Journal Highlights

The following are highlights from the current issues of RSNA's two peer-reviewed journals.

Thin-Section CT of the Secondary Pulmonary Lobule: Anatomy and the Image—The 2004 Fleischner Lecture

The secondary pulmonary lobule is a fundamental unit of lung structure and reproduces the lung in miniature. Airways, pulmonary arteries, veins, lymphatics and the lung interstitium are all represented at the secondary lobule level. Several components of the secondary lobule are normally visible on thin-section CT lung scans.

In an article in the Reviews section of the May issue of Radiology (RSNA.org/radiologyjnl), W. Richard Webb, M.D., of the Department of Radiology at the University of California San Francisco, discusses how recognizing lung abnormalities relative to secondary lobule structures is fundamental to interpreting thin-section CT scans. Pathologic alterations in secondary lobular anatomy visible on thin-section CT scans include interlobular septal thickening and diseases with peripheral lobular distribution and centrilobular and panlobular abnormalities. The differential diagnosis of lobular abnormalities is based on comparisons between lobular anatomy and lung pathology.

Dr. Webb emphasizes:

• Pulmonary disease occurring predominantly in relation to interlobular septa and the periphery of lobules is termed “perilobular;” this disease distribution may reflect abnormalities of the interlobular septa or peripheral alveoli.
  
• Centrilobular abnormalities visible on thin-section CT scans may consist of nodular opacities; the tree-in-bud appearance, which usually indicates a small-airways abnormality; increased visibility of centrilobular structures due to thickening or infiltration of the surrounding interstitium; or abnormal low-attenuation areas related to bronchiolar dilatation or emphysema.

Interlobular septal thickening in pulmonary edema.

Transverse thin-section CT scan shows thickened septa (small arrows) in upper lobes. Smooth thickening of interlobular septa outline a number of secondary pulmonary lobules. Visible lobules vary in size, at least partly because of the position of lobules relative to the scan plane. Pulmonary veins (large arrows) in septa are visible as small rounded dots or linear or branching opacities. Septa are well developed in the apices, and septal thickening is often well depicted in this region.

(Radiology 2006;239:322–338)

Peripheral lobular fibrosis in idiopathic pulmonary fibrosis.

(a) Transverse thin-section CT scan through right upper lobe in a patient with idiopathic pulmonary fibrosis shows irregular reticular opacities (arrows). (b) Histologic specimen from open lung biopsy in a different patient with idiopathic pulmonary fibrosis shows irregular fibrosis (arrows) in periphery of secondary pulmonary lobules. (Hematoxylin-eosin stain; original magnification, ×4.)

©  RSNA, 2006. All rights reserved. Printed with permission.

CT Enterography as a Diagnostic Tool in Evaluating Small Bowel Disorders: Review of Clinical Experience with Over 700 Cases

Increased speed and resolution have made multi-detector row CT a first-line modality for examining small bowel disease and an important alternative to traditional fluoroscopy in assessing other small bowel disorders such as celiac sprue and small bowel neoplasms.

In an article in the May-June issue of RadioGraphics (RSNA.org/radiographics), Scott R. Paulsen, B.S.. of the Mayo Clinic College of Medicine in Rochester, Minn., and colleagues:

• Describe methods for performing CT enterography
• Discuss various considerations in achieving small bowel distention
• Discuss and illustrate CT enterographic findings in common diseases, including Crohn disease, ulcerative colitis, small bowel tumors and celiac disease, and incidental findings

Paulsen and colleagues reviewed records for 756 patients who underwent CT enterography at the Mayo Clinic from March 2001 and March 2004. The team notes that the number of CT enterography examinations performed at the institution increased from 99 in 2001 to more than 900 in 2004, as referring clinicians gained confidence in the examination.

The researchers note that CT enterography has several advantages over traditional small bowel follow-through examination, including how it displays the entire thickness of the bowel wall. CT enterography also allows assessment of solid organs and provides a global overview of the abdomen, they said.

“CT enterography is a powerful tool in the evaluation of small bowel disease,” Paulsen and colleagues conclude. “Adequate luminal distention can usually be achieved with oral ingestion of a large volume of neutral enteric contrast material in the evaluation of diseases affecting the mucosa and bowel wall, thereby obviating nasogastric intubation and making CT enterography a useful, well-tolerated study in this setting.”

Spectrum of segmental mural hyperenhancement indicating active inflammatory Crohn disease.

(a) Active jejunal Crohn disease in a 19-year-old woman. CT enterogram shows mural hyperenhancement (arrows). Compare the normal enhancement of the unaffected small bowel (arrowhead). (b) Active ileal Crohn disease in an asymptomatic 38-year-old man. CT enterogram depicts mural hyperenhancement (arrows) with mural stratification within the thickened bowel wall. Note that the mucosal aspect of the small bowel is thickened and hyperattenuating relative to the serosa. (c) Duodenal Crohn disease in a 42-year-old woman. CT enterogram demonstrates mucosal hyperenhancement (arrows) and stratification (arrowhead). The diagnosis was confirmed at endoscopy.

Active Crohn disease in a 14-year-old patient.

The patient had been treated medically since undergoing ileal resection one year earlier. Follow-up CT enterogram shows engorged vasa recta producing the comb sign (arrows) involving two ileal loops with asymmetric enhancement and wall thickening.
(RadioGraphics 2006;26:641-662)

©  RSNA, 2006. All rights reserved. Printed with permission.