Swyer-James Syndrome (SJS)

Axial Computed Tomography of the chest reveals a small hyperlucent left lung with atresic vascular structures and evidence of air trapping characteristic of the Swyer-James syndrome.

The condition was first described in Canada in the 1950s by :

• Paul Robert Swyer : English paediatrician in Canada,
• William Mathieson MacLeod : English pulmonologist (1917 - 1977),
• George C. W. James : Canadian radiologist.

It has also been referred to as MacLeod syndrome, but this is not advised to be used du to the presence of a rare genetic syndrome resulting in slowly progressive degeneration of a variety of tissues including blood, brain, peripheral nerves, muscle and heart - bearing a very closely similar name: McLeod syndrome.

Swyer-James syndrome (SJS) is a manifestation of postinfectious obliterative bronchiolitis. In SJS, the involved lung or portion of the lung does not grow normally and is slightly smaller than the opposite lung. The characteristic radiographic appearance is that of pulmonary hyperlucency, caused by overdistention of the alveoli in conjunction with diminished arterial flow.

Plain X-ray Chest revealed the left lung is smaller and more lucent compared to the right. In addition, the pulmonary vessels on the left are smaller and don't extend as far peripherally as those on the right.

For patients with Swyer-James syndrome, chest computed tomography (CT) scanning with thin collimation sections on inspiration and expiration is the preferred examination. The appearance of the lungs on forced expiration is important in the assessment of SJS with CT scanning; therefore, the patient's co-operation is essential. The patient should be placed in the prone position to help identify the typical mosaic pattern of the syndrome.

In Swyer-James syndrome, the bronchi have a pruned appearance. A mosaic pattern of air trapping in acini is seen, along with air trapping during expiration. The appearance is similar to that of hypoplastic lung syndrome. In addition, the appearance of Swyer-James syndrome is the same as that of bronchiolitis obliterans, but bronchiolitis obliterans is more frequently a diffuse process.

CT aids in the differential diagnosis between SJS, bronchial obstruction and congenital vascular anomalies like unilateral pulmonary artery agenesis or scimitar syndrome, showing preserved anatomy of tracheobronchial tree and pulmonary arteries. Currently available post-processing tools improve MDCT diagnostic performances; in particular the combination of multiplanar reformatted images with maximum intensity projection (MIP) is most effective in vascular imaging while minimum intensity projection (minIP) reconstructions help to disclose differences in lung attenuation and depiction of bronchial structures.

a.Chest X-rays showing reduced left lung volume and herniation of hyperinflated right lung (arrow).

b, c. Axial CT scan and minIP coronal reconstruction reveal hyperlucency of left lung and airways patency.

d. Contrast enhanced MIP coronal reconstruction reveal left pulmonary arteries have strikingly decreased caliber.

Ancient Chinese Yin-Yang Symbol

Ancient Chinese Yin-Yang Symbol.

In Asian philosophy, the concept of yin yang (simplified Chinese: 阴阳; traditional Chinese: 陰陽; pinyin: yīnyáng), which is often referred to in the West as "yin and yang", is used to describe how polar opposites or seemingly contrary forces are interconnected and interdependent in the natural world, and how they give rise to each other in turn. Opposites thus only exist in relation to each other. The concept lies at the origins of many branches of classical Chinese science and philosophy, as well as being a primary guideline of traditional Chinese medicine, and a central principle of different forms of Chinese martial arts and exercise, such as baguazhang, taijiquan (t'ai chi), and qigong (Chi Kung) and of I Ching divination. Many natural dualities — e.g. dark and light, female and male, low and high, cold and hot — are thought of as manifestations of yin and yang (respectively).

Yin yang are not opposing forces (dualities), but complementary opposites that interact within a greater whole, as part of a dynamic system. Everything has both yin and yang aspects as light cannot exist without darkness and vice-versa, but either of these aspects may manifest more strongly in particular objects, and may ebb or flow over time. The concept of yin and yang is often symbolized by various forms of the Taijitu symbol, for which it is probably best known in western cultures.

Yin Yang is represented by the Taijitu symbol, which is a diagram of the supreme Ultimate. It is a circle divided into two teardrop shaped halves, one white, the other black, each containing a small circle of the opposite colour.

There is a perception (especially in the West) that yin and yang correspond to evil and good. However, Taoist philosophy generally discounts good/bad distinctions and other dichotomous moral judgments, in preference to the idea of balance. Confucianism did attach a moral dimension to the idea of yin and yang, but the modern sense of the term largely stems from Buddhist adaptations of Taoist philosophy.

Meigs' Syndrome and Meige's Syndrome...Is There Any Difference?!

Meigs' syndrome:

Meigs syndrome is defined as the triad of benign ovarian tumor with ascites and pleural effusion that resolves after resection of the tumor. The ovarian tumor in Meigs syndrome is a fibroma.

In 1934, Salmon described the association of pleural effusion with benign pelvic tumors. In 1937, Meigs and Cass described 7 cases of ovarian fibromas associated with ascites and pleural effusion. In 1954, Meigs proposed limiting true Meigs syndrome to benign and solid ovarian tumors accompanied by ascites and pleural effusion, with the condition that removal of the tumor cures the patient without recurrence. Histologically, the benign ovarian tumor may be a fibroma, thecoma, cystadenoma, or granulosa cell tumor.

Pseudo-Meigs syndrome consists of pleural effusion, ascites, and benign tumors of the ovary other than fibromas. These benign tumors include those of the fallopian tube or uterus and mature teratomas, struma ovarii, and ovarian leiomyomas. This terminology sometimes also includes ovarian or metastatic gastrointestinal malignancies.

Meige's syndrome:

It is a type of dystonia. It is also known as Brueghel's syndrome and oral facial dystonia. It is actually a combination of two forms of dystonia, blepharospasm and oromandibular dystonia (OMD). When OMD is combined with Blepharospasm, it may be referred to as Meige’s Syndrome named after Henri Meige, the French neurologist who first described the symptoms in detail in 1910. The symptoms usually begin between the ages of 30 and 70 years old and appear to be more common in women than in men (2:1 ratio). The combination of upper and lower dystonia is sometimes called cranial-cervical dystonia.

The Drooping Lily Sign

Drooping lily.

The drooping lily sign can be identified at excretory urography in patients with duplicated renal collecting systems. The sign consists of inferolateral displacement of a functioning lower pole moiety and lateral displacement of the most superior calices of the lower pole collecting system, usually by a nonopacified, hydronephrotic upper pole collecting system. The appearance of the lower pole collecting system is reminiscent of a lily flower that is wilting or drooping.

Radiograph obtained at excretory urography in a 1-month-old female patient in the supine position demonstrates inferior and lateral displacement of the lower pole moiety (arrow) of a right duplicated collecting system: the drooping lily sign. The left collecting system is normal.

The drooping lily sign is due to inferior and lateral displacement of the lower pole moiety of a duplex kidney, rather than displacement of an entire kidney. An obstructed, poorly functioning upper pole moiety exerts a mass effect on the lower pole collecting system, which is responsible for the abnormal axis of the lower pole calices and which causes the droop of the lily. Because only the lower pole collecting system is opacified with intravenously administered contrast material, a decreased number of calices are depicted, as no calices extend cephalad from the renal pelvis. 

The sign is often accompanied by a bladder filling defect, representing a ureterocele, which is associated with the ectopic insertion of the upper moiety ureter. As the frequency of excretory urography wanes, the “classic” drooping lily is less frequently encountered. Diagnostic consideration should be given to the presence of a duplication anomaly whenever a process is discovered in only one portion of a kidney.      

The Lemon Sign

The lemon sign refers to the shape of the fetal skull at ultrasonography (US) when the frontal bones lose their normal convex contour and appear flattened or inwardly scalloped. This gives the skull a shape similar to that of a lemon. The sign is seen on transverse sonograms of the fetal cranium obtained at the level of the ventricles.

Transverse cranial sonogram of a 20-week-old fetus with spina bifida. Image obtained at the level of the ventricles demonstrates the lemonlike configuration of the fetal skull due to biconcavity (arrows) of the frontal bones.

            Transverse cranial sonogram of an 18-week-old fetus demonstrates the normal contour of a fetal skull.                       

 The lemon sign has a strong association with spina bifida. Although the exact pathogenesis is unknown, it has been postulated that the decrease in the intraspinal pressure in neonates with spina bifida causes the brain to shift downward. This shift decreases the intracranial pressure, which is reflected onto the fetal cranium. The frontal bones are the most vulnerable to the decreased intracranial pressure and respond by flattening or scalloping inward.

As the fetus matures, the lemon sign disappears because the frontal bones become stronger and are able to withstand the decreased pressure. In addition, the majority of neonates with spina bifida develop hydrocephalus as they mature. This increase in intracranial pressure can lead to reversal of the flattening. However, this theory does not explain why the lemon sign is present in fetuses with a normal posterior fossa.

Therefore, an alternative theory has been proposed that the lemon sign might be due to a primary skeletal developmental disorder and that the contour of the skull is a result of mesenchymal dysplasia of the cranium.      

The lemon sign is very useful in the detection of spina bifida in a high-risk population before 24 weeks of gestation. The lemon sign is not exclusive to spina bifida. It has been seen in a variety of conditions such as encephalocele, Dandy-Walker malformation with encephaloceles, thanatophoric dysplasia, cystic hygroma, diaphragmatic hernia, agenesis of the corpus callosum, fetal hydronephrosis, and umbilical vein varix and two-vessel cord.

Detection of the spinal defect by using prenatal US can be very difficult and depends on the experience and skill of the sonographer. The spinal defect may be detected approximately 80% of the time when the examination is performed by a highly qualified sonographer who is carefully evaluating the spine. In contrast, the sensitivity for detection of a spinal lesion is lower than 50% when US is performed in a low-risk population, by an inexperienced sonographer, or by using less-advanced equipment.

            Longitudinal sonogram of a fetal spine demonstrates a spinal defect (arrow) covered by membrane. 


                    

The lemon sign is a useful tool to aid in the detection of spina bifida. Detection of the lemon sign does not require the high level of skill that is needed for US evaluation of the spine. If the lemon sign is present, this should signal the possibility of spina bifida and should prompt the sonographer to look for other cranial markers of spina bifida and to perform a more detailed evaluation of the spine.

           

Ultrasonography of Breast Fibroadenoma

While doing your regular breast self-examamination of youe breasts, you may feel a breast fibroadenoma. Women sometimes refer to them as “breast mice” because they tend to run away from fingers while examening the breast.

Fibroadenomas of the breast, are lumps composed of fibrous and glandular tissue. Because breast cancer can also appear as a lump, doctors may recommend a tissue sample (biopsy) to rule out cancer in older patients. Unlike typical lumps from breast cancer, fibroadenomasare easy to move, with clearly defined edges.

 Ultrasound appearance of  the mass which is oval, measured about 10 x 5 mm. and showed smooth margins which were well defined. The lesion was non-calcific and seemed extremely mobile on probe pressure.



Power Doppler image shows poor vascularity of the lesion.

The typical case is the presence of a painless, non-tender although may get tender especially right before the menstrual period, when it may swell due to hormonal changes, firm, solitary, freely mobile, slowly growing lump in the breast of a woman of childbearing years. A fibroadenoma is usually diagnosed through clinical examination, ultrasound or mammography, and often a needle biopsy sample of the lump may be recommended.

Fibroadenomas arise in the terminal duct lobular unit of the breast. They are the most common breast tumor in adolescent women. They also occur in a small number of post-menopausal women. Their incidence declines with increasing age, and, in general, they appear before the age of thirty years. Fibroadenomas are partially hormone-dependent and frequently regress after menopause. They are hypovascular compared to typical (especially malignant) neoplasms.

The Mount Fuji Sign

The Mount Fuji sign is a finding that can be observed on computed tomographic (CT) scans of the brain, in which bilateral subdural hypoattenuating collections cause compression and separation of the frontal lobes. The collapsed frontal lobes and the widening of the interhemispheric space between the tips of the frontal lobes have the appearance of the silhouette of Mount Fuji—hence, the Mount Fuji sign.

A photo of The Mount Fuji.

Unenhanced transverse CT image of the brain demonstrates bilateral subdural areas of hypoattenuation (∗) with compression of the frontal lobes.                       

Unenhanced transverse CT image of the brain obtained caudal to image shown in previous figure. Widening of the interhemispheric space between the tips of the frontal lobes is noted. The medial surface of each frontal lobe is marked (arrows).                       

The hypoattenuating collections are caused by the entry of air into the cranial vault, a condition that can occur in iatrogenic and noniatrogenic disruption of the skull base or calvaria. However, tension pneumocephalus (i.e, subdural air causing mass effect on the brain) requires conditions that lead to increased air pressure within the subdural space. The increased pressure of air is assumed to be due to a ball-valve mechanism. This implies that air enters into the subdural space by means of a dehiscence in the skull base or calvaria and that the egress of air is blocked by an obstruction. An additional mechanism (ie, posterior fossa surgery in the sitting position) has been postulated, but it was later discredited. In these cases, it was believed that nitrous oxide, which was used as an anesthetic, diffused into air-filled spaces and expanded the gaseous volume. Irrespective of the mechanism, the increased pressure may lead to extra-axial mass effect with subsequent compression of the frontal lobes. The presence of air between the frontal tips suggests that the pressure of the air is at least greater than that of the surface tension of cerebrospinal fluid between the frontal lobes.                 

The Mount Fuji sign on CT scans of the brain is useful in discriminating tension pneumocephalus from nontension pneumocephalus. Tension pneumocephalus can be considered a neurosurgical emergency, unlike nontension pneumocephalus. Tension pneumocephalus occurs most commonly after the neurosurgical evacuation of a subdural hematoma.

The Mount Fuji sign on CT scans of the head in trauma patients and in postoperative patients can be a critical finding made by the radiologist. Identification of this sign can have immediate and important clinical implications for patient care and outcome.                 

                

The Golf Ball–on-Tee Sign

The golf ball–on-tee sign is seen during excretory urography and appears as a contrast agent–filled cavity (the golf ball) that lies adjacent to a blunted calyx (the tee).

Excretory urogram (frontal view) displaying the left side of the collecting system shows contrast material in a large papillary cavity, the “golf ball” (∗). A blunted calyx, the “tee,” is adjacen (arrow).                          

Photograph of a golf ball on a tee.

The collecting tubules within the medullary pyramid come together to form the papillary ducts that penetrate the papillary tip and drain into a calyx. Normally, individual collecting tubules are not visualized; rather, the normal papilla has a distinctive blush that fades with time. In papillary necrosis, however, central necrosis and sloughing of the papilla create a cavity, which is occasionally large, that fills with contrast material and communicates with the calyceal concavity. Thus, the golf ball–on-tee sign is created, indicating necrosis.  

The common etiology of papillary necrosis can be conveniently remembered with Dunnick's mnemonic NSAID: nonsteroidal anti-inflammatory medications, sickle cell hemoglobinopathies, analgesic nephropathy (specifically aspirin and phenacetin), infection (specifically tuberculosis), and diabetes. Some less-common causes include renal vein thrombosis, hypotension, and obstructive uropathy. The papillary necrosis seen in tuberculosis and severe pyelonephritis is a direct result of the infection.               

Adenomyosis

This is a relatively common condition that affects women of reproductive age and is considered to be a variant of endometriosis. The histologic diagnosis of adenomyosis is made when endometrial glands and stroma are seen within the myometrium. It is found to coexist with  endometriosis in up to 20% of women. Adenomyosis typically presents in women who are in the latter part of their reproductive years and multiparous. The classic presenting symptoms are dysmenorrhea and menorrhagia. The disease is more common in women who have had previous uterine surgery, most commonly dilatation and curettage and cesarean section. On clinical examination, the uterus might be enlarged, especially on the posterior uterine wall, where adenomyosis is usually more extensive.

The ultrasound diagnosis of adenomyosis is problematic because there are no characteristic features. In most cases, the uterus appears normal or enlarged, and the posterior uterine wall might appear thickened. The myometrium can appear heterogenous with areas of both hyperechogenicity and hypoechogenicity representing areas of small myometrial cysts. These cysts contain the remnants of menstrual flow from the ectopic endometrium.

An adenomyoma is a focal, localized area of endometriosis and might be distinguishable as a focal echo-poor mass. However, the appearances can be very similar to a uterine fibroid, which might be a coexistent pathology.

Human Chorionic Gonadotrophin (hCG)

Most commercially available monoclonal antibody-based urine pregnancy tests can detect the presence of human chorionic gonadotrophin (hCG) at a level above 25 IU/L, which corresponds to day 24–25 of a regular 28-day cycle. In normal early pregnancies, serum hCG levels double approximately every 2 days. In clinical practice, the measurement of serum hCG is used to diagnose ectopic pregnancy; to help select patients for expectant, medical and surgical management of early pregnancy failure; and to assess the efficacy of treatment at follow-up visits.

Traditionally, an ectopic pregnancy is suspected in women in whom intrauterine pregnancy is not demonstrated on ultrasound. In this situation, many clinicians resort to the assessment of the daily rate of serum hCG levels. An ectopic pregnancy is suspected if the hCG does not double in 2–3 days. Another approach to the diagnosis of ectopic pregnancy is to use a cut-off level above which an intrauterine pregnancy should be seen on ultrasound. With the use of transvaginal sonography this level has been set to the serum hCG level of 1000 IU/L (the first International Standard). However, neither abnormal doubling time nor the cut-off method is sensitive or specific enough to diagnose ectopic pregnancy.

Serum hCG measurement is also used for selection of women for conservative or medical management of ectopic pregnancy. Expectant management of ectopic pregnancy is likely to be successful if the initial hCG is < 1000 IU/L and medical treatment of tubal ectopic is rarely used if the hCG > 15 000 IU/L because the risk of failure and complications is increased.

Last Menstrual Period

The most accurate way to calculate the length of pregnancy is by knowing the date of conception. Delivery would then be expected to occur 38 weeks (266 days) later. However, as most women are unaware of the date of conception, the first day of the last menstrual period (LMP) is used to calculate the expected date of delivery (EDD). This is done by applying Naegele’s formula to the LMP as follows:
1. Add 7 to the days
2. Subtract 3 from the months
3. Add 1 to the years.

This means that pregnancy is 40 weeks (280 days) long and assumes that conception occurs 2 weeks after the LMP.

The LMP is unreliable (and therefore Naegele’s formula cannot be used) if:

• The date of the LMP is not accurately known.
• The menstrual cycle is not 28 days long.
• The menstrual cycle is irregular.
• The woman has only stopped taking the combined oral contraceptive pill (‘the pill’) within the last 3 months.
• The woman has bled in early pregnancy.
• The woman is breast feeding or has been pregnant in the preceding 3–6 months.

Fabella

The fabella (Latin for little bean) is a small sesamoid bone found in some mammals embedded in the tendon of the lateral head of the gastrocnemius muscle behind the lateral condyle of the femur. It is a variant of normal anatomy and present in humans in 10% to 30% of individuals. Rarely, there are 2 or 3 of these bones (fabella bi- or tripartita). It can be mistaken for a loose body or osteophyte. On radiographs it appears as a small bony shadow behind the knee joint. Intra-articular fluid in the knee may sometimes cause displacement of the fabella what is called fabella sign.

Plain film lateral with fabella indicated (arrow)

MRI Sagittal T1 with fabella indicated by arrow; normal low signal cortex and high signal marrow

In osteoarthritis of the knee, the fabella may undergo cartilaginous fibrillation and erosion and bone proliferation. Flattening and sclerosis may be observed radiographically on the anterior surface. An enlarged, malpositioned or even normal fabella may lead to entrapment or peroneal nerve injury. Other pathologic conditions involving the fabella include fractures, dislocations and, in younger patients, chondromalacia.

The American College of Radiology (ACR) Breast Imaging Reporting and Data System (BI-RADS)

There are 7 ACR BI-RADS standardized categories:

• Category 0, or "need additional imaging evaluation," is used if additional imaging is needed (this category is almost always used in a screening situation and should be used only rarely after a full imaging workup; additional imaging evaluation includes the use of spot compression and magnification views, along with other tailored mammographic views and ultrasonography).
 
• Category 1, or "negative," is used if there are no findings to comment on; for example, the breasts are symmetrical, and no masses, architectural disturbances, or suspicious calcifications are present.
 
• Category 2, or "benign finding(s)," is used if the radiologist wishes to describe a benign finding while still concluding that there is no mammographic evidence of malignancy.
 
• Category 3, or "probably benign finding initial short-interval follow-up suggested," is used when a noted finding has a very high probability of being benign; the finding is not expected to change over the follow-up interval, but the radiologist prefers to establish its stability over time.
 
• Category 4, or "suspicious abnormality–biopsy should be considered," is used when a finding has a definite probability of being malignant.
 
• Category 5, or "highly suggestive of malignancy–appropriate action should be taken," is used when a finding has a high probability of being cancerous. 
 
• Category 6, or "known biopsy-proven malignancy-appropriate action should be taken," is "reserved for lesions identified on imaging study with biopsy proof of malignancy prior to definitive therapy".      

Skeletal Bone Age Assessment

Bone age assessment is a procedure frequently performed in pediatric radiology. Based on a radiological examination of skeletal development of the left-hand wrist, bone age is assessed and then compared with the chronological age. A discrepancy between these two values indicates abnormalities in skeletal development. The procedure is often used in the management and diagnosis of endocrine disorders and it can also serve as an indication of the therapeutic effect of treatment. Generally, it can indicate whether the growth of a patient is accelerating or decreasing. In many cases the decision whether to treat a patient with growth hormones depends on the outcome of this test. Another relevant application is in the social field. In fact, a considerable percentage of asylum seekers that come to European countries claim to be a minor to increase their chance to obtain a residence permit. Since these people usually don’t have identity papers, determination of the skeletal maturity can help in the determination of the true age of such a person.

This examination is universally used due to its simplicity, minimal radiation exposure, and the availability of multiple ossification centers for evaluation of maturity. Automatic skeletal age assessment has the potential to reduce the time required to examine the image and to increase the reliability of the analysis.

Functional Brain MR Imaging (fMRI)

Functional magnetic resonance imaging (fMRI) is a relatively new procedure that uses MR imaging to measure the tiny metabolic changes that take place in an active part of the brain. fMRI is becoming the diagnostic method of choice for learning how a normal, diseased or injured brain is working, as well as for assessing the potential risks of surgery or other invasive treatments of the brain.

The Disappearing Basal Ganglia Sign

The disappearing basal ganglia sign is a finding that can be seen at computed tomography (CT). It appears as a loss of the normal delineation of the basal ganglia, with the affected basal ganglia exhibiting abnormal morphologic features. This is best appreciated when a comparison is made between the affected basal ganglia and the contralateral side of the brain.

Transverse CT scans obtained without intravenous contrast material demonstrate the disappearing basal ganglia sign.Note the loss of the normal contour of the right basal ganglia. The left basal ganglia (arrow) are normal. The right insular cortex is obscured, and there is a loss of the gray matter-white matter junction.

The disappearing basal ganglia sign is representative of cerebral infarction. The sign is usually caused by incomplete to complete occlusion of the MCA as a result of thromboembolic disease. Other differential diagnostic considerations include arterial dissection, trauma, vasculitis, and hemolytic uremic syndrome. If injury occurs bilaterally, diagnostic considerations include global hypoperfusion; respiratory arrest; near drowning; strangling; barbiturate overdose; methanol toxicity; cyanide poisoning; osmotic myelinolysis; hypoglycemia; Leigh disease; mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes (also known as MELAS); and infectious causes.

Transverse CT scan from the same patient described in the previous CT image but 36 hours later. The right middle cerebral artery infarct (arrows) has now matured, creating a large area of hypoattenuation in the right basal ganglia, right temporal lobe, and posterior portion of the right frontal lobe. The left basal ganglia retain normal morphologic features and attenuation.                       

Normally, the lentiform nucleus and caudate nucleus are slightly hyperattenuated when compared with the surrounding white matter. When present, a vascular insult will usually manifest at CT as areas of hypoattenuation, which occur when the normal cellular requirements are not met. Normal cell volume must be maintained with normal intra- and extracellular electrolyte concentration gradients. When there is an interruption of blood flow, cellular injury occurs. This, in turn, causes a loss of homeostasis and creates an influx of sodium, chloride, calcium, and water into the cells, thereby causing metabolic acidosis. This intracellular influx of fluid will lead to cytotoxic edema. The areas of hypoattenuation may also be interpreted as an indicator of severe focal ischemia.

Normal CT Brain.

Swan-Neck and Boutonniere Deformities

The chronic inflammatory changes of rheumatoid arthritis in the joints of the fingers produce retraction of the tendons. The swan-neck deformity is caused by hyperextension of the proximal interphalangeal joint with simultaneous flexion of the distal interphalangeal joint. If you try this manipulation on yourself, you will clearly recognize the etiology of the name. The boutonniere (or buttonhole) deformity is caused by hyperextension of the distal interphalangeal joint with simultaneous flexion of the proximal interphalangeal joint. 

Swan-Neck Deformity.

 

Swan Neck



Boutonniere Deformity.

Boutonniere.

The Hot Nose Sign

The hot nose sign is a finding that can be observed on scintigraphic brain flow scans. It is defined as the presence of early, increased activity in the nasopharyngeal region at radionuclide blood flow scanning.

The hot nose sign may be seen in patients who have diminished blood flow in one or both internal carotid arteries. Decreased internal carotid blood flow leads to increased or collateral flow through the external carotid artery on the involved side, producing markedly increased perfusion to the nasal region. The result is a blush of increased nasopharyngeal radiotracer activity, or “hot nose”, that can be seen on radionuclide blood flow scans.

Computed Tomography Artifacts

In computed tomography (CT), the term artifact is applied to any systematic discrepancy between the CT numbers in the reconstructed image and the true attenuation coefficients of the object. CT images are inherently more prone to artifacts than conventional radiographs because the image is reconstructed from something on the order of a million independent detector measurements. The reconstruction technique assumes that all these measurements are consistent, so any error of measurement will usually reflect itself as an error in the reconstructed image.

Streak artifact:

Streaks are often seen around materials that block most X-rays, such as metal or bone. These streaks can be caused by undersampling, photon starvation, motion, beam hardening, or scatter. This type of artifact commonly occurs in the posterior fossa of the brain, or if there are metal implants.The streaks can be reduced using newer reconstruction techniques.

The streak artifacts emanating from the implant.

Partial volume effect:

This appears as "blurring" over sharp edges. It is due to the scanner being unable to differentiate between a small amount of high-density material (e.g., bone) and a larger amount of lower density (e.g., cartilage). The processor tries to average out the two densities or structures, and information is lost. This can be partially overcome by scanning using thinner slices.

Diagram showing partial volume effect.

Motion artifact:

This is seen as blurring and/or streaking, which is caused by movement of the object being imaged. Motion blurring might be reduced using a new technique called incompressible flow tomography (IFT).

CT brain displaying a motion artifact.

Beam hardening:

This can give a "cupped appearance". It occurs when there is more attenuation in the center of the object than around the edge. This is easily corrected by filtration and software.

CT brain displaying a beam hardening artifact.

Windmill:

Streaking appearances can occur when the detectors intersect the reconstruction plane. This can be reduced with filters or a reduction in pitch.

CT image of a 12-mm-diameter acrylic sphere supported in air, obtained with 0.6-mm section acquisition and beam pitch of 1.75, shows windmill artifact.

Picture of a windmill.