Monday, November 30, 2009

Peak Filling and Ejection Rates

Peak filling rate (PFR) is measured during diastole in a MuGA (Multiple Gated Acquisition) study. The raw PFR is determined from the curve of left ventricular volume as a function of time. The peak slope of this curve during diastole gives the raw PFR in ml/sec. The normalized peak filling rate is the raw PFR divided by end-diastolic volume. The time to PFR is the time between end-diastole to the point at which PFR is achieved. The peak ejection rate (PER) is also derived from the volume curve of the left ventricle. It is the peak slope during systole.

The PFR is related to the compliance of the ventricles and the pressure gradient between the atrium and ventricle. Peak filling rates normally decline with age. A normal PFR is greater than or equal to 2.5 end-diastolic volumes per second. The time to PFR should be less than 180 msec. I can't find normal values for PER and time to PER.

The PFR is decreased in
  • Coronary artery disease
  • Congestive heart failure: About 40% of patients with CHF have preserved systolic function, but impaired diastolic function.
  • Cardiomyopathies
  • Aortic valve disease
  • Rejection following cardiac transplant
  • Hypertension: Isolated decreased PFR may be an early indicator of hypertensive heart failure.
  • Medications: Nitroglycerin, beta blockers, doxorubicin
The PFR may be elevated in the following conditions:
  • Constrictive pericarditis (not always)
  • Mitral regurgitation
  • Medications: Calcium channel blockers
Having said all that, apparently no one uses these parameters for diagnostic purposes.

References

  • Mettler FA and Guiberteau MJ. Chapter 6: Cardiovascular System. In Essentials of Nuclear Medicine Imaging. Fifth Edition. Saunders, Philadelphia. 2006.
  • Williams S. Equilibrium MUGA. Aunt Minnie. 2002.

Sunday, November 29, 2009

Deep Lateral Femoral Notch Sign

The deep lateral femoral notch sign suggests an impacted osteochondral fracture of the lateral femoral condyle, and may be seen with an anterior cruciate ligament tear. On the lateral radiograph of the knee, there is an abnormally deep depression of the lateral femoral notch (condylopatellar sulcus).

Here we see a radiograph (top image) with a deep lateral femoral notch (gray arrow) and an effusion (pink arrow). The bottom image is a fluid-sensitive MR sequence showing an osteochondral defect along the lateral femoral condyle (gray arrow) and abnormal signal in the posterolateral tibial plateau ("kissing contusions"). This pediatric patient did not have an anterior cruciate ligament tear.

A lateral femoral notch deeper than 1.5-2.0 mm in depth (depending on the study) is thought to be a highly suggestive, but inconsistent, indirect sign of an anterior cruciate ligament injury.

References

Pao DG. The lateral femoral notch sign. Radiology. 2001 Jun;219(3):800-1.

Saturday, November 28, 2009

Extensor Digitorum Brevis Avulsion

The extensor digitorum brevis is the only muscle that originates on the dorsum of the foot. Its tendons insert into the proximal phalanges of the 2nd through 5th toes and aid in extension.

The mechanism of injury is forced inversion of the foot, rapidly stretching the extensor digitorum brevis. The patient whose frontal ankle radiograph is shown here presented after an inversion injury.

On radiography, there is a characteristic appearance of a fracture fragment along the dorsolateral aspect of the calcaneus on frontal views of the ankle (top image) and foot (bottom image).

References

Norfray JF, Rogers LF, Adamo GP, Groves HC, Heiser WJ. Common calcaneal avulsion fracture. AJR Am J Roentgenol. 1980 Jan;134(1):119-23.

Friday, November 27, 2009

Pitfalls in DXA

DXA may be falsely elevated due to the following factors:
  • Aortic calcifications
  • Scoliosis
  • Osteoarthritic changes
  • Compression fractures
  • Enteric contrast
  • Renal stones
  • Bone grafts
DXA may be falsely decreased due to the following factors:
  • Laminectomy
  • Lytic lesions

References

Mettler FA and Guiberteau MJ. Chapter 9: Skeletal System. In Essentials of Nuclear Medicine Imaging. Fifth Edition. Saunders, Philadelphia. 2006

Thursday, November 26, 2009

Time to Visualization of Fractures on Bone Scan

Virtually all fractures (except skull fractures) will show increased activity on bone scan by 2 weeks. Occult hip fractures in elderly patients take about 3 days to show up on bone scans, so MRI is likely a better choice in these cases. Stress fractures are often apparent on bone scans by the time of clinical presentation.

The age of the patient does not seem to have a significant impact on the time to bone scan visualization of fractures.

90% of fractures of weight bearing bones return to normal activity on bone scan in 2 years. It may take longer for bone scan activity to return to normal in elderly patients.

References

Mettler FA and Guiberteau MJ. Chapter 9: Skeletal System. In Essentials of Nuclear Medicine Imaging. Fifth Edition. Saunders, Philadelphia. 2006

Wednesday, November 25, 2009

Differential Diagnosis of a "Super Scan" Appearance on Bone Scan

Super scan (superscan) refers to the diffuse skeletal uptake of MDP with resultant low or absent activity in the kidneys and bladder and high ratio of bone to soft tissue activity. Focal lesions in the skeleton may be obscured in some cases.

Differential considerations include:
  • Metabolic disease: Renal osteodystrophy, osteomalacia, myelofibrosis. Often has a diffuse and homogeneous appearance on bone scan.
  • Metastatic disease: Typically prostate, lung, and breast. May see some focal areas of increased uptake on bone scan.
This is a posterior view from a 99mTc-MDP scan of a patient with colorectal cancer. There is diffusely increased radiotracer uptake in the thoracolumbar spine and poor visualization of the kidneys, consistent with a super scan.

More recently a super-superscan has been described, representing superimposed metastatic and metabolic superscan. This appearance may obscure recognition of osseous metastases.

References

  • Liu Y. Super-superscan on a bone scintigraphy. Clin Nucl Med. 2011 Mar;36(3):227-8.
  • Mettler FA and Guiberteau MJ. Chapter 9: Skeletal System. In Essentials of Nuclear Medicine Imaging. Fifth Edition. Saunders, Philadelphia. 2006

Tuesday, November 24, 2009

Lymphoscintigraphy for Lymphedema

74-296 MBq of 99mTc with filtered (smaller than 22 microns) sulfur colloid particles suspended in 0.10 mL of saline is injected into the dorsum of the hand or foot or between the digits. The area is massaged for 2 minutes. Dynamic and delayed images (up to 4 hours) are obtained.

Lymphedema can be classified as primary and secondary. Primary lymphedema usually affects younger patients without a history of trauma or radiation and may be unilateral or bilateral. Secondary lymphedema in the developed world is often the result of trauma (iatrogenic or otherwise) or radiation therapy. In developing countries, infectious causes (e.g., filariasis) are common.

Contrary to what is found in Mettler and Guiberteau's book (5th ed), it is now thought that primary and secondary lymphedema cannot be reliably differentiated from each other based on lymphoscintigraphy alone.

Abnormal findings on lymphoscintigraphy include:
  • Decreased numbers of non-obstructed lymphatic channels
  • Lack of migration of radiotracer from the injection site
  • Slow transport from injection site
  • Decreased numbers of visualized lymph nodes
  • Diffuse dermal activity
  • Multiple tortuous collateral channels
Clinical mimickers of lymphedema include
  • Obesity
  • Venous disease
  • Systemic disease (e.g., hypoproteinemia)

References

Moshiri M, Katz DS, Boris M, Yung E. Using lymphoscintigraphy to evaluate suspected lymphedema of the extremities. AJR Am J Roentgenol. 2002 Feb;178(2):405-12.

Monday, November 23, 2009

Ulnocarpal Ligaments

The ulnocarpal ligaments are extrinsic ligaments that connect the ulna to the carpal bones. They can be divided into palmar and dorsal. The ulnocarpal ligaments seen on MRI all arise from the palmar and dorsal radioulnar ligaments.

Palmar
  • Palmar ulnotriquetral ligament: The palmar ulnotriquetral ligament originates from the palmar radioulnar ligament and extends distally to attach to the palmar aspect of the triquetrum. Course best seen in the sagittal plane. Cross section best seen in the transverse plane.

  • Ulnolunate ligament: The ulnolunate ligament originates on the radial side of the palmar radioulnar ligament, with attachments to both the ulna and radius. It extends distally to attach onto the palmar aspect of the lunate. The fibers of the radiolunotriquetral ligament make a stop on the lunate at the same insertion site. Course best seen in the sagittal plane. Cross section best seen in the transverse plane.

  • Ulnocapitate ligament: The ulnocapitate ligament is not seen on MR images, so we'll pretend it doesn't exist.
Dorsal
  • Dorsal ulnotriquetral: The dorsal ulnotriquetral ligament originates from the dorsal radioulnar ligament and travels distally to attach onto the dorsal aspect of the triquetrum together with the fibers of the dorsal radiotriquetral ligament. Course best seen in the sagittal plane. Cross section best seen in the transverse plane.

References

Theumann NH, Pfirrmann CW, Antonio GE, Chung CB, Gilula LA, Trudell DJ, Resnick D. Extrinsic carpal ligaments: normal MR arthrographic appearance in cadavers. Radiology. 2003 Jan;226(1):171-9.

Sunday, November 22, 2009

Radiocarpal Ligaments

The radiocarpal ligaments are extrinsic ligaments that connect the radius to the carpal bones. They can be divided into palmar, dorsal, and lateral.

Palmar
  • Radioscaphocapitate ligament (RSC): The RSC ligament originates from the palmar and radial aspects of the radial styloid process in association with the radiolunotriquetral (RLT) fibers (see below). It runs obliquely across the carpus, passing through a groove in the waist of the scaphoid, stopping to attach to the palmar aspect of the distal pole of the scaphoid, before terminating on the center of the palmar aspect of the capitate. Course best seen in the sagittal plane. Cross section best seen in the transverse plane.

  • Radiolunotriquetral (long radiolunate) ligament (RLT): The RLT fibers originate with and to the ulnar side of the fibers of the RSC on the palmar aspect of the radial styloid process. Its fibers pass through the aforementioned groove of the scaphoid waist, proximal to the RSC fibers, stopping to insert on the palmar aspect of the lunate before heading out to attach along the radial side of the pisotriquetral joint. Course best seen in the transverse plane. Cross section best seen in the sagittal plane.

  • Short radiolunate ligament: The short radiolunate ligament gets short-changed because it is not well-seen on MRI.

  • Radioscapholunate ligament: The radioscapholunate "ligament" is most likely a mesocapsule for neurovascular branches from the distal radial arterial arch. It originates from the palmar aspect of the distal radius and inserts along the proximal palmar aspect of the scapholunate ligament. On MRI, it doesn't appear hypointense on T1-weighted images.

Dorsal
  • Dorsal radiotriquetral ligament (dRT): The radiotriquetral ligament, also known as the dorsal radiocarpal, ligament originates on the dorsal aspect of the distal radius, crosses over the lunate, before attaching to the dorsal aspect of the triquetrum.Course best seen in the transverse plane. Cross section best seen in the sagittal plane.

  • Dorsal radiolunate ligament (dRL): The dorsal radiolunate ligament forms from the fibers of the dorsal radioulnar (dRU) ligament that insert onto the dorsal aspect of the lunate.
Lateral
  • Radial collateral ligament (RC): The radial collateral ligament originates on the tip of the radial styloid process lateral to the origin of the RSC and RLT fibers and inserts onto the radial aspect of the scaphoid waist before blending with the capsule to insert into the trapezium. Course best seen in the coronal plane. Cross section best seen in the transverse plane.

References

Theumann NH, Pfirrmann CW, Antonio GE, Chung CB, Gilula LA, Trudell DJ, Resnick D. Extrinsic carpal ligaments: normal MR arthrographic appearance in cadavers. Radiology. 2003 Jan;226(1):171-9.

Saturday, November 21, 2009

Baastrup Disease

Baastrup disease is caused by excessive hordosis or extensive disk-space loss that leads to close approximation and contact of adjacent spinous processes with resultant enlargement, flattening, and reactive sclerosis of the spinous processes.

References

Resnick D. Degenerative diseases of the vertebral column. Radiology. 1985 Jul;156(1):3-14.

Friday, November 20, 2009

Glenoid Shape and Recurrent (Atraumatic) Posterior Shoulder Instability

Atraumatic posterior instability refers to posterior subluxation of the humerus due to to laxity of supporting structures and/or the shape of the bony glenoid and labrum. In contrast to traumatic posterior subluxation, a reverse Hill-Sachs lesion is not common in patients with recurrent posterior instability.

Weishaupt et al (2000), described three shapes of the posteroinferior glenoid on CT in an attempt to diagnose recurrent posterior instability:
  • Normal: No posterior bony deficiency is present.
  • Lazy J: Rounding of the posteroinferior glenoid rim. Glenoid deficiency.
  • Delta: Triangular deficiency of the posterior glenoid. Glenoid deficiency.
A deficient posteroinferior glenoid rim, however, was not significantly more common in unstable shoulders compared to normal shoulders. They did find that the craniocaudad length of the posterior glenoid deficiency could differentiate patients with recurrent posterior instability from those with stable shoulders.

The average craniocaudad length of the posterior glenoid deficiency in patients with recurrent posterior instability was 14.3 mm (±9.9 mm), while in patients with stable shoulders, the average length was 5.0 mm (±4.6 mm). The authors suggest a value of 12 mm as a cut-off for a sensitivity and specificity for diagnosing recurrent posterior instability of 87% and 83%, respectively.

It must be noted, however, that the CT findings could not be extended to MRI due to poor differentiation of the labrum from adjacent cortical bone

References

  • Mulligan ME, Pontius CS. Posterior-inferior glenoid rim shapes by MR imaging. Surg Radiol Anat. 2005 Nov;27(4):336-9.
  • Weishaupt D, Zanetti M, Nyffeler RW, Gerber C, Hodler J. Posterior glenoid rim deficiency in recurrent (atraumatic) posterior shoulder instability. Skeletal Radiol. 2000 Apr;29(4):204-10.

Thursday, November 19, 2009

Subcoracoid Bursa

The subcoracoid bursa is located anterior to the subscapularis muscle and deep and inferior to the coracoid process and does not communicate with the glenohumeral joint. The subcoracoid bursa does communicate with the subacromial bursa in about 10% of cases, although rates as high as 55% have been reported.

The subcoracoid bursa can be differentiated from the adjacent superior subscapularis recess based on the saddlebag appearance of the latter over the subscapularis muscle. In addition, the superior subscapularis recess communicates with the glenohumeral joint (best seen on oblique sagittal MR images).

Effusions of the subcoracoid bursa are associated with tears of the anterior rotator cuff and tears of the rotator interval.

References

Grainger AJ, Tirman PF, Elliott JM, Kingzett-Taylor A, Steinbach LS, Genant HK. MR anatomy of the subcoracoid bursa and the association of subcoracoid effusion with tears of the anterior rotator cuff and the rotator interval. AJR Am J Roentgenol. 2000 May;174(5):1377-80.

Wednesday, November 18, 2009

Panda Signs and Wilson Disease

The "face of the giant panda" sign refers to the characteristic appearance of Wilson disease on T2-weighted MRI of the midbrain:
  • High signal intensity in the tegmentum sparing the red nucleus. The relatively hypointense red nucleus makes up the eyes.
  • Preservation of signal intensity of the lateral portion of the pars reticulata of the substantia nigra makes up the ears.
  • Low signal intensity of the superior colliculus makes up the chin.
Panels B and C of this figure give a good demonstration.

Some people also see the "face of the miniature panda" or "face of the panda cub" more inferiorly in the pontine tegmentum. To me this looks more like a mustachioed man wearing a turban, but people like consistency.
  • The relative hypointensity of the medial longitudinal fasciculi and central tegmental tracts give the eyes of the panda.
  • The hyperintensity of the aqueduct opening into the fourth ventricle results in the nose and mouth of the panda
  • The normal superior cerebellar peduncles form the panda's cheeks.
An image of the baby panda can be found here.

References

  • Hitoshi S, Iwata M, Yoshikawa K. Mid-brain pathology of Wilson's disease: MRI analysis of three cases. J Neurol Neurosurg Psychiatry. 1991 Jul;54(7):624-6.
  • Jacobs DA, Markowitz CE, Liebeskind DS, Galetta SL. The "double panda sign" in Wilson's disease. Neurology. 2003 Oct 14;61(7):969.
  • Shivakumar R, Thomas SV. Teaching NeuroImages: face of the giant panda and her cub: MRI correlates of Wilson disease. Neurology. 2009 Mar 17;72(11):e50.

Tuesday, November 17, 2009

Left Ventricular Hypertrophy in Myocardial Perfusion Imaging

The presence of left ventricular hypertrophy (LVH) causes a decrease in the normal lateral-to-septal ratio. In other words, the normal finding of increased counts in the lateral wall compared to the septum (due to distance from the camera) is decreased, lost, or even reversed. Failure to take this into consideration may lead to false positive finding of a fixed defect in the lateral wall.

On a broader level, there is concern that the increased prevalence of LVH due to increased prevalence of obesity and diabetes may lead to a decrease in SPECT specificity.

References

Jaber WA, DiFilippo FP, Cerqueira MD. Left ventricular hypertrophy and SPECT myocardial perfusion imaging: finding the diamonds in the rough. J Nucl Cardiol. 2007 May-Jun;14(3):398-407.

Monday, November 16, 2009

Patellar Tendon–Lateral Femoral Condyle Friction Syndrome

Patellar tendon–lateral femoral condyle friction syndrome, also known as supero-lateral fat-pad impingement syndrome, is a common cause of chronic anterolateral knee pain. Patients present with knee pain exacerbated by hyperextension and focal tenderness at the lateral side of the inferior pole of the patella. Conservative treatment consisting of taping of the superior pole of the patella is often used.

MRI shows edema in the inferolateral aspect of the patellofemoral joint in the majority of patients. Cystic changes may also be seen adjacent to the lateral femoral condyle. In a minority of patients, these cystic changes may be all that is seen. Some patients will also demonstrate patella alta or lateral subluxation of the extensor mechanism.

References

Chung CB, Skaf A, Roger B, Campos J, Stump X, Resnick D. Patellar tendon-lateral femoral condyle friction syndrome: MR imaging in 42 patients. Skeletal Radiol. 2001 Dec;30(12):694-7.

Sunday, November 15, 2009

Seminal Vesicle Cysts

Seminal vesicle cysts can occur in a number of conditions. Bilateral seminal vesicle cysts (seen in this image) occur in about 50% of patients with autosomal dominant polycystic kidney disease. Congenital seminal vesicle cysts are associated with ipsilateral renal agenesis or dysgenesis in 2/3 of cases. Other associations include agenesis of the vas deferens or ectopic ureteral insertion into the seminal vesicle, ejaculatory duct, vas deferens or prostatic urethra.

Seminal vesicle cysts can also be mimicked by various conditions, including obstruction of the seminal vesicles, ejaculatory duct, or vas deferens. Other conditions that can mimic seminal vesicle cysts include a dilated ectopic ureter, ureterocele, Müllerian duct cyst, prostatic utricular cyst, and ejaculatory duct cyst.

References

Kim B, Kawashima A, Ryu JA, Takahashi N, Hartman RP, King BF Jr. Imaging of the seminal vesicle and vas deferens. Radiographics. 2009 Jul-Aug;29(4):1105-21.

Saturday, November 14, 2009

Grading Medial Collateral Ligament Injuries

The clinical grades of medial collateral ligament (MCL) injury correspond to MR appearance.
Grade 1: Sprain. High signal in soft tissues medial to the MCL.
Grade 2: Severe sprain or partial tear. High signal in soft tissues medial to the MCL and partial disruption of the fibers.
Grade 3: Complete tear.

Friday, November 13, 2009

MRI Appearance of Enchondroma

Enchondromas may be incidentally seen on MRI. They are lobulated with multiple thin septa, low to intermediate signal intensity on T1-weighted images, and hyperintense on T2-weighted images. Calcifications may be seen as signal voids on all sequences. Contrast enhancement in rings and arcs is seen.

The main differential consideration is a low-grade chondrosarcoma, which may have similar findings. Patients with chondrosarcoma will often have pain, but so will a number of patients with enchondroma. Findings that help differentiate the two are:
  • Deep endosteal scalloping: Chondrosarcomas tend to demonstrate endosteal scalloping greater than two-thirds of cortical thickness
  • Extensive endosteal scalloping: The longer the extent of endosteal scalloping relative to lesion length, the more likely is it for the lesion to represent chondrosarcoma.
  • Cortical destruction
  • Soft-tissue mass
  • Periosteal reaction
  • Marked uptake of radionuclide: Chondrosarcomas tend to demonstrate uptake greater than the anterior iliac crest on bone scan.

References

Murphey MD, Flemming DJ, Boyea SR, Bojescul JA, Sweet DE, Temple HT. Enchondroma versus chondrosarcoma in the appendicular skeleton: differentiating features. Radiographics. 1998 Sep-Oct;18(5):1213-37;

Thursday, November 12, 2009

The Patellar Facets

The patella is divided into 7 facets. On the medial and lateral sides, there are superior, middle, and inferior facets. The "odd" facet is medial to the medial facet and does not articulate with the femur until flexion exceeds 90 degrees. On deep flexion the patella rotates and the odd facet articulates with the medial femoral condyle. The odd facet is frequently the first part of the patella to be affected in premature degeneration of articular cartilage.

References

Goodfellow J, Hungerford DS, Zindel M. Patello-femoral joint mechanics and pathology. 1. Functional anatomy of the patello-femoral joint. J Bone Joint Surg Br. 1976 Aug;58(3):287-90.

Wednesday, November 11, 2009

Osteoid Osteoma: MRI Appearance

On T1-weighted images (first panel from left), the nidus of osteoid osteoma is isointense to muscle. The radiolucent areas of the nidus are iso- to hyperintense on T2-weighted images (middle panel). Dynamic imaging reveals peak enhancement during the arterial phase (third panel from left) with early partial washout of the nidus. There is slower, progressive enhancement of adjacent bone marrow. Extensive bone marrow edema may be seen.

References

Bredella MA. StatDx.

Tuesday, November 10, 2009

Pneumatosis Cystoides Intestinalis

Pneumatosis cystoides intestinalis, also known as cystic pneumatosis coli, is the primary form of pneumatosis intestinalis, and accounts for 15% of the cases of pneumatosis intestinalis. It is a benign, idiopathic condition characterized by multiple thin-walled submucosal or subserosal gas-filled cysts mostly on the mesenteric border. The cysts contain mainly hydrogen and occur mostly in the descending and sigmoid colon.

Pneumatosis cystoides intestinalis is usually an incidental finding; however, the cysts may protrude into the lumen and mimic polyps or carcinomas on barium enema.

References

  • Florin TH. Alkyl halides, super hydrogen production and the pathogenesis of pneumatosis cystoides coli. Gut. 1997 Dec;41(6):778-84.
  • Pickhardt PJ, Kim DH, Taylor AJ. Asymptomatic pneumatosis at CT colonography: a benign self-limited imaging finding distinct from perforation. AJR Am J Roentgenol. 2008 Feb;190(2):W112-7.

Monday, November 9, 2009

Differentiating Benign and Clinically Worrisome Pneumatosis Intestinalis in Children

Pneumatosis intestinalis can have a benign or complicated course in children beyond the neonatal period. Benign cases are self-limited and can be managed conservatively. Benign causes of pneumatosis intestinalis include
  • Asthma
  • Bronchitis
  • Scleroderma
  • Systemic lupus erythematosus
  • AIDS
  • Postsurgical anastomosis
  • Endoscopy
  • Corticosteroids
  • Organ transplantation
CT can be used to suggest whether pneumatosis intestinalis reflects a benign or clinically worrisome cause.

CT Finding Benign Worrisome
Extensive involvement +  
Bowel wall thickening   +
Peri-bowel stranding   +
Free Fluid   +


The following CT findings are not helpful in differentiating benign and clinically worrisome cases of pneumatosis intestinalis in children:
  • Morphology of gas (cystic vs linear)
  • Distribution (small bowel, large bowel, or both)
  • Free peritoneal gas
  • Bowel dilatation
  • Small bowel obstruction
  • Portal venous gas

References

Olson DE, Kim YW, Ying J, Donnelly LF. CT predictors for differentiating benign and clinically worrisome pneumatosis intestinalis in children beyond the neonatal period. Radiology. 2009 Nov;253(2):513-9.

Sunday, November 8, 2009

Myocardial Fatty Infiltration

Differential diagnosis for fatty infiltration of the myocardium:
  • Prior ischemic damage: Usually thin and curvilinear subendocardial lesions.
  • Normal heart: Right ventricular fat increases with age.
  • Tuberous sclerosis complex (TSC): There is a high prevalence of well-circumscribed, mainly ovoid, myocardial fatty foci is TSC. The majority of fatty foci are in the interventricular septum and the left ventricular wall.
  • Arrhythmogenic right ventricular dysplasia: Usually diffuse fat infiltration of the right ventricle.
  • Primary cardiac hemangioma: May contain fat. Isointense to myocardium on T1-weighted images, hyperintense on T2-weighted images, and intense early enhancement that can be heterogeneous. There is filling on delayed phases of enhancement.
  • Intramyocardial lipoma: Small lesions with irregular contour and capsule.
  • Liposarcoma: Typically demonstrate mass effect and invasion.

References

  • Adriaensen ME, Schaefer-Prokop CM, Duyndam DA, Zonnenberg BA, Prokop M. Fatty foci in the myocardium in patients with tuberous sclerosis complex: common finding at CT. Radiology. 2009 Nov;253(2):359-63.
  • .Diagnostic features of cardiac hemangioma on cardiovascular magnetic resonance, a case report. Int J Cardiovasc Imaging. 2006 Oct;22(5):699-702.
  • Pigato JB, Subramanian VA, McCaba JC. Cardiac hemangioma. A case report and discussion. Tex Heart Inst J. 1998; 25(1): 83–85.

Saturday, November 7, 2009

Epinephrine Dose for Contrast Reactions

  • Intramuscular: This is the first-line treatment. Use 1:1,000 concentrated epinephrine injected in the lateral aspect of the thigh. Dose is 0.01 mg/kg body weight up to a total of 0.5 mg. Usual doses: 0.1–0.5 mg of 1:1,000 concentrated epinephrine.
  • Intravenous: Must be dilute, given slowly, and titrated for effect in a monitored patient. Fatal adverse reactions, though rare, can occur. Intravenous route may have to be used for a life-threatening reaction unresponsive to intramuscular injection. Usual doses: 5 mcg to 0.5 mg of 1:10,000 concentrated epinephrine.
  • Subcutaneous: Not as effective. May be no better than placebo. The 1:1,000 concentrated epinephrine is used. Usual doses: 0.1–0.5 mg of 1:1,000 concentrated epinephrine.

References

Lightfoot CB, Abraham RJ, Mammen T, Abdolell M, Kapur S, Abraham RJ. Survey of radiologists' knowledge regarding the management of severe contrast material-induced allergic reactions. Radiology. 2009 Jun;251(3):691-6.

Friday, November 6, 2009

Mayfield Perilunate Instability Pattern

Mayfield et al described the pattern of perilunate injury when extension, ulnar deviation, and intercarpal supination stress was applied to the wrist. They divided the injuries into 4 stages based on the magnitude and duration of loading.
  • Stage I: There is rotatory subluxation of the scaphoid caused by acute dorsiflexion of wrist with resultant injury to the scapholunate ligament. Look for signs of scapholunate dissociation. Also, look for associated distal radial fractures.
  • Stage II: Perilunate dislocation. Look for a triangular lunate on the frontal view. On the lateral view, there is slight anterior rotation of lunate and posterior subluxation of other carpal bones with respect to the lunate. Look for associated scaphoid waist and ulnar styloid fractures.
  • Stage III: Midcarpal dislocation is the result of ligamentous injury to the lunotriquetral ligament. There is a triangular appearance to the lunate on the frontal view (similar to the lunate dislocation). The lateral view shows dorsal dislocation of the capitate and volar tilt and subluxation of the lunate (i.e., neither the lunate or capitate is aligned with the radius).
  • Stage IV: Lunate dislocation from the radiolunate fossa. There is volar dislocation and anterior rotation of the lunate, which gives a triangular appearance to the lunate on the frontal view. On the lateral view, the capitate remains aligned with the radius, but the lunate is dislocated volarly from the radiolunate fossa.

References

Mayfield JK, Johnson RP, Kilcoyne RK. Carpal dislocations: pathomechanics and progressive perilunar instability. J Hand Surg Am. 1980 May;5(3):226-41.

Thursday, November 5, 2009

Triquetral Fracture

Triquetral fractures are the second most common carpal fractures (after scaphoid fractures). Unlike the scaphoid, the triquetrum has a rich vascular supply.

Triquetral fractures can be classified based on the location of the fracture and severity of associated injuries.
  • Type 1: Most common type of triquetral fracture. Isolated avulsion or shear fractures involving the dorsal cortex, usually seen following a hyperflexion injury. Considered benign fractures that heal well following immobilization. Best seen on the lateral view.
  • Type 2: Less common. Comminuted fracture of the triquetral body. Considered more serious and seen in association with other carpal fractures.
  • Type 3: Rare. Fracture of the volar aspect of the triquetrum. Associated with injury to perilunate ligaments. Best seen on posteroanterior views with radial deviation of the wrist.
The top patient presented following a hyperflexion injury. The frontal and oblique views failed to reveal a fracture. On the lateral view, we see a bony fragment at the dorsal aspect of the proximal row, consistent with a type 1 fracture. Another type 1 triquetral fracture is seen in the bottom image. This patient also had a comminuted distal right radius fracture, which is appreciated in this coned-down view as abnormal dorsal angulation of the distal radius.

Osteochondral fractures of the triquetrum have also been described, but are thought to be very rare. They are thought to be associated with subluxation or dislocation of the pisiform.

References

  • Smith DK, Murray PM. Avulsion fractures of the volar aspect of triquetral bone of the wrist: a subtle sign of carpal ligament injury. AJR Am J Roentgenol. 1996 Mar;166(3):609-14.
  • Suzuki T, Nakatsuchi Y, Tateiwa Y, Tsukada A, Yotsumoto N. Osteochondral fracture of the triquetrum: a case report. J Hand Surg Am. 2002 Jan;27(1):98-100.

Wednesday, November 4, 2009

The Rosenberg View

The maximum stresses in the knee joint occur between 30 and 60 degrees of flexion; therefore, standard anteroposterior weight-bearing radiographs on extension are not ideal for evaluation of cartilage loss as indicated by joint space narrowing. The Rosenberg view was created to address this issue.

The Rosenberg view is a 45-degree flexion, posteroanterior, weight-bearing view of the knee with the patellae touching the image receptor. The x-ray tube is 40 inches (101.6 cm) away from the image receptor, centered at the patellae, and pointing caudad 10 degrees.

The Rosenberg view is more sensitive and specific for joint space narrowing than the conventional extension weight-bearing anteroposterior views, and is useful for the assessment of knees with early degenerative change.

References

  • Rosenberg TD, Paulos LE, Parker RD, Coward DB, Scott SM. The forty-five-degree posteroanterior flexion weight-bearing radiograph of the knee. J Bone Joint Surg Am. 1988 Dec;70(10):1479-83.
  • Mason RB, Horne JG. The posteroanterior 45 degrees flexion weight-bearing radiograph of the knee. J Arthroplasty. 1995 Dec;10(6):790-2.

Tuesday, November 3, 2009

Gamna-Gandy Bodies

Gamna-Gandy bodies of the spleen are organized hemorrhagic foci caused by portal hypertension. They appear as low-signal lesions throughout the spleen on MRI. Here we see T2-weighted (top) and pre-contrast (middle) and portal venous phase gradient echo T1-weighted images showing multiple hypointense splenic lesions in a patient with cirrhosis and hepatocellular carcinoma. CT didn't show any focal splenic lesions.

References

Sagoh T, Itoh K, Togashi K, Shibata T, Nishimura K, Minami S, Asato R, Noma S, Fujisawa I, Yamashita K, et al. Gamna-Gandy bodies of the spleen: evaluation with MR imaging. Radiology. 1989 Sep;172(3):685-7.

Monday, November 2, 2009

Glomus Tumors of the Hand

Glomus tumors of the hand are hamartomas developed from the neuromyoarterial apparatus, which normally function as a controlled arteriovenous anastomosis to regulate peripheral blood flow in the digits.

Glomus tumors are most commonly found in the subungual region. The lesion shown here is located in the lateral portion of the proximal nail fold and demonstrates T2 hyperintensity (top) and mild, heterogeneous enhancement (bottom). The lesion was not seen on T1-weighted images (not shown).

Most glomus tumors are T1 iso- or slightly hyperintense to the dermal layers of the nail bed and strongly hyperintense on T2-weighted images. Glomus tumors usually demonstrate heterogeneous enhancement, likely reflecting the mixed histology of these tumors, which contain vessels, glomus cells, and mucoid tissue. It must be noted that the normal dermis beneath the nail matrix demonstrates strong, homogeneous enhancement.

Differential considerations include
  • Mucoid cysts: Classically located in the proximal nail fold; painless. There is no contrast enhancement and there is a pedicle communicating with the distal interphalangeal joint.
  • Angiomas: Have the same signal features as gloomus tumors, but are more superficial and located in the papillary dermis and the epidermis.

References

Drapé JL, Idy-Peretti I, Goettmann S, Wolfram-Gabel R, Dion E, Grossin M, Benacerraf R, Guérin-Surville H, Bittoun J. Subungual glomus tumors: evaluation with MR imaging. Radiology. 1995 May;195(2):507-15.

Sunday, November 1, 2009

Adhesive Capsulitis

Primary adhesive capsulitis (AC) is a self-limited, idiopathic condition that is most commonly seen in women over 40 years of age. It is characterized by atraumatic and gradual onset of symptoms of pain and limited range of motion (ROM). Risk factors include diabetes mellitus and hypothyroidism. Secondary adhesive capsulitis can be seen following severe trauma, iatrogenic or otherwise.

Contrast-enhanced MRI may show enhancement in the rotator interval and enhancing soft-tissue partially encasing the biceps anchor. Arthrographic criteria of adhesive capsulitis include:
  • Limited (7–10 cc) capacitance of the glenohumeral joint to contrast injection
  • Small, dependent axillary fold
  • Irregularity of the anterior capsular insertion at the anatomic neck of the humerus
Four stages of AC have been defined based on clinical criteria. There is some correlation between clinical stage and MRI findings:
Stage Clinical and Pathologic Findings MRI Findings
1
0–3 months
Pain with active and passive motion
Limitation of forward flexion, abduction, internal rotation, external rotation
Pathology: hypertrophic, hypervascular synovitis; normal capsule
 
Capsular and synovial thickening measured in the axillary pouch (mean of 4 mm)
Rotator interval scarring.
2
3-9 months
Chronic pain with active and passive motion
Significant limitation of forward flexion, abduction, internal rotation, external rotation
Pathology: hypertrophic, hypervascular synovitis with perivascular and subsynovial scar, scar formation in the underlying capsule
 
Capsular and synovial thickening measured in the axillary pouch (mean of 7.5 mm)
Rotator interval scarring.
Increased signal intensity of the joint capsule and synovium
3
9-15 months
Minimal pain except at end motion
Significant limitation of motion with rigid "end feel"
Pathology: "burned out" synovitis without significant hypertrophy or hypervascularity. Dense scar formation of the capsule
 
Capsular and synovial thickening measured in the axillary pouch (mean of 5.5 mm)
Rotator interval scarring.
4
15-24 months
Minimal pain
Progressive improvement in ROM
Capsular and synovial thickening measured in the axillary pouch (mean of 4 mm)
Rotator interval scarring.

References

Sofka CM, Ciavarra GA, Hannafin JA, Cordasco FA, Potter HG. Magnetic resonance imaging of adhesive capsulitis: correlation with clinical staging. HSS J. 2008 Sep;4(2):164-9.