Pigmented Villonodular Synovitis (PVNS) of the Ankle

Figures 1&2: Sagittal MR images in T1 (fig.1) and STIR (fig.2) show a heterogeneous para-articular mass (arrows) anterior to the ankle joint that demonstrates areas of internal low T1 and T2 signal intensity (arrowheads), consistent with hemosiderin deposits.

Facts: PVNS

• Inflammatory synovial lesion of unknown etiology
• Young to middle-aged adult, usually male
• Histology shows connective tissue hyperplasia, phagocytes and hemosiderin deposition
• Two types: localized and diffuse
• Common involvement: knee, hip, ankle/foot
• It is a "joint" disease that can produce mass and erode adjacent bones
• MRI is the imaging modality of choice for suspected case of PVNS

MR Imaging Features

• Heterogeneous para/intra-articular soft tissue mass with low T1 and T2 signal (due to hemosiderin deposition)
• Blooming of low T2 areas in gradient echo imaging
• Diffuse intense enhancement
• Variable amount of joint effusion
• Imaging mimics: rheumatoid arthritis, hemophiliac joint, amyloidosis

Reference:

Ofluoglu O. Pigmented villonodular synovitis. Orthop Clin N Am 2006;37:23-33.

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Pericardial Effusion - Oreo Cookie Sign

Figure 1: Lateral chest radiograph shows separation of the retrosternal (dark line parallel to the sternum anterior to the yellow star) and epicardial fat stripes (dark line behind the yellow star). This patient also has an anterior mediastinal mass due to lymphoma.
Figure 2: Axial contrast-enhanced CT image shows a large pericardial effusion (stars) separating the retrosternal fat stripe (double-headed arrow) and epicardial fat stripe (arrowheads).

Facts: Pericardium

• Pericardium has two layers: visceral (attached to myocardial surface and proximal great vessels) and parietal (free wall of pericardial sac)
• Pericardial sac normally contains 20-50 mL of fluid

Facts: Pericardial Effusion

• Most common cause = myocardial infarction with left heart failure
• Other causes: uremia, hypoalbuminemia, myxedema, infection, drug reaction, trauma, neoplasm, autoimmune disease
• Can be seen on radiography if volume exceeds 250 mL

Imaging Features

• PA or AP radiograph: water bottle-shaped morphology of the cardiomediastinal shadow
• Lateral view: separation of retrosternal and epicardial fat stripes by more than 2 mm (Oreo cookie sign)
• Oreo cookie sign: epicardial fat and retrosternal fat stripes = outer dark cookie layers; opaque fluid = white fluff of the cookie

Oreo cookies pictures

Reference:

Parker MS, Chasen MH, Paul N. Radiologic signs in thoracic imaging: case-based review and self-assessment module. AJR 2009;192:S34-S48.

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Lipid Poor Adrenal Adenoma

Facts

• Most adenomas can be characterized as lipid rich on precontrast scan, which will show attenuation value of less than 10 HU
• Some adenomas are lipid poor, therefore demonstrate a higher attenuation value. This can be further characterized by performing an adrenal mass CT protocol
• Adrenal mass CT consists of 1) precontrast, 2) portovenous phase postcontrast (60-70 sec) and 3) delayed phase (10-15 min)
• Measurement of region of interests (ROI) over > half of the mass at different phases. Values are used to calculate absolute and relative percentage washout

Absolute Percentage Washout (APW) = 100 x (portovenous attenuation - delayed attenuation)/(delayed attenuation - precontrast attenuation)

Relative Percentage Washout (RPW) = 100 x (portovenous attenuation - delayed attenuation)/delayed attenuation

Adenomas typically show rapid washout

• APW > 60% OR
• RPW > 40%

Reference:

Johnson PT, Horton KM, Fishman EK. Adrenal imaging with multidetector CT: evidence-based protocol optimization and interpretative practice. RadioGraphics 2009;29:1319-1331.

Multiple Well-Defined Soft-Tissue Opacities in the Breasts

Mediolateral oblique mammogram of both breasts show multiple, innumerable, well-defined soft-tissue opacities (arrows) and enlarged nipples in a 40-year-old woman.

Differential Diagnosis

• Cysts
• Fibroadenomas: 10-20% are multiple
• Skin lesions: such as neurofibromas
• Intramammary lymph nodes
• Metastasis: melanoma (most common), lymphoma (2nd most common), lung, ovary, soft tissue sarcoma (breast metastasis has a very poor prognosis)

Our case: neurofibromatosis

Reference:

Davies SG. Chapman & Nakielny's Aids to radiological differential diagnosis, fifth edition, 2009.

Left Inferior Vena Cava (IVC)

Axial contrast-enhanced CT images show the left IVC (arrows) crossing the midline from left to right of the aorta, joining the left renal vein that units with the right renal vein to be a normal right sided suprarenal IVC. Image at the lower section shows the IVC located to the left of the aorta. Without scrutinization, this anomaly can be misdiagnosed as left paraaortic adenopathy.

Facts: IVC Anomalies

• As many as 14 forms of IVC anomalies are theoretically possible
• More than one anomaly can coexist in a patient, for example, double IVC + retroaortic right renal vein + hemiazygos continuation
• Common anomalies are circumaortic left renal vein, retroaortic left renal vein, left IVC, double IVC, azygos continuation of IVC

Left IVC

• Regression of the right supracardinal vein with persistence of the left supracardinal vein
• Prevalence 0.2% - 0.5%
• Left IVC joins the left renal vein, which crosses anterior to the aorta and units with the right renal vein to form a normal right sided suprarenal IVC.
• Clinical significance: potential for misdiagnosis as left paraaortic adenopathy, difficulty placement of IVC filter

Reference:

Bass JE, Redwine MD, Kramer LA, et al. Spectrum of congenital anomalies of the inferior vena cava: cross-sectional imaging findings. RadioGraphics 2000;20:639-652.