Nonvisualization of the Gallbladder with HIDA Scan

HIDA (Tc-99m hydroxy iminodiacetic acid) scan shows normal uptake in the liver with excretion into the extrahepatic bile duct (arrow) and in the bowel (arrowheads) at 25-30 minutes after radiotracer injection. Intravenous morphine was administered at 60 minutes. The images obtained up to 2 hours show no activity in the gallbladder.

Facts: HIDA scan

• Also known as hepatobiliary scan
• Liver uptakes HIDA and excretes it into bile that drains into the bowel
• Normal activity should be seen immediately in the liver, at one hour in gallbladder and into the bowel
• The scan can be done to help diagnose acute cholecystitis, postoperative bile leak
• Morphine can be utilized to shorten the examination time for the diagnosis of acute cholecystitis if the gallbladder is not seen at 1 hour but the bile duct and bowel activity is visualized.
• Cholecystokinin or fatty meal can be used to help diagnose chronic cholecystitis.

Findings on HIDA scan

Nonvisualization of gallbladder WITH bowel activity

• Acute cholecystitis
• Previous cholecystectomy
• Non-fasting patient (including IV feeding)
• Severe hepatic disease
• Chronic cholecystitis (usually fills after 1 hour)

Nonvisualization of gallbladder WITHOUT bowel activity

• Biliary obstruction of any cause
• Severe hepatic disease
• Opiates (because of their effect on the sphinctor of Oddi)

Our patient: acute cholecystitis confirmed at surgery

References:

1. Sharp PF, Gemmell HG, Murray AD. Practical nuclear medicine, 3rd edition, 2005.

2. Chapman S, Nakielny R. Aids to radiological differential diagnosis, 4th edition, 2003

Popliteal Artery Aneurysm

Figure 1: Gray-scale ultrasound of the let popliteal ultrasound shows a fusiform aneurysm of the popliteal artery, measuring 2 cm.
Figure 2: Color Doppler US image shows partial thrombosis of the aneurysm.

Facts:

• Most common peripheral artery aneurysm
• Most commonly due to atherosclerosis
• More common in male
• Commonly bilateral (need to examine the contralateral popliteal artery), and commonly associated with abdominal aortic and iliac artery aneurysm in about half of all cases.
• Presentation: cold lower extremity from acute thrombosis or distal embolization, asymptomatic pulsatile popliteal fossa mass, rarely rupture

Indication for Repair

1. Size 2 cm or greater
2. Intraluminal thrombus

Imaging Strategy

• Doppler US for diagnosis and follow up
• MDCT for planning of repair (surgical or endovascular): extent, location of associated peripheral vascular disease, nearby branch vessels, size and angulation of the aneurysm

References

1. Blackbourne LH. Surgical recall, 5th ed, 2008.

2. Funaki B, Lorenz J, Ha TV. Teaching atlas of vascular and non-vascular interventional radiology, 2007.

An Expert's Response to the Recent USPSTF Recommendations for Mammography

A recent release of the US Preventive Services Task Force (USPSTF) recommendations for breast cancer screening has brought about so many controversies. Below is the summary view of Dr. Daniel B. Kopans, a Mass General radiologist and Harvard professor, internationally known as a breast imaging expert:

Mass General Imaging believes that the USPSTF recommendations are based on flawed analysis of the data and continues to support the scientifically based recommendations of the American Cancer Society for the early detection of breast cancer:

1. Annual mammographic screening should begin at age 40
2. Women at high risk for developing breast cancer should have annual MRI screening in addition to mammography

View full article by Dr. Kopans (MGH Radiology Rounds) HERE

Read more controversies in the New York Times and Washington Post

Read where the American College of Radiology stands

Additional opinions from the New England Journal of Medicine (November 25, 2009)
- Screening mammography and the "R" word
- On mammography - more agreement than disagreement

New Guidelines for Cervical Cytology Screening Released

The American College of Obstetricians and Gynecologists (ACOG) released its new clinical management guidelines for cervical cytology screening today.

New Recommendations

• Screening should begin at age 21 years (previously at the age of first sexual intercourse)
• Frequency of screening: every two years for women aged 21-29 years; for women aged 30 and older -- if results have been negative for intraepithelial lesions and malignancy for three times they may be screened at every three years
• More frequent screening may be done in high-risk groups including: HIV infection, immunosuppression, exposure to diethylstilbestrol in utero, previously treated for CIN2, CIN3 or cancer
• Discontinue screening: at either 65 or 70 years in women with three or more negative cytology test results in a row and no abnormal results in the past 10 years; immediately after total hysterectomy for benign indications and no prior history of high-grade CIN
• Both liquid-based and conventional methods for cervical cytology are acceptable for screening
• Co-testing with a combination of cytology and HPV DNA testing: appropriate for women older than 30 years.

Full text from the ACOG (Free)

New York Times story (Free)

Updated Recommendation for Breast Cancer Screening

The update of the U.S. Preventive Services Task Force (USPSTF) recommendation statement on screening for breast cancer in the general population has been published today in the Annals of Internal Medicine.

The USPSTF Recommends

• Against routine screening mammography in women aged 40-49 years
• Biennial (every two years) screening mammography for women between the ages of 50 and 74 years

Based on the USPSTF review, the current evidence is insufficient to assess benefits and harms of ...

• Screening mammography in women 75 years or older
• Clinical breast examination beyond screening mammography in women 40 years or older
• Either digital mammography or magnetic resonance imaging instead of film mammography as screening modalities for breast cancer

What Has Changed from the Previous Recommendations, and Why?

• Recommendations against universal screening mammography for women aged 40 to 49 years, based in part on an updated systematic review of screening mammography randomized, controlled trials that showed lower yield of reduced breast cancer mortality and higher false-postive results with screening in this population
• Recommendation of biennial screening mammography for women aged 50 to 69. Based on statistical models, annual versus biennial screening showed similar degree of breast cancer mortality reduction and similar likelihood of late-stage disease at diagnosis.
• Extension of screening mammography to women aged 70 to 74 years. Models estimate that approximately 2 additional breast cancer deaths are averted per 1000 women screen at this age.

Read full text here (free)

Reference:

1. U.S. Preventive Services Task Force. Screening for breast cancer: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med 2009;151:716-726.

2. Kerlikokowske K. Evidence-based breast cancer prevention: the importance of individual risk. Ann Intern Med 2009;151:750-752.

Os Terminale - Os Odontoideum Complex (3)

A sagittal-reformated CT image shows a characteristic appearance of os odontoideum (O). Note a wide gap between the os and the hypoplastic dens (D). The anterior arch of C1 (A) is hypertrophied.

Facts: Os Odontoideum

• Ossicle either in a normal odontoid tip (orthotopic) or near basi-occiput (dystrophic)
• Often fixed to the anterior C1 ring and the two move as a single unit
• Often asymptomatic (found incidentally) but some patients may have symptoms of C1-2 instability or at risk of developing cord injury following severe trauma

Imaging Features

• Smooth, small or large ossicle, can be rounded or oval or very bizarre and irregular in shape
• Hypoplastic dens. Wide gap between the os and dens
• Anterior arch of C1 is hypertrophied
• Jigsaw sign (a narrow joint space between the anterior C1 arch and the os, and an interdigitating joint line)

Differentiation of Unstable Os Odontoideum from Ununited Dens Fracture

• In ununited dens fracture, the dens is normal in size and configuration but there is nonunion through the base of the dens. Nonunited fragment becomes hypermobile and behave like an os odontoideum. However, either of this would need surgical stabilization

Clinical Implication

• The whole complex is variably unstable; therefore superimposed cervical spine trauma can make it more unstable and even can lead to acute cord injury
• Suggest instability if 1) forward flexion of C1 on C2 more than 2 mm on flexion view, or 2) the os is posterior to its normal location

References:

1. Fagan AB, Askin GN, Earwaker JWS. The jigsaw sign. A reliable indicator of congenital aetiology in os odontoideum. Eur Spine J 2004;13:295-300.

2. Truumees E. Os odontoideum. E-medicine, updated September 12, 2008.

3. Swischuk L. Imaging of cervical spine in children, 2004.

Os Terminale - Os Odontoideum Complex (2)

Sagittal reformatted CT image shows an os terminale, sitting on top of the normal-sized dens.

Os Terminale

• Derived from the 4th occipital sclerotome but does not undergo fusion with the dens
• The dens is normal in size and shape
• If it enlarges, coupled with dens hypoplasia -- it is called os odontoideum
• Usually single, smooth
• Sometimes can show bony fragmentation mimicking a comminuted fracture (but one should be aware that an extensively comminuted fracture at the tip of the dens is extremely rare or nonexistent)

Reference:

Swischuk L. Imaging of the cervical spine in children, 2004.

Os Terminale - Os Odontoideum Complex (1)

Diagram showing a range of dens anomalies from normal, os terminale and os odontoideum (hypoplastic dens). Adapted from Reference #1.

"I have always considered them [os terminale and os odontoideum] to be the same, believing that the os terminale becomes the os odontoideum when it enlarges in association with hypoplasia of the dens." - Leonard Swischuk, MD

Development of os terminale/os odontoideum complex

• Os terminale is derived from the 4th occipital sclerotome
• Os terminale develops and then fuses with the dens in most cases (becoming the tip of the dens)
• If the os terminale does not fuse with the dens, it can overgrow and become the os odontoideum while the dens becomes hypoplasia. At the same time C1-2 stabilizing ligaments will be underdeveloped and predispose this section to hypermobility and instability

Imaging Appearance

• Both os terminale and os odontoideum typically is a single, smooth ossicle
• Sometimes, they can show bony fragmentation, bizarre and irregular in shape
• If found posterior to its normal location, one can presume that there is some degree of instability
• Anterior arch of C1 can overgrow (hyperplastic); this does not suggest that there is ununited fracture of the dens

Reference:

1. Swischuk L. Imaging of the cervical spine in children, 2004.

Totally Accessible MRI: A User's Guide to Principles, Technology, and Applications

Book title: Totally Accessible MRI: A User's Guide to Principles, Technology, and Applications
Cover type: Soft cover
Name of author: Michael L. Lipton, MD, PhD
Number of pages: 313
Publisher: Springer
City and state of publication: New York, USA
Year of publication: 2008

Totally Accessible MRI is an outgrowth of more than a decade of experience of Dr. Michael L. Lipton, MD, PhD, in teaching magnetic resonance imaging (MRI) course at the Albert Einstein Medical College in New York. It is intended to anyone who has interest to understand MRI as it is used in clinical imaging and its behind-the-scene physics.........

Continue reading the review at this link (hosted by www.radRounds.com)

Choroid Plexus Mass

Figure 1: Axial T2 MR image of the brain of a 24-year-old man shows a heterogeneous mass (arrows) in the temporal horn of the right lateral ventricle. Note a CSF cleft (arrowhead) anterolateral to the mass and low T2 signal intensity within the mass. There is no edema of the adjacent brain parenchyma.
Figure 2: Axial T1 post-contrast image shows homogeneous enhancement of the mass.

Facts: Choroid Plexus

• Starts differentiating in week 6 and has an adult appearance by week 20 of gestation
• Choroid plexus epithelium + capillaries are lined by ependymal cells. Capillaries are fenestrated allowing free movement of small molecules (lack of blood brain barrier), but epithelial cells connect each other with tight junction preventing passage of most macromolecules into CSF.
• Forms CSF and actively regulates CSF constituents

Choroid Plexus Mass

• Choroid plexus papillomas and carcinomas are common in young children (under 5 years old)
• Papillomas are benign tumor arising from choroidal epithelial cells; 5%-10% degenerate into carcinomas
• Papillomas are common in the first year of life, boys > girls, usually presenting with hydrocephalus (due to either CSF overproduction or obstruction in subarachnoid/intraventricular CSF pathways)

Imaging Findings: Choroid Plexus Papilloma

• Lobulated intraventricular mass; 25% calcified
• Isoattenuation on non-contrast CT
• Homogeneously enhanced after IV contrast administration
• On T2W MR image, central hypointensity is characteristic
• "Aggressive" papillomas may show irregular margins and grow into adjacent white matter causing edema

Suspect Choroid Plexus Carcinomas When:

• Presents with focal neurological deficits
• Grows into adjacent brain parenchyma, causing vasogenic edema
• Metastasize through CSF

Our case: choroid plexus papilloma in a young adult. Given our patient's age, differential diagnosis of meningioma, lymphoma and metastasis should also be entertained.

Reference:

Naeini RM, Yoo JH, Hunter JV. Spectrum of choroid plexus lesions in children. AJR 2009;192:32-40