Chronic Pulmonary Embolism

Fig.1: Perfusion lung scan (posterior view) with Tc-99m MAA shows multiple small peripheral perfusion defects in both lungs. There is a matched defect in the right lung that corresponds to abnormality on chest radiograph (not shown).
Fig. 2: Ventilation scan (posterior view) shows normal ventilation in areas of perfusion defects, except only in the right lung. Combined with perfusion scan findings, there are multiple small mismatches in both lungs and a matched defect in the right lung. This patient was considered having intermediate probability for pulmonary embolism. Subsequent pulmonary CTA did not show an acute PE but evidence of mosaic perfusion, typical of chronic pulmonary embolism.

Facts:

• Natural course of pulmonary emboli includes complete resolution, partial resolution, persistent defects or presence of new abnormalities
• Lung scans may show false positivity in patients with unresolved pulmonary emboli
• Those patients likely to delay clearing of pulmonary emboli: elderly, with underlying chronic lung disease, heart failure or having very extensive pulmonary infarction
• Serial lung scans may be helpful in management of patients with thromboembolic disease(decision whether to continue anticoagulant therapy, new abnormalities may influence more invasive therapy, provision of new baseline)
• If an embolus is going to clear, it will do so by three months. What is left after three months will persist indefinitely

Reference:

Fogelman I, Maisey MN, Clarke SEM. An atlas of clinical nuclear medicine, 1994, 2nd edition.

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RiTradiology Celebrating 5,000 and 50,000 Strong

For the first time, we hit the record high of 5,000 visitors per month today and reach an all-time high for total visits of 50,000 as well. We would like to thank you for continued interest. We'll do our best to keep the blog going forward.

If you have more time, please check out our partner social networking site, www.radRounds.com, and blogs of interest - Roentgen Ray Reader (Radiology) and BeyondApples.org (Preventive Medicine).

-RiTradiology Team

Vertebral Burst Fracture

Fig.1: Posterior bone scan image shows a linear increased uptake at T12 (arrow) in an old patient with osteoporosis and low back pain.

Fig.2: Sagittal reformatted CT image reveals a burst fracture involving T12, corresponding with findings on bone scan.

Tc-99m MDP Bone Scan & Osteoporosis

• Bone scan may be helpful in symptomatic osteoporotic patients for identification of cause of back pain
• Negative bone scan rules out a recently occurred osteoporotic fracture
• Positive bone scan (hot spot) mandates further investigation to differentiate between degenerative change, fracture and malignancy
• Linear uptake (like in our case) usually indicates acute/subacute fracture.

Reference:

van Goethem J, van den Hauwe L, Parizel PM. Spinal imaging: diagnostic imaging of the spine and spinal cord, 2007.

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Rim-rent Tear of Supraspinatous Tendon

Fig.1: Oblique sagittal PD MR image shows focal fluid signal intensity at articular surface of the anterior insertion of the supraspinatous tendon. There is bone marrow edema at the site of the insertion.
Fig.2: Coronal T2 MR image with fat suppression confirms similar findings. Partial involvement of the tendon, fluid signal intensity, location (articular side, at tendon insertion) are characteristic of a rim-rent tear of the supraspinatous tendon.

Facts: Partial-Thickness Tear of Supraspinatous Tendon

• Partial-thickness tears are common cause of shoulder pain
• Believed to be due to multiple factors including intrinsic degeneration, microtrauma, trauma, hypovascularity and subacromial impingement
• Partial-thickness tear of the supraspinatous tendon can be on the articular or bursal side, at the tendon insertion or at the critical zone
• Critical zone tear is located at 1-2 cm proximal to the cuff tendon insertion on the greater tuberosity, it was once thought to be the most common type of partial-thickness tear

Rim-rent Tear

• Partial-thickness tear on the articular side at the tendon insertion on the greater tuberosity
• Considered to be the most common type of partial-thickness tear of supraspinatous tendon
• Can be difficult to visualize on MR imaging because of patient's positioning (too much internal rotation) and it was not well-known to radiologists
• Potential to progress into a full-thickness tear
• Tricks: on coronal images - inspect the leading edge of the supraspinatous tendon just lateral to the bicipital grove; on sagittal images - inspect closely at the insertion of tendons

Reference:

Vinson EN, Helms CA, Higgins LD. Rim-rent tear of the rotator cuff: a common and easily overlooked partial tear. AJR 2007;189:943-946

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Solid Splenic Lesion

Fig.1: Axial T2 with fat saturation MR image shows a slightly T2 hyperintense lesion in the spleen (arrow).
Fig.2: Axial T1 post contrast with fat saturation reveals homogeneous enhancement of this lesion.

Splenic Lesion Approach

• Solid versus cystic (distinguish by T2 signal intensity and enhancement pattern)
• If solid, is it classic for hemangioma? Is there a history of malignancy elsewhere?
• If cystic, usually represent false cyst (post-traumatic), congenital cyst, abscess

Solid Splenic Lesion

• Benign tumors: hemangioma (most common benign tumor of spleen, same character as liver hemangioma), hamartoma
• Malignant tumors: lymphoma, metastasis (history, multiplicity)
• Others: sarcoidosis, langerhans cell histiocytosis

Our case: splenic metastasis from lung cancer [on imaging, this was not a cyst or hemangioma because its T2 signal was not as high as CSF. It enhanced so it definitely was solid. Differential diagnosis with this solitary solid lesion was hamartoma, solitary metastasis and primary malignancy. Lymphoma, sarcoidosis and LCH usually are multiple].

Reference:

1. Davies SG. Chapman & Nakielny's Aids to Radiological Differential Diagnosis, 5th ed, 2009.
2. Elsayes KM, Narra VR, Mukundan G, et al. MR imaging of the spleen: spectrum of abnormalities. Radiographics 2005;25:967-982.

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Mammography Quality Control

Facts

• In the US, the Food and Drug Administration (FDA) developed the Mammography Quality Standard Act (MQSA) requiring all mammography facilities to be "certified" (currently there are more than 10,000 facilities)
• The MQSA became effective since April 1999
• It is against federal law to practice mammography without certification by FDA
• To obtain "certification" by the FDA, the facility must be "accredited" by an approved body such as the American College of Radiology (ACR)

What Are Accreditation Requirements of the ACR?

• Requires combined effort of physicians, technologists and medical physicists
• Physician requirements: all interpreting physicians must participate in medical outcome audit, have documentation that they have interpreted at least 200 mammograms in the previous 24 months, ensure qualification of technologist training, assign one technologist to oversee Quality Control (QC) program, assign one physicist to perform annual testing and select one individual to oversee the radiation protection program
• Technologist requirements: QC program is performed on different aspects of mammography on a daily, weekly, monthly, quarterly and semiannual basis. For example, processor QC is performed daily.
• Physicist requirements: medical physicists must be trained in mammography, perform at least 6 annual medical physics surveys every 2 years and receive the required CME credits; image quality, equipments and patient dose are assessed by medical physicists
• ACR phantom is used to check image quality; to pass the test, the phantom image must show a minimum of 4 fibers, 3 speck groups and 3 masses (out of 6 fibers, 5 speck groups and 5 masses on the phantom) and image artifacts are minimal
• Average glandular dose (AGD) for a 4.2 cm thick breast should be less than 3 mGy per image with a grid. If there is no grid, AGD should be less than 1 mGy per image

Author's Notes

• In a new era of quality-minded health care, it is inevitable that medical practice will be increasingly overseen by the public, government and other non-medical authorities. In the case of MQSA, the FDA gives credits to the ACR for certification of each facility.
• It is important for us not only to do best at our routine interpretative work, but also to get involve in quality procedures in the department and professional society. This will help ensure that we serve our patients well and we are the one who will define our own destiny.

Reference:

Huda W. Review of Radiologic Physics, 3rd edition, 2009.

Image credit: www.gammex.com

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Kartagener Syndrome

Figure 1: Frontal chest radiograph demonstrates dextrocardia (cardiac apex pointing to the right with right aortic arch - arrowheads), bibasilar coarse reticular opacities and loss of volumes in the lower lungs in a patient with Kartagener syndrome.
Figure 2: Coronal reformatted CT image confirms the presence of extensive bibasilar bronchiectasis (arrows) and situs inversus. Bronchiectasis in patients with this syndrome tends to involve the dependent parts of the lungs.

Facts: Kartagener Syndrome

• Genetically transmitted (autosomal recessive) syndrome characterized by bronchiectasis, situs inversus and chronic sinusitis
• Genetic disorder first described in 1904, but identified as a syndrome by Manes Kartagener, a Swiss internist, in 1933
• It is a subtype of primary cilia dyskinesia
• Incidence 1:32000 live births
• Abnormal function of cilia is believed to be responsible for visceral asymmetry (abnormal movement of cilia in certain embryonic epithelial tissues), respiratory disease, etc.

Diagnosis

• Onset of upper and lower respiratory tract symptoms shortly after birth in the presence of situs inversus
• Family history of primary ciliary dyskinesia or Kartagener syndrome
• Confirmation with biopsy of respiratory mucosa or microscopic examination of sperms
• Other clinical signs: chronic rhinitis with nasal polyposis, agenesis of frontal sinuses, repeated otitis media, bronchiectasis (usually dependent parts of the lungs in contrast to cystic fibrosis that tends to affect the upper lobes), situs inversus (complete or partial)

Reference:

Bissonnette B, Luginbuehl I, Dalens BJ. Syndromes: rapid recognition and perioperative implications, 2006.

Right Lower Lobe Atelectasis

Figure 1: Chest radiograph shows loss of right lung volume, abnormal opacity in the right lower lung obscuring the right hemidiaphragm, inferior displacement of the major fissure (arrows) and right hilum.

Figure 2: Coronal CT image revealed a large right hilar mass (star) resulting in right lower lobe atelectasis.

Imaging Findings

• Lower lobe atelectasis occurs in posterior, inferior and medial direction because of the presence of pulmonary ligaments
• Medial/inferior shift of major fissure; minor fissure may not shift
• Obscuration of hemidiaphragm, paraspinal interface; right heart border still visible
• Vertical orientation of lower lobe bronchi
• Inferior and medial displacement of ipsilateral hilum
• Triangular opacity of atelectatic lobe, with apex toward the hilum and base toward the hemidiaphragm

Our case: Right hilar mass causing obstructive right lower lobe atelectasis (squamous cell carcinoma)

Reference:

Parker MS, Rosado de Christenson ML, Abbott GF. Teaching atlas of chest imaging, 2006.

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Blunt Traumatic Vertebral Artery Dissection

Fig.1: Axial CT image of the cervical spine shows a fracture of the right facet (arrows) extending to the transverse foramen of C6 in a neurologically intact blunt trauma patient.
Fig.2: Subsequent CT angiography of the neck shows a long-segment occlusion (red arrows) of the right vertebral artery from C6 up to base of the skull.

Why Screening for Blunt Cerebrovascular Injury (BCVI) in Trauma Patients?

• If left untreated, carotid and vertebral artery injury can have a stroke rate ranging from 3-100% and 6-100% respectively
• Stroke rate by BCVI depends on grade of injury: the higher the grade, the higher stroke rate
• Screening protocols based on patient injury patterns and mechanism of injury have been instituted prior to neurologic sequelae to identify these injuries in asymptomatic patients and to initiate stroke-preventive treatment.
• Based on current studies, early anticoagulant therapy reduces stroke rates and prevents neurologic morbidity from BCVI

Facts: Denver Screening Criteria

• General guidelines to determine which blunt cerebrovascular injury (BCVI) patients should be evaluated for arterial injury.
• Signs/symptoms of BCVI: arterial hemorrhage, cervical bruit in patient less than 50 years of age, expanding cervical hematoma, focal neurologic deficit, neurologic exam incongruous with head CT scan findings, stroke on secondary CT scan
• Risk factors for BCVI: high-energy transfer mechanism with LeFort II or III fracture, cervical spine fracture pattern (subluxation, fracture extending into the transverse foramen, fractures of C1-C3), basilar skull fracture with carotid canal involvement, diffuse axonal injury with a Glasgow Coma Scale score less than 6, near hanging with anoxic brain injury

Facts: Denver Grading Scale for BCVI

• Grade I: irregularity of the vessel wall or a dissection/intramural hematoma with less than 25% luminal stenosis
• Grade II: intraluminal thrombus or raised intimal flap is visualized, or dissection/intramural hematoma with 25% or more luminal narrowing
• Grade III: pseudoaneurysm
• Grade IV: vessel occlusion
• Grade V: vessel transection

Injury Patterns on Imaging That Should Raise a Suspicion for BCVI

• Interfacet subluxation/dislocation
• Fracture lines reaching an arterial structure
• C1-C3 fracture
• Basilar skull fracture with carotid canal involvement
• LeFort II or III fracture due to high-impact trauma

Reference:

1. Cothren CC and Moore EE. Blunt cerebrovascular injuries. Clinics 2005;60:489-496.

2. Delgado Almandoz JE, Schaefer PW, Kelly HR, et al. Multidetector CT angiography in the evaluation of acute blunt head and neck trauma: a proposed acute craniocervical trauma scoring system. Radiology 2010 (published online before print December 17, 2009).

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Zenker's Diverticulum

Lateral view of barium esophagogram shows a large diverticulum (arrow) arising in the midline from the posterior wall of the cervical esophagus (arrowheads).

Facts:

• Most common form of esophageal diverticulum
• Protrusion of mucosa posteriorly just proximal to cricopharyngeus muscle
• Believed to be due to oropharyngeal discoordination and upper esophageal sphinctor dysfunction
• Many patients are asymptomatic, but can present with dysphagia, regurgitation, throat discomfort
• Usually in 5th to 8th decades of life

Diagnosis and Treatment

• Barium esophagogram is an optimal method to demonstrate the diverticulum
• Intradiverticular filling defects usually represent food, but carcinoma is in the differential diagnosis.
• Large diverticulum can present on chest radiograph as a superior mediastinal mass
• Endoscopy not required, but if it is to be done it should be done with caution because of a risk of inadvertent perforation
• Treatment: diverticulectomy with or without cricopharyngeal myotoma, endoscopic stapling and division of common wall between cervical esophagus and diverticulum

Reference:

Grendell JH, et al. Current Diagnosis & Treatment in Gastroenterology, 2nd edition, 2003.

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Cerebral Toxoplasmosis

Axial T1W MR image post contrast shows a ring enhancing mass with "target appearance" in the left lentiform nucleus with marked surrounding edema, resulting in midline shift in an AIDS patient.

Facts: Cerebral Toxoplasmosis

• Infection with parasite Toxoplasma gondii
• Manifested clinically as acute, symptomatic infection or reactivation of latent infection in immunocompromised hosts. It can be seen as a self-limited infection in immunocompetent hosts, or congenital infection
• Etiology: ingestion of raw or undercooked meat, food or water containing tissue cysts or oocytes, transplacental, blood transfusion, solid organ transplantation
• In immunocompromised hosts, 50% presents with CNS disease (encephalitis, meningoencephalitis, seizures, mental status change, etc)

MR Imaging Appearance

• Ring enhancing lesions with marked surrounding edema
• Most common location = basal ganglia and gray-white matter junction of cerebral hemisphere
• Low signal on T1WI, intermediate/low/high signal on T2WI. May be hemorrhagic

Distinguishing Features from Lymphoma

• Toxoplasmosis and lymphoma are two most common enhancing intracranial masses in AIDS patients
• Toxoplasmosis tends to be multiple, and lesions are usually smaller than lymphoma
• On conventional MRI, they may look similar.
• On DWI/ADC, toxoplasmosis shows less restriction than in lymphoma.
• On MR spectroscopy, toxoplasmosis shows increased lactic and lipid peak (opposite in lymphoma)
• Toxoplasmosis is metabolically inactive on FDG-PET
• After 2-4 weeks of antitoxoplasma treatment, some healing should be seen on imaging of toxoplasmosis

Reference:

1. Lin EC, et al. Practical differential diagnosis for CT and MRI, 2008.
2. Domino FJ. 5-minute Clinical Consult 2007.
3. Castillo M. Neuroradiology companion: methods, guidelines, and imaging fundamentals, 3rd edition, 2006.

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