel detectors (FPDs) FPDs are classified in two main categories: Indirect FPDs: Amorphous silicon (a-Si) is the most frequent used FPD in the medical imaging industry today Combining a-Si detectors with a scintillator in the detector’s outer layer, which is made from Cesium Iodide (CsI) or Gadolinium Oxysulfide (Gd2O2S), converts X-ray to light Because the X-ray energy is converted to light, the a-Si detector is considered an indirect image capture technology The light is then channeled through the a-Si photodiode layer where it is converted to a digital output signal The digital signal is then read out by Thin Film Transistors (TFTs) or by fiber coupled Charged Couple Devices (CCDs) The image data file is sent to a computer for display Direct FPDs: Amorphous Selenium Flat Panel Detectors (a-Se) are known as “direct” detectors because X-ray photons are converted directly to charge The outer layer of the flat Computed and Digital Radiography 139 Fig 12.2: Schematic diagram showing types of DR flat panel detectors (FPD): (i) Direct conversion flat panel detectors: X-rays are converted to electronic signal by amorphous selenium photoconductor; (ii) Indirect conversion flat panel detector: X-rays are converted to visible light by scintillator, which is further converted to electronic signal by silicon photodiode Electronic signal is converted to digital image by TFT arrays panel in this design is typically a high voltage bias electrode The bias electrode accelerates the captured energy from an X-ray exposure through the amorphous selenium layer X-ray photons flowing through the selenium layer create electron hole pairs These electron holes transit through the selenium based on the potential of the bias voltage charge As the electron holes are replaced with electrons, the resultant charge pattern in the selenium layer is read out by a TFT array The image data file is sent to a computer for display Computed radiography (CR) and DR use a medium to capture X-ray energy and produce a digital image Both also present an image within seconds of exposure CR involves the use of a cassette that houses the imaging plate, similar to traditional film-screen systems to record the image whereas DR captures the image directly onto a flat panel detector without the use of a cassette Image processing or enhancement can be applied on both DR and CR images due to the digital format DR may offer improved workflow for routine procedures due to the elimination of cassette manipulation and processing, as well as a greater capacity to limit radiation exposure CR continues to offer flexible position of the image receptor for procedures such as those done for portable film, trauma, surgical cases and crosstable lateral projections 13 C H A PT E R Picture Archiving and Communication System Picture archiving and communication system (PACS), is based on universal DICOM (Digital imag­ ing and communications in medicine) format DICOM solutions are capable of storing and retrieving multi­ modality images in a proficient and secure manner in assisting and improving hospital workflow and patient diagnosis (Flow chart 13.1) The aim of PACS is to replace conventional radiographs and reports with a completely electronic network These digital images can be viewed on monitors in the radiology department, emergency rooms, inpatient and outpatient departments, thus saving time, improving efficiency of hospital and avoid incurring the cost of hard copy images in a busy hospital The three basic means of rendering plain radiographs images to digital are computed radiography (CR) using photostimulable phosphor plate technology; direct digital radiography (DDR) and digitizing conventional analog films Non image data, such as scanned documents like PDF (portable document format) is also incorporated in DICOM format Dictation of reports can be integrated into the system The recording is automatically sent to a transcript writer’s workstation for typing, and can also be made available for access by physicians, avoiding typing delays for urgent results Radiology has led the way in developing PACS to its present high standards Picture archiving and communication system (PACS) consists of four major components: The hospital information system (HIS) with imaging modalities such as radiography, computed radiography, endoscopy, mammography, ultrasound, CT, PET-CT and MRI, a secured network for the transmission of patient infor­mation, workstations for interpreting and reviewing images and archives for the storage and retrieval of images and reports Backup copies of patient images are made provisioned in case the image is lost from the PACS There are several methods for backup storage of images, but they typically involve automatically sending copies of the images to a separate computer for storage, preferably off-site In PACS, no patient is irradiated simply because a previous radiograph or CT scan has been lost; the image once acquired onto the PACS is always available when needed Simultaneous multilocation viewing of the same image is possible on any workstation connected to the PACS Numerous post-processing soft copy manipulations are possi­ble on the viewing monitor Film packets are no longer an issue as PACS provides a filmless solution for all images The PACS can be integrated into the local area network and images from remote villages can be sent to the tertiary hospital for reporting Picture archiving and communication system (PACS) is an expensive investment initially but the costs can be recovered over years period It requires a dedicated maintenance It is important Picture Archiving and Communication System 141 Flow chart 13.1: Picture archiving and communication system (PACS) to train the doctors, technicians, nurses and other staff to use PACS effectively Once PACS is fully operational no films are issued to patients Picture archiving and communication system (PACS) breaks the physical and time barriers associated with traditional film-based image retrieval, distribution and display PACS can be linked to the internet, leading to teleradiology, the advantages of which are that images can be reviewed from home when on call, can provide linkage between two or more hospitals, outsourcing of imaging examinations in understaffed hospitals The PACS is offered by all the major medical imaging equipment manufacturers, medical IT companies and many independent soft­ware companies 14 C H A PT E R Computed Tomography Contrast Media IODINATED INTRAVASCULAR AGENTS Intravascular radiological contrast media are iodine containing chemicals which add to the details in any given CT scan study and thereby aid in the diagnosis Contrast overall enhances the body tissues It helps to show the lesion which could not be appreciated on plain scan or shows the lesion better than what was seen in the plain scan Contrast was first introduced by Moses Swick Iodine (atomic weight 127) is an ideal choice element for X-ray absorption because the korn (K) shell binding energy of iodine (33.7) is nearest to the mean energy used in diagnostic radiography and thus maximum photoelectric inter­actions can be obtained which are a must for best image quality These compounds after intravascular injection are rapidly distributed by capillary per­ meability into extravascularextracellular space and almost 90 percent is excreted via glomerular filtration by kidneys within 12 hours Following iodinated contrast media are available: Ionic monomers, e.g Diatrizoate, Iothalamate, Metrizoate Nonionic monomers, e.g Iohexol, Iopamidol, Iomeron Ionic dimer, e.g Ioxaglate Nonionic dimer, e.g Iodixanol, Iotrolan The amount of contrast required is usually 1-2 ml/kg body weight Normal osmolality of human serum is 290 mOsm/kg Ionic contrast media have much higher osmolality than normal human serum and are known as high osmolar contrast media (HOCM), while nonionic contrast media have lower osmolality than HOCM and are known as low osmolar contrast media (LOCM) Side effects or adverse reactions to contrast media are divided as: Idiosyncratic anaphylactoid reactions Nonidiosyncratic reactions like nephrotoxicity and cardiotoxicity Adverse reactions are more with HOCM than LOCM, hence LOCM are preferred Delayed adverse reactions although very rare are, however, more common with LOCM and include iodide mumps, systemic lupus erythematosus (SLE) and Stevens-Johnson syndrome Principles of treat­ ment of adverse reaction involves mainly five basic steps: ABCDE A: Maintain proper airway B: Breathing support for adequate breathing C: Maintain adequate circulation Obtain an IV access D: Use of appropriate drugs like antihistaminics for urticaria, atropine for vasovagal hypotension and bradycardia, beta agonists for bronchospasm, hydrocortisone, etc Computed Tomography Contrast Media 143 143 E: Always have emergency back-up ready including ICU care Following intravascular iodinated agent arterial opacification takes place at approximately 20 seconds with venous peak at approximately 70 seconds The level then declines and the contrast is finally excreted by the kidneys These different phases of enhancement are used to image various organs depending on the indication Spiral CT, being faster is able to acquire images during each phase, thus provide much more information of barium (37) is near to the mean energy used in diagnostic radiography and thus maximum photoelectric interactions can be obtained which are a must for best image quality Moreover, barium sulfate is nonabsorbable, nontoxic and can be prepared into a stable suspension For CT scan of abdomen, 1000-1500 ml of 1-5 percent w/ vol barium sulfate suspension can be used Severe adverse reactions are rare Rarely mediastinal leakage can lead to fibrosing mediastinitis while peritoneal leakage can cause adhesive peritonitis ORAL CONTRAST Iodinated Agents The bowel is usually opacified in CT examinations of the abdomen and pelvis as the attenuation value of the bowel is similar to the surrounding structures and as a result pathological lesions can be obscured Materials used are barium or iodine based preparations, which are given to the patient to drink preceding the examination to opacify the gastro­intestinal tract Iodine containing oral contrast agents like gastro­ graffin and trazograf are given for evaluating gastro­intestinal tract on CT scan Barium Sulfate Barium sulfate preparations are used for evaluating gastrointestinal tract Barium (atomic weight 137) is an ideal choice element for X-ray absorption because the K shell binding energy AIR Air is used as a negative per rectal contrast medium in large bowel during CT abdomen and during CT colonography CARBON DIOXIDE Rarely, carbon dioxide is used for infradiaphragmatic CT angiography in patients who are sensitive to iodinated contrast Index Page numbers followed by f refer to figure and t refer to table A Abdominal angiography 81 aorta 81, 95f branches 82 radiograph 34 Acromion process 130 Advantages over conventional radiography 137 Amorphous selenium flat panel detectors 138 Analog-to-digital converter 137 Anatomical segmental division of lungs 28 Angiogram of abdominal aorta 82f celiac arterial trunk 83f posterior cerebral circulation arterial phase 74f, 75f capillary phase 75f, 76f venous phase 77f renal arteries in pyeloureterogram phase 87f right anterior cerebral circulation arterial phase 70f, 71f capillary phase 71f, 72f venous phase 72f, 73f right renal artery early arterial phase 85f late arterial phase 86f nephrogram phase 86f superior mesenteric artery 84f Angiography of lower limb 95f, 97f-101f Angle of Louis 79 Ankle joint 60 Anterior cerebral artery 69 communicating artery 69 interosseous artery 90f spinal arteries 73 Arch of aorta 80f Artery of foregut 83 midgut 85 Ascending thoracic aorta curves 80f Atlantoaxial junction 20f Axillary artery 89f, 93f B Barium enema 111 study 111f sulfate 143 swallow 103 study 104f, 105f Base of distal phalanges 131 middle phalanges 131 proximal phalanges 131 Basilar artery 73 Body of clavicle 130 scapula 130 Brachial artery 89f, 93f Branches of aortic arch 67 external carotid artery 67 Bucky table 121 Cervical spine 13 Cervicothoracic junction 18f Circle of Willis 68 Clivus canal angle 27 Coccyx 16 Computed radiography 137, 139, 140 contrast media 142 Coupled charged couple devices 138 Craniovertebral angle 27 D Dacrocystogram 125, 125f, 126f Deep cerebral veins 74 palmar arch 92f vein 92 Digital radiography 138 subtraction angiography 135 veins 91 Direct digital radiography 140 Distal femur 132 phalanges 131 Dorsolumbar spine 14 Dural sinuses 76, 79 C E Calcaneus 132 Capitellum 130 Carbon dioxide 143 Cavernous portion of internal carotid artery 67 Celiac arterial trunk 83 trunk 81 Cephalic veins 91 Cerebral circulation 67, 68 cortical veins 74 Elbow joint 41, 128f, 130t Epiphysis 132 External iliac and common iliac artery 97f, 98f Extracranial carotid arteries 67 F Fallopian tubes 123, 123f, 124 Femoral head 131 Fibular shaft 132 Forearm 44 146 Atlas on X-ray and Angiographic Anatomy G Greater trochanter 131 tuberosity 130 H Head of humerus 130 radius 130 Hilgenreiner’s line 49 Hip joint 49, 129f, 131t Hysterosalpingogram 121, 122f-124f I Inferior angle of scapula 130 mesenteric artery 84 Internal carotid artery 67-69 J Jugular bulb 78 K Knee joint 55, 129f, 132 L Lateral cuneiform 132 decubitus 34 epicondyle 130 Leech-Wilkinson cannula 124 Lesser trochanter 131 tuberosity 130 Locating lesions of lungs 31 Location of arches of foot 64f Low osmolar contrast media 142 Lower end of radius 131 ulna 131 limb 49 angiography 95 arterial system 96 venous system 102 Lumbosacral spine 14, 24f X-ray 25f, 26f Lung fissures 31 M Medial border of scapula 130 cuneiform 132 end of clavicle 130 epicondyle 130 Metacarpal heads 131 veins 91 Metatarsal shafts 132 Micturating cystourethrogram 117, 118f, 119f Middle cerebral artery 69 cuneiform 132 of coracoid process 130 phalangeal base 132 phalanges 131 Multiplanar reconstructed CT scan image of elbow joint 42f forearm 44f hand and wrist joint 46f shoulder joint 37f upper arm 40f reconstructed images of abdomen 35f joint 61f foot with ankle 63f knee joint 56f lower leg with ankle 59f thorax 29f N Nasal cavity septum Normal intracranial arterial system 67 venous system 74 venous anatomy of brain 78 O Olecranon process 130 Orbit 10 Ossification centers 127 P Paranasal sinuses 6f, 10 Patella 132 Pelvic phleboliths 34 Perkin’s line 49 Petrous portion of internal carotid artery 67 Phalangeal shafts 132 Pituitary fossa 5f Popliteal artery 97, 100, 100f Posterior cerebral arteries 69, 73 communicating arteries 67, 69 fossa veins 74, 78 inferior cerebellar artery 69 Production of X-rays 133 Profunda femoris artery 96 Proximal femoral shaft 131 phalanges 131 tibia 132 R Radial arteries 90f, 94 Radiological anatomy of female reproductive organs 121 importance of craniovertebral junction 27 vertebral column in spinal injuries 24 Renal artery 88 angiogram 87 Index Retrograde urethrogram 120 Root of coracoid process 130 S Sacrum and coccyx X-ray 27f Shaft of humerus 130 Shoulder joint 37, 127f, 130t Sim’s speculum 124 Spinal canal 21 cord 21 Subclavian artery 89f Superficial femoral artery 96, 99f palmar arch 91f veins 91 Superior internal carotid artery 69 mesenteric arteriogram 85 artery 83 Systemic lupus erythematosus 142 T Teres minor 37 Thoracic aorta 79, 80f Tibial shaft 132 tubercle 132 Trochlea 130 Turkish saddle U Ulnar artery 90f, 94 shaft 130 Upper arm 38 gastrointestinal tract 104f, 105f limb 37 angiography 88 venous system 94 V Vein of Galen 74 Trolard and Labbe 74 Venous system 91 Vertebral arteries 69 Vertebrobasilar circulation 69 W Wrist joint and hand 44 147 X X-ray 28 abdomen 36f ankle and foot 63f joint 62f cervical spine 15f-20f open mouth 20 right posterior oblique for intervertebral foramina 19f cervicothoracic junction 18f chest 29f-32f dorsolumbar spine 22f, 23f elbow joint 42f, 43f foot 64f, 65f forearm 45f hand and wrist joint 47f hip joint with pelvis 52f knee joint 57f skyline 58f KUB region 114f leg 60f, 61f pelvis with both hip joints 51f right hip joint 51f, 52f shoulder joint 38f, 39f skull 3f, 4f, 5, 5f, 6, 6f-8f, 11f, 12f thigh 54f, 55f upper arm 40f, 41f ... 75 76 Atlas on X-ray and Angiographic Anatomy Fig 7. 12: Angiogram of posterior cerebral circulation capillary phase—Lateral view pontomesencephalic vein runs along the ventral surface of pons,... calcification may be noted at this site The arch of aorta passes above the left bronchus and to 80 Atlas on X-ray and Angiographic Anatomy Fig 7.15: Outline of the thoracic aorta on chest X-ray PA... subclavian artery and axillary artery Fig 7 .25 : Angiogram showing brachial artery 89 90 Atlas on X-ray and Angiographic Anatomy Fig 7 .26 : Angiogram showing radial and ulnar arteries Fig 7 .27 : Angiogram