Steinstrasse

Plain abdominal radiograph shows multiple tiny stones (arrows) lined in the distal right ureter. The patient has had a recent extracorporeal lithotripsy.

Facts: Steinstrasse

• Steinstrasse is a German word, meaning "stone street" or "street of stones" first coined by the German pioneer of lithotripsy
• After lithotripsy, tiny stones line up in the ureter producing an appearance resembling a cobbled street on plain radiograph
• Steinstrasse can develop in 1 day to 3 months after stone fragmentation. It can develop after the first ESWL, or after several sessions.
• Incidence increases with stone size
• Most common location = distal ureter, followed up upper ureter
• It often passes by itself. 25% of patients, however, may experience obstruction at the ureteral level. If obstructed, percutaneous drainage or ureteral stent placement may be needed to manage ureteral obstruction until the fragments become dislodged and pass

Imaging

• Steinstrasse best detected with plain radiography
• Ultrasound is the most appropriate imaging mean to detect associated obstruction (hydronephrosis)

References:

1. Zagoria RJ. Genitourinary Radiology The Requisites, 2nd edition.

2. Sayed MA, El-Taher AM, Aboul-Ella HA, Shaker SE. Steinstrasse after extracorporeal shockwave lithotripsy: aetiology, prevention and management. BJUI 2001; 88:675-678.

ILO International Classification of Radiographs of Pneumoconioses (1)

PA chest radiograph of an 80-year-old man who was a miner decades ago shows multiple large opacities (arrows, large opacity = parenchymal opacity greater than 1 cm) and several tiny rounded opacities in the right lower and left mid/lower lung zones. With the history of exposure, adequate lag time and chest radiographic findings, the patient has findings consistent with coal worker pneumoconiosis.

Background: ILO

• ILO (International Labour Office, based in Geneva) produces guidelines on how to classify chest radiographs of persons with pneumoconioses
• The guidelines aim to standardize classification and facilitate comparisons of data internationally
• The last ILO revision of this classification was in 2000, it is specific for postero-anterior (PA) chest radiography only
• Because interpreting chest radiography for pneumoconiosis has shown an unacceptable variability, the US's National Institute for Occupational Safety and Health (NIOSH) began the "B" reader program in 1978. The "B" reader has to pass the certification examination organized by NIOSH.

Classification

• It is important to note that there is no pathognomonic imaging sign of pneumoconioses*. Diagnosis requires a combination (2 out of 3) of history of exposure, radiographic findings and pathological findings.
• Based on ILO classification, these informations on PA chest radiographs are required for reporting: technical quality of the film, parenchymal abnormalities, pleural abnormalities, symbols (findings other than that of pneumoconiosis) and comments.
• Parenchymal opacities are divided into small and large opacities. Small opacities can be rounded or irregular. These are further subdivided based on their size
• Pleural abnormalities can be focal plaque, costophrenic angle obliteration and diffuse pleural thickening

References:

1. ILO. Guidelines for the use of the ILO international classification of radiographs of pneumoconioses, revised edition 2000.

2. Wikipedia. "B" reader.

Thymic Involution

Axial CT image shows a normal-appearing thymus (arrows) with minimal soft tissue strands and mostly fat replacement of the gland. The gland has concaved margins.

Facts: Thymic Involution

• Thymus undergoes a gradual loss of cortical lymphotcytes and atrophy of epithelial cells and replacement by fat
• Believed to start at puberty but new data suggest that it actually starts from the first few years of life
• By the age of 40 to 45 years, more than 50% of thymus is replaced by adipose tissue
• Speed of involution increased with stress and other factors

Imaging

• Normal/involuted thymus: normal-shaped, flat or concaved margin, fat replacement increases with age and by the age of 40 the thymus is usually mostly fatty
• Thymic hyperplasia: convex margin, diffusely enlarged gland but normal shape, homogeneous attenuation similar to normal thymic tissue
• Thymoma: homogeneous, well-defined soft tissue mass, calcification, homogeneous enhancement

Our case-- thymic involution in a patient with myasthenia gravis, confirmed at surgery.

Reference:

1. Bogot NR, Quint LE. Imaging of thymic disorders. Cancer Imaging 2005; 5:139-149.

2. Greer JP, et al. Wintrobe's Clinical Hematology, 12th ed, 2009.

Dual Energy CT (2)

One Basic Reason for Use of Dual Energy CT: Material Differentiation

• By scanning a patient at two different energy spectra (on an example above, at 56 kV and 76 kV), the attenuation difference of the same material is different.
• Iodine has higher attenuation difference, compared to bone
• With this nature, scanning allows the computer to process bone and iodine content on images differently.

Routine Use of Dual-energy CT for Material Differentiation

• Creation of 3D vascular images ("Direct Angio") by easy removal of bony structures
• Plaque analysis (calcified vs. soft plaques)
• Lung perfusion
• Virtual unenhanced scan (creation of unenhanced scan from enhanced images by deleting iodine content from the images)
• Calculi characterization (uric acid vs. others)

Reference: Fletcher JG, Takahashi N, Hartman R, et al. Dual-energy and dual-source CT: is there a role in the abdomen and pelvis? Radiol Clin N Am 2009; 47:41-57.

Dual Energy CT (1)

A Growing Need for a New Kind of CT

• We need a better delineation of tissue components than just simple Hounsfield Units
• We need to scan faster to image the beating heart (decrease temporal resolution), esp. in cases with high heart rate, irregular heart rate

What Is Dual Energy CT?

• CT that uses the data of two different energy spectra to display anatomy and physiology (regular CT scans utilize one energy spectrum to create images)
• Dual-source CT describes CT that has two x-ray sources and two detectors mounted on a single gantry. The x-ray sources can produce two different energy spectra, or one spectrum. Dual-source CT can run in either dual- or single-energy mode

What Are Possible Hardware Configurations for Dual Energy CT?

• Two x-ray sources (dual-source CT)
• Rapid kV switching (single-source CT)
• Sandwich detector CT (two layers of detectors detecting x-rays at different energy spectra)

Image credit: medical.siemens.com

Reference:

Fletcher JG, Takahashi N, Hartman R, et al. Dual-energy and dual-source CT: is there a role in the abdomen and pelvis? Radiol Clin N Am 2009; 47:41-57.

Non Accidental Injury (NAI): Rib Fractures

Chest radiography of a 2-month-old baby shows multiple bilateral rib fractures of different ages. Left-sided rib fractures (arrowheads) appear to have callus formation, while the right sided fractures (arrows) do not. Note right pleural effusion/thickening laterally.

Facts: Fractures in Non-Accidental Injury

• Second most common findings of child abuse after dermatologic findings (bruises, contusions, burns)
• Can be found throughout the whole skeleton
• Likely multiple and in diverse stages of healing
• Long bone fractures are the most common, with some oblique or spiral components (due to torsion force)
• Classic metaphyseal lesions and location of fractures (ie, posterior rib fractures) are more suspicious than others

Rib Fractures in NAI

• Highly predictive of child abuse in the absence of accidental trauma or certain skeletal diseases (e.g., osteogenesis imperfecta), particularly in children less than 3 years old
• In children with rib fractures, the likelihood of NAI decreases with increasing age
• Multiple rib fractures are more likely to be seen in NAI compared to single fractures
• NAI is more likely in the presence of posterior rib fracture

Our case: non-accidental injury with multiple rib fractures in various stages of healing

Reference:

Medina LS, Applegate KE, Blackmore CC. Evidence-based Imaging in Pediatrics, 2010.

Hepatic Portal Venous Gas

An abdominal radiograph shows diffuse distention of the small bowel, relative paucity of colonic gas and hepatic portal venous gas at the corner of the image.

Facts:

• Rare condition occurring when intraluminal gas and/or gas produced by intestinal bacteria enters the portal venous circulation
• Initially thought to be an ominous sign with an estimated mortality of 75%-80% (more recently, mortality rates are 25%-35%)
• Main factors that allow development of portal venous gas: intestinal wall alteration, bowel distention, ischemia and sepsis

Etiology:

• Most common = intestinal ischemia with or without documented mesenteric thrombosis, necrotizing enterocolitis (NEC)
• Others = C.difficile colitis, peptic ulcer disease, gastric cancer, diverticulitis, abdominal trauma, intra-abdominal abscess, inflammatory bowel disease
• Iatrogenic = complications of endoscopic and radiological procedures

Imaging

• Diagnosis can be made by abdominal x-ray or ultrasound, but CT is the gold standard
• Branching lucencies extending to within 2 cm of the liver capsule (predominantly in the anterior-superior aspect of the left lobe)
• On US, it appears as echogenic particles flowing within the portal vein

Our case - patient with sepsis, severe ischemic/infarcted colitis and end-staged pancreatic cancer

Reference:

Alqahtani S, Coffin CS, Burak K, et al. Hepatic portal venous gas: a report of two cases and a review of the epidemiology, pathogenesis, diagnosis and approach to management. Can J Gastroenterol 2007; 21:309.

Infantile Hypertrophic Pyloric Stenosis

Longitudinal scan of the stomach (as labeled) shows a thickened (5 mm) wall of the pylorus and elongation of the pyloric canal. Labe

Facts: Pyloric Stenosis

• Most common surgical etiology for young infant presenting emergently with nonbillous vomiting
• Incidence: 2 to 5 of every 1,000 infants
• Multifactorial etiology: genetic, biochemical and environmental association
• Hypertrophy of the pyloric muscle, leading to gastric outlet obstruction (vomiting, dehydration, poor weight gain and hypochloremic metabolic alkalosis)
• Average age of presentation = 3 weeks old (rare before 1 week, or after 3-4 months)

Imaging

• US is now the imaging modality of choice for diagnosis of this condition. It can directly show the pyloric muscle
• Elongation of the pyloric canal
• Persistent spasm of pyloric canal with little, if any, fluid passing into the duodenum
• Persistent thickening of the circular muscle in the canal
• Pyloric muscle thickness (one wall) greater than 4 mm, or pyloric length greater than 16 mm (cutoff values vary depending on the sensitivity, specificity needed to make the diagnosis)
• Imaging differential diagnosis is pylorospasm. In pylorospasm, there is usually no thickening of the pylorus (can be up to 2-3 mm) and when visualized in real time the pylorus can open
• If ultrasound is negative, UGI series or nuclear medicine to evaluate for reflux may be necessary.

References:

1. Swischuk LE. Imaging of the newborn, infant and young child, 5th edition.

2. Hernanz-Schulman M, Berch BR, Neblett WW. Imaging of infantile hypertrophic pyloric stenosis (IHPS). Evidence-based Imaging in Pediatrics 2010; 5:447-457.

Peritoneal Sarcomatosis

Axial CT image of the abdomen shows soft-tissue implants and omental caking (arrows) with small ascites.

Peritoneal Surface Malignancy

• Carcinomatosis
• Lymphomatosis
• Sarcomatosis
• Mesothelioma
• Desmoplastic small round cell tumor

Peritoneal Sarcomatosis

• Disseminated intraperitoneal spread of sarcoma in the absence of significant extraabdominal sites of disease
• Rare disease.
• Most commonly due to GI stromal tumor (GIST), liposarcoma and leiomyosarcoma

Imaging Findings

• Similar to other peritoneal surface malignancy: soft-tissue implants along peritoneum and omentum
• Often hypervascular, and with variable amount of ascites (differ from other peritoneal surface tumors)

Our case: Sarcomatosis due to GIST. Ascites is believed to be due to treatment with imatinib

Reference:

Oei TN, Jagannathan JP, Ramaiya N, Ros PR. Peritoneal sarcomatosis versus peritoneal carcinomatosis: imaging findings at MDCT. AJR 2010; 195:W229-W235.

Image Wisely Campaign Launched

Image Wisely is a campaign to encourage imaging providers to

• Optimize imaging examinations to use only the radiation necessary to produce diagnostic quality images
• Convey messages to the imaging team to ensure that the facility optimizes its use of radiation when imaging patients
• Communicate optimal patient imaging strategies to referring physicians, and be available for consultation
• Routinely review imaging protocols to ensure the use of the least amount of radiation necessary to acquire a diagnostic quality image for each exam

Image Wisely is a collaborative initiative of the ACR, RSNA, ASRT and AAPM

Imagine Wisely campaign initially focuses on CT

Take the PLEDGE

More information: www.imagewisely.org

Leptomeningeal Enhancement

Sagittal T1W MR image post gadolinium shows extensive leptomeningeal enhancement (arrrows) along the cerebral sulci and cerebellar folia.

Differential Diagnosis:

• Leptomeningeal carcinomatosis: usually due to breast or lung metastasis, or primary CNS tumor. In children, the most common cause is medulloblastoma.
• Meningitis (bacterial, tuberculosis, coccidiodomycosis)
• Neurosarcoidosis: often involves the basal cistern

Facts: Leptomeningeal Carcinomatosis

• Hematogenous spread of malignancy (i.e., breast, lung) or direct extension by CNS tumor
• MRI with contrast administration best imaging tool to detect this abnormality, much more sensitive than CT
• Imaging Findings: smooth or nodular enhancement along the leptomeninges (extending into sulci), hyperintensity of sulci on FLAIR, hydrocephalus (which may be the only sign seen on CT)

Our case: Leptomeningeal carcinomatosis from esophageal cancer

References:

1. O'Brien WT. Top 3 differentials in radiology: a case review, 2009.

2. Lev MH, Heisserman J, Shetty S. Q&A color review of neuroimaging, 2008.

PET/CT and Breast Cancer

A coronal fused PET/CT image shows a large right breast mass with a ring-like FDG uptake (arrows).

Performance of PET in Breast Cancer

• Sensitivity 89%, specificity 80%
• Sensitivity highly depends on tumor size and grade. Unlikely to pick up tumor less than 0.5 cm, low chance of detecting tumor less than 1 cm
• PET is less sensitive but more specific than MRI for characterizing and detecting breast lesions

Pearls

• Any focal abnormal uptake of FDG should undergo further work-up (irrespective of its standardized uptake value). Note that breast cancer, in general, has lower metabolic activity than most other malignancies
• Incidentally detected breast abnormality on PET has high likelihood of malignancy
• Delayed/dual time point imaging increases sensitivity and accuracy of PET. Tumors accumulate FDG over time (normal breast tissue will not)

Differential Diagnosis of Focal FDG Uptake in the Breast

• Inflammatory: abscess, soft tissue inflammation, TB, sarcoidosis
• Trauma: post-biopsy, hematoma, seroma
• Benign neoplasms: ductal adenoma, fibrous dysplasia, fibroadenoma (rare)

Our case: spindle cell sarcoma of the breast.

Reference:

Lin EC, Alavi A. PET and PET/CT a clinical guide, 2nd edition, 2008.

National Lung Screening Trial (NLST) Initial Results

What is the NLST?

• A multicenter, randomized controlled trial (RCT) comparing low-dose helical CT with standard chest radiography in the screening of men and women at risk for lung cancer
• Sponsored by the National Cancer Institute
• Starting in August 2002, the trial enrolled more than 53,000 participants, current or former heavy smokers, ages 55 to 74, at 33 sites over a 20 month period
• Participants were randomly assigned to received 3 annual screens with either low-dose helical CT or standard chest radiograph. Endpoint = death from lung cancer
• "Heavy smoker" = at least 30 pack-years and were either current or former smokers without signs, symptoms or history of lung cancer
• "Low-dose CT" = helical CT with 120-140 kVp, 40-80 mAs, detector collimation equal to or less than 2.5 mm

Findings To Date

• 354 deaths from lung cancer among participants in the CT arm of the study, v.s. 442 lung cancer deaths in the chest radiograph arm. 20% reduction in lung cancer mortality among participants screened with low-dose helical CT.
• All-cause mortality (deaths due to any factor) was 7% lower in those screened with low-dose CT than in those with chest radiograph

Reference:

National Lung Screening Trial Research Team. The National Lung Screening Trial: overview and study design. Radiology 2010, published online before print on November 2, 2010.

Contrast Agents for Liver MRI

Gadolinium Chelates

• Most commonly used contrast agent
• Standard dose 0.1 mmol Gd/kg
• Bolus injection, dynamic study during arterial (20-30s) to detect hypervascular lesions, portovenous phase (60-90s) to detect hypovascular lesions, and equilibrium phase (between 2-10 min) to allow hemangiomas to fill-in and cholangiocarcinoma and inflammation to enhance

Liver-Specific Agents

• Teslascan (Mn-DPDP)
• MultiHance (gadobenate dimeglumine)
• Primovist (gadoxetic acid)
• SPIO (Endorem/Feridex)

Teslascan

• Hepatocyte-specific MR contrast agent
• Uptake into hepatocyte and partially excretes into the bile
• Drip infusion
• Increased T1 signal intensity
• Differentiate tumors of hepatocellular origin from nonhepatocellular origin

MultiHance

• 4% biliary excretion
• Can be bolus injected, images also taken 1-2 hours later for tumor detection (uptake into liver parenchyma to increase conspicuity of metastases)

Primovist

• Strong biliary excretion
• Can be bolus injected (doses 0.025 mmol/kg), images on delayed phase can be taken as early as 20 min

Superparamagnetic Iron Oxide Particles (SPIO)

• Accumulates within phagocytes in the liver (typically, there is absence of phagocytes in malignancy)
• On T2WI, normal tissues or lesions with phagocytes (ie, FNH, hepatocellular adenoma, well-differentiated HCC) appear dark
• Drip infusion
• Imaging done several hours after contrast administration

Above image: gadolinium metal, from www.emovendo.net

Reference:

Reimer P, Parizel PM, Meaney JFM, Stichnoth FA. Clinical MR Imaging, 2010

ACR Appropriateness Criteria on Colorectal Cancer Screening

Rationale for Colorectal Cancer Screening

• Colorectal cancer is the 2nd leading cause of cancer death in the USA
• Treatment for localized disease is associated with high survival rate
• Almost all colorectal cancers develop from benign adenomas and this process is slow (average of 10 years)

Current Screening Recommendation

• By WHO, US Agency for Health Care Policy and Research, US Preventive Service Task Force: 4 options = annual or biennial fecal occult blood test (FOBT), flexible sigmoidoscopy every 5 years, double-contrast barium enema (DCBE) every 5 years, and colonoscopy every 10 years
• By the American Cancer Society (jointly issued with the US Multi-Society Task Force on Colorectal Cancer and the ACR): adding CT colonography (CTC) every 5 years as an option

ACR Appropriateness Criteria Rating

• Average-risk individual, age greater than 50 years: CTC every 5 years after negative screen (rate 8), DCBE every 5 years after negative scan (rate 7)
• Average-risk individual after positive FOBT indicating relative elevation in risk: CTC every 5 years after negative scan (rate 8), DCBE every 5 years after negative scan (rate 7)
• Individual of any risks after incomplete colonoscopy: CTC (rate 9), DCBE (rate 7)
• High-risk individual with hereditary nonpolyposis colorectal cancer, ulcerative colitis or Crohn's colitis: colonoscopy preferred for ability to obtain biopsies to look for dysplasia

Reference:

Yee J, Rosen MP, Blake MA, et al. ACR appropriateness criteria on colorectal cancer screening. JACR 2010; 7:670-678.

Bennett's Fracture Dislocation

Facts:

• Most frequent fracture at the base of the first metacarpal
• Fracture dislocation resulting from axial loading to a partially flexed thumb (i.e., in a fist fight)
• Oblique fracture involves the carpometacarpal joint, resulting in a volar fragment attached to the trapezium and the distal metacarpal fragment displacing proximally/radially/dorsally by pull of abductor pollicis longus
• First CMC joint is a saddle-shaped bone, any minor malalignment results in substantial articular incongruity. This fracture dislocation frequently requires open reduction and fixation

Imaging

• Oblique fracture line with a triangular fragment at the first metacarpal base
• Proximal displacement of the metacarpal
• Important to note the size of the triangular volar fragment and the degree of displacement of the metacarpal fragment

References:

1. Robinson P. Essential Radiology for Sports Medicine, 2010.

2. Bennett's Fracture Dislocation. Wheeless' Textbook of Orthopedics

Abdominal Wall Fibromatosis

An axial T2W MR image of a 32-year-old woman shows a large well-defined heterogeneous mass in the anterior abdominal wall involving the right rectus abdominis. There are a few linear band (arrowheads) of low signal intensity with in the mass, which are seen in all pulse sequences.

Facts:

• Also known as abdominal desmoid
• Predilection to develop in women of child-bearing age (usually 20-30 years)
• Mass in abdominal wall typically develops following pregnancy
• Most common muscle involved: rectus abdominis, internal oblique
• Some of the masses have estrogen receptor
• May be seen as a manifestation of Gardner's syndrome
• Rx = surgical removal but recurrence rate 15-40%

Imaging Findings

• Heterogeneous intramuscular mass (well- or ill-defined)
• Non-enhancing bands of low signal within the mass on all pulse sequences (probable fibrosis)
• Linear fascial extension "fascial tail sign"

Reference:

Kransdorf MJ, Murphy MD. Imaging of soft tissue tumors, 2nd ed, 2006.

Jefferson Fracture

Axial CT image shows double fractures of the anterior arch and a single fracture of the posterior arch of atlas (C1) (arrows) with mild displacement.

Facts:

• C1 fracture believed to be due to compression causing fracture of the arch of atlas
• Often in combination with avulsion of the transverse ligament of the C1
• Simultaneous injuries to other C spine are common
• Three types: fracture of only anterior arch (type 1), fracture of only posterior arch (type 2), and fractures of both anterior and posterior arches (type 3)
• Type 3 fracture is unstable
• Fractures rare in children, but one needs to know that anterior synchondroses fuse at age 7, posterior at age 4.

Imaging Findings

• MDCT is imaging modality of choice, able to demonstrate fracture lines and degree of displacement
• On radiograph, displacement of the lateral masses may be seen on the odontoid view.
• Mimicker = failure of fusion of the vertebral arch, this pseudo-fracture lines are less sharply defined and/or sclerotic.

References:

1. Imhof H, et al. Spinal Imaging, 2008.

2. Atlas Frx / Jefferson Fracture in Wheeless' Textbook of Orthopedics

Caval Index

Longitudinal ultrasound images of the IVC in an asymptomatic patient demonstrate a normal inferior vena cava (IVC) during inspiration and expiration, in which the diameters (yellow double-headed arrows) do not change significantly. In this case, the diameters of the IVC were measured 2-3 cm below the right atrial border (yellow lines).

Facts: IVC Diameter

• IVC diameter changes following total body volume (increases with increasing total body volume, and decreases with volume depletion)
• IVC normally collapses with inspiration (decreased intra-thoracic pressure) and expands with expiration (but this collapsibility should not exceed 50%)

Caval Index

• Caval Index = 100 x (diam expiration - diam inspiration)/diam expiration
• Where to measure the IVC? Several ways exist, and none is perfect yet. Easy way is to measure with a longitudinal view of the IVC - find the junction of the atrium and IVC and measure the IVC at 2-3 cm below the junction
• Interpretation: studies vary greatly as to significance of values in different patient populations. In general, if caval index is greater than 50% it suggests low central venous pressure (CVP less than 8 mmHg) and high probability of fluid responsiveness

Reference:

Nagdev AD, Merchant RC, Tirado-Gonzalez A, et al. Emergency department bedside ultrasonographic measurement of the caval index for noninvasive determination of low central venous pressure. Ann Emerg Med 2010; 55:290-295.

Anastomotic Leakage After Bowel Surgery

Two coronal-reformatted CT images of the abdomen show a localized fluid collection (arrows) in the right abdomen, which contains air bubbles, fluid and oral contrast material, in a patient who had recent small bowel resection.

Facts: Anastomotic Disruption

• One of the most fearful complication after intestinal surgery
• Can present early or late. The latter can be difficult to distinguish from other postoperative infectious complications
• In a prospective study of 1223 patients who had intestinal resection and anastomosis without fecal diversion, the incidence of anastomotic leak was 2.7%.
• Location of anastomosis is among the most significant factors associated with leak. Those in the pelvis have a higher rates of leakage
• Clinical presentation: pain, tachycardia, high fevers, rigid abdomen accompanied by hemodynamic instability. Typically, leak is discovered 5-7 days after surgery.

Imaging

• CT is helpful to determine whether there is an associated abscess. Gastrograffin enema may aid the diagnosis of leak.
• Visualization of administered contrast (on CT or enema) is the direct sign of anastomotic leak. Neither CT nor enema is perfect to show the leak, unfortunately.
• Many CT features of postoperative bowel overlap between patients with and without a leak. The most specific feature of a leak is the presence of extraluminal contrast.

Reference:

1. Hyman N, Manchester TL, Osler T, Burns B, Cataldo PA. Anastomotic leaks after intestinal anastomosis. Ann Surg 2007; 245:254-258.

2. Mulholland MW, Doherty GM. Complications in Surgery, 2005.

Bronchial Atresia

Chest radiograph shows a well circumscribed tubular mass in the left upper lobe with distal localized emphysema in a 41-year-old asymptomatic patient.

Coronal-reformatted CT image demonstrate the mass to be a dilated segment of left upper lobe bronchus filled with mucus. Localized emphysema in the left upper lobe is confirmed.

Facts: Bronchial Atresia

• Absence of communication between a segment or subsegmental bronchus and the central airways.
• Most cases are found incidentally on imaging (asymptomatic)
• Most common location = apical posterior segment of the left upper lobe.

Imaging Features

• Mucus plug surrounded by hyperlucent lung.
• Absence of enhancement (enhanced CT and/or endoscopic examination may be required to exclude an endoluminal obstructing lesion)
• Absence of communication with pulmonary vessels

Differential Diagnosis

• Mucous plug distal to bronchial obstruction (endobronchial neoplasm, for example)
• Focal bronchiectasis with mucus plugging
• Pulmonary sequestration
• Allergic bronchopulmonary aspergillosis
• Vascular malformation

Reference:

Parker MS, Rosado de Christenson ML, Abbott GF. Teaching Atlas of Chest Imaging, 2005.

Hyperechoic Renal Mass

A longitudinal sonographic view of the right kidney shows a hyperechoic mass in the upper pole of the kidney (arrow) in this asymptomatic woman.

Differential Diagnosis: Hyperechoic Renal Mass

• Angiomyolipoma (AML)
• Renal cell carcinoma (RCC) (esp. papillary type)

Facts

• Most common cause of hyperechoic renal mass = AML
• 20% - 50% of small RCCs (less than 3 cm) are hyperechoic
• Hence, on the basis of echotexture along, ultrasound cannot reliably differentiate an AML from renal cell carcinoma
• US features suggestive of RCC: 1) anechoic rim, 2) cystic area within the mass (intratumoral cyst)
• CT or MRI is warranted to further evaluate a hyperechoic renal mass

Our case: subsequent CT shows fat within the mass, consistent with AML.

References:

1. Yamashita Y, Ueno S, Makita O, et al. Hyperechoic renal tumors: anechoic rim and intratumoral cysts in US differentiattion of renal cell carcinoma from angiomyolipoma. Radiology 1993; 188:179-182.

2. Vikram R, Ng CS, Tamboli P, et al. Papillary renal cell carcinoma: radiologic-pathologic correlation and spectrum of disease. RadioGraphics 2009; 29:741-754.

Centrilobular Nodules with Tree-in-Bud Pattern

Axial CT image shows multiple micronodules in the left lung. Most are not subpleural. They are non-uniform and there are some that have V- or Y shape.

Facts: Centrilobular Nodules

• Nodules limited to centrilobular structure (central core), sparing pleural surfaces
• Most peripheral nodules are centered 5-10 mm from fissures or pleural surface
• Evenly distribulted
• Common cause: without tree-in-bud - infection, inflammation, hypersensitivity, vascular disease
• Common cause: with tree-in-bud - infection

Random Nodules

Axial CT image shows multiple micronodules throughout both lungs. Some of the nodules are subpleural, and they are uniform in distribution.

Facts: Random Nodules

• Nodules are randomly, and evenly distributed relative to structures of the lung and lobule
• They tend to be symmetric
• Often involve pleural surfaces (with subpleural nodules)
• Common cause: hematogenous metastasis, miliary infection (TB, fungus)

Our case: hematogenous metastasis.

Perilymphatic Nodules

Axial CT image shows multiple micronodules and small nodules throughout both lungs. Note that there are subpleural nodules (best seen along the fissures), and they arrange in a non-uniform fashion.

Facts: Perilymphatic Nodules

• Located along pulmonary lymphatics (wall and central core structure of the secondary pulmonary lobule)
• Most notable along the fissures (subpleural region)
• Can be peribronchovascular in distribution
• Common causes: sarcoidosis and lymphangitic carcinomatosis
• Less common cause: silicosis, coal-worker pneumoconiosis

Our case: sarcoidosis

Imaging Approach to Pulmonary Micronodules and Small Nodules

Definition:

• Micronodule = nodules of less than 3 mm
• Small nodules = nodules of less than 2 cm

Steps for Decision Making

1. Decide whether there are multiple micronodules or small nodules
2. Where are the nodules? Are they subpleural?
3. If they are subpleural, are they uniformly distributed throughout the lungs or secondary pulmonary lobules?
4. If they are not subpleural, they are likely centrilobular. The next question is whether there is tree-in-bud pattern or not.
5. Look for associated findings as a clue to limit differential diagnoses

Osteochondroma: Imaging Features of Malignant Degeneration

A radiograph of the right shoulder shows a large pedunculated lytic mass (long arrows) in the proximal metadiaphysis of the humerus, with continuous cortex and marrow cavity. Note areas of disrupted cortex (short arrows).

Facts: Osteochondroma

• Benign bone tumor usually recognized on radiography as a lesion perpendicular to the parent bone, with a continuous cortex and marrow cavity.
• Pain from an osteochondroma is commonly caused by fracture, burisitis or compression of surrounding structures. Malignant degeneration of a single osteochondroma is rare.

Facts: Malignant Transformation of Osteochondroma

• 1% of solitary osteochondroma, 20% of hereditary form
• If transformed, most are to chondrosarcoma
• Average age of malignant transformation = 30 years

Imaging Features Suggesting Malignant Transformation

• Clinical: 30 years old, location at pelvis and shoulder, increasing pain and mass at site of known osteochondroma
• Imaging: thick/irregular calcified cap, bone destruction, soft tissue mass, altered appearance on sequential studies

Our case: pedunculated osteochondroma in a middle-aged patient presenting with increasing pain, suspicious for malignant transformation. Awaiting pathologic results.

References:

1. Yochum TR, Rowe LJ. Essentials of Skeletal Radiology, 3rd ed. 2005

2. Tehranzadeh J. Musculoskeletal Imaging Cases, 2009

Adrenal Myelolipoma

Axial CT image shows a large right adrenal mass (arrows) which contains several foci of macroscopic fat (arrowhead).

Facts:

• Benign biochemically inactive tumor of the adrenal gland thought to be due to metaplastic change of reticuloendothelial system of capillaries
• Contains mature adipose tissue and normal hematopoietic cells
• Most commonly occurs in adrenal glands, but can be seen in other tissues (ie, retroperitoneum presacral region)
• Most are asymptomatic (found incidentally on imaging). If large, or symptomatic, it can be treated with surgical excision and/or adrenalectomy
• Rare, less than 0.2% in population

Imaging Features

• Adrenal mass containing fat attenuation, virtually diagnostic of adrenal myelolipoma (bright on ultrasound, fat on CT and MR)
• May contain calcification

Reference:

Adrenal myeloliopma at URL: http://path.upmc.edu/cases/case165/dx.html

Perinephric Stranding with Dilated Ureter

Axial CT images show mild enlargement of the right kidney, perinephric fat stranding and dilated right renal pelvis, right ureter to the right ureterovesical junction (UVJ).

Differential Diagnosis

• UVJ obstruction (tumor, stricture, nonopaque calculus)
• Recently passed ureteric calculus
• Renal trauma
• Acute pyelonephritis (usually no dilatation of collecting system)
• Renal vein thrombosis (usually no dilatation of collecting system)

Our case -- passed ureteric stone, seen at the base of the urinary bladder. Make sure to scan the entire length of the urethra, or ask the patient if there has been any sudden relief of symptoms.

Radiologists Need to See Patients

The followings are summarized from the article "The Constantly Changing Field of Radiology: Maintaining Professionalism in an Era of Electronic Communication" by Alexander R. Margulis, MD.

PACS: Disruptive Innovation

• Good: streamlining imaging process, allowing almost instant availability of images and of reports, eliminating film loss, speeding up patient care
• Bad: reducing personal contact between radiologists and referring physicians, and radiologists and patients, making possible image interpretation from remote sites without any personal contact with treating physicians and little or no clinical information

The Problem

• "These developments threaten to change radiology into a commodity and radiologists, in patients' eyes, into nonparticipants in their care."
• Radiologists are not known by (or exist to) patients
• The notion endangers the role of radiologist as a physician, and the existence of radiology specialty

Suggestions

• See patients. "Radiologists need to see patients before imaging examinations to make it clear that they are supervising and will later interpret the examinations."
• "If possible and appropriate, they should even give patients preliminary readings."
• This can start in teaching centers, where faculty, fellows and/or residents take turns as "officer of the day" greet patients, determine examination protocols, and participate when the cases are reviewed

At the end of the article, Dr. Margulis predicts that "the radiologists of tomorrow will return to playing their full role as physicians. They will not only sit in front of PACS monitors interpreting images, but will see patients and remain continuously in touch with their clinical colleagues."

Reference

Margulis AR. The constantly changing field of radiology: maintaining professionalism in an era of electronic communication. Radiology 2010; 257:22-23.

Parotitis

Axial CT image of the neck shows an enlarged left parotid gland (star) with blurry margins, nearby fat stranding. There is no internal low attenuation areas.

Facts:

• Infection of the parotid gland caused by bacterial, viral pathogen or is calculus-induced.
• Acute suppurative parotitis is usually unilateral
• Bacterial parotitis is usually caused by S aureus (greater than 50% of cases) and anaerobic bacteria
• May be complicated by abscess formation, thrombophlebitis, cranial nerve VII dysfunction
• Treatment: hydration, antibiotics, possible drainage if an abscess develops

CT Findings:

• Diffuse enlargement and enhancement of the parotid gland
• Blurred margins of the gland
• Internal low attenuation indicative of abscess formation

Reference:

Capps EF, Kinsella JJ, Gupta M, et al. Emergency imaging assessment of acute, nontraumatic conditions of the head and neck. Radiographics 2010; 30:1335-1352.

Lung Cancer: Chest Wall and Pleural Invasion

Axial CT image shows a large left upper lobe mass (star) with adjacent rib destruction (arrow) in a patient with T3 lung cancer.

Facts

• Contiguity of the neoplasm with pleural surface is not equivalent to invasion
• Major CT finding of pleural and chest wall invasion is bone destruction or a chest wall mass
• Other CT criteria: extent of contact of the mass and its angle with the pleura, presence of fat plane between the tumor and chest wall
• Chest wall and pleural invasion is considered T3 disease

Reference:

UyBico SJ, Wu CC, Suh RD, et al. Lung cancer staging essentials: the new TNM staging system and potential imaging pitfalls. Radiographics 2010; 30:1163-1183.

Partial Anomalous Pulmonary Venous Return (PAPVR)

Figures 1-3: Contiguous axial contrast-enhanced CT images show an abnormal left upper lobe pulmonary vein draining into the left vertical vein (arrows) that subsequently empties into the left brachiocephalic vein (BCV).

Facts: PAPVR

• Common venous anomalies of the thorax (0.5% prevalence in general population)
• Pulmonary-to-systemic, left-to-right shunt
• Anomalous pulmonary vein drains into the right sided circulation (SVC, azygos, brachiocephalic, IVC, coronary sinus, right atrium)
• Symptomatic if large or associated with other cardiopulmonary anomalies
• Most common form = right upper lobe vein draining into SVC, left upper lobe vein draining into left vertical vein
• Surgical correction recommended if pulmonary-to-systemic flow ratio greater than 1.5 to avoid progression to pulmonary hypertension and right ventricular failure

Reference

Martinez-Jimenez S, Heyneman LE, McAdams HP, et al. Nonsurgical extracardiac vascular shunts in the thorax: clinical and imaging characteristics. Radiographics 2010; 30,e41-.

Post-Endovascular Rx of Thoracic Aortic Injury

An axial CT image shows a normal appearance of an endovascular stent in the descending thoracic aorta in a patient who suffered thoracic aortic injury.

Facts: Treatment and Follow Up of Thoracic Aortic Injury (TAI)

• Open thoracotomy with direct repair of TAI is a traditional means for Rx of TAI. However, endovascular Rx has become more common given its less invasiveness and many reports demonstrating smaller mortality rate
• Endovascular Rx is used to exclude pseudoaneurysm from systemic arterial pressure
• Patients who had endovascular Rx for TAI will require regular imaging follow-ups. Most institutions perform CT angiography at the time of discharge, at 1-3 months, at 6 months, at 1 year and then annually.
• Purpose of follow up CT angiography after endovascular Rx is to 1) assess quality of pseudoaneurysm exclusion, 2) detect related complications
• Complications potentially detectable on imaging (rare): endoleak, graft collapse, branch vessel complications (stroke, arm ischemia), stent migration, etc

Normal Imaging Findings

• Endograft = metallic framework with a zigzag appearance (covered by polytetrafluorethylene or polyester material)
• Must compare the CT angiography with prior angiography (post-stent) or prior post-operative CT
• Check for position of endograft (should be unchanged), apposition/seal with the aortic wall (should be completely sealed), patent endograft lumen (without narrowing or sharp angulation), total exclusion of aortic injury

Reference

Morgan TA, Steenburg SD, Siegel EL, Mirvis SE. Acute traumatic aortic injuries: posttherapy multidetector CT findings. Radiographics 2010; 30:851-867

Painful Bipartite Patella

Coronal T1W MR image of the right knee in a patient with anterior knee pain shows a bipartite patella. Note cartilage lining of the synchondrosis (red arrowheads).

Axial fat-suppressed T2W image shows bone marrow edema within the bipartite segment (arrow) with small joint fluid (yellow arrowhead).

Facts: Bipartite Patella

• Developmental variation of an unfused accessory ossification center
• Typical location at superolateral aspect of the patella, at insertion of vastus lateralis
• This ossification center begins to ossify at age 3-5, and fuse by age 12; if unfused - it is called bipartite patella
• Almost always bilateral, male much more common than female
• Prevalence about 2% of population
• Most discovered incidentally

Painful Bipartite Patella

• Unrecognized cause of anterior knee pain
• It is postulated that synchondrosis of bipartite patella becomes disrupted due to overuse or acute injury, allowing abnormal motion, friction and subsequent edema
• "Rather than discounting it as a normal variant, a detailed search should be undertaken for signs of edema both within the bipartite fragment and along the margins of the synchondrosis or pseudarthrosis, especially in patients presenting with anterior knee pain." -- quoted from Kavanagh EC, et al (paper referenced below)
• In one study of 53 patients with bipartite patella, almost half of them had findings consistent with marrow edema in the bipartite segment (which probably responsible for pain)

Reference

Kavanagh EC, et al. MRI findings in bipartite patella. Skeletal Radiol 2007;36:209-214.

Krukenberg Metastasis

Fig. 1: Axial CT image shows circumferential thickening of the gastric antrum.
Fig. 2: Axial CT image of the pelvis shows bilateral, predominantly solid, less than 10 cm, ovarian masses (stars). There is small ascites.

Facts: Krukenberg Metastasis

• Originally described by Dr. Krukenberg in reference to a rare form of malignant ovarian signet-ring tumor that distinction between primary and metastatic signet-ring tumors from the stomach was difficult
• Differentiation between Krukenberg metastatic signet-ring ovarian tumors vs. primary has implication for management and prognosis. Primary signet-ring ovarian tumors can be treated with resection if found early. Krukenberg tumors are indicative of late-stage disease
• Primarily from gastrointestinal adenocarcinoma (stomach, colon)

Imaging Findings

• Distinction between primary and metastatic ovarian tumors can be difficult on imaging. There is no reliable, consistent feature that is accurate enough to differentiate the two
• Radiologist may suggest possible Krukenberg metastasis if ovarian lesions are solid, less than 10 cm, involve both ovaries and present late.

Our case: Signet-ring adenocarcinoma of the stomach with bilateral ovarian metastases (Krukenberg metastasis)

References

1. Brown DL, Zou KH, Tempany CMC, et al. Primary versus secondary ovarian malignancy: imaging findings of adnexal masses in the radiology diagnostic oncology group study. Radiology 2001;219:213-218.

2. Zagoria RJ, Mayo-Smith WW, Fielding JR. Genitourinary imaging case review series, 2nd edition, 2008.

Mesoblastic Nephroma

A 10-day-old infant presented with hematuria. Multiple CT images show a large heterogeneous mass originating from the lower pole of the right kidney (cortical beak sign noted, pink arrow). The mass extends into the right renal pelvis and causes mild hydronephrosis.

Facts

• Synonyms: mesoblastic nephroma, leiomyomatous hamartoma, mesenchymal hamartoma, renal fibroma, Bolande tumor.
• It is the most common solid renal tumor in the newborn.
• This tumor is believed to arise from metanephric blastema or secondary mesenchyme.
• Patients usually presents with a palpable flank mass.
• Prognosis is excellent with nephrectomy and wide resection

Imaging Findings

• Large solid intrarenal mass, which typically involves or extends to the renal sinus.
• Hemorrhage, necrosis or cystic portions are uncommon.

Table: Age Presentation of Renal Tumors in Children

References

1. Donnelly LF. Diagnostic imaging pediatrics. Amirsys. Manitoba. 2005.

2. Lowe LH, Isuani BH, Heller RM, Stein SM, Johnson JE, Navarro OM, Hernanz-Schulman M. Pediatric renal masses: Wilms tumor and beyond. Pediatric renal masses: Wilms tumor and beyond. Radiographics. 2000; 20:1585-603.