Computed Tomography (CT)
Images
Prof. Dr. Lucas Ferrari de Oliveira
UFPR
Informatics Department
CT Images
www.pbs.org
CT Images
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History:
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Based in the X-rays;
CT was the revolution in medicine;
Word “Tomography” is derived from the Greek
words:
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“Tomos” means to cut;
“Graphein” means to write;
Linear Tomography was the first step (1958).
CT Images
http://ksaenz921.blogspot.com.br/2009/03/linear-tomography_19.html
CT Images
William (Sandy) Wells. Course materials for HST.582J / 6.555J / 16.456J, Biomedical Signal and Image Processing, Spring 2007.
MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on 15 September 2014.
CT Images
http://ksaenz921.blogspot.com.br/2009/03/linear-tomography_19.html
CT Images
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Example:
http://ctscans.hawkelibrary.com/Intoduction-to-CT-Scans/Conv_Tomography
CT Images
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CT Equipments Generations:
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1st Generation;
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2nd Generation;
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3rd Generation;
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4th Generation;
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5th Generation – EBCT;
Helical;
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Multislice.
http://ctscans.hawkelibrary.com/Intoduction-to-CT-Scans/Conv_Tomography
CT Images
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CT Equipments Generations:
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1st Generation:
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Translation and rotation (1° each time);
High collimated (pencil beam);
One or two detectors;
Five minutes.
http://rle.dainf.ct.utfpr.edu.br/hipermidia/images/documentos/Tomografia_computadorizada_tecnologia_e_funcionamento_eq
uipamentos.pdf
CT Images
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CT Equipments Generations:
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1st Generation:
http://rle.dainf.ct.utfpr.edu.br/hipermidia/images/documentos/Tomografia_computadorizada_tecnologia_e_funcionamento_eq
uipamentos.pdf
CT Images
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CT Equipments Generations:
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2nd Generation:
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Translation and rotation (6° each time);
Divergent (fan beam);
30 detectors;
Twenty seconds.
http://rle.dainf.ct.utfpr.edu.br/hipermidia/images/documentos/Tomografia_computadorizada_tecnologia_e_funcionamento_eq
uipamentos.pdf
CT Images
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CT Equipments Generations:
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2nd Generation:
http://rle.dainf.ct.utfpr.edu.br/hipermidia/images/documentos/Tomografia_computadorizada_tecnologia_e_funcionamento_eq
uipamentos.pdf
CT Images
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CT Equipments Generations:
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3rd Generation:
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Rotation-rotation (360°);
Divergent (fan beam);
Detectors: arc-shaped (30° to 40°);
~ one second;
Limitations: High voltage cables.
http://rle.dainf.ct.utfpr.edu.br/hipermidia/images/documentos/Tomografia_computadorizada_tecnologia_e_funcionamento_eq
uipamentos.pdf
CT Images
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CT Equipments Generations:
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3rd Generation:
http://rle.dainf.ct.utfpr.edu.br/hipermidia/images/documentos/Tomografia_computadorizada_tecnologia_e_funcionamento_eq
uipamentos.pdf
CT Images
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CT Equipments Generations:
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4th Generation:
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Rotation-stationary (360°);
Divergent (fan beam);
Detectors: arc-shaped 360° (400 detectors);
Lower than one second.
http://rle.dainf.ct.utfpr.edu.br/hipermidia/images/documentos/Tomografia_computadorizada_tecnologia_e_funcionamento_eq
uipamentos.pdf
CT Images
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CT Equipments Generations:
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4th Generation:
http://rle.dainf.ct.utfpr.edu.br/hipermidia/images/documentos/Tomografia_computadorizada_tecnologia_e_funcionamento_eq
uipamentos.pdf
CT Images
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CT Equipments Generations:
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5th Generation - EBCT:
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Stationary-stationary;
Electron beam (photons);
Tungsten rings;
50 milliseconds;
Cardiac images.
http://rle.dainf.ct.utfpr.edu.br/hipermidia/images/documentos/Tomografia_computadorizada_tecnologia_e_funcionamento_eq
uipamentos.pdf
CT Images
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CT Equipments Generations:
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5th Generation - EBCT:
http://rle.dainf.ct.utfpr.edu.br/hipermidia/images/documentos/Tomografia_computadorizada_tecnologia_e_funcionamento_eq
uipamentos.pdf
CT Images
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CT Equipments Generations:
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Helical:
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Rotation-rotation;
Cone beam;
Single row;
Lower than 1 second;
Many anatomical regions.
http://rle.dainf.ct.utfpr.edu.br/hipermidia/images/documentos/Tomografia_computadorizada_tecnologia_e_funcionamento_eq
uipamentos.pdf
CT Images
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CT Equipments Generations:
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Helical:
http://tech.snmjournals.org/content/35/3/115/F11.large.jpg
http://www.personal.psu.edu/afr3/blogs/SIOW/2011/12/helical-ctlung-cancer.html
CT Images
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CT Equipments Generations:
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Helical:
https://miac.unibas.ch/PMI/03-ComputedTomography.html
CT Images
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CT Equipments Generations:
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Multislice:
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Rotation-rotation;
Cone beam;
Multiple - simultaneous acquisition;
Fractions of seconds;
Many anatomical regions.
http://rle.dainf.ct.utfpr.edu.br/hipermidia/images/documentos/Tomografia_computadorizada_tecnologia_e_funcionamento_eq
uipamentos.pdf
CT Images
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CT Equipments Generations:
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Multislice:
http://mixic.ece.ust.hk/images/research/CMOS_imaging_detector_for_computed_to
mography.jpg
http://tech.snmjournals.org/content/36/2/57/F1.expansion.html
CT Images
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CT Equipments Generations:
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Multislice:
https://miac.unibas.ch/PMI/03-ComputedTomography.html
CT Images
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CT Equipments Generations:
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Multislice:
http://commons.wikimedia.org/wiki/File:Matrix_array_multi-slice_CT_detector.jpg
CT Images
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CT Filters
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Bow tie Filter:
http://www.toshibamedicalsystems.com/tmd/english/products/dose/lowdose/img/imgmachine02.jpg
CT Images
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CT Filters
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Bow tie Filter:
http://iopscience.iop.org/0031-9155/58/8/2609/article
CT Images
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CT Detectors:
http://www.ndt.net/article/wcndt00/papers/idn754/idn754.htm
CT Images
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Image Reconstruction:
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Many projections;
Back projection technique.
http://en.wikibooks.org/wiki/Basic_Physics_of_Nuclear_Medicine/X-Ray_CT_in_Nuclear_Medicine
CT Images
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Image Reconstruction:
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Back projection.
http://en.wikibooks.org/wiki/Basic_Physics_of_Nuclear_Medicine/X-Ray_CT_in_Nuclear_Medicine
CT Images
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Image Reconstruction:
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Back projection Filter.
http://en.wikibooks.org/wiki/Basic_Physics_of_Nuclear_Medicine/X-Ray_CT_in_Nuclear_Medicine
CT Images
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CT Number and Housnfield Scale:
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CT number range -1000 to +1000;
-1000 air, 0 (zero) water e +1000 bone;
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Measure unit in Hounsfield;
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Equipments with 4096 values (212);
To calculate:
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Where:
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µT is linear attenuation coefficient of the tissue;
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µwater is liner attenuation coefficient of water;
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K is a constant or contrast factor (=1000).
CT Images
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CT Number and Housnfield Scale:
http://rle.dainf.ct.utfpr.edu.br/hipermidia/images/documentos/Tomografia_compu
tadorizada_tecnologia_e_funcionamento_equipamentos.pdf
CT Images
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Visualization and Image Processing:
– 4096 gray scale in image (212);
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Screen limitation (210) or 1024 gray scale;
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Windowing to specific structures;
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Window width is the range of CT numbers selected;
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Window Level (central value) the average CT value of
structures to study.
CT Images
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Visualization and Image Processing:
Effect of window width and level on CT image display: (a) Level = 50; Width = 200. (b) Level = 50; Width =
400. The image in (a) is displayed with greater contrast and appears noisier than that in (b).
http://en.wikibooks.org/wiki/Basic_Physics_of_Digital_Radiography/The_Applications
CT Images
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Visualization and Image Processing:
Effect of window width and level: (a) Level = -600; Width = 1700. (b) Level = -60; Width = 400. Image (a)
displays the lung tissue more clearly, while image (b) can be used to highlight any pulmonary lesions.
http://en.wikibooks.org/wiki/Basic_Physics_of_Digital_Radiography/The_Applications
CT Images
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Examples:
This 56 year-old male presented with abdominal pain on a background of known gastric carcinoma. The axial CT image shows heterogeneous fat / soft-tissue density within
the greater omentum (arrows). There is also moderate ascites. The appearance is typical of omental cake. The patient also had extensive liver metastases. Omental cake
refers to infiltration of the omental fat by material of soft-tissue density. The most common causes are metastases from ovary, stomach or colon. Tuberculous peritonitis may
also give this appearance. Masses on the peritoneal surfaces may also be present. Malignant ascites may be present.
Core biopsy may be helpful if the primary tumour is unknown.
References:
1. Weissleder R, Wittenberg J, Harisinghani MG. Primer of Diagnostic Imaging 3rd edition. Mosby 2003
2. Roche C, et al. Selections from the Buffet of Food Signs in Radiology. Radiographics 2002; 22: 1369-1384.
Credit: Dr Laughlin Dawes
http://www.radpod.org/2007/02/08/omental-cake/
CT Images
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Examples:
This multiphase CT shows the typical imaging features of liver haemangioma. There is peripheral nodular enhancement in the arterial phase which gradually fills in in later
phases (portal venous and delayed). Haemangiomas are the most common benign tumour of the liver (78%), and the second most common liver tumour after metastases.
Reference: Dahnert W. Radiology Review Manual 5th ed. Lippincott Williams & Wilkins
Credit: Dr Laughlin Dawes
http://www.radpod.org/2011/08/04/liver-haemangioma/
CT Images
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Examples:
This curved reformat of a CT angiogram nicely shows an arterial-phase enhancing lesion situated between the internal and external carotid arteries. This is the typical location
and appearance of a carotid body tumour. Carotid body tumour is a paraganglioma of the carotid body; this is the most common site of paraganglioma in the head & neck.
Other sites include glomus jugulare / jugulotympanicum, glomus vagale, glomus tympanicum, or rarely glomus faciale (along the course of the facial nerve). Malignant
features may be seen in 6% of head & neck paragangliomas, and possibly as high as 16% for glomus vagale.
Reference: Valvassori’s Imaging of the Head and Neck 2nd ed. Mafee MF et al. Thieme 2005.
Credit: Dr Laughlin Dawes
http://www.radpod.org/2011/07/02/carotid-body-tumour-2/
CT Images
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Examples:
48yo female, sent for ultrasound +/- FNA for ?cervical lymphadenopathy. Ultrasound showed multiple enlarged hypervascular lymph nodes, and uncomplicated biopsy was
performed. A CT of the skull base and neck was recommended. The midline sagittal reconstruction shows an avidly enhancing lesion in the cribriform plate region destroying
the anterior skull base and infiltrating the basal frontal lobes and the superior nasal cavity. Axial and coronal reconstructions showed invasion of both orbits, and extensive
multilevel cervical lymphadenopathy. Several marginal fluid-filled compartments were noted at the infiltrating tumour margin adjacent to the brain, with adjacent vasogenic
oedema. The appearances are typical of esthesioneuroblastoma, which was confirmed on FNA.
Esthesioneuroblastoma (otherwise known as “olfactory neuroblastoma”) is a rare neoplasm thought to arise from the olfactory epithelium. Despite its rarity, it has a relatively
typical appearance on imaging. It is usually highly malignant and because of its location is usually very locally advanced by the time of diagnosis, with brain and orbital
invasion occurring commonly and early.
Credit: Dr Jason Wenderoth
http://www.radpod.org/2011/05/09/esthesioneuroblastoma/
CT Images
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Examples:
Staphyloma is the term given to an eye whose sclero-uveal coats are stretched (aka ectasia). This most commonly occurs posteriorly, athough anterior staphyloma also is
recognised.
Posterior staphyloma
* progressive myopia (aka mega myope) most common cause.
* glaucoma
* scleritis
* necrotizing infection
* surgery / trauma
* radiotherapy
Anterior staphyloma
Seen seconday to inflammation or infection of the sclero-corneal lining of the eye.
References:
1. M Mafee, GE Valvassori, M Becker “Imaging of the Head and Neck” Thieme 2005 2nd Ed.
2. D Osborne, GN Foulks “Computed Tomographic Analysis of Deformity and Dimensional Changes in the Eyeball” Radiographics 1985; 153:699-674
Credit: Dr Frank Gaillard
http://www.radpod.org/2008/07/30/staphyloma/
CT Images
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Examples:
CTA of this patient shows bilateral popliteal artery aneurysms, patent on the left and thrombosed on the right.
Popliteal artery aneurysms are the most common peripheral arterial aneurysm. They are usually true aneurysms resulting from atherosclerosis or arteriomegaly. False
aneurysms may arise from knee trauma, surgery or infection.
True aneurysms of the popliteal artery are commonly bilateral (50 to 70%) and frequently associated with abdominal aortic aneurysms (30 to 50% have a AAA). There is a
strong male preponderance with a male to female ratio of 15:1. These aneurysms rarely rupture; the main complications are thrombosis and distal embolism. For this reason
asymptomatic aneurysms greater than 2 cm diameter are considered for elective treatment with endovascular insertion of a covered stent, or with open surgical repair.
Reference: Radiopaedia.org
Credit: Dr Donna D'Souza
http://www.radpod.org/2008/08/20/bilateral-popliteal-artery-aneurysms/
CT Images
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Examples:
Two month-old girl presented with respiratory distress. CT scan shows multiple large cysts (>2cm) involving the lower lobe of left lung. The cysts are air-filled, expand the
lower lobe, cause mediastinal shift and hypoplasia of right lung. The condition was complicated by spontaneous pneumothorax for which intercostal drain was inserted.
Lobectomy was performed.
CCAM consists of a multicystic intralobar mass of disorganized lung tissue, derived primarily from bronchioles. It can involve an entire lobe. Lower lobes are most often
involved, but any lobe can be affected. The treatment of choice is excision of the affected lobe.
CCAMs are often classified into 3 types which have different histology, gross pathologic findings, radiographic appearance and prognosis.
Radiological differential diagnosis: Congenital diaphragmatic hernia, congenital lobar emphysema, localized persistent pulmonary interstitial emphysema and pneumatocele.
Reference: Webb & Higgins. Thoracic imaging, Pulmonary and cardiovascular radiology. Lippincott Williams & Wilkins 2005.
Credit: Dr Ahmed Haroun
http://www.radpod.org/2008/02/28/congenital-cystic-adenomatoid-malformation/
CT Images
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Examples:
After implantation of a silicone or saline breast implant, a fibrous capsule (scar) forms around the implant shell. In an intracapsular rupture the contents of the implant are
contained by the fibrous scar while the shell appears as a group of wavy lines. This has been termed the “Linguine Sign” and has been most commonly described with MR
imaging. Here, the same findings are seen on CT imaging in a patient with bilateral ruptured saline implants.
Reference: Safvi A. Linguine Sign. Radiology 2000; 216: 838-839.
Credit: Dr Evan Stein
http://www.radpod.org/2008/02/28/congenital-cystic-adenomatoid-malformation/
CT Images
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Examples:
This young adult male patient collapsed on an international flight.
A cerebral CT was performed for ongoing reduced level of consciousness.
An abdominal CT was performed.
The radiological findings are:
Bilateral globus pallidus hypodensity consistent with hypoxic brain injury.
Rounded heterogeneous structures in stomach and bowel (drug packets).
The “knot sign” – an eccentric low density nodule on the drug packet, representing the knot in the condom.
These findings together suggest drug packet rupture followed by collapse, hypoxia and subsequent brain injury.
Credit: Dr Laughlin Dawes
http://www.radpod.org/2008/02/20/hypoxic-brain-injury-following-drug-packet-rupture-2/
CT Images
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Examples:
This young patient was found belatedly after a collapse secondary to drug overdose. Note the extensive cerebral oedema with loss of normal grey-white matter differentiation.
The patient never regained consciousness and eventually died with increased intracranial pressure.
Cerebral oedema is divided into vasogenic oedema and cytotoxic oedema.
Vasogenic is due to disruption of the blood brain barrier with leakage of fluid out of capillaries, and is most frequently seen around brain tumours (both primary and secondary)
and cerebral abscesses, although some vasogenic oedema is also seen around maturing cerebral contusions and cerebral haemorrhages.
Cytotoxic oedema, (as in this case) in contrast, is due to cellular swelling from lack of ATP, and is typically seen in an area of cerebral ischaemia or cerebral hypoxia.
Reference:
Primer of Diagnostic Imaging by Weissleder
Credit: Dr Frank Gaillard
http://www.radpod.org/2008/02/08/cerebral-oedema/
CT Images
This febrile neutropaenic patient had pulmonary nodules surrounded by ground-glass opacity consistent with angioinvasive fungal infection. One week after antifungal
treatment his follow-up CT chest showed
signs of healing with one of the nodules demonstrating the air crescent sign.
In angioinvasive fungal infection, the nodules are composed of infected haemorrhagic and infarcted lung tissue. As the neutrophil count recovers and the patient mounts an
immune response, peripheral reabsorption of necrotic tissue causes the retraction of the infarcted centre and air fills the space in between. This creates an air crescent within
the nodules and is a good prognostic finding because it marks the recovery phase of the infection. This sign is seen in approximately 50% of patients.
Reference: Abramson S. The Air Crescent Sign. Radiology. 2001; 218:230-232
Credit: Dr Donna D'Souza
http://www.radpod.org/2008/01/25/air-crescent-sign/