Korean J Radiol.  2019 Apr;20(4):599-608. 10.3348/kjr.2018.0557.

Measurement of Pancreatic Fat Fraction by CT Histogram Analysis to Predict Pancreatic Fistula after Pancreaticoduodenectomy

• Hong W
• Ha HI
• Lee JW
• Lee SM
• Kim MJ

• KMID: 2440483
• DOI: http://doi.org/10.3348/kjr.2018.0557

Abstract

OBJECTIVE
To evaluate the effectiveness of computed tomography (CT) Hounsfield unit histogram analysis (HUHA) in postoperative pancreatic fistula (PF) prediction.
MATERIALS AND METHODS
Fifty-four patients (33 males and 21 females; mean age, 65.6 years; age range, 37-89 years) who had undergone preoperative CT and pancreaticoduodenectomy were included in this retrospective study. Two radiologists measured mean CT Hounsfield unit (CTHU) values by drawing regions of interest (ROIs) at the level of the pancreaticojejunostomy site on preoperative pre-contrast images. The HUHA values were arbitrarily divided into three categories, comprising HUHA-A ≤ 0 HU, 0 HU < HUHA-B < 30 HU, and HUHA-C ≥ 30 HU. Each HUHA value within the ROI was calculated as a percentage of the entire area using commercial 3-dimensional analysis software. Pancreas texture was evaluated as soft or hard by manual palpation.
RESULTS
Fifteen patients (27.8%) had clinically relevant PFs. The PF group had significantly higher HUHA-A (p < 0.01) and significantly lower mean CTHU (p < 0.01) values than those of the non-PF group. The HUHA-A value had a moderately strong correlation with PF occurrence (r = 0.60, p < 0.01), whereas the mean CTHU had a weak negative correlation with PF occurrence (r = −0.27, p < 0.01). The HUHA-A and mean CTHU areas under the curve (AUCs) for predicting PF occurrence were 0.86 and 0.65, respectively, with significant difference (p < 0.01). The HUHA-A and mean CTHU AUCs for predicting pancreatic softness were 0.86 and 0.64, respectively, with significant difference (p < 0.01).
CONCLUSION
The HUHA-A values on preoperative pre-contrast CT images demonstrate a strong correlation with PF occurrence.

Keyword

Pancreaticoduodenectomy; Pancreatic fistula; MDCT; Histogram analysis; Attenuation; Pancreatic softness

MeSH Terms

Area Under Curve
Female
Humans
Male
Palpation
Pancreas
Pancreatic Fistula*
Pancreaticoduodenectomy*
Pancreaticojejunostomy
Retrospective Studies

Figure

• 

  Fig. 1 Patient selection flowchart.BL = biochemical fistula, CT = computed tomography, PD = pancreaticoduodenectomy, PF = pancreatic fistula

• 

  Fig. 2 Measurement of HUHA.ROIs were drawn on axial and corresponding sagittal preoperative pre-contrast CT images at level of pancreas neck near pancreaticojejunostomy site with reference to postoperative CT images. Three-dimensional analysis software automatically generated each HUHA-A (−1024–0 HU), HUHA-B (1–29 HU), HUHA-C (30–3071 HU), and mean CTHU value. Each HUHA value within ROI was calculated as percentage of entire area in real time.Axial (A) and sagittal (B) images from 76-year-old male patient without PF who underwent pylorus-preserving PD for pancreatic cancer show HUHA-A of 2.1% and mean CTHU of 36 HU. Axial (C) and sagittal (D) images from 77-year-old female patient with grade B PF who underwent pylorus-preserving PD for ampulla of Vater cancer show HUHA-A of 17.6% and mean CTHU of 27.5 HU. CTHU = CT Hounsfield unit, HUHA = Hounsfield unit histogram analysis, ROI = region of interest, SD = standard deviation

• 

  Fig. 3 Bland-Altman plots of inter-observer agreement for HUHA and mean CTHU measurements.A-D. Differences (y axis) between two observers are plotted against mean value (x axis) of their measurements. 95% limits of agreements of HUHA-A (A), HUHA-B (B), HUHA-C (C), and mean CTHU (D) ranged from −10.5% to 11% (mean, 0.3%), from −59% to 62.2% (mean, 1.6%), from −51.3% to 50.5% (mean −0.4%), and from −18.0 HU to 21.4 HU (mean 1.7 HU), respectively. Solid line indicates mean difference. Top and bottom dashed lines correspond to upper and lower margins of 95% limits of agreement. With probability of 95%, differences in normalized scores of future examinations will be between upper and lower limits of agreement (mean ± variability estimate = 1.96 × SD).

• 

  Fig. 4 ROC curve to predict PF using HUHA-A (AUC = 0.86), HUHA-B (AUC = 0.67), HUHA-C (AUC = 0.71), and mean CTHU (AUC = 0.65) values.AUC = area under curve, ROC = receiver operating characteristic

• 

  Fig. 5 ROC curve to predict pancreatic softness using HUHA-A (AUC = 0.86), HUHA-B (AUC = 0.71), HUHA-C (AUC = 0.74), and mean CTHU (AUC = 0.64) values.

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