Thursday, June 30, 2011

Tumor Lysis Syndrome

Tumor lysis syndrome refers to a metabolic derangement due to high tumor burden and rapid cell turnover, resulting in release of intracellular contents. Patients may present with acute renal failure and metabolic derangements, including:
  • Hyperuricemia from purine metabolism
  • Hyperkalemia
  • Hyperphosphatemia
  • Hypocalcemia caused by hyperphosphatemia and the resultant precipitation of calcium phosphate.
While tumor lysis syndrome is most commonly a complication of treatment of blood-borne malignancies such as acute lymphocytic leukemia and poorly differentiated lymphomas (e.g., Burkitt), cases of tumor lysis syndrome related to treatment of solid organ tumors have also been reported. Treatment modalities that can lead to tumor lysis syndrome include chemotherapy, radiation therapy, immunotherapy, interferon therapy, hormonal therapy, surgery, chemoembolization, and radiofrequency ablation. Cases of spontaneous tumor lysis syndrome have also been reported.

The Cairo-Bishop definition includes two classes of tumor lysis syndrome:
Laboratory tumor lysis syndrome: Any 2 of the following:
  • Uric acid > 8 mg/dL or 25% increase
  • Potassium > 6 mEq/L or 25% increase
  • Phosphate > 4.5 mg/dL or 25% increase
  • Calcium < 7 mg/dL or 25% decrease
Clinical tumor lysis syndrome: Laboratory tumor lysis syndrome plus one or more of the following:
  • Creatinine > 1.5x upper limit of normal
  • Seizure
  • Cardiac arrhythmia
  • Sudden death
Management focuses on prevention in high-risk patients with allopurinol and hydration. Treatment after renal failure has occurred involves hydration and loop diuretics to maintain urine flow, recombinant uricase (catalyzes insoluble uric acid), and hemodialysis.

Imaging findings can include nephromegaly, renal stone formation with obstructive uropathy, and findings of posterior reversible encephalopathy syndrome (PRES).

References

  • Cairo MS, Bishop M. Tumour lysis syndrome: new therapeutic strategies and classification. Br J Haematol. 2004 Oct;127(1):3-11.
  • Kaito E, Terae S, Kobayashi R, Kudo K, Tha KK, Miyasaka K. The role of tumor lysis in reversible posterior leukoencephalopathy syndrome. Pediatr Radiol. 2005 Jul;35(7):722-7.
  • Lehner SG, Gould JE, Saad WE, Brown DB. Tumor lysis syndrome after radiofrequency ablation of hepatocellular carcinoma. AJR Am J Roentgenol. 2005 Nov;185(5):1307-9.
  • Parisi MT, Fahmy JL, Kaminsky CK, Malogolowkin MH. Complications of cancer therapy in children: a radiologist's guide. Radiographics. 1999 Mar-Apr;19(2):283-97.

Wednesday, June 29, 2011

Intraventricular Oligodendrogliomas

Intraventricular oligodendrogliomas are rare tumors that have imaging characteristics different from oligodendrogliomas arising in the brain parenchyma. Patients tend to present with headaches due to increased intracranial pressure and usually have a shorter duration of symptoms. This is in contrast to patients with parenchymal lesiosn, who tend to present with focal neurologic deficits or seizures.

It has been suggested that some cases of intraventricular oligodendrogliomas may actually represent central neurocytomas due to the similar imaging and histopathologic findings.

CT shows a high-attenuation lesions that enhance on contrast administration and attach to the ventricular wall. MRI reveals lesion heterogenous signal intensity on T1- and T2-weighted images with cystic and solid components and intense enhancement.

The images above show a mass in the trigone of the left lateral ventricle with heterogeneous attenuation on non-contrast CT. The mass has cystic and solid components on MRI, as well as areas of susceptibility roughly corresponding to the areas of higher attenutation on CT, likely representing calcification. The solid components enhanced on post-gadolinium images.

References

  • Atasoy Ç, Karagülle AT, Erden İ, Akyar S. primary oligodendroglioma of the lateral ventricle: computed tomography and magnetic resonance imaging findings. Journal of ankara medical school, 2002; 55(1): 39-44.
  • Koeller KK, Rushing EJ. From the archives of the AFIP: Oligodendroglioma and its variants: radiologic-pathologic correlation. Radiographics. 2005 Nov-Dec;25(6):1669-88.
  • McConachie NS, Worthington BS, Cornford EJ, Balsitis M, Kerslake RW, Jaspan T. Review article: computed tomography and magnetic resonance in the diagnosis of intraventricular cerebral masses. Br J Radiol. 1994 Mar;67(795):223-43.

Tuesday, June 28, 2011

Fibrothecoma of the Ovary

Fibrothecomas are benign sex cord–stromal tumors of the ovary composed of various proportions of fibromas and lipid-rich, estrogenic thecomas. Fibrothecomas can occur in pre- and post-menopausal women and are the most common of the sex cord–stromal tumors.

On US, fibrothecomas usually appear as a homogeneous hypoechoic mass with posterior acoustic shadowing, but in most cases the appearance of the tumor is nonspecific. CT reveals a homogeneous solid tumor with delayed enhancement. Dense calcifications are often seen.

Fibrothecomas have low signal intensity on T1- and T2-weighted images, representing the fribous component. Scattered high-signal-intensity areas in the mass represent edema or cystic degeneration. In masses with cystic degeneration, the solid component is usually located peripherally.

Differential considerations include uterine leiomyomata and other ovarian masses with fibrous components (fibroma, cystadenofibroma, and Brenner tumor). Differentiation from uterine leiomyomata can be made by noting that ovarian masses are usually supplied by ovarian arteries or by the ovarian branches of the uterine arteries that course along the fallopian tubes. The presence of interface vessels between the uterus and the adnexal mass can help differentiate a uterine leiomyoma from an ovarian fibromous tumor.

The images above show a hypoechoic right adnexal mass. A cystic component (not shown) was also visualized. It was initially felt that the mass was contiguous with the uterus and represented a pedunculated leiomyoma; however, because the right ovary could not be seen on ultrasound, an ovarian mass was also considered, and an MRI performed. MRI showed a right ovarian mass with heterogeneous signal intensity on T2-weighted images and low signal intensity on T1-weighted images (pink arrow). A peripheral cystic component (c) was also seen. No enhancement was seen following contrast administration.

References

  • Jung SE, Lee JM, Rha SE, Byun JY, Jung JI, Hahn ST. CT and MR imaging of ovarian tumors with emphasis on differential diagnosis. Radiographics. 2002 Nov-Dec;22(6):1305-25.
  • Outwater EK, Wagner BJ, Mannion C, McLarney JK, Kim B. Sex cord-stromal and steroid cell tumors of the ovary. Radiographics. 1998 Nov-Dec;18(6):1523-46. Review.

Monday, June 27, 2011

Sella Turcica Dimensions on Radiographs

The length of the sella is determined by taking the greatest distance from the anterior wall of the sella to the most posterior portion of the posterior wall. The height is measured from the level of the tuberculum sellae to the most inferior portion of the floor of the sella.

The lower limits of normal for length and height of the sella on radiographs are 5 mm and 4 mm, respectively. The upper limits of normal for length and height of the sella on radiographs are 17 mm and 13 mm, respectively.

An abnormally small sella may indicate primary pituitary or growth hormone insufficiency, but is usually of no pathologic significance. An enlarged sella turcica may represent a normal variant or be due to a tumor (adenoma, prolactinoma, craniopharyngioma, meningioma), cystic lesion (Rathke cleft cyst, mucocele), aneurysm, pituitary hyperplasia (primary hypothyroidism), or empty sella syndrome.

In the case shown above, the length and height of the sella are 17 mm and 15 mm, respectively. As of this post, no follow-up study is available.

Special thanks to Dr. Jason Tsai for the case.

References

  • Robertson WD, Newton TH. Radiologic assessment of pituitary microadenomas. AJR Am J Roentgenol. 1978 Sep;131(3):489-92.
  • Taveras JM, Wood EH. Diagnostic neuroradiology: Williams & Wilkins Co, Baltimore (1964), pp. 1.96–1104.

Sunday, June 26, 2011

Cystic Vestibular Schwannoma

Vestibular schwannomas are the most common lesions of the cerebellopontine angle. Cystic vestibular schwannomas are less common and present with different clinical and imaging features. They tend to be larger and have a shorter clinical course prior to symptomatic presentation. Also, due to the possibility of rapid enlargement of the cystic elements, conservative management with follow-up is not recommended.

The rate of postoperative complications may also be different between cystic and solid vestibular schwannomas. The main postoperative complication is damage to the facial nerve near its entrance into the porus acusticus, especially when there are multiple cysts or when the cysts are on the anterior surface of the tumor.

On imaging, cystic vestibular schwannomas can have a single small cyst or multiple intramural cysts of variable size. The intramural cysts may have higher signal intensity than that of cerebrospinal fluid, but may also be isointense to cerebrospinal fluid on both T1- and T2-weighted images. Intramural cysts also demonstrate circumferential enhancement.

The images above reveal a predominantly cystic mass at the left cerebellopontine angle with extension into the porus acusticus (red arrow). There is thin circumferential enhancement with a thin septum with the cystic component. There is a solid component anteriorly that demonstrates homogeneous enhancement. The FLAIR image reveals mild edema within the adjacent cerebellum and middle cerebellar peduncle. No restricted diffusion was seen within the cystic component (not shown).

References

  • Benech F, Perez R, Fontanella MM, Morra B, Albera R, Ducati A. Cystic versus solid vestibular schwannomas: a series of 80 grade III-IV patients. Neurosurg Rev. 2005 Jul;28(3):209-13.
  • Tali ET, Yuh WT, Nguyen HD, Feng G, Koci TM, Jinkins JR, Robinson RA, Hasso AN. Cystic acoustic schwannomas: MR characteristics. AJNR Am J Neuroradiol. 1993 Sep-Oct;14(5):1241-7.

Saturday, June 25, 2011

Dermatomyositis in Children: MRI Findings

Childhood dermatomyositis is a multisystemic disease characterized by diffuse nonsuppurative inflammation of muscle fibers and skin. The disease affects blood vessels and is classified as a systemic vasculopathy.

Patients initially present with proximal lower extremity weakness, followed by proximal upper limb weakness and contractures. The skin lesions typically include discoloration of the upper lids and malar aspect of the face.

Radiographs and CT reveal sheet-like calcifications aligned along the planes of muscle and fascia in a symmetric distribution.

MR images reveal increased T2 signal in infarcted muscles affected by the vasculitis (yellow arrows) with edema in the fascial planes and subcutaneous fat. Children with dermatomyositis may also have extensive subcutaneous and intermuscular calcium-rich fluid collections (pink arrows), which can be differentiated from abscesses by the minimal peripheral enhancement seen in the former.

Muscle calcification, although rare, is more common in children, and occurs after a long evolution.

The main differential considerations are:
  • Polymyositis: Has a similar distribution and MRI appearance, but affects an older age group. Edema-like abnormalities are said to be more common and muscle atrophy less common in dermatomyositis compared with polymyositis.
  • Fasciitis:
  • Infectious myositis: Asymmetric distribution. May have abscesses with peripheral enhancement.
  • Muscle injury: Asymmetric muscular distribution
  • Subacute muscle denervation:
  • Radiation therapy: Asymmetric with with a well-delineated, sharp margin of abnormalities in the radiation field
  • Rhabdomyolysis:

References

  • Garcia J. MRI in inflammatory myopathies. Skeletal Radiol. 2000 Aug;29(8):425-38.
  • Hernandez RJ, Sullivan DB, Chenevert TL, Keim DR. MR imaging in children with dermatomyositis: musculoskeletal findings and correlation with clinical and laboratory findings. AJR Am J Roentgenol. 1993 Aug;161(2):359-66.
  • Chan WP, Liu GC. MR imaging of primary skeletal muscle diseases in children. AJR Am J Roentgenol. 2002 Oct;179(4):989-97.

Friday, June 24, 2011

Abdominal Sarcoidosis

Sarcoidosis typically presents with lung involvement; however, abdominal viscera are frequently involved as well.
  • Liver: Most common imaging abnormality is hepatomegaly (30%). May also have multiple low-attenuation intrahepatic septa on contrast-enhanced CT; multiple low-attenuation, low-intensity (on all sequences), and poorly enhancing nodules nodules.
  • Bile ducts: Involvement of intrahepatic bilde ducts can result in a cholestatic picture, mimicking that of primary biliary cirrhosis. Involvement of the extrahepatic ducts can produce strictures that mimic cholangiocarcinoma, while enlargement of portal lymph nodes can compress the biliary tree to produce obstructive jaundice.
  • Spleen: Splenomegaly is seen in about 30%. Low-attenuation/intensity (on all pulse sequences) splenic nodules are seen in 5% - 30% of patients. Isolated/predominant nodular splenic disease is more common than isolated/predominant hepatic nodular disease. Punctate calcifications may also be seen.
  • Lymph nodes: Our patient's only manifestation of sarcoidosis on the unenhanced CT was adbominal adenopathy. In fact, one study found that abdominal adenopathy was the only abnormal finding in approximately 50% of patients in one study.

    Abdominal adenopathy is seen in about 30% of patients. Nodal calcification is unusual in sarcoidosis. The main differential, lymphoma, has essentially the same distribution of adenopathy, although retrocrural lymph nodes are seen more frequently (70%) in patients with lymphoma compared to those with sarcoidosis (20%). Our patient had retrocrural, retroperitoneal, and mesenteric adenopathy, and lymphoma was considered as a possibility.
  • Pancreas: Direct pancreatic involvement is uncommon, but may result in diabetes or pancreatitis. Sarcoid-associated hypercalcemia may also result in acute pancreatitis.
  • Kidneys: While the kidney is involved in 5%-20% of cases at autopsy, a radiographically detectable renal mass is unusual. Nephromegaly or renal atrophy may be the only manifestation. The appearance of granulomas in renal sarcoid is similar to that previously described for the liver and the spleen. The main differential considerations are lymphoma and metastasis.

    The most common effect of renal sarcoidosis is hypercalciuria (more common) or hypercalcemia, which may result in nephrocalcinosis, nephrolithiasis, and interstitial calcium deposition. However, radiographically detectable nephrocalcinosis is uncommon, having been reported in 1%–4% of patients. The mechanism is increased conversion of 25-hydroxyvitamin D3 to active 1,25 dihydroxyvitamin D by macrophages in granulomas, resulting in increased intestinal calcium absorption.

    An interesting result of this disturbance in calcium metabolism is the effect of sunlight. Acute sunlight exposure can precipitate hypercalcemia in this setting, resulting in malaise, dehydration, or acute pancreatitis.
  • Gastrointestinal Tract: Radiographically visible involvement of the gastrointestinal tract appears to be uncommon, with appearances ranging from plaques and ulcers to linear and polypoid filling defects. The stomach is most commonly affected, where involvement can result in mucosal nodularity and thickened irregular folds that mimics Ménétrier disease, or a linitis plastica appearance that can mimic gastric adenocarcinoma.

References

Warshauer DM, Lee JK. Imaging manifestations of abdominal sarcoidosis. AJR Am J Roentgenol. 2004 Jan;182(1):15-28.

Thursday, June 23, 2011

Anterior Rib Lucencies

Normal areas of lucency may be encountered at the anterior ends of the first ribs. Fairly constant in their location, these appear to correspond to deep indentations for the subclavian veins. They may be unilateral or bilateral and should not be confused with a destructive process.

References

Keats TE and Anderson MW. Atlas of Normal Roentgen Variants That May Simulate Disease. 8th edition, page 485; Mosby (2004).

Wednesday, June 22, 2011

Sclerosis of the Medial Ends of the Clavicles

Differential considerations include:
  • Normal variant: This appears to be the case shown above. The patient was asymptomatic, and the image is identical to that presented in Keats (5-109).
  • Osteitis condensans: Rare. Invariably unilateral. Primarily affects women between the ages of 20 to 60. Patients present after months or years of intermittent or steady pain localized to the medial end of the involved clavicle.
  • Osteoarthritis: Joint space narrowing and subchondral sclerosis and subchondral cysts on both sides of the joint.
  • Sternoclavicular hyperostosis: Rare. Typically bilateral. Hyperostosis and soft tissue ossification between the clavicles and anterior portions of the upper ribs and the sternum.
  • Infection: Osteomyelitis or septic arthritis of the sternoclavicular joint. May see joint space narrowing, bone destruction, periosteal reaction, and soft tissue swelling.
  • Friedrich disease: Rare. Ischemic necrosis of the medial clavicular epiphysis. Soft tissue swelling and pain over the medial end of the clavicle are typically present. A notch defect may be seen at the clavicular head. More commonly seen in adolescents and children.

References

  • Brower AC, Sweet DE, Keats TE. Condensing osteitis of the clavicle: a new entity. Am J Roentgenol Radium Ther Nucl Med. 1974 May;121(1):17-21.
  • Abdelwahab IF, Hermann G, Ramos R, Klein MJ, Kenan S, Lewis MM. Case report 623. Osteitis condensans of the left clavicle (OCC). Skeletal Radiol. 1990;19(5):387-9.
  • Harden SP, Argent JD, Blaquiere RM. Painful sclerosis of the medial end of the clavicle. Clin Radiol. 2004 Nov;59(11):992-9.
  • Keats TE and Anderson MW. Atlas of Normal Roentgen Variants That May Simulate Disease. 8th edition, page 452; Mosby (2004).

Tuesday, June 21, 2011

Ulnar Impaction Syndrome

Ulnar impaction syndrome is a degenerative condition caused by chronic impaction between the ulnar head and the triangular fibrocartilage complex and the ulnar carpus. This results in degenerative tear of the triangular fibrocartilage; chondromalacia of the lunate, triquetrum, and distal ulnar head; instability or tear of the lunotriquetral ligament; and, osteoarthritis of the ulnocarpal and distal radioulnar joints.

The most common predisposing factor include congenital positive ulnar variance (although neutral and negative ulnar variance can also be seen), malunion of the distal radius, premature physeal closure of the distal radius, and previous radial head resection. Ulnar impaction syndrome may also occur due to activities that cause excessive intermittent loading of the ulnar carpus.

Radiographs and CT may reveal subchondral sclerosis and cystic changes in the ulnar head, ulnar aspect of the proximal lunate, and proximal radial aspect of the triquetrum. As the disease progresses, ulnocarpal osteoarthritis may be seen in these areas.

MRI in the early stage of ulnar impaction syndrome reveals fibrillation of the cartilage of the ulnar head and ulnar carpus. Later, T2 hyperintensity and T1 hypointensity can be seen in the ulnar head, ulnar aspect of the proximal lunate (seen above), and proximal radial aspect of the triquetrum. More advanced disease is characterized by sclerosis, which is of low signal intensity on both T1- and T2-weighted images. Tears of the triangular fibrocartilage and lunotriquetral ligament may also be seen, although MR arthrography is better at demonstrating these findings.

Differential considerations include:
  • Asymptomatic senescent changes: Lack of positive ulnar variance.
  • Intraosseous ganglia: Area of lucency on radiographs that have sharp margins. No signal intensity change in the triquetrum or ulnar head.
  • True cysts: Area of lucency on radiographs that have sharp margins. No signal intensity change in the triquetrum or ulnar head.
  • Vascular groove: Central proximal radiolucent defect that communicates with the radiolunate joint space.
  • Kienböck disease: More diffuse. Affects the radial half of the lunate bone. The triquetrum and ulnar head are not affected.

References

Cerezal L, del Piñal F, Abascal F, García-Valtuille R, Pereda T, Canga A. Imaging findings in ulnar-sided wrist impaction syndromes. Radiographics. 2002 Jan-Feb;22(1):105-21.

Monday, June 20, 2011

Organizing Pneumonia: Causes and Associations

The histologic hallmark of organizing pneumonia is granulation tissue polyps in the alveolar ducts and alveoli. The granulation tissue is all the same age, contains few inflammatory cells, and results from organization of inflammatory intraalveolar exudates. Patchy lung involvement with preservation of lung architecture is typical.

When a definite cause or characteristic associated context is not present, organizing pneumonia can be referred to as cryptogenic.

A wide variety of conditions may result in organizing pneumonia. Other conditions have reported associations with organizing pneumonia.

Determined causes

  • Infection: Non-resolving pneumococcal pneumonia. Variety of viral, bacterial, fungal, and parasitic infections.
  • Drugs: For example, bleomycin.
  • Radiation: May involve irradiated or nonirradiated areas of the lung. May be migratory.
  • Toxins: Aerosolised textile dye Acramin FWN, benzalkonium compounds, cocaine use.
  • Gastroesophageal reflux: Possibly related to occult aspiration.

Manifestation of an inflammatory and/or immune process

  • Connective tissue disorders: Dermatomyositis–polymyositis, rheumatoid arthritis, systemic lupus erythematosus, scleroderma, CREST, primary biliary cirrhosis (case shown above), and Sjögren syndrome.
  • Lung transplantation:
  • Bone marrow transplant:
  • Hematological disorders: Acute myelomonocytic leukemia, acute lymphoblastic leukemia, chronic myelomonocytic leukemia, myelodysplastic syndrome, T-cell adult leukemia, Evans syndrome.
  • Cancer: Ewing sarcoma, Hodgkin disease, other cancers with or without radiation therapy to the chest, lung cancer.
  • Inflammatory bowel disease:

References

  • Cordier JF.Cryptogenic organising pneumonia. Eur Respir J. 2006 Aug;28(2):422-46.
  • Mueller-Mang C, Grosse C, Schmid K, Stiebellehner L, Bankier AA. What every radiologist should know about idiopathic interstitial pneumonias. Radiographics. 2007 May-Jun;27(3):595-615.
  • Strobel ES, Bonnet RB, Werner P, Schaefer HE, Peter HH. Bronchiolitis obliterans organising pneumonia and primary biliary cirrhosis-like lung involvement in a patient with primary biliary cirrhosis. Clin Rheumatol. 1998;17(3):246-9.

Sunday, June 19, 2011

Bertolotti Syndrome

Bertolotti syndrome refers to anomalous enlargement of the transverse process(es) of the lowermost lumbar vertebra with articulation or fusion with the sacrum or ilium. It is thought that because of the lack of motion at the lowermost disc level, isolated L4-L5 disc disease is more commonly seen. Bertolotti syndrome is seen in about 4% - 8% of the population, the majority of whom are asymptomatic.

Patients may present with pain related to arthritis at the pseudoarticulation or the facets or disc disease at the level above the pseudoarticulation. Radiographs reveal a large transverse process (left in the case shown above). Planar projections in bone scans may be cold; however, single-photon emission computed tomography may reveal areas of increased uptake (seen in images above).

References

  • Almeida DB, Mattei TA, Sória MG, Prandini MN, Leal AG, Milano JB, Ramina R. Transitional lumbosacral vertebrae and low back pain: diagnostic pitfalls and management of Bertolotti's syndrome. Arq Neuropsiquiatr. 2009 Jun;67(2A):268-72.
  • Quinlan JF, Duke D, Eustace S. Bertolotti's syndrome. A cause of back pain in young people. J Bone Joint Surg Br. 2006 Sep;88(9):1183-6.

Saturday, June 18, 2011

Partial Articular Surface Tendon Avulsion (PASTA)

A partial articular surface tendon avulsion (PASTA) is a frequently encountered articular-sided partial-thickness tear of the supraspinatus tendon. Also referred to as "rim-rents," these tears are patients younger than 45 years of age and those who participate in overhead sports. Without treatment, they can turn into full-thickness tears.

More recently, a bony PASTA lesion has been described. The bony PASTA lesion is a partial avulsion of the bony footprint of the supraspinatus tendon without disruption of the tendon fibers or avulsion of the entire greater tuberosity.

References

  • Bhatia DN, de Beer JF, van Rooyen KS. The bony partial articular surface tendon avulsion lesion: an arthroscopic technique for fixation of the partially avulsed greater tuberosity fracture. Arthroscopy. 2007 Jul;23(7):786.e1-6.
  • Millstein ES, Snyder SJ. Arthroscopic management of partial, full-thickness, and complex rotator cuff tears: indications, techniques, and complications. Arthroscopy. 2003 Dec;19 Suppl 1:189-99.

Friday, June 17, 2011

Congenital Absence of the C1 Laminae

Ossification of the posterior arch of C1 usually proceeds from ossification centers around the lateral masses, forming two half arches that fuse between the ages of 3 and 5. In about 2% of cases, there is an additional ossification center in the region of the posterior tubercle (rudimentary form of the spinous process) that unites with the lateral processes of the C1 arch.

Problems with the development of the posterior arch can cause median, uni-, and bilateral clefts. In the extreme form, there is complete lack of ossification of the posterior arch, which is the case shown here.

Isolated absence of the posterior arch of C1 may be asymptomatic; however, intermittent quadriparesis has been reported and absence of the posterior arch may be associated with atlantoaxial instability and may predispose the patient to osteoarthritis later in life.

Special thanks to Dr. Jason Tsai for the case.

References

  • Logan WW, Stuard ID. Absent posterior arch of the atlas. Am J Roentgenol Radium Ther Nucl Med. 1973 Jun;118(2):431-4.
  • Schulze PJ, Buurman R. Absence of the posterior arch of the atlas. AJR Am J Roentgenol. 1980 Jan;134(1):178-80.

Thursday, June 16, 2011

Multiple Myeloma: MRI Findings

Multiple myeboma is the malignant proliferation of plasma cells. The classic radiographic appearance is multiple lytic lesions affecting the axial skeleton. The median age at diagnosis is 65, with wide dissemination throughout the red marrow being the general rule.

Lesions are intermediate to low signal intensity compared to surrounding bone marrow on T1-weighted images (second panel) and high signal intensity on T2 and STIR images (third panel). Post-contrast images reveal enhacement (not shown). The may be also associated soft tissue masses.

Differential considerations based on imaging findings include:
  • Metastases:
  • Lymphoma:
  • Leukemia:
  • Langerhans cell histiocytosis:

References

Libshitz HI, Malthouse SR, Cunningham D, MacVicar AD, Husband JE. Multiple myeloma: appearance at MR imaging. Radiology. 1992 Mar;182(3):833-7.

Wednesday, June 15, 2011

Solitary Choroid Plexus Lipoma

Choroid plexus lipomas are rare lesions that are thought to result from maldifferentiation of the meninx primitiva. While lipomas are usually associated with brain malformations (e.g., midline deformities), isolated choroid plexus lipomas can be seen and may not be as rare as previously thought. They are most commonly found at the trigone, as in the case shown above. Imaging findings are as expected: fat attenuation on CT and signal intensity that follows fat on MRI.

References

  • Naeini RM, Yoo JH, Hunter JV. Spectrum of choroid plexus lesions in children. AJR Am J Roentgenol. 2009 Jan;192(1):32-40.
  • Uchino A, Hasuo K, Matsumoto S, Masuda K. Solitary choroid plexus lipomas: CT and MR appearance. AJNR Am J Neuroradiol. 1993 Jan-Feb;14(1):116-8.

Tuesday, June 14, 2011

Amyloid Arthropathy

Amyloid arthropathy refers to the accumulation of amyloid in and around joints. It is most commonly seen in patients undergoing chronic hemodialysis (amyloid protein: β2-microglobulin) and in patients with plasma cell dyscrasia (amyloid protein: immunoglobulin light chain fragments), but can also be seen in patients with rheumatoid arthritis, familial Mediterranean fever, and chronic osteomyelitis (amyloid protein: serum amyloid A).

Findings are most frequently seen in the shoulders, hips, knees, and wrists and include juxtaarticular soft-tissue masses, periarticular osteopenia, subchondral cysts, joint effusions, erosions, and preserved joint spaces. Amyloid deposits are low to intermediate signal intensity on all MRI pulse sequences and do no demonstrate paramagnetic effects on gradient-echo MR images (as opposed to pigmented villonodular synovitis).

The images above are from a patient on long-term hemodialysis. A) CT of the right shoulder in soft tissue window reveals an erosion in the humeral head and a moderate joint effusion. B) CT of the right shoulder in bone window reveals another erosion in the humeral head. C) Radiograph of the left hip reveals extensive atherosclerotic calcifications. An erosion is seen along the inferior margin of the femoral neck. D) CT of the pelvis reveals bilateral joint effusions associated with soft tissue components. Erosions are seen in the right ischium and left acetabular roof. E) CT of the left hip better demonstrates the erosion seen on radiograph.

References

Sheldon PJ, Forrester DM, Learch TJ. Imaging of intraarticular masses. Radiographics. 2005 Jan-Feb;25(1):105-19.

Monday, June 13, 2011

Fat within the Urinary Bladder Wall

Intramural fat in the urinary bladder typically appears as a thin low-attenuation band along the anterior and superior portions of the urinary bladder. It is seen in about 2% of cases, and is more common in men. It can be a normal histological finding that can be seen on CT in patients with nondistended urinary bladders.

References

Thickman D. Fat within the wall of the urinary bladder: computed tomographic appearance. J Comput Assist Tomogr. 2009 Sep-Oct;33(5):695-7.

Sunday, June 12, 2011

Calcifications in the Urinary Bladder Wall

Differential considerations for urinary bladder wall calcifications include:
  • Schistosomiasis: The most frequent cause of bladder wall calcification. Intense inflammation causes fibrosis and subsequent submucosal calcification of the dead ova trapped in the lamina propria of the urinary bladder.
  • Tuberculosis: Seen in 1O%-20% of patients with late genitouninany tuberculosis. It is usually the result of a descending infection, and extensive tuberculous changes are usually present in the kidneys and ureters by the time calcifications are seen on radiographs.
  • Primary carcinoma: Less than 1% of bladder calcifications due to tumor are visible on radiographs. Calcification is most commonly present in epithelial lesions (transitional cell and squamous cell), but may also be seen in leiomyosarcoma, hemangioma, neuroblastoma, and osteosarcoma.
  • Alkaline encrusted cystitis: May see calcifications on radiographs in a small percentage of cases. The calcifications may be linear, flocculent, or nodular.
  • Cyclophosphamide (Cytoxan)-induced cystitis: Due to bladder necrosis.
  • Radiation cystitis:
  • Amyloidosis: The rarest cause of bladder wall calcification. Submucosal calcifications may be arranged in sheets or discrete nodular masses.
Cystoscopy with biopsy is almost always necessary for confirmation and to rule out bladder neoplasia.

References

Pollack HM, Banner MP, Martinez LO, Hodson CJ. Diagnostic considerations in urinary bladder wall calcification. AJR Am J Roentgenol. 1981 Apr;136(4):791-7.

Saturday, June 11, 2011

Apical Hypertrophic Cardiomyopathy

Apical hypertrophic cardiomyopathy is a subtype of hypertrophic cardiomyopathy that predominantly involves the apex of the left ventricle. It is a common form of hypertrophic cardiomyopathy in Asian countries, but relatively rare in Western populations.

While apical hypertrophic cardiomyopathy has a low rate of cardiovascular mortality, severe clinical manifestations have been reported (e.g., arrhythmias and myocardial infarction with segmental aneurysm formation).

Because the diagnostic accuracy of echocardiography for apical hypertrophic cardiomyopathy is limited without using contrast or 3-dimensional echocardiography, MRI has an important role in diagnosis.

The diagnostic criteria for apical hypertrophic cardiomyopathy:
  • Absolute apical wall thickness > 15 mm, OR
  • A ratio of apical to basal left ventricular wall thicknesses of 1.3–1.5
A characteristic spade-like shape of the left ventricular cavity can be seen at end diastole on vertical long-axis views and on ventriculography. This configuration is caused by localized apical hypertrophy.

Other findings on MRI include apical aneurysms and delayed enhancement in the hypertrophic or nonhypertrophic segments.

The vertical long-axis image above shows circumferential increased wall thickness in the apical portion of the left ventricle, measuring up to 16 mm. This results in a spade-like appearance of the left ventricular cavity. Delayed enhancement at the cardiac apex is compatible with myocardial fibrosis.

References

  • Chun EJ, Choi SI, Jin KN, Kwag HJ, Kim YJ, Choi BW, Lee W, Park JH. Hypertrophic cardiomyopathy: assessment with MR imaging and multidetector CT. Radiographics. 2010 Sep;30(5):1309-28.
  • Fattori R, Biagini E, Lorenzini M, Buttazzi K, Lovato L, Rapezzi C. Significance of magnetic resonance imaging in apical hypertrophic cardiomyopathy. Am J Cardiol. 2010 Jun 1;105(11):1592-6.

Friday, June 10, 2011

Posterior Mediastinal Mass

  • Nerve sheath tumors: Schwannoma, neurofibroma.
  • Aortic aneurysm:
  • Paraspinal Hematoma:
  • Sympathetic ganglion tumor: Neuroblastoma (younger than 3), ganglioneuroblastoma (3-10), ganglioneuroma (older than 10), paraganglioma.
  • Paraspinal Abscess:
  • Lateral meningocele: Cerebrispinal fluid attenuation/signal meningeal protrusion through a neural foramen. More common in the thoracic spine and on the right. Strong association with neurofibromatosis type 1 (bilateral). Can also be seen with Marfan syndrome.
  • Extramedullary hematopoiesis: Multiple lobulated posterior mediastinal masses associated with ribs and vertebral bodies with prominent trabeculae. No calcification. Heterogeneous enhancement.
  • Esophageal duplication cyst (shown above): Duplication cysts are defined by a well-developed smooth muscle, epithelial lining of a part of the gastrointestinal tract, and past or present attachment to a part of the gastrointestinal tract. Esophageal duplication cysts are more common on the right side and in the lower half of the chest. 30% contain gastric mucosa. They often have associated vertebral anomalies (neurenteric cyst).

Thursday, June 9, 2011

99m-Tc MAA Simulation for Yttrium-90 Microsphere Treatment of Non-resectable Liver Neoplasm

  • The patient is brought to the angiography suite.
  • Angiography is performed and arterial supply to the tumor is determined, with special attention to variant hepatic artery anatomy.
  • The arterial supply is carefully evaluated to ensure that
    • The majority of microspheres can be reliably delivered to the tumor, and
    • Small arteries leading from the main hepatic arteries to other organs can be avoided during implantion of the microspheres to prevent unintentional irradiation of these organs. Embolization of these vessels should be performed if it is felt that they cannot be reliably avoided during implantion of the microspheres.
  • Once it is determined that a safe route exists for implantation of the microspheres, the patient is injected with 4 mCi 99mTc macro-aggregated albumin (MAA) through an arterial catheter.
  • The catheter must be placed in a similar manner to that which will be used to deliver the Yttrium-90 Microspheres later.
  • The patient is brought to the nuclear medicine department.
  • The liver is imaged in anterior and posterior projections for a set number of counts or a set duration duration (700k counts or 5 minutes at our institution).
  • The lung is imaged in anterior and posterior projections for the same number of counts or duration as the anterior liver image.
  • SPECT imaging of the liver is performed if the partition method (vs. empiric method) is to be used for calculation of dose/activity of the microspheres.
  • Total counts for the lung and the liver are obtained using regions of interest
  • The shunt fraction is determined:
     ,

    where GMLung and GMLiver are the geometric means of the counts from the lung and liver, respectively. Geometric means are calculated from the anterior and posterior counts (countsant and countspost, respectively) as:
  • The shunt fraction is used along with information from SPECT images and CT to ensure that the radiation dose to the normal liver and lung parenchyma is safe.
  • The final dose for 90Yttrium can be determined using the empiric method or the partition method.
  • Empiric method
    • A standard amount of activity is prescribed based on the percentage of the liver that is replaced with tumor (based on CT).
    • A variant of the empiric method also takes into account the patient's body surface area.
      Lung shunt fraction Reduce implanted activity by
      0% – 10% No reduction required
      11% – 15% Reduce by 20%
      16% – 20% Reduce by 40%
      > 20% Do not treat
  • Partition method
    • The partition method method tries to implant the highest possible activity to the tumor while limiting radiation dose to sensitive tissues such as the lung (< 25 Gray) and the normal liver parenchyma (< 80 Gray in normal livers and < 70 Gray in cirrhotic livers).
    • Practically speaking, this method can only be used in cases of a discrete tumor mass that allows the tumor to be drawn as a region-of-interest on SPECT images. This is usually only possible for patients with primary hepatocellular carcinoma, where there is often a large single tumor mass.
    • CT is used to determine the volume of tumor and normal liver.
    • SPECT images are used to measure the proportion of 99mTc-MAA activity that lodges in the tumor, in the normal liver, and in the lung.
    • The shunt fraction is then used along with tumor volume and liver volume from the SPECT images, to calculate an optimal dose for the patient.

References

Wednesday, June 8, 2011

Coronary Artery Aneurysm

Coronary artery aneurysms (diameter 1.5 times larger than adjacent segments) are uncommon lesions, occurring in about 1.5% of cases and in 5% of patients undergoing angiography. Pseudoaneurysms are segments of dilatation that do not include all layers of the vessel wall, and can be seen following trauma (e.g., cardiac catheterization, surgery) or infection.

The right coronary artery is most commonly involved, followed by the left anterior descending coronary artery (case above) and left circumflex coronary artery.

Coronary artery aneurysms can be caused by atherosclerotic disease (most common in the United States), Kawasaki disease (most common worldwide), Takayasu aortitis, cocaine use, and genetic syndromes (Loeys-Dietz syndrome).

Diagnosis

Coronary angiography, the standard reference technique for diagnosing coronary aneurysms, is invasive and expensive. Further, by only allowing depiction of flow within the lumen it may underestimate the true size of the aneurysm.

Coronary CTA is noninvasive and allows accurate assessment and characterization of the aneurysm, providing information on size, location and the amount of thrombus and calcification.

MRI can also be used with the understanding of its inferior spatial resolution compared to that of CT and its poor detection of mural calcifications.

Complications

Coronary aneurysms may uncommonly present as an acute life-threatening process with angina, myocardial infarction, congestive heart failure, or sudden death. The acute presentation seems to be more common in patients with infectious causes and Kawasaki disease. Hemopericardium is an ominous sign of rupture or impending rupture.

Other complications include thrombosis, emboli, arteriovenous fistula, vasospasm, and rupture.

Between 20% and 40% of untreated patients with Kawasaki disease develop coronary artery abnormalities, with 50% regressing within five years. Giant aneurysms (> 8 mm) are unlikely to resolve, with some leading to stenosis with risk of coronary thrombosis, myocardial infarction, and death.

Overall, the prognosis of coronary artery aneurysms depends on the extent of underlying stenosis.

Management

Patients with Kawasaki disease and coronary artery aneurysms are treated with long term aspirin (can be discontinued if the aneurysms resolve). Depending on the size of the aneurysms, electrocardiography, and echocardiography performed 6–12 monthly is recommended.

Kawasaki patients with aneurysms > 8 mm may require stress testing and coronary angiography to identify stenotic lesions, the addition of warfarin to aspirin therapy (although good data are lacking in this regard), and limitation of strenuous activity. Patients with coronary artery stenoses may require revascularisation.

In adults initial management is with with anticoagulants and antiplatelet agents. Coronary artery bypass surgery is the primary surgical technique for failure of medical management (significant coronary stenosis or angina despite adequate medical treatment).

References

Tuesday, June 7, 2011

Soft Tissue Calcifications

The differential diagnosis for soft tissue calcifications include:
  • Heterotopic ossification: Lamellar bone forming in soft tissues (skin, subcutaneous tissues, skeletal muscle, ligaments, and tendons). Three types:
    • Myositis ossificans progressiva: Rare pediatric metabolic disease characterized by ossification of the skeletal muscle.
    • Neurogenic heterotopic ossification: Follows burns or neurologic injury.
    • Traumatic heterotopic ossification: Follows injury to tissue surrounding bones and joints.
  • Ectopic calcification: Mineral deposition (not bone formation, as seen in heterotopic ossification) in soft tissues due to trauma.
  • Metastatic calcification:
    • Secondary hyperparathyroidism: Calcinosis of chronic renal failure. Soft tissue calcifications usually involve the extremities. Look for other skeletal findings of secondary hyperparathyroidism: Osteopenia, cortical thinning, subperiosteal bone resorption, resorption of secondary trabeculae and accentuation of primary trabeculae.
    • Hypervitaminosis D: Large, calcified, periarticular masses with associated ligamentous & intervertebral disc calcifications.
  • Collagen vascular disease:
    • Dermatomyositis: Shown above. Look for muscle, fascial or subcutaneous calcifications.
    • Scleroderma: Soft-tissue calcifications may be diffuse or focal, with an amorphous or linear, sheetlike appearance
  • Tumors/masses: Lipoma, synovial cell sarcoma, infantile myofibromatosis, venous malformations, metastatic osteosarcoma.
  • Calcium pyrophosphate dihydrate crystal deposition disease:
  • Infection: Parasitic infestation, cysticercosis, dracunculiasis.
  • Tumoral calcinosis: Hereditary disease of phosphate metabolic dysfunction that leads to the formation of characteristic lobulated, well-demarcated soft tissue calcifications distributed most commonly around the extensor surface of large joints.

References

  • Olsen KM, Chew FS. Tumoral calcinosis: pearls, polemics, and alternative possibilities. Radiographics. 2006 May-Jun;26(3):871-85.
  • Seipel R, Langner S, Platz T, Lippa M, Kuehn JP, Hosten N. Neurogenic heterotopic ossification: epidemiology and morphology on conventional radiographs in an early neurological rehabilitation population. Skeletal Radiol. 2011 Feb 18.

Monday, June 6, 2011

Carpal Boss

The carpal boss (carpe bossu) is a bony protuberance at the carpometacarpal joints of the index and middle fingers. It is most commonly caused by an osteophyte at the base of the metacarpal bones originating from the carpometacarpal joint, or less commonly, by a supernumerary bone (e.g, an os styloideum), as seen in the image above. A carpal boss may be accompanied by a small ganglion cyst.

References

Conway WF, Destouet JM, Gilula LA, Bellinghausen HW, Weeks PM. The carpal boss: an overview of radiographic evaluation. Radiology. 1985 Jul;156(1):29-31.

Sunday, June 5, 2011

Testicular Microlithiasis

Testicular microlithiasis is an infrequent incidental finding on scrotal ultrasound. An association between testicular microlithiasis and germ cell tumors and testicular carcinoma in situ has been reported. Testicular microlithiasis has also been suggested as a feature of the testicular dysgenesis syndrome, which is thought to be related to subfertility, testicular atrophy, cryptorchidism, germ cell tumors, and other abnormalities of sexual development.

Management of patients with testicular microlithiasis has varied across institutions. A recent review in Nature Reviews: Urology makes the following suggestions:
  • Initial evaluation of all patients with testicular microlithiasis: Search for personal and family history of testicular dysgenesis syndrome (e.g., symptoms of subfertility, cryptorchidism, testicular atrophy and germ cell tumors). Obtain a baseline chest radiograph and abdominal ultrasound.
  • Asymptomatic and healthy patients 13 to 39 years of age and no features of testicular dysgenesis syndrome: Initial evaluation as above. Monitor with testicular self-examination.
  • One or more features of testicular dysgenesis syndrome: Initial evaluation as above plus serum tumor markers. Testicular biopsy for testicular carcinoma in situ may be considered. Annual follow-up with scrotal ultrasound and serum tumor markers.

References

Tan MH, Eng C. Testicular microlithiasis: recent advances in understanding and management. Nat Rev Urol. 2011 Mar;8(3):153-63.

Saturday, June 4, 2011

Management of Incidentally Detected Gallbladder Polyps

Gallbladder polyps are seen in about 5% of patients who undergo abdominal ultrasound. The majority of gallbladder polyps are nonneoplastic (cholesterol or inflammatory polyps), and about 30% actually represent small stones misdiagnosed as polyps. The main concern is the rare gallbladder carcinoma, which has a poor prognosis (5-year survival rate of approximately 10%).

The risk of malignancy increases for polyps larger than 10 mm, sessile polyps, single polyps, and polyps with adjacent wall thickening or invasion, and with increasing patient age.

The most recent data suggest that incidentally detected gallbladder polyps ≤ 6 mm may require no additional follow-up. While the data are inconclusive in regards to management of polyps > 7 mm in diameter, cholecystectomy seems to be warranted for lesions > 10 mm.

References

  • Corwin MT, Siewert B, Sheiman RG, Kane RA. Incidentally detected gallbladder polyps: is follow-up necessary?--Long-term clinical and US analysis of 346 patients. Radiology. 2011 Jan;258(1):277-82.
  • Ito H, Hann LE, D'Angelica M, Allen P, Fong Y, Dematteo RP, Klimstra DS, Blumgart LH, Jarnagin WR. Polypoid lesions of the gallbladder: diagnosis and followup. J Am Coll Surg. 2009 Apr;208(4):570-5.

Friday, June 3, 2011

Churg-Strauss Syndrome

Churg-Strauss syndrome is a systemic vasculitis involving multiple organs. It is seen almost exclusively in patients with asthma, with a mean age of onset of ~40 years. Almost all patients have eosinophilia and up to 75% may have positive ANCA. Eosinophil infiltration into the endocardium induces endocardial thickening, thrombus formation, and myocardial dysfunction, which can be seen in up to 50% of patients. Peripheral neuropathy can also be seen.

The most common findings on radiographs are transient, patchy, nonsegmental opacities without a zonal predilection. Small noncavitary nodules or diffuse reticular opacities may also bee seen.

CT may reveal small (< 10 mm) centrilobular nodules (60% of cases), ground-glass opacities (50%), bronchial wall thickening (50%), bronchial dilatation (50%), consolidation (40%), interlobular septal thickening (40%), mosaic perfusion (50%), and unilateral or bilateral pleural effusion (50%).

Differential considerations include:
  • Simple pulmonary eosinophilia: Löffler syndrome.
  • Chronic eosinophilic pneumonia:
  • Subacute hypersensitivity pneumonitis: May also have small centrilobular nodules or nodular ground-glass opacity.
  • Metastatic calcification: May also have small centrilobular nodules or nodular ground-glass opacity.
  • Microscopic polyangiitis: May also have small centrilobular nodules or nodular ground-glass opacity.
  • Systemic lupus erythematosis: May also have small centrilobular nodules or nodular ground-glass opacity.
  • Respiratory bronchiolitis-interstitial lung disease: May also have small centrilobular nodules or nodular ground-glass opacity.

References

Chung MP, Yi CA, Lee HY, Han J, Lee KS. Imaging of pulmonary vasculitis. Radiology. 2010 May;255(2):322-41.

Thursday, June 2, 2011

Drainage of the Accessory Hemiazygos Vein into the Left Brachiocephalic Vein

The accessory or superior hemiazigos vein (AHAzV) normally courses to the left of the thoracic spine and crosses to the right at the T7-T8 level to join the azygos vein. In ~75% of cases, there is a small connection between the accessory hemiazygos vein and the left superior intercostal vein (SICV), which normally drains into brachiocephalic vein (BCV). In about 2% of cases, this connection is large enough to allow the accessory hemiazygos vein to drain into the brachiocephalic vein. This is shown in the images above. This variant anatomy may become clinically significant as a collateral pathway in cases of venous obstruction.

This patient also has an azygos lobe and an aberrant right subclavian artery (ARSCA).

SVC, superior vena cava; Ao, aorta.

Radiology

Galwa RP, Prakash M, Khandelwal N. 16-MDCT depiction of accessory hemiazygos vein draining into the left brachiocephalic vein. Indian J Radiol Imaging 2007;17:50-1.

Wednesday, June 1, 2011

Froupie (4/1998 - 6/1/2011)

The image above shows an enhancing mass of an undifferentiated sarcoma with central necrosis overlying the right shoulder of the best cat in the world. There is involvement of the supraspinatus muscle.

Ovarian Vein Thrombosis

Ovarian vein thrombosis is being diagnosed more frequently due to increased imaging. It can be seen in postpartum women and in women with pelvic inflammatory disease, or a history of pelvic surgery. Bland or tumor thrombosis can be seen in patients with cancer.

Patients may be asymptomatic or present with vague abdominal pain. Pulmonary embolism, sepsis, or even death are dreaded and rare complications.

CT will classically show a "filling defect in a tubular structure anterior to the psoas muscle with a central round low-attenuation center and peripheral higher-attenuation rim."

Postpartum patients and women with pelvic inflammatory disease are treated with intravenous heparin and antibiotics. Patients with a history of pelvic surgery or malignancy are not generally treated unless complicated by thrombophbebitis or pulmonary embolism.

References

  • Karaosmanoglu D, Karcaaltincaba M, Karcaaltincaba D, Akata D, Ozmen M. MDCT of the ovarian vein: normal anatomy and pathology. AJR Am J Roentgenol. 2009 Jan;192(1):295-9.
  • Yassa NA, Ryst E. Ovarian vein thrombosis: a common incidental finding in patients who have undergone total abdominal hysterectomy and bilateral salpingo-oophorectomy with retroperitoneal lymph node dissection. AJR Am J Roentgenol. 1999 Jan;172(1):45-7.