December 30, 2008

Lingual Thyroid

Fig: Arrows point to the ectopic thyroid tissue at the tongue base, above the epiglottis (arrowhead) on this sagittal-reformatted CT image.


  • Thyroid tissue at the tongue base
  • Most common location for ectopic thyroid
  • Only site of active functioning thyroid tissue in 70% of cases
  • Uncommon clinical problem but seen in approximately 10% of autopsy cases
  • Become symptomatic at any age but usually during puberty, menses or pregnancy (increased metabolic demand)
  • Malignant transformation very rare, incidence less than 1%. Suspected when a known patient with lingual thyroid develops new symptoms or clinical evidence of enlargement
CT Findings
  • Characteristic location = in midline, at the tongue base (other types of ectopic thyroid can be anywhere from tongue base to anterior to the heart)
  • Characteristic attenuation and enhancement = similar to thyroid tissue (very enhanced, may contain calcifications or low attenuation areas)
  • Absent thyroid tissue in the expected normal location
Kennedy TL, et al. Lingual thyroid carcinoma with nodal metastasis. Laryngoscope 2007 (November)

December 27, 2008

Pulmonary Laceration

Fig. Axial CT image shows a 'hole' in the lung with air-fluid level (arrow), surrounded by ground glass opacity (arrowheads) in a trauma patient. Findings represent pulmonary laceration surrounded by contusion.


  • Laceration in the lung tissue results in a 'hole' instead of a linear tear because of elastic recoil of the lungs stretching the tear.
  • Most lacerations in an acute phase contain blood and air (hematopneumatocele).
  • Most lacerations are surrounded by contusion.
  • Four types of lung laceration include compression rupture (central location), compression shear (paravertebral), rib penetration tear (near rib fracture) and tear associated with underlying lung fibrosis.
  • Most common type of pulmonary laceration is a compression rupture tear.
This patient had a compression-shear pulmonary laceration.

Kaewlai et al. MDCT of blunt thoracic trauma. RadioGraphics 2008 (October)

December 24, 2008

Tsunami Sinusitis

Fig.1: Water's view of the skull shows air-fluid levels (arrows) in bilateral maxillary sinuses in a victim of tsunami trauma.
Fig.2: Direct coronal CT image performed 1 month after Fig.1 shows resolution of left maxillary sinusitis but persistent right sided sinusitis. There is a conglomerate mass of high attenuation (arrowheads) with air in the right maxillary sinus.


  • Sinusitis may occur in patients with tsunami trauma
  • Found in 10% of all cases in one series
  • Usually polymicrobial
  • Sand may be present in the sinus, which is hyperattenuating on CT (likely related to sand composition) and located in the dependent portion of the sinuses. Sand and seawater may enter sinuses through ostia and retain within.
Today, 4 years ago, was the day of one of the world's worst natural disasters -- tsunami. More than 200 000 people were killed and missing. More than a million people were displaced.

1. Kaewlai, et al. Radiologic findings in tsunami trauma: experience with 225 patients injured in the 2004 tsunami. Emerg Radiol 2007;14:395
2. Limchawalit, et al. Images in clinical medicine. Tsunami sinusitis. N Engl J Med 2005

December 21, 2008

Imaging of Facial Trauma Part 3

December 18, 2008

Distal Intestinal Obstruction Syndrome (DIOS)

Fig.1: Axial CT without IV contrast shows absence of pancreas (star), which is a feature of cystic fibrosis. The colon (arrow) is filled with fecal materials.
Fig.2: CT image at the lower cut reveals 'fecalization' of small bowel, and collapsed descending colon. This patient has known cystic fibrosis status post recent lung transplantation. He developed intermittent abdominal distension and diarrhea. He did not have peritoneal irritation sign on physical exam.


  • DIOS is short for 'distal intestinal obstruction syndrome'. Also known as meconium ileus equivalent (MIE)
  • Unique to cystic fibrosis (CF)
  • 10% - 15% of patients with CF
  • Caused by accumulation of mucous and feces in small bowel and ascending colon
  • Common in older child or young adult
  • Predisposing factors: after transplantation (probably due to dehydration and medications), dehydration, pancreatic enzyme supplement cessation, unknown
Radiographic Features
  • Fecal materials in terminal ileum, cecum and ascending colon
  • Thickened mucosal fold of bowel
1. Moody AR, et al. CT monitoring of therapy for meconium ileus. J Comput Assist Tomogr 1990 (November/December)
2. Agrons GA, et al. Gastrointestinal manifestations of cystic fibrosis: radiologic-pathologic correlation. Radiographics 1996 (July)

December 16, 2008

Hounsfield Unit

What is Hounsfield Unit?

  • CT number
  • Unit used to measure attenuation of tissue on CT
  • A representative of relative attenuation coefficient of tissues, using water as a reference
  • Water is defined as zero Hounsfield unit
  • Matters with higher physical density (g/cm3), higher electron density (e/cm3) than water will have higher HU; and vice versa
  • HU depends on kV peak (used in CT image acquisition) and filtration technique (used in CT image reconstruction)
  • HU values on an image are only approximate (because it will change if kV changes)
Who is Hounsfield?
  • Godfrey Hounsfield is a British electrical engineer
  • He shared a 1979 Nobel Prize in physiology or medicine with Allan Cormack for the development of computed tomography (CT)
Huda W, et al. Review of radiology physics. 2003

December 15, 2008

ARRS 2008 Registration Opens

Registration for the annual meeting of the American Roentgen Ray Society (ARRS) opens today (December 15, 2008)!

A brief history of the ARRS as quoted on its website:
"The American Roentgen Ray Society, founded in 1900, is the first and oldest radiology society in the United States. The society has been a forum for progress in radiology since shortly after the discovery of the X-ray and is dedicated to the goal of the advancement of medicine through the science of radiology and its allied sciences. The goal of the ARRS is maintained through an annual scientific and educational meeting and through publication of the American Journal of Roentgenology."

December 12, 2008

Meniscal Bucket-Handle Tear

Fig: Coronal T2 image (with fat suppression) shows a displaced fragment (arrow) of medial meniscus into the intercondylar notch of the knee. Note intact ACL (arrowheads).

What is 'Bucket-Handle' Tear?

  • Longitudinal, peripheral tear of the meniscus with displacement of fragment toward the intercondylar notch of the knee
  • Leads to locked knee and surgery (debridement or repair) is necessary
  • If occurs at the outer 1/3 (white/white zone), only debridement; if middle and peripheral third (white/red, red/red zones) require repair
How to Diagnose?
  • Using MRI with coronal and sagittal planes
  • Look for extra-structure in the intercondylar notch on coronal image!
  • Double PCL (posterior cruciate ligament) on sagittal image
  • Donor meniscus (usually medial) look smaller than usual (key to differentiate bucket-handle tear from normal oblique intermeniscal ligament)
Stoller DW, et al. Diagnostic imaging: orthopedics. 2004

December 10, 2008

Crazy-Paving Pattern

Fig. Axial CT of the chest shows diffuse bilateral ground-glass opacities superimposed by interlobular septal thickening (arrowheads) and intralobular lines (blue arrows). Note a left chest tube used to treat left pneumothorax, which brought this patient to the hospital.

What is "Crazy-Paving" Pattern?
  • Ground-glass opacity superimposed with interlobular septal thickening and intralobular lines
  • Can be scattered or diffuse
  • Can be caused by alveolar filling process, interstitial process, or a combination

What Can Cause "Crazy-Paving" Pattern?
  • CLASSIC: Pulmonary alveolar proteinosis 
  • COMMON: Pneumocystis jirovecii pneumonia (PCP), pulmonary edema (ARDS), pulmonary hemorrhage
  • NOT COMMON: Bronchioloalveolar carcinoma, alveolar sarcoidosis, nonspecific interstitial pneumonitis (NSIP), Cryptogenic organizing pneumonia (COP), lipoid pneumonia
Our case is a patient with biopsy proven pulmonary alveolar proteinosis.

1. Rossi SE, et al. "Crazy-Paving" Pattern at Thin-Section CT of the Lungs: Radiologic-Pathologic Overview. Radiographics 2003;23:1509.
2. Johkoh T, et al. Crazy-paving Appearance at Thin-Section CT: Spectrum of Disease and Pathologic Findings. Radiology 1999;211:155.

December 9, 2008

Who is Aunt Minnie?

Beside 'Aunt Minnie' as a popular radiology website, do you know who really is Aunt Minnie?

A few communications in Radiology and AJR provided the answer.

Aunt Minnie

  • Constellation of observations virtually pathognomonic of an entity (usually of an unusual or unexpected disease)
  • Subliminal or subconscious pattern recognition of disease (similar to recognizing Aunt Minnie among a large group of similar women)
  • The term attributed to two figures in radiology history: Ed Neuhauser (previous Chief at Children Hospital Boston) and Ben Felson (neither had an aunt named Minnie)
Hall, et al. Gestalt: Radiology's Aunt Minnie. AJR 2008 (October)

Image source:

December 6, 2008

Traumatic Aortic Injury (TAI)

Fig.1: Portable chest radiograph shows widening of the superior mediastinum (two-sided arrow), deviation of the NG tube (arrowheads) and trachea to the right.
Fig.2: Axial CT with IV contrast shows a large periaortic hematoma (stars) displacing the NG tube (arrowhead) to the right.
Fig.3: Axial CT at the level below the arch demonstrates a pseudoaneurysm (red arrow) anterior to the true lumen (red arrowhead). Hematoma (stars) and NG tube (yellow arrowhead)

Radiographic Findings

  • Widening of superior mediastinum (subjective 'eyeball' estimation)
  • Blurring of aortic contour
  • Deviation of nasogastric tube to the right
  • Normal - not common but x-ray can be normal if there is no or minimal periaortic hematoma (Normal chest radiograph does not exclude TAI in a trauma patient with suspicious mechanism)

CT Findings
  • Direct signs: Pseudoaneurysm, intimal flap, irregularity of aortic wall, pseudocoarctation, thrombus with in the wall
  • Indirect sign: Periaortic hematoma (not isolated anterior mediastinal hematoma)
Do We Need Aortography?
  • Studies of MDCT (16- and 64-MDCT) showed accuracy of near 100% using surgery or follow-up CT as standard references
  • When a direct sign is present, TAI can be diagnosed confidently without aortography
  • Aortography can be reserved for equivocal cases, evaluation of aortic branch vessels and endovascular therapy
1. Kaewlai, et al. MDCT of blunt thoracic trauma. Radiographics 2008 (October)
2. Steenburg, et al. Acute traumatic thoracic aortic injuries: experience with 64-MDCT. AJR 2008 (November)

December 3, 2008

Chest Wall Fat Mimicking Tumor

Fig.1: Chest radiograph shows abnormal opacity in the periphery of the right upper lobe, which is broad-based to the pleura and partially well defined on the side opposing the lung. Based on this appearance, pleural location is likely. Differential diagnosis is broad and may include pleural effusion (loculated), thickening, plaque, or mass.
Fig.2: Axial CT shows an extrapleural fat (arrowheads) deep to the costal margin.


  • Extrapleural costal fat can be mistaken for pleural lesions including plaque and tumor
  • Thickening of the extrapleural costal fat can be associated with lung scarring
  • CT is an easy tool to use differentiate between fat and soft tissue mass
  • Fat can be drawn into fissures (as seen on Fig.1). It looks as if it is in the pleural space, but it is covered by parietal pleura - therefore is extrapleural
Fisher ER, et al. Extrapleural fat collections: pseudotumors and other confusing manifestations. AJR 1993 (July)

November 29, 2008

Avulsion Fracture of Base of 5th Metatarsal & Os Peroneum

Figure: Oblique radiograph of the foot shows a transverse avulsion fracture (arrow) of the 5th metatarsal bone with displacement and extension into the cuboid-metatarsal joint. Note a nearby 'os peroneum' (arrowhead).

Avulsion Fracture of Base of 5th Metatarsal

  • Most common fracture at this location
  • Usually extra-articular
  • Due to sudden contraction of peroneus brevis muscle or lateral band of plantar fascia during inversion
  • Treated conservatively, unless there is displacement or large fragment involving cuboid-metatarsal joint
  • Other two types of fractures (at proximal 5th metatarsal) are Jones (AKA fracture at metadiaphyseal junction within 1.5 cm distal to tuberosity of 5th metatarsal), and stress fracture.
Key Things to Include in Report
  1. Location (tip, tuberosity, metadiaphyseal junction, diaphysis)(to distinguish between different types of proximal 5th metatarsal fractures)
  2. Joint involvement (cuboid-metatarsal, 4th-5th intermetatarsal)
  3. Displacement
Os Peroneum = ossicle in peroneus longus, seen at the tip of 5th metatarsal base, common

Nunley JA. Fractures of the base of the fifth metatarsal. Orthopedic Clinics of North America (January 2001)

November 26, 2008

A child with scalp mass

Sagittal T1W image demonstrates a parieto-occipital scalp mass with a band of soft tissue anterosuperior to the mass running through a small skull defect which appears to connect to the intracranial compartment.

Sagittal T2W image demonstrates a persistent embryonic falcine sinus/vertically oriented straight sinus and prominence of the superior cerebellar cistern.

The mass shows a thin peripheral enhancement as well as enhancement of the soft tissue band.

Atretic (en)cephalocele
- A midline mass typically parietal in location, occasionally seen in occipital region.
- Contain meninges and neural rests. A fibrous stalk connects the lesion to the dura.
- A vertically positioned straight sinus/persistent embryonic falcine sinus commonly
associated with these malformations. Anomalies of the tentorial incisura and superior sagittal
sinus have also been reported.
- Associated intracranial anomalies are variable, and some children may have normal clinical outcomes with no associated intracranial anomalies

AJNR Am J Neuroradiol 19:791–795, April 1998
RadioGraphics 2004; 24:1655–1674

November 24, 2008

Nipple Shadows?

Fig.1: Chest radiograph shows a suspicious nodule in the right lower lung. Fig.2: Repeat exam with nipple markers (arrowheads) confirmed the nodule to be a nipple shadow. Note that the left nipple shadow is visualized on this exam but not on the previous one performed on the same date.

Classic Nipple Shadows

  • Bilateral symmetric
  • Fuzzy margins with radiolucent halo, or sharp lateral but poorly defined medial margins
  • Characteristic location (fifth or sixth anterior ribs or near bottom of breast shadow)
  • Not present on a very recent film
  • Could be identified on lateral film
  • Nipple shadows can be seen in up to 10% of chest radiographs
  • Although most of these can be resolved as 'classic nipple shadows' and no further imaging is needed, about 1.4% need repeat examination
  • Repeat examinations are related to increased cost, time and burdensome to patients
Nipple Markers
  • A 1.5 mm lead shot that, given its size, should not obscure a true pulmonary nodule
  • Very helpful to determine whether the suspicious nodule is actually a nipple shadow, or not.
  • Chance of having a true pulmonary nodule lying beneath the nipple shadow is very slim
Miller WT, et al. The troublesome nipple shadow. AJR 1985 (September)

November 21, 2008

Gastric Cancer on CT

Figure: Axial CT shows thickening (arrows) and mucosal enhancement of the lesser curvature of the stomach in a patient with known gastric carcinoma. The fat plane is preserved. No lymphadenopathy is seen.

Gastric Carcinoma

  • Etiology: atrophic gastritis, adenomatous polyp, Lynch syndromes, gastric stump cancer, Menetrier's disease
  • Usually present in advanced stage
  • Major determination of staging of gastric carcinoma = extent of tumor beyond gastric wall and lymph node involvement
  • CT usually used to determine presence and extent of perigastric spread
Gastric Carcinoma on CT
  • Wall thickening, soft tissue mass (polypoid or ulcerated mass), perigastric fat stranding, lymphadenopathy
  • Differentiation from lymphoma: lymphoma usually has a very thick wall, no perigastric stranding, and bulky lymph nodes
  • CT accuracy for staging is better with multiplanar reformations (coronal and sagittal), better for T staging than N staging
T Staging by CT
  • T1 lesion = focal thickening of the inner layer of the wall
  • T2 lesion = transmural thickening of the wall without or with minimal perigastric stranding
  • T3 lesion = blurring of at least 1/3 of tumor extent or wide reticular stranding around tumor border
  • T4 lesion = invasion of adjancent organ or fat plane obliteration between tumor and adjacent organ
  • Accuracy based on this description was 77% in one study, when axial + MPR images were used
Hur J, et al. Diagnostic accuracy of multidetector row computed tomography in T- and N staging of gastric adenocarcinoma with histopathologic correlation. J Comput Assist Tomogr 2006 (May/June)

November 18, 2008

Calcium Pyrophosphate Dihydrate (CPPD) Crystal Deposition Disease of the Wrist

Fig. Frontal radiograph of the wrist shows calcifications of the lunotriquetral ligament (arrowhead) and triangular fibrocartilage (red arrow). Joint space narrowing with sclerosis of the trapezioscaphoid and carpometacarpal joints (yellow arrows) are noted. Note absence of osteophytes.

This patient presents with classic radiographic features of CPPD, which include:

  1. Chondrocalcinosis
  2. Degenerative change without apparent osteophytosis
  • At the wrist, the most common location of calcification in the area of triangular fibrocartilage is at the lunotriquetral ligament > triangular fibrocartilage > lunotriquetral cartilage.
  • Degenerative change in CPPD differs from osteoarthritis in that there is less osteophyte formation.

1. Yang B, et al. Distribution of calcification in the triangular fibrocartilage region in 181 patients with calcium pyrophosphate dihydrate crystal deposition disease. Radiology 1995; 196:547.
2. Saffar P. Chondrocalcinosis of the wrist. J Hand Surg [Br] 2004; 29:486.

November 15, 2008

Colon Cutoff Sign

Fig. 1: Supine abdominal radiograph in a 30-year-old man with acute abdominal pain shows gas in the transverse colon (C) with an abrupt termination at the level of splenic flexure (arrowheads). The more distal colon is decompressed. S = stomach
Fig. 2: Axial CT image of the same patient (done a few hrs later) shows extensive inflammation and necrosis of the pancreas (arrows) with free fluid in the abdomen (stars).

What is Colon Cutoff Sign?
Abrupt termination of gas in proximal colon at the level of the splenic flexure.
Applied to radiography, CT and contrast enema studies

What Can Cause Colon Cutoff Sign?

  • Most common = acute pancreatitis
  • True colonic obstruction e.g. colonic malignancy
  • Other causes of colonic inflammation
Why Does It Occur?
In acute pancreatitis, inflammatory exudates in retroperitoneal space extend into 'phrenicocolic ligament' causing spasm of the splenic flexure wherer the colon returns to retroperitoneum. (Remember - transverse colon in peritoneal cavity, descending colon in retroperitoneum, phrenicocolic ligament is a transition point where transverse and descendinc colon is separated)

Available in Podcast (Thai language only): website | iTunes

Pickhardt P. The colon cutoff sign. Radiology 2000;215:387.

November 12, 2008

Metformin and Iodinated Contrast Agents

Facts about Metformin

  • Medication for treatment of type II diabetes
  • Decreases hepatic glucose production and enhance glucose uptake in peripheral tissues (by increase insulin sensitivity)
  • May be in a pure form or in combination with other antihyperglycemic drugs
  • Renal excretion
  • Most significant reaction is lactic acidosis, which has a high mortality (up to 50%)
  • Most metformin associated lactic acidosis (MALA) occured in patients with coexisting renal dysfunction (high level of metformin due to poor excretion)
Why Do We Worry About Metformin and Iodinated Contrast Agents?
  • The use of iodinated contrast agents in patients with pre-existing renal dysfunction can lead to significant contrast-induced nephropathy - that could, in turn, worsen MALA.
In Whom We Should Worry?
  • Patients with pre-existing renal dysfunction
  • Patients with comorbidities that could give rise to lactic acidosis (liver dysfunction, alcohol abuse, heart failure, myocardial ischemia, peripheral muscle ischemia, sepsis, severe infection)
What To Do?
  • Patients with normal renal function and no known comorbidities -> no need to discontinue metformin prior to IV contrast administration
  • Patients with known comorbidities -> Discontinue metformin at time of IV contrast administration, and withheld for 48 hours
  • Patients with known renal dysfunction -> suspend metformin at time of IV contrast administration, renal function follow-ups until safe reinstitution of metformin can be assured
American College of Radiology. Manual on Contrast Media version 6 (2008).

McCartney MM, et al. Metformin and contrast media - a dangerous combination? Clin Radiol 1999;54:29.

November 9, 2008

When to Obtain Ankle Radiographs

- Ankle radiography was the third most common study ordered in the emergency department.
- Majority of patients with ankle radiographs did not receive adequate physical examination before radiographs were obtained.
- Only 17% of extremity radiographs obtained had abnormality that would alter treatment.

Guidelines for Obtaining Ankle Radiographs (Ottawa Rule)

  1. Inability to bear weight immediately after the injury OR
  2. Point tenderness (over medial malleolus, posterior edge or inferior tip of lateral malleolus, talus, calcaneus) OR
  3. Inability to ambulate for four steps in the emergency room
Sensitivity approaches 100% in excluding significant ankle fractures
Decrease number of ankle and midfoot radiographs by 19% - 36%

Podcast of this post is available in iTunes Store or a website.

ACR Appropriateness Criteria "Suspected Ankle Fracture", revised 2005.

November 6, 2008

Air-Fluid Levels at Different Heights in the Same Loop of Bowel

Upright abdominal radiograph of the same patient shows multiple air-fluid levels in the small bowel. Note 'different heights of air-fluid levels in the same loop' (arrows). SB = small bowel, C = colon.

Differential Air-Fluid Levels

  • Two distinct air-fluid interfaces on an upright abdominal radiograph that are at different heights but within the same loop of bowel.
  • Once believed to be strongly suggestive of mechanical small bowel obstruction (due to ongoing peristalsis against mechanical blockage BUT it can be found in both mechanical obstruction and ileus (in one series, 50% of mechanical obstruction and 29% of ileus)
  • Helpful to suggest mechanical small bowel obstruction if a differential air-fluid level is 2 cm or greater (however, not the other way around!) with a reasonable positive predictive value (PPV). As height increases, PPV and specificity increases.
  • Differential height of 2.5 cm or greater is suggestive of high-grade small bowel obstruction.
This case: partial, low-grade small bowel obstruction, likely due to adhesion (history of multiple previous abdominal surgery).

1. Harlow CL, et al. Diagnosis of bowel obstruction on plain abdominal radiographs: significance of air-fluid levels at different heights in the same loop of bowel. AJR Am J Roentgenol 1993;161:291.
2. Lappas JC, et al. Abdominal radiography findings in small bowel obstruction: relevance to triage for additional diagnostic imaging. AJR Am J Roentgenol 2001;176:167.

November 3, 2008

Preseptal Cellulitis

Axial contrast-enhanced CT image of the orbit shows soft tissue thickening of the right preseptal region (between arrows). The retroorbital fat is normal (arrowheads).


  • 'Periorbital' or 'preseptal' infection = infection of tissues anterior to orbital septum.
  • Orbital septum separates preseptal space from orbit. Orbital septum is a connective tissue extension of periosteum reflected into upper and lower eyelids. It serves as a barrier to spread of infection to the orbit.
  • Most common cause of preseptal cellulitis is localized infection of eyelid or adjacent structures (mostly due to S. aureus)

1. Wald ER. Periorbital and orbital infections. Infect Dis Clin N Am 2007;21:393.
2. Lui I, et al. Preseptal and orbital cellulitis: a 10-year review of hospitalized patients. J Chin Med Assoc 2006;69:415.

October 31, 2008

Periportal Halo

Contrast-enhanced CT image (coronal reformat) shows circumferential zone of low attenuation around the portal vein branches. Seen en face (arrows) and in profile (arrowheads).

Features of Periportal Halo

  • Circumferential (differentiating feature from dilated bile ducts)
  • Low attenuation (could represent fluid, lymph, or blood)
  • Peripheral portal veins
Differential Diagnosis
  • Liver trauma (blood tracks in periportal space)
  • Edema (CHF, burn, volume resuscitation)
  • Hepatitis
  • Lymphatic obstruction (obstructing portal lymph nodes or malignancy)
It may be the most prominent sign of malignancy! Look carefully for lymph nodes in the portal region and lesser omentum before signing it out as due to other more benign causes.

Our patient is a young man with toxic hepatitis. Periportal halo is due to his hepatitis.

Lawson TL, et al. Periportal halo: a CT sign of liver disease. Abdom Imaging 1993;18:42.

October 28, 2008

Features Suggestive of Malignant Thyroid Nodules

Fig. 1 Longitudinal ultrasound of the thyroid reveals an ill-defined hypoechoic nodule in the upper pole of the thyroid lobe (between calipers). Note microcalcification (yellow arrow).
Fig. 2 Color Doppler ultrasound of the nodule shows intranodular vascularity (green arrow).

Both pictures illustrate three important findings on ultrasound that are suggestive of malignancy (these are independent risk factors of nonpalpable malignant thyroid nodule):

  1. Irregular margin
  2. Intranodular vascular spots
  3. Microcalcifications
Other Facts:
  • Thyroid nodules are increasingly common because widespread use of neck ultrasound
  • Management of incidentally detected thyroid nodule is still largely controversial
  • When needed, cytological evaluation by fine needle aspiration biopsy (FNA) is the best method to assess thyroid nodule
  • Other signs that ones should look for: extracapsular growth and nodal involvement. These are helpful in predicting malignancy.
  • Prospective study had shown that size (<1 cm vs. larger), number (solitary vs. multinodular), and echogenicity (hypoechoic vs. iso-hyperechoic) were not different in groups with benign or malignant nodules.
Papini E, et al. Risk of Malignancy in Nonpalpable Thyroid Nodules: Predictive Value of Ultrasound and Color-Doppler Features. J Clin Endocrinol Metab 2002;87:1941.

October 25, 2008

Adverse Events in Radiology: Management

What to do when an adverse event occurs?
  • Treat the patient FIRST! Always.
  • Report the incidence to supervisor at a higher level
  • Document the incidence in medical record
  • Secure evidence
  • In a group (e.g. quality assurance group), analyze the incidence
  • Review the incidence
  • Look for causes of incidence (both human and non-human factors), better not blaming a particular person, look at a big picture, consider other related causes
  • Reveal the incidence
  • Implement changes for the existing guideline, protocol
  • Monitor the results of changes
  • สิ่งสำคัญที่สุดเมื่อเกิด adverse event คือต้องรักษาคนไข้ก่อนเสมอ
  • สิ่งที่ตามมาคือการรวบรวมหลักฐาน และบันทึกเหตุการณ์เพื่อเป็นหลักฐาน การรวบรวมหลักฐานและบันทึกสามารถทำได้เป็นกลุ่มโดยให้ความเห็นร่วมกัน
  • ในเวลาต่อมาควรรวมกลุ่ม (หรือใช้กลุ่มที่ทำงานด้านคุณภาพในหน่วยงาน) เพื่อวิเคราห์หาสาเหตุของ adverse event
  • ในการวิเคราห์หาสาเหตุ ควรหลึกเล่ียงการลงโทษ หรือการมองหาคนผิด แต่ให้มองที่ภาพรวม และภาพใหญ่มากกว่า และควรมองหาปัจจัยร่วมที่ส่งผลให้เกิดเหตุด้วย
  • พิจารณาดูว่าแนวทางการปฏิบัติของหน่วยงานนั้นดีอยู่แล้วหรือควรปรับปรุง
  • เมื่อได้ปรับปรุงแนวทางปฏิบัติ ให้แจ้งให้บุคลากรทราบและติดตามผลด้วย
Kruskal et al. Managing an acute adverse event in a radiology department. Radiographics 2008;28:1237.

October 22, 2008

How Doctors Think: Chapter 5

"Faith, a well-recognized source of solace, of strength to endure, can also give people the courage to recognize uncertainty, acknowledge not only their own fallibility but also their physicians', and thereby contribute to the search for solutions."

In this chapter, Groopman described a case of Rachel and Shira, a U.S. mom with an adopted Vietnamese girl. Shira developed extensive pneumonias from multiple organisms and was initially diagnosed with SCID, when she arrived in Boston from Vietnam. She was tested for immune status, negative HIV test, and given extreme treatment for her infections. Bone marrow transplantation was planned at her improvement of infections. However, Rachel insisted to a team of doctors that Shira being tested (for the third time) for immune function because she believed that Shira had malnutrition, not SCID. The third test results confirmed that Shira did not have SCID. The teaching point of this topic is mainly about the patient and their caring family -- to have faith and to learn more about diseases -- to be able to ask physicians about their diagnosis and appropriately challange them when needed. Also to teach a physician to learn to understand patient and their family, with open minds.

ในตอนนี้ Groopman ให้ชื่อว่า A New Mother's Challenge ทั้งบทกล่าวถึงเรืื่องราวของ Rachel กับ Shira. Rachel เป็นนักธุรกิจชาวอเมริกันซึ่งตัดสินใจรับบุตรบุญธรรมจากประเทศเวียดนามเพื่อนำมาเลี้ยงเป็นลูกตัวเอง, ลูกบุญธรรมคนดังกล่าวชื่อว่า Shira ซึ่งเป็น newborn. Groopman เล่าเรื่องตั้งแต่วัันที่ Rachel เดินทางจากอเมริกาไปเวียดนามเพื่อไปพบ Shira, ทำพิธีส่งมอบ และเดินทางกลับมาที่อเมริกา. Shira ดูแปลกเหมือนเด็กป่วย ระหว่างเดินทางมาไม่ยอมกินอาหาร ทำให้ Rachel พาไปตรวจที่ L.A. ระหว่างเปลี่ยนเครื่อง พบว่าเป็น sinusitis. เมื่อเดินทางกลับมาถึงบอสตัน อาการของ Shira แย่ลงอย่างรวดเร็ว Rachel พาไปตรวจที่ ER ของ Children's Hospital Boston พบว่าต้องใช้ ECMO และ admit เข้า ICU และได้รับการวินิจฉัยว่าเป็น Pneumocystis, CMV, Klebsiella และ Candida pneumonia. ผลตรวจ HIV negative และได้รับการวินิจฉัยว่าเป็น SCID. Rachel ตกใจมากและสงสัยในกระบวนการส่งมอบ Shira ที่เวียดนาม และสงสัยในการวินิจฉัยของหมอ แต่ก็ไม่ย่อท้อ ศึกษาหาความรู้จากเพื่อนที่เป็นแพทย์ (รวมทั้ง Groopman) และทางอินเตอร์เน็ต. เรื่องแปลกอยู่ที่ว่า SCID นั้นพบในเด็กผู้ชายมากกว่าผู้หญิงมากๆ เนื่องจากเป็น X-link genetic disorder. อย่างไรก็ตาม ทีมแพทย์ยังคิดว่า Shira เป็น 'atypical' SCID และวางแผนรักษาด้วยการทำ bone marrow transplantation หลังจากอาการดีขึ้น. Shira อาการดีขึ้นเรื่อยๆ สามารถออกจาก ICU ได้ และได้รับการตรวจระดับ T cell & function ไป 2 ครั้งและผลผิดปกติ. วันหนึ่งขณะที่แพทย์เข้่ามาแจ้งข่าวเรื่องการทำ bone marrow transplantation, Rachel ยืนยันขอให้แพทย์ตรวจ T cell อีกครั้ง แพทย์ไม่ค่อยเต็มใจแต่ก็ส่งตรวจให้. ปรากฎว่าผลตรวจครั้งสุดท้ายกลับมาปกติ T cell function ปกติ ซึ่งแปลว่า Shira ไม่ได้เป็น SCID. การวินิจฉัยสุดท้าย คือ Shira ป่วยจากภาวะ malnutrition.

เรื่องของ Shira แสดงให้เห็น bias ที่เกิดในการวินิจฉัยโรคของแพทย์. Groopman แสดงให้เห็นว่าทำไมแพทย์จึงติดอยู่กับการวินิจฉัยบางอย่าง ลืมคิดถึงโรคอื่นๆ โดยยกตัวอย่างว่าเวลา round, แพทย์มักเริ่มต้นว่า "ผู้ป่วยเด็กหญิงอายุ.. วินิจฉัยว่าเป็น atypical SCID มาด้วยอาการ...." นานไปทำให้ทุกคนลืมคิดไปว่าที่บอกว่าคนไข้เป็นโรคนั้น วินิจฉัยได้จากอะไร ยืนยันได้อย่างไร และทำให้กรอบความคิดแคบ ลืมนึกถึงโรคอื่นๆไปได้. นอกจากนี้เรื่องของ Rachel ยังเป็นเครื่องบ่งบอกถึงพลังของญาติผู้ป่วย (ที่ขยันขวนขวายหาความรู้เกี่ยวกับโรคและการรักษา) ที่มีบทบาทสำคัญ ช่วยในการวินิจฉัยโรคของแพทย์ด้วย

Jerome Groopman ปัจจุบันเป็น Professor (medicine) ที่ Beth Israel Deaconess Hospital (Boston). เขาจบแพทย์จาก Harvard Medical School และทำ internship กับ medicine ในรั้ว Harvard ที่ Massachusetts General Hospital. เขาเคยทำงานที่ UCLA Medical Center ก่อนจะย้ายกลับมาอยู่ที่บอสตัน.

October 19, 2008

Usual Interstitial Pneumonitis (UIP) Pattern

Fig.1: Chest radiograph of a 68-year-old man with chronic dyspnea shows diffuse reticular opacities with peripheral and basal predominance (red stars). The lung volumes are normal. Note that the heart border looks 'shaggy irregular'.
Fig. 2: Axial chest CT at midsection of the lungs shows subpleural opacities (arrowheads) and traction bronchiectasis (arrows).
Fig. 3: Axial CT at the lung bases show extensive subpleural honeycombing bilaterally.

In this case, typical findings of UIP are illustrated. Honeycombing is a core finding of UIP that allows differentiation from other chronic interstitial pneumonias (esp. nonspecific interstitial pneumonitis or NSIP).

UIP is a pattern seen on imaging, not a diagnosis. It can be due to various causes: idiopathic (idiopathic pulmonary fibrosis - IPF), connective tissue disorder, hypersensitivity, drug toxicity, asbestosis.

ภาพข้างบนแสดงให้เห็นลักษณะสำคัญของ UIP ในเอกซเรย์และ CT โดยจะเห็นว่ามี reticular opacity ที่เด่นใน subpleural และ lung bases ร่วมกับมี traction bronchiectasis และ honeycombing. ลักษณะ honeycombing ถือเป็นสิ่งสำคัญที่ช่วยในการวินิจฉัย UIP และวินิจฉัยแยกจาก NSIP.

UIP เป็น imaging description. ถ้าการตรวจทางคลินิกและ pathology ไม่พบสาเหตุของ UIP, เราจะวินิจฉัยว่าผู้ป่วยเป็น IPF. สาเหตุอื่นที่ทำให้เกิด UIP เช่น connective tissue disease, hypersensitivity, drug toxicity และ asbestosis เป็นต้น.

Atilli AK, et al. Smoking-related interstitial lung disease: radiologic-clinical-pathologic correlation. Radiographics 2008 (September 2008)

October 16, 2008

Pericardial Effusion on Lateral Chest Radiograph

Fig. 1. Lateral chest radiograph shows small bilateral pleural effusions. Enlarged cardiac silhouette with abnormal bands of density noted anterior to the heart (between arrows). Of note, this band of density consists of a central soft tissue sandwiched by lucent stripes.
Fig. 2. Sagital CT image of the same patient correlates well with lateral radiograph in Fig. 1. It shows that the 'sandwich' seen anterior to the heart represents pericardial effusion (star) bounded by epicardial and pericardial fat.


  • Pericardial effusion can be transudate or exudate (pus, blood, infection)
  • Symptoms depend on the size and rate of accumulation of effusion
  • Chest radiography is not diagnostic of pericardial effusion in most cases
  • CT and MRI used to assess size and extent of pericardial effusion
  • Measurement of pericardial effusion by CT/MRI tends to be larger than in echocardiography
Radiographic Signs of Pericardial Effusion
All four signs are sensitive (71-100%) but not specific (12-46%).
  • Enlarged cardiac silhouette with sharp margin, "water bottle" silhouette
  • Pericardial fat stripe (separation of pericardial layers)
  • Predominantly left-sided pleural effusion
  • Increased transverse cardiac diameter compared with previous radiograph

Listen to podcast HERE (Thai language).

1. Eisenberg MJ, et al. Diagnostic value of chest radiography for pericardial effusion. J Am Coll Cardiol 1993; 22:588-593
2. Guidelines on the Diagnosis and Management of Pericardial Diseases of the European Society of Cardiology. Eur Heart J 2004; 25:587-610

October 15, 2008

The Scan That Didn't Scan - An Article from Today's NY Times

Full article can be read at the New York Times
Picture above is from the New York Times
A very interesting article in one of the most read newspapers in the USA described an experience of the author (and a friend) having MRI scans at some New York hospitals. The author injured the foot and received the first MRI scan at a 'local' radiology center. They found nothing wrong and she was treated with medication without limiting activity. However, she hurt so much and got a second opinion at the Hospital for Special Surgery in New York. The second scan showed a stress fracture. The first scan quality was probably not good enough to detect the lesion (it missed the lesion), or the qualification of the first radiologist (general radiologist) is not enough.

The article also included several opinions from prominent radiologists including Dr Forman from Yale, Drs. Gazelle and Thrall from MGH.

I think the article is very important and any radiologists should read it because:

  • Being optimistic, the story brought radiologists to the light, criticized by lay people. It emphasizes how important radiologists are in the practice of medicine.
  • It teaches us that quality of the images produced, and experience of radiologists are very important for interpretation and subsequent patient care. Good quality images = good quality interpretation. Good training of radiologists, technologists and good-quality scanners are crucial.
  • It raises an issue of the training and qualification of radiologists. One day, patients may ask "Who read my scans? Is he or she qualified for this interpretation?" Strangely, this article coincides with a few articles in the current issue of JACR (Journal of the American College of Radiology) talking about sub-specialization in Radiology.
  • It also tells us to 'treat the patient, not the images'. Lesson learned for the clinicians. Like Dr. Thrall said in this article, "scans, as good as they are, are not perfect."
Listen to an accompanied Podcast HERE (in Thai language)

October 13, 2008

Leptomeningeal Carcinomatosis

Fig. Sagital T1 (post contrast) MR image shows nodular/irregular enhancement of the leptomeninges, especially in the posterior fossa (arrows). The patient was found to have esophageal carcinoma.


  • Most common tumors metastasize to meninges are breast, lung, melanoma
  • No identifiable primary malignancy in 2-4% of cases
  • Headache is the most common presenting symptom.
  • Diagnosis relies on cytological examination (CSF cytology or leptomeningeal biopsy). CSF markers and radiographic findings also can strongly support diagnosis.
  • Short median survival even with aggressive treatment
Radiographic Findings
  • Hydrocephalus
  • Meningeal enhancement
  • Thick, clumped nerve roots
  • Enhancing nodular deposits on surface of roots or CNS structures
  • Coexisting parenchymal, epidural or bony metastases

Balm M, et al. Leptomeningeal carcinomatosis: presenting features and prognostic factors. Arch Neurol 1996 (July 1996).

October 10, 2008

Hypervascular Hepatic Mass

Fig. 1. Arterial phase of gadolinium-enhanced MRI shows an enhancing mass (arrow) arising from the right hepatic lobe. Note the aorta is vividly enhanced (arrowhead).
Fig. 2. Portal phase of the same MRI reveals that the mass is isointense to the rest of the liver parenchyma with mild rim enhancement.

Differential Diagnosis of Hypervascular Hepatic Mass in Normal Appearing Liver

  • Hepatocellular carcinoma (HCC)
  • Hypervascular metastasis (carcinoid, RCC, melanoma, islet cell tumor)
  • Hemangioma
  • Focal fat sparing
  • Transient hepatic attenuation difference (THAD)
How to Differentiate
  • HCC: typical in cirrhotic liver, heterogeneous enhancement if large, portal vein thrombosis, lymphadenopathy, elevated serum AFP
  • Hypervascular metastasis: usually multiple, varying size, non-cirrhotic liver, known history of malignancy elsewhere
  • Hemangioma: some small hemangioma may enhance vividly on arterial phase exam, non-cirrhotic liver
  • Focal fat sparing: vessels going through lesion without mass effect, rest of liver appears fatty
Final diagnosis in this case: HCC

ไม่ว่าจะทำ CT หรือ MRI ในการวินิจฉัย liver mass, จำเป็นต้องทำ arterial phase ด้วย (ปกติที่ 25-30 วินาทีหลังจากฉีด contrast โดยใช้ injector และ MDCT). ถ้าเห็นว่ามี hypervascular mass ใน cirrhotic liver ต้องคิดถึง HCC ก่อนเสมอ (โดยเฉพาะเมื่อพบร่วมกับ portal vein thrombosis, lymphadenopathy) และสามารถตรวจยืนยันได้ด้วย serum AFP หรือ biopsy.

Slone RM, et al. Body CT a practical approach. 2000.

October 7, 2008

Imaging of Facial Trauma Part 2

Imaging of Facial Trauma Part 1

October 6, 2008

Pulmonary Langerhans Cell Histiocytosis

Fig. 1 & 2: Axial CT images (at mid portion of the lungs and lung bases) of a 50-year-old man with dry cough and dyspnea for 2-3 months show multiple cystic airspaces with irregular walls (arrows) and small nodule (arrowhead), predominantly in the upper and mid lung zones sparing the lung bases. 

Main differential diagnoses for multiple diffuse cystic airspaces in the lungs:
  • Emphysema - no perceptible cyst wall, smoking
  • LCH (or eosinophilic granuloma) - smoking
  • LAM (lymphangiomyomatosis) - evenly distributed cysts, young reproductive women
  • Cystic bronchiectasis - cystic spaces can be traced up and down, and connected to the bronchi
In this case, a constellation of clinical and imaging findings are characteristic of pulmonary LCH. Irregular walls of cystic airspaces, predominant upper and midzones and presence of nodules are common findings in pulmonary LCH.

เวลาที่เห็น cystic airspaces ใน lung ให้มองดูเสมอว่ามี wall ล้อมรอบหรือไม่ และมีหลอดเลือดวิ่งผ่านเข้าไปข้างในหรือไม่ ลักษณะ 2 อย่างนี้ใช้แยกว่าเป็น emphysema หรือ cystic lung disease. ถ้า cysts ไม่มี wall และมีหลอดเลือดวิ่งเข้าไปข้างใน ก็เป็นลักษณะของ emphysema.

หลังจากนั้นต้องแยก bronchiectasis ออกจาก cystic lung disease ด้วยการมองว่ามี connection ระหว่าง cysts กับ bronchi หรือไม่ 

ลักษณะสำคัญของ pulmonary LCH ดังที่กล่าวไว้คือ cysts มักอยู่ upper/mid lung zones, wall ไม่เรียบ และพบร่วมกับ nodule ด้วย (pulmonary LCH เริ่มจากการเป็น nodule ก่อนแล้วจึงกลายตัวเป็น cyst)

Attili AK, et al. Smoking-related interstitial lung disease: radiologic-clinical-pathologic correlation. Radiographics 2008 (September 2008)

October 3, 2008

Adverse Events in Radiology: Definition

A 68-year-old man, with diabetes and hypertension, went for a chest CT for a suspicious abnormality seen on a previous chest x-ray. He developed acute dyspnea, wheezing and hypotension after administration of IV contrast material. He passed away after extensive resuscitation effort.

What are adverse events in radiology?
  • Events in which a patient suffers unexpected harm +
  • Due to diagnostic imaging study or intervention +
  • Unrelated to patient's underlying medical condition 
Examples of adverse events:
  • Unintended retention of foreign object in patient
  • Fall
  • Medication error
  • Intervention on wrong body part, wrong side
  • Wrong intervention performed
  • Contamination of drugs, devices or biologics
What is "sentinel event"?
= Adverse events causing death or serious physical or psychologic injury

The above scenario illustrated a rare adverse event that could happen in any radiology department. It is a 'sentinel' adverse event since it brought about death to the case example. What and how to respond to the event?

Kruska JB, et al. Managing an acute adverse event in a radiology department. Radiographics 2008 (September 2008)