Arterial Closure Devices

Initially used by cardiologists during percutaneous coronary interventions, arterial closure devices (ACDs) have made their way into the interventional radiology suite. With the potential to achieve rapid hemostasis and reducing patient time to ambulation, ACDs are increasingly favored over manual compression for arteriotomies especially since preliminary data demonstrates no significant difference in complications between the two methods. 

ACDs can either provide active (or intravascular) closure by engaging the vessel wall via clips, sutures, or plugs, versus passive (or extravascular) closure by introducing thrombosing agents or sealants via the sheath to plug the arteriotomy site. Few clinical trials exist demonstrating the benefit of intravascular versus extravascular closure. It is felt that intravascular ACDs are a better choice in patients who are anticoagulated. However, using a device with intravascular components introduces a nidus for potential infection. Additional complications include device embolization, arterial laceration, and limb ischemia due to luminal obstruction.

While additional research is needed to define the safety and efficacy profiles of ACDs, their use should certainly be considered by interventional radiology departments, especially due to their potential to improve patient care. 


REFERENCES
Dauerman HL, Applegate RJ, Cohen DJ. Vascular closure devices: the second decade. J Am Coll Cardiol 2007;50(17):1617-26.

Mycetoma Formation in Fungal Sinusitis

A mycetoma (fungal ball) is an uncommon sequela of fungal sinusitis and is thought to be secondary to deficient mucociliary clearance of a fungal organism which incites an inflammatory response. The fungal ball usually appears as a mass within a sinus (usually the maxillary sinus) and is typically unilateral. Bone window CT will show a mass within the sinus with punctate calcifications. A fungal ball is typically of low signal intensity on T1W MR due to low water content. On T2WI the mycetoma will be hypointense relative to the hyperintense inflamed sinus mucosa.


REFERENCES
Aribandi M, McCoy VA, Bazan C. Imaging features of invasive and noninvasive fungal sinusitis: a review. Radiographics 2007;27:1283-96.

The Double Duct Sign

The double duct sign refers to the concomitant dilatation of the common bile duct and pancreatic duct seen on MRCP (although the same can be visualized on CT, US, and ERCP). Visualization of the double duct sign typically suggests the presence of a malignancy - either and ampullary or pancreatic head carcinoma. Other malignancies with this appearance include cholangiocarcinoma of the distal common bile duct, lymphoma, metastases, and in rare cases, Kaposi's sarcoma. Primary retroperitoneal fibrosis has also been reported to cause simultaneous dilatation of both bile ducts. 

However, some studies have shown that the double duct sign is not as specific a predictor of pancreatic malignancy as initially thought to be since benign entities can present similarly. The most common benign causes are chronic pancreatitis and ampullary stenosis. Plumley et al., have suggested that the specific bile duct morphology on ERCP is a better predictor of benign versus malignant causes of ductal dilatation: abrupt stenosis of a bile duct with irregular margins is more likely to indicate malignancy while gradual ductal stenosis, especially when associated with smooth margins, is more indicative of benign lesions. Other predictors of benign disease include glandular calcifications and ectasia of the branching bile ducts (seen in chronic pancreatitis).


REFERENCES
Ahualli J. The Double Duct Sign. Radiology 2007;244:314-5.
Edge MD, Hoteit M, Patel AP. Clinical significance of main pancreatic duct dilation on computed tomography: single and double duct dilation. World J Gastroenterol 2007;31(11):1701-5.
Plumley TF, Rohrmann CA, Freeny PC, et al. Double duct sign: reassessed significance in ERCP. Am J Roentgenol 1982;138:31-5.

Internal Derangement of the Temporomandibular Joint

Internal Derangement of the Temporomandibular Joint (TMJ), more commonly known as dislocation of the TMJ, occurs due to an abnormal positional and functional relationship between the articular disc and the articulating surface. The images above are from a patient with anterior dislocations of the bilateral TMJs.

While this abnormality can usually be detected on plain films or bone NECT, MRI is the best modality to evaluate the TMJ especially in cases of recurrent derangement. On MRI, the low signal intensity articular disc will be displaced relative to the mandibular condyle. T1WI can show specific disc abnormalities including perforation, fibrosis or adhesions. The presence of a joint effusion can be detected as high signal on T2WI. The presence of synovitis can be detected as enhancement of the disc on T1WI after administration of contrast.


REFERENCES
Sommer OJ, Aigner F, Rudisch A, et al. Cross-sectional and functional imaging of the temporomandibular joint: radiology, pathology, and basic biomechanics of the jaw. Radiographics 2003;23:e14.
Tomas X, Pomes J, Berenguer J, et al. MR imaging of temporomandibular joint dysfunction: a pictorial review. Radiographics 2006;26:765-81.

Intramedullary Osteosclerosis

A nonhereditary condition that effects the long bones of the lower extremities (tibia > femur, fibula). On imaging studies it presents with endosteal sclerosis extending into the medullary canal, possibly obliterating the canal. There is no associated periosteal reaction or soft tissue swelling. Bone scan will show intense radiopharmaceutical uptake.This condition is more common in women and usually presents as pain that is exacerbated by activity.

Differential diagnosis:
1. Ribbing disease - may look exactly the same. The main difference is that Ribbing disease tends to have a familial inheritance pattern (thought to be autosomal recessive).
2. Stress fracture - usually a focal sclerosis and periosteal reaction will be present.
3. Sclerotic metastases - patchy, discontinuous presentation, population tends to be older.
4. Progressive diaphyseal displasia (Camurati-Engelmann disease) - presents in young boys, has skull and vertebral body involvement, disease begins in the diaphysis of long bones and may extend to the metaphysis, has periosteal and endosteal sclerosis. 
5. Melorheostosis (Leri-Weill disease) - a sclerosing bone dysplasia which presents unilaterally in a long bone of the upper or lower extremity and may have associated soft tissue calcifications.

REFERENCES
Balkissoon ARA and Hayes CW. Intramedullary osteosclerosis. Radiology 1999;212:708-10.
Chanchairujira K, Chung CB, Lai YM, et al. Intramedullary osteosclerosis: imaging features in nine patients. Radiology 2001;220:225-30.

Name the Device

Deep Brain Stimulator: electrodes implanted in the thalamus for treatment of Parkinson's disease. 

REFERENCES
Hunter TB, Yoshino MT, Dzioba RB, et al. Medical devices of the head, neck, and spine. Radiographics 2004;24:257-285.

Normal Variants in the Pediatric Cervical Spine

Interpreting cervical spine x-rays in the pediatric population can be a challenge due to normal anatomic variants. At age 8-10 a child's cervical spine reaches adult proportions. Normal variants to be considered in the younger populations include:

1. The atlantodens interval (ADI) may be up to 5mm in the pediatric patient whereas the upper limit of normal is 3mm in an adult.
2. Pseudo-Jefferson fracture: up to 6mm displacement of the lateral masses of atlas on the axis on the open mouth view is normal for children up to age 7.
3. Pseudo-subluxation of C2 on C3 (and to a lesser extent C3 on C4): normal mobility of upper cervical spine (due to ligamentous laxity) can cause up to a 4mm anterior displacement of C2 on C3. The Swischuk line - a line drawn through the posterior arch of C2 should be within 2mm of the spinolaminar line drawn at C1-C3 - can be used to determine whether this finding is normal or due to possible hangman's fracture. A discrepancy of > 2mm can indicate a fracture.
4. Anterior "wedging" of up to 3mm is a normal finding. 
5. Ossification centers and unfused apophyses may mimic fractures.
6. Absence of cervical spine lordosis may be seen up to age 16.

REFERENCES
Curtin P and McElwain J. Assessment of the "nearly normal" cervical spine radiograph: C2-C3 pseudosubluxation in an adult with whiplash injury. Emerg Med J 2005;22:907-8.
Lustrin ES, Karakas SP, Ortiz AO, et al. Pediatric cervical spine: normal anatomy, variants, and trauma. Radiographics 2003;23:539-60.