title: A new, simple method for estimating pleural effusion size on CT scans.
abstract: BACKGROUND
  There is no standardized system to grade pleural effusion size on CT scans. A validated, systematic grading system would improve communication of findings and may help determine the need for imaging guidance for thoracentesis.
  
  
  METHODS
  CT scans of 34 patients demonstrating a wide range of pleural effusion sizes were measured with a volume segmentation tool and reviewed for qualitative and simple quantitative features related to size. A classification rule was developed using the features that best predicted size and distinguished among small, moderate, and large effusions. Inter-reader agreement for effusion size was assessed on the CT scans for three groups of physicians (radiology residents, pulmonologists, and cardiothoracic radiologists) before and after implementation of the classification rule.
  
  
  RESULTS
  The CT imaging features found to best classify effusions as small, moderate, or large were anteroposterior (AP) quartile and maximum AP depth measured at the midclavicular line. According to the decision rule, first AP-quartile effusions are small, second AP-quartile effusions are moderate, and third or fourth AP-quartile effusions are large. In borderline cases, AP depth is measured with 3-cm and 10-cm thresholds for the upper limit of small and moderate, respectively. Use of the rule improved interobserver agreement from κ = 0.56 to 0.79 for all physicians, 0.59 to 0.73 for radiology residents, 0.54 to 0.76 for pulmonologists, and 0.74 to 0.85 for cardiothoracic radiologists.
  
  
  CONCLUSIONS
  A simple, two-step decision rule for sizing pleural effusions on CT scans improves interobserver agreement from moderate to substantial levels.
authors: Department of Radiology, Albert Einstein College of Medicine & Montefiore Medical Center, Bronx, NY.
authors: Matthew P
authors: MP
authors: Moy
authors: Department of Radiology, Albert Einstein College of Medicine & Montefiore Medical Center, Bronx, NY. Electronic address: jlevsky@montefiore.org.
authors: Jeffrey M
authors: JM
authors: Levsky
authors: Department of Radiology, Albert Einstein College of Medicine & Montefiore Medical Center, Bronx, NY.
authors: Netanel S
authors: NS
authors: Berko
authors: Department of Radiology, Albert Einstein College of Medicine & Montefiore Medical Center, Bronx, NY.
authors: Alla
authors: A
authors: Godelman
authors: Department of Radiology, Albert Einstein College of Medicine & Montefiore Medical Center, Bronx, NY.
authors: Vineet R
authors: VR
authors: Jain
authors: Department of Radiology, Albert Einstein College of Medicine & Montefiore Medical Center, Bronx, NY; Department of Medicine, Albert Einstein College of Medicine & Montefiore Medical Center, Bronx, NY.
authors: Linda B
authors: LB
authors: Haramati
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D015999:Multivariate Analysis; D015588:Observer Variation; D010996:Pleural Effusion / Q000145:classification* / Q000000981:diagnostic imaging* / Q000473:pathology; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*
references: Radiology. 1994 Jun;191(3):681-4
references: 8184046
references: Am J Respir Crit Care Med. 2000 Nov;162(5):1987-2001
references: 11069845
references: Acad Radiol. 1996 Feb;3(2):103-9
references: 8796649
references: Am J Crit Care. 2011 Mar;20(2):119-27; quiz 128
references: 21362716
references: Chest. 1995 Aug;108(2):299-301
references: 7634854
references: N Engl J Med. 2002 Jun 20;346(25):1971-7
references: 12075059
references: Chest. 2002 Dec;122(6):1913-7
references: 12475826
references: J Thorac Imaging. 1999 Apr;14(2):122-5
references: 10210486
references: Respirology. 2004 Aug;9(3):300-12
references: 15363000
references: Proc IEEE Int Symp Biomed Imaging. 2009;2009:241-244
references: 20407621
references: Radiology. 2011 Mar;258(3):776-84
references: 21193598
references: Chest. 1987 Jun;91(6):817-22
references: 3581930
references: Chest. 2006 Jun;129(6):1709-14
references: 16778292
references: JAMA. 1976 Nov 8;236(19):2183-6
references: 989808
references: Respir Med. 2005 Sep;99(9):1183-7
references: 16085221
references: Eur Respir J. 2001 Aug;18(2):402-19
references: 11529302
references: Thorax. 2010 Aug;65 Suppl 2:ii4-17
references: 20696692
references: Biometrics. 1977 Mar;33(1):159-74
references: 843571
references: Acad Radiol. 2010 Jul;17(7):841-8
references: 20399688
references: Radiol Clin North Am. 1989 Nov;27(6):1241-55
references: 2685883