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Value of Intravoxel Incoherent Motion for Hepatocellular Carcinoma Grading
Value of Intravoxel Incoherent Motion for Hepatocellular Carcinoma Grading Bedriye Koyuncu Sokmena,*, Soheil Sabeta, Aysegül Oza, Sadık Servera, Esat Namalb, Murat Dayangacc, Gülen Bülbül Dogusoye, Yaman Tokatd, and Nagihan Inana a Department of Radiology, Istanbul Bilim University, Sisli Florence Nightingale Hospital, Istanbul, Turkey; bDepartment of Medical Oncology, Istanbul Bilim University, Sisli Florence Nightingale Hospital, Istanbul, Turkey; cDepartment of General Surgery, Medipol University, Istanbul, Turkey; dDepartment of General Surgery and Liver Transplantation, Istanbul Bilim University, Sisli Florence Nightingale Hospital, Istanbul, Turkey; and eDepartment of Pathology, Istanbul Bilim University, Sisli Florence Nightingale Hospital, Istanbul, Turkey
ABSTRACT Background. To evaluate the diagnostic accuracy of intravoxel incoherent motion (IVIM) parameters in estimation of hepatocellular carcinoma (HCC) grading. Materials and methods. Twenty-nine patients with histopathologically diagnosed as 42 HCC at explant were included in this retrospective study. All patients were examined by 1.5T magnetic resonance imaging with the use of 4-channel phased array body coil. In addition to routine pre- and postcontrast sequences, IVIM (16 different b factors varying from 0 to 1300 s/mm2) and conventional diffusion-weighted imaging (3 different b factors of 50, 400, 800 s/mm2) were obtained with single-shot echo planar spin echo sequence. Apparent diffusion coefficient (ADC) and IVIM parameters including mean D (true diffusion coefficient), D* (pseudo-diffusion coefficient associated with blood flow), and f (perfusion fraction) values were calculated. Histopathologically, HCC was classified as low (grade 1, 2) and high (grade 3, 4) grade in accordance with the Edmondson-Steiner score. Quantitatively, ADC, D, D*, and f values were compared between the low- and high-grade groups by Student t test. The relationship between the parameters and histologic grade was analyzed using the Spearman’s correlation test. To evaluate the diagnostic performance of the parameters, receiver operating characteristic analysis was performed. Results. High-grade HCCs had significantly lower ADC and D values than low grade groups (P ¼ .005 and P ¼ .026, retrospectively); ADC and D values were inversely correlated with tumor grade (r ¼ e0.519, P ¼ .011, r ¼ e0.510, P ¼ .026, respectively). High-grade HCCs had significantly higher f values when compared with the low-grade group (P ¼ .005). The f values were positively correlated with tumor grade (r ¼ 0.548, P ¼ .007). The best discriminative parameter was f value. Cut-off value of 32% of f values showed sensitivity of 75.6% and a specificity of 73.5%. Conclusion. ADC values and IVIM parameters such as f values appear to reflect the grade of HCCs.
A
S we know, several predictive factors such as Milan criteria (tumor size and number), serum tumor marker levels (alpha fetoprotein), histopathologic findings (tumor grade, microvascular invasion), and activity on positron ª 2019 Elsevier Inc. All rights reserved. 230 Park Avenue, New York, NY 10169
Transplantation Proceedings, 51, 1861e1866 (2019)
*Address correspondence to Bedriye Koyuncu Sokmen, Istanbul Bilim University, Sisli Florence Nightingale Hospital, Abide-I, Hurriyet Street, No:164, Istanbul, Turkey. Tel: þ902122244954. E-mail: [email protected] 0041-1345/19 https://doi.org/10.1016/j.transproceed.2019.02.027
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emission tomographyecomputed tomography images had been described until now in the literature. In daily routine, diagnosis and also management of hepatocellular carcinomas (HCCs) depends on radiologic findings alone. Biopsy is not routinely recommended because of tumor seeding risk and tumoral heterogeneity, causing a false negative result. Because of that reason, radiologic prediction of HCC grade was very popular in radiology research in recent last years. There are many reports about magnetic resonance imaging (MRI) findings and HCC grade in the literature, such as precontrast T1W and T2W signal intensity, contrast enhancement pattern on postcontrast dynamic images, and hepatobiliary phase images and diffusion restriction on diffusion weighted images. A number of studies have reported implication of conventional diffusion-weighted imaging (DWI) for this purpose [1e5]. To our knowledge, conventional DWI reflects both microscopic diffusion of water molecules and capillary perfusion in tissue at the same time. It cannot separate each other. This capillary perfusion, named pseudodiffusion, represents bulk motion within voxels. The effect of pseudodiffusion on the signal attenuation is also b value dependent. Therefore, pseudodiffusion role diminishes at higher b values, while its effect is more significant at lower b values. In recent years, a new diffusion imaging technique named as intravoxel incoherent motion (IVIM) has emerged, which can characterize the relation between signal intensity (SI) and b value. The IVIM approach uses biexponential function to describe diffusion-weighted MRI data and assumes that the signal attenuation measured in diffusion-weighted MRI includes a mixture of tissue perfusion and tissue diffusion effects. Regarding to this biexponential model, IVIM can separate the diffusion of water molecules from microcapillary perfusion of the tissues [6e9]. This technique estimates perfusion of the tissues without the use of intravenous contrast agents, and therefore it is beneficial in cirrhotic patients with renal insufficiency. If we calculate tumor perfusion with this technique, we can estimate tumoral grade because we know that tumoral grade is associated with neoangiogenesis. To the best of our knowledge, there are few reports in the literature evaluating the correlation of IVIM parameters and HCC grade based on biopsy or resected specimens, but correlation based on explant liver was not previously studied [10,11]. The purpose of this study is to evaluate the IVIM parameters in estimation of HCC grade at explant. MATERIALS AND METHODS The institutional review board approved the study; the requirement for informed consent was waived since the study was retrospective investigation.
Patients Between January 2015 and October 2016, 78 liver explants with histopathologically proven HCC at the explant liver were retrospectively evaluated. Forty-nine of them had to be excluded for the
SOKMEN, SABET, OZ ET AL Table 1. Result of the Quantitative Analysis of the Diffusion Weighted Imaging and IVIM Parameters
ADC (x 10e3 mm2/sn) D (x 10e3 mm2/sn) D* (x 10e3 mm2/sn) f (%)
Low Grade (n ¼ 28) High Grade (n ¼ 14) P Value
1.28 1.06 38.97 24.33
0.28 0.15 13.06 12.29
0.99 0.89 91.21 41.33
0.15 0.15 16.00 9.25
.005 .026 .42 .005
Abbreviations: ADC, apparent diffusion coefficient; D, true diffusion coefficient; D*, pseudo-diffusion coefficient associated with blood flow; f, perfusion fraction; IVIM, intravoxel incoherent motion.
following reasons: delay of more than 90 days between MRI and explantation (10 patients), nonstandard imaging protocol (18 patients), HCCs smaller than 1 cm (9 patients), and previous interventional treatment (12 patients). Finally, 29 patients (20 men and 9 women; mean age of 54.74 8 years, range 43e70) diagnosed with 42 HCCs were included in this study. All of them had chronic liver disease and etiology as follows; 19 patients had hepatitis B virus, 3 patients had hepatitis C virus, 3 patients had nonalcoholic steatohepatitis, 2 patients had alcoholic liver cirrhosis, and 2 patients had cryptogenic cirrhosis.
Magnetic Resonance Imaging All of the patients were examined using a 1.5 T MRI unit (Siemens, Magnetom Symphony, Erlangen, Germany) with the use of 4-channel phased array body coil. Initially, all of the patients underwent precontrast routine upper abdomen sequences including axial in-phase (TR/TE/FA:179/2.4/70) and out-of-phase (TR/TE/FA:179/4.8/70) T1-weighted (W) turbo field echo, axial, and coronal T2-W single-shot turbo spin echo (TSE) (TR/TE/TSEfactor/NEX:1350/92/281/1). Subsequently, respiratory-triggered IVIM with 16 different b values of 0, 50, 100, 150, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, and 1300 s/mm2 and respiratory-triggered conventional DWI with 3 different b factors of 50, 400, and 800 s/mm2 were obtained with single-shot echo-planar imaging (EPI) sequence. Dynamic T1-W volumetric interpolated breath-hold examination (TR/TE/NEX/FA: 4.86/2.39/1/10.0) were performed after administration of intravenous gadoxetic acid (Primovist, Bayer Schering Pharma, Berlin, Germany) at a dose of 0.025 mmol/kg in all of the patients. Postcontrast arterial phase (25 s), portal venous phase (60 s), and delayed phase (180 s) images were obtained. Fat suppression was acquired with the spectral adiabatic inversion recovery method. All images were obtained with parallel acquisition and a sensitivity encoding (generalized autocalibrating partially parallel acquisitions) technique (R factor of 2). The acquisition time for IVIM sequence and for total upper abdominal MRI were 10 3 minutes and 40 to 45 minutes, respectively. All sequences consisted of a multisection acquisition (slice thickness/ intersection gap: 5 mm/1 mm) with imaging matrix of 115 192. The field of view varied between 240 and 380 mm. Table 2. Correlation of Histologic Grade With ADC and IVIM Parameters IVIM Parameter
ADCcon D f D*
r
P
e0.519 e0.510 0.548 0.184
.011 .026 .007 .40
Abbreviations: ADC, apparent diffusion coefficient; D, true diffusion coefficient; D*, pseudo-diffusion coefficient associated with blood flow; f, perfusion fraction; IVIM, intravoxel incoherent motion.
INTRAVOXEL INCOHERENT MOTION
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Fig 1. Low-grade HCC in a 56-year-old man with cirrhosis. (A) Axial T2 weighted (W) image shows a HCC in the right lobe at segment 8 (white arrow). (B) It shows hyperintensity on diffusion trace image with b value of 1000 s/mm2 (white arrow). (C) ADC is calculated as 1.14 x 103 mm2/s (white arrow). (D) D value is calculated as 1.12 x 103 mm2/s. (E) IVIM parameters were acquired from trace sequences obtained through 16 different b values varying from 0 to 1300 s/mm2, and f value is calculated as 8% consistent with lowgrade HCC.
Histopathologic Assessment All specimens were evaluated by an experienced hepatologist (B.G). Histologic grade was assessed according to the modified Edmondson and Steiner criteria as well-differentiated grade 1, moderately differentiated grade 2, poorly differentiated grade 3, and undifferentiated grade 4 [12]. Pathologic staging was performed according to TNM, 7th edition [12]. Grade 1 and 2 were accepted as low grade (28 HCCs), and grade 3 and 4 were accepted as high grade (14 HCCs).
Image Analysis Quantitative analysis was performed by a work station with dedicated software (AW Volume Share 04, GE Medical Systems, Chicago, Ill, USA) by a radiologist (B.K.S.) who was aware of the pathologic HCC classification but blinded to the histopathologic grade. For quantitative analysis of conventional DWI, an apparent diffusion coefficient (ADC) map was reconstructed automatically from conventional DWI using all b values. For quantitative evaluation of IVIM, the SI was calculated manually from each b value varying between 0 and 1300 s/mm2. Regions of interest (ROIs) were placed by comparing DWI with T2W and postcontrast T1W images. Three ROIs were placed on similar locations in DWI and IVIM images, covering at least two-thirds of the diameter of lesions to prevent interference from the vascular and adjacent structures. The same ROI mask was propagated to all b values. The mean ROI was 60.8 mm2 (range, 33 to 385 mm2). The average of the 3 consecutive measurements was regarded as the final value.
IVIM parameters including D (true diffusion coefficient), D* (pseudo-diffusion coefficient associated with blood flow), and f (perfusion fraction) values were postprocessed using a freely available specific software program based on the website (http:// yamarad.umin.ne.jp/ivim/simplex_en.html) with the following approach according to the IVIM model: SIb/SI0 ¼ (1-f) . exp (-bD) þ fexp(-bD*) Eq. (SI0 ¼ signal intensity at b0; SIb ¼ signal intensity for a given b value.)
Statistical Analysis Histopathology was considered as standard reference for the statistical evaluation. For the statistical evaluation of conventional DWI and IVIM parameters; ADC, D, D*, and f values of the HCCs were compared. The fitness of numeric data set to normal distribution was determined by Kolmogorov-Smirnov test. Subsequently, the differences in those values were analyzed by Student t test. The correlation of conventional DWI and IVIM parameters with HCCs grade were analyzed with Spearman’s correlation test. To evaluate the diagnostic value of parameters for detection of grade and to describe the sensitivity and specificity of the tests, receiver operator characteristic (ROC) analysis was performed. All analyses were reported with SPSS (IBM, Armonk, NY, United States).
RESULTS
The results of quantitative analysis of the conventional DWI and IVIM parameters were reviewed in Table 1. Correlation
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Fig 2. High-grade HCC in a 52-year-old woman with cirrhosis. (A) Axial T2 weighted (W) image shows an HCC in the right lobe at segment 6 (white arrow). (B) It shows hyperintensity on diffusion trace image with b value of 1000 s/mm2 (white arrow). (C) ADC is calculated as 0.72 x 103 mm2/s (white arrow). (D) D value is calculated as 0.68 x 103 mm2/s. (E) IVIM parameters were acquired from trace sequences obtained from 16 different b values varying from 0 to 1300 s/mm2, and f value is calculated as 30% consistent with highgrade HCC.
of histologic grade with ADC and IVIM parameters were reviewed in Table 2. High-grade HCCs had significantly lower ADC and D values than those of the low-grade HCCs (P ¼ .005 and P ¼ .026, retrospectively) (Fig 1). ADC and D values were inversely correlated with tumor grade (r ¼ e0.519, P ¼ .011, r ¼ e0.510, P ¼ .026, respectively). Highgrade HCCs had higher f values in comparison with low grade group (P ¼ .005) (Fig 2). The f values were positively correlated with tumor grade (r ¼ 0.548, P ¼ .007). The best discriminative parameter was f value and the area under the ROC curve was 0.866. With a cut-off value of 32%, f had a sensitivity of 75.6% and a specificity of 73.5% (Table 3). The area under the ROC curve was 0.857 0.109 for ADCcon (P ¼ .032). With a cut-off value 1.10 x 103 mm2/sn, ADC had a sensitivity of 71.4% and a specificity of 67.7% (Table 3). The area under the ROC curve was 0.833 0.152 for D (P ¼ .046). With a cut-off value 1.02 x 103 mm2/sn, D had a sensitivity of 63.6% and a specificity of 66.7% (Table 3).
DISCUSSION
In this study, we found that ADC and D value were significantly lower in high-grade HCC, and ADC and D value were inverse correlate with grade. There are a few studies about the use of DWI for grading of HCCs [13e18]. Most of them reported similar results with us. For example, Nishie et al [4] reported significant difference between ADC values and the histologic grade of HCCs in a series of 85 resection specimen. This reduced diffusion is most likely associated with higher cellular density in higher-grade HCC [19]. Jiang et al [14] evaluated SI of HCCs quantitatively on diffusionweighted imaging instead of ADC values and found a weak negative correlation between SI and HCC grade. We also found that f value was significantly higher in high-grade HCC and that value was positive with grade. The f value reflects increased perfusion and neovascularization of high-grade HCC. During the hepatogenesis (neoangiogenesis, the formation and development of blood vessels, progress), these arteries are present with
Table 3. ROC Analysis
f (%) ADCcon D
Area SD
P
Sensitivity
Specificity
Cut-off
0.866 0.857 0.109 0.833 0.152
.028 .032 .046
75.6% 71.4% 63.6%
73.5% 67.7% 66.7%
32% 1.10 x 103 mm2/sn 1.02 x 103 mm2/sn
Abbreviations: ADC, apparent diffusion coefficient; D, true diffusion coefficient; f, perfusion fraction; ROC, receiver operator characteristic; SD, standard deviation.
INTRAVOXEL INCOHERENT MOTION
increasing size and number in progressed HCCs [20,21]. The results of a study performed by Woo et al [11] revealed significant correlation of f values and arterial contrast enhancement among 42 surgically confirmed cases, similar to our results. As higher arterial enhancement is expected in high-grade HCCs, increased f values detected in our study could be explained by increased vascular perfusion in highgrade groups. We obtained IVIM images with 16 different b values providing higher accuracy of the parameters and optimal signal-to-noise resolution compared with the formerly mentioned study. The main advantage of IVIM technique is underlined by the estimation of the tissue perfusion without administration of contrast agent, and this technique is useful for the evaluation of hypervascular abdominal pathologies such as neuroendocrine tumor, renal cell carcinoma, HCC grading [8,9,21e24], as well as diagnosis of cirrhosis [9]. IVIM can also assess treatment response of antiangiogenic agents for specific tumors (HCC, liver metastases of colon carcinoma) [4]. In our study, ADC showed greater diagnostic accuracy than IVIM parameters in grading HCCs. Statistically insignificancy of f values is thought to be due to restricted number of cases and also lack of grade 4 HCCs among the high-grade group. This result is also compatible with outcomes of a study performed by Granata et al [11] including 62 biopsy-proven HCC series that revealed higher diagnostic performance of ADC compared to f and D values in differentiation of high- and low-grade HCCs. The main limitation of this study is low patient number, necessitating further studies with larger series to provide a consensus on these parameters. The low SNR of the 1.5 T for DWI is another limitation of this study. The EPI sequence obtained in 1.5 T MRI scanner has a relatively low SNR, which results in significant image distortion. Furthermore, EPI has additional anatomic distortion because of susceptibility effects. Also, choice and execution of the mathematic models for IVIM remains a complex issue that might require the development of further sophisticated diffusion quantitative parameters to be applied as biomarkers [6]. In conclusion, conventional DWI in combination with IVIM parameters in addition to the routine MRI protocols can have a potential role in the estimation of HCC grade and can be used for the diagnosis and follow-up of HCC patients with renal or hepatic insufficiency to avoid harmful effects of intravenous contrast agents.
REFERENCES [1] Nasu K, Kuroki Y, Tsukamoto T, Nakajima H, Mori K, Minami M. Diffusion-weighted imaging of surgically resected hepatocellular carcinoma: imaging characteristics and relationship among signal intensity, apparent diffusion coefficient, and histopathologic grade. AJR Am J Roentgenol 2009;193(2):438e44.
1865 [2] Heo SH, Jeong YY, Shin SS, et al. Apparent diffusion coefficient value of diffusion weighted imaging for hepatocellular carcinoma: correlation with the histologic differentiation and the expression of vascular endothelial growth factor. Korean Radiol 2010;11(3):295e303. [3] Nakanishi M, Chuma M, Hige S, et al. Relationship between diffusion-weighted magnetic resonance imaging and histological tumor grading of hepatocellular carcinoma. Ann Surg Oncol 2012;19(4):1302e9. [4] Nishie A, Tajima T, Asayama Y, et al. Diagnostic performance of apparent diffusion coefficient for predicting histological grade of hepatocellular carcinoma. Eur J Radiol 2011;80(2): e29e33. [5] Muhi A, Ichikawa T, Motosugi U, et al. High-value diffusionweighted MR imaging of hepatocellular lesions: estimation of grade of malignancy of hepatocellular carcinoma. J Magn Reson Imaging 2009;30(5):1005e11. [6] Koh DM, Collins DJ, Orton MR. Intravoxel incoherent motion in body diffusion-weighted MRI: Reality and challenges. AJR 2011;196:1351e61. [7] Le Bihan D, Breton E, Lallemand D, Aubin ML, Vignaud J, Laval-Jeantet M. Separation of diffusion and perfusion in intravoxel incoherent motion MR imaging. Radiology 1988;168:497e505. [8] Klauss M, Mayer P, Maier-Hein K, et al. IVIM-diffusionMRI for the differentiation of solid benign and malign hypervascular liver lesionsdEvaluation with two different MR scanner. Eur J Radiol 2016;85(7):1289e94. [9] Patel J, Sigmund EE, Rusinek H, Oei M, Babb JS, Taouli B. Diagnosis of cirrhosis with intravoxel incoherent motion diffusion MRI and dynamic contrast-enhanced MRI alone and in combination: preliminary experience. J Magn Reson Imaging 2010;3: 589e600. [10] Woo S, Lee JM, Yoon JH, et al. Intravoxel incoherent motion diffusion-weighted MR imaging of hepatocellular carcinoma: correlation with enhancement degree and histologic grade. Radiology 270:758e767. [11] Granata V, Fusco R, Catalano O, et al. Intravoxel incoherent motion (IVIM) in diffusion-weighted imaging (DWI) for hepatocellular carcinoma: correlation with histologic grade. Oncotarget 2016;48:79357e64. [12] Ruby SG. Protocol for the examination of specimens from patients with hepatocellular carcinoma and cholangio carcinoma, including intrahepatic bile ducts a basis for check lists. Arch Pathol Lab Med 2000;124:41e5. [13] Guo W, Zhao S, Yang Y, Shao G. Histological grade of hepatocellular carcinoma predicted by quantitative diffusionweighted imaging. Int J Clin Exp Med 2015;8(3):4164e9. [14] Jiang T, Xu JH, Zou Y, et al. Diffusion-weighted imaging (DWI) of hepatocellular carcinomas: a retrospective analysis of the correlation between qualitative and quantitative DWI and tumour grade. Clin Radiol 2017:e1e8. [15] Shankar S, Kalra A, Bhatia A, et al. Role of diffusion weighted imaging (dwi) for hepatocellular carcinoma (hcc) detection and its grading on 3T MRI: a prospective study. J Clin Exp Hepatol 2016;6:303e10. [16] Byrd RH, Schnabel RB, Shultz GA. Approximate solution of the trust region problem by minimization over two-dimensional subspaces. Math Program 1988;40:247e63. [17] Kim SH, Lim HK, Choi D, et al. Percutaneous radiofrequency ablation of hepatocellular carcinoma: effect of histologic grade on therapeutic results. Am J Roentgenol 2006;186: S327e33. [18] Li X, Zhang K, Shi Y, Wang F, Meng X. Correlations between the minimum and mean apparent diffusion coefficient values of hepatocellular carcinoma and tumor grade. J Magn Reson Imaging 2016;44:1442e7.
1866 [19] Nasu K, Kuroki Y, Tsukamoto Y, Nakajima H, Mori K, Minami M. Diffusion weighted imaging of surgically resected hepatocellular carcinoma: imaging characteristics and relationship among signal intensity, apparent coefficient and histopathologic grade. Am J Radiol 2009;193:438e44. [20] Choi JY, Lee J-M, Sirlin CB. CT and MR imaging diagnosis and staging of hepatocellular carcinoma: part I. Development, growth, and spread: key pathologic and imaging aspects. Radiology 2014;272(3). [21] Choi JY, Lee J-M, Sirlin CB. CT and MR imaging diagnosis and staging of hepatocellular carcinoma: part II. Extracellular agents, hepatobiliary agents, and ancillary imaging features. Radiology 2014;273(1).
SOKMEN, SABET, OZ ET AL [22] Shirota N, Saito K, Sugimoto K, Takara K, Moriyasu F, Tokuuye K. Intravoxel incoherent motion MRI as a biomarker of sorafenib treatment for advanced hepatocellular carcinoma: a pilot study. Cancer Imaging 2016;16:1e6. [23] Ding Y, Zeng M, Rao S, Chen C, Fu C, Zhou J. Comparison of biexponential and monoexponential model of diffusion-weighted imaging for distinguishing between common renal cell carcinoma and fat poor angiomyolipoma. Korean J Radiol 2016;17(6):853e63. [24] Chandarana H, Lee VS, Hecht E, Taouli B, Sigmund EE. Comparison of biexponential and monoexponential model of diffusion weighted imaging in evaluation of renal lesions: preliminary experience. Invest Radiol 2011;46:285e91.
ABSTRACT Background. To evaluate the diagnostic accuracy of intravoxel incoherent motion (IVIM) parameters in estimation of hepatocellular carcinoma (HCC) grading. Materials and methods. Twenty-nine patients with histopathologically diagnosed as 42 HCC at explant were included in this retrospective study. All patients were examined by 1.5T magnetic resonance imaging with the use of 4-channel phased array body coil. In addition to routine pre- and postcontrast sequences, IVIM (16 different b factors varying from 0 to 1300 s/mm2) and conventional diffusion-weighted imaging (3 different b factors of 50, 400, 800 s/mm2) were obtained with single-shot echo planar spin echo sequence. Apparent diffusion coefficient (ADC) and IVIM parameters including mean D (true diffusion coefficient), D* (pseudo-diffusion coefficient associated with blood flow), and f (perfusion fraction) values were calculated. Histopathologically, HCC was classified as low (grade 1, 2) and high (grade 3, 4) grade in accordance with the Edmondson-Steiner score. Quantitatively, ADC, D, D*, and f values were compared between the low- and high-grade groups by Student t test. The relationship between the parameters and histologic grade was analyzed using the Spearman’s correlation test. To evaluate the diagnostic performance of the parameters, receiver operating characteristic analysis was performed. Results. High-grade HCCs had significantly lower ADC and D values than low grade groups (P ¼ .005 and P ¼ .026, retrospectively); ADC and D values were inversely correlated with tumor grade (r ¼ e0.519, P ¼ .011, r ¼ e0.510, P ¼ .026, respectively). High-grade HCCs had significantly higher f values when compared with the low-grade group (P ¼ .005). The f values were positively correlated with tumor grade (r ¼ 0.548, P ¼ .007). The best discriminative parameter was f value. Cut-off value of 32% of f values showed sensitivity of 75.6% and a specificity of 73.5%. Conclusion. ADC values and IVIM parameters such as f values appear to reflect the grade of HCCs.
A
S we know, several predictive factors such as Milan criteria (tumor size and number), serum tumor marker levels (alpha fetoprotein), histopathologic findings (tumor grade, microvascular invasion), and activity on positron ª 2019 Elsevier Inc. All rights reserved. 230 Park Avenue, New York, NY 10169
Transplantation Proceedings, 51, 1861e1866 (2019)
*Address correspondence to Bedriye Koyuncu Sokmen, Istanbul Bilim University, Sisli Florence Nightingale Hospital, Abide-I, Hurriyet Street, No:164, Istanbul, Turkey. Tel: þ902122244954. E-mail: [email protected] 0041-1345/19 https://doi.org/10.1016/j.transproceed.2019.02.027
1861
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emission tomographyecomputed tomography images had been described until now in the literature. In daily routine, diagnosis and also management of hepatocellular carcinomas (HCCs) depends on radiologic findings alone. Biopsy is not routinely recommended because of tumor seeding risk and tumoral heterogeneity, causing a false negative result. Because of that reason, radiologic prediction of HCC grade was very popular in radiology research in recent last years. There are many reports about magnetic resonance imaging (MRI) findings and HCC grade in the literature, such as precontrast T1W and T2W signal intensity, contrast enhancement pattern on postcontrast dynamic images, and hepatobiliary phase images and diffusion restriction on diffusion weighted images. A number of studies have reported implication of conventional diffusion-weighted imaging (DWI) for this purpose [1e5]. To our knowledge, conventional DWI reflects both microscopic diffusion of water molecules and capillary perfusion in tissue at the same time. It cannot separate each other. This capillary perfusion, named pseudodiffusion, represents bulk motion within voxels. The effect of pseudodiffusion on the signal attenuation is also b value dependent. Therefore, pseudodiffusion role diminishes at higher b values, while its effect is more significant at lower b values. In recent years, a new diffusion imaging technique named as intravoxel incoherent motion (IVIM) has emerged, which can characterize the relation between signal intensity (SI) and b value. The IVIM approach uses biexponential function to describe diffusion-weighted MRI data and assumes that the signal attenuation measured in diffusion-weighted MRI includes a mixture of tissue perfusion and tissue diffusion effects. Regarding to this biexponential model, IVIM can separate the diffusion of water molecules from microcapillary perfusion of the tissues [6e9]. This technique estimates perfusion of the tissues without the use of intravenous contrast agents, and therefore it is beneficial in cirrhotic patients with renal insufficiency. If we calculate tumor perfusion with this technique, we can estimate tumoral grade because we know that tumoral grade is associated with neoangiogenesis. To the best of our knowledge, there are few reports in the literature evaluating the correlation of IVIM parameters and HCC grade based on biopsy or resected specimens, but correlation based on explant liver was not previously studied [10,11]. The purpose of this study is to evaluate the IVIM parameters in estimation of HCC grade at explant. MATERIALS AND METHODS The institutional review board approved the study; the requirement for informed consent was waived since the study was retrospective investigation.
Patients Between January 2015 and October 2016, 78 liver explants with histopathologically proven HCC at the explant liver were retrospectively evaluated. Forty-nine of them had to be excluded for the
SOKMEN, SABET, OZ ET AL Table 1. Result of the Quantitative Analysis of the Diffusion Weighted Imaging and IVIM Parameters
ADC (x 10e3 mm2/sn) D (x 10e3 mm2/sn) D* (x 10e3 mm2/sn) f (%)
Low Grade (n ¼ 28) High Grade (n ¼ 14) P Value
1.28 1.06 38.97 24.33
0.28 0.15 13.06 12.29
0.99 0.89 91.21 41.33
0.15 0.15 16.00 9.25
.005 .026 .42 .005
Abbreviations: ADC, apparent diffusion coefficient; D, true diffusion coefficient; D*, pseudo-diffusion coefficient associated with blood flow; f, perfusion fraction; IVIM, intravoxel incoherent motion.
following reasons: delay of more than 90 days between MRI and explantation (10 patients), nonstandard imaging protocol (18 patients), HCCs smaller than 1 cm (9 patients), and previous interventional treatment (12 patients). Finally, 29 patients (20 men and 9 women; mean age of 54.74 8 years, range 43e70) diagnosed with 42 HCCs were included in this study. All of them had chronic liver disease and etiology as follows; 19 patients had hepatitis B virus, 3 patients had hepatitis C virus, 3 patients had nonalcoholic steatohepatitis, 2 patients had alcoholic liver cirrhosis, and 2 patients had cryptogenic cirrhosis.
Magnetic Resonance Imaging All of the patients were examined using a 1.5 T MRI unit (Siemens, Magnetom Symphony, Erlangen, Germany) with the use of 4-channel phased array body coil. Initially, all of the patients underwent precontrast routine upper abdomen sequences including axial in-phase (TR/TE/FA:179/2.4/70) and out-of-phase (TR/TE/FA:179/4.8/70) T1-weighted (W) turbo field echo, axial, and coronal T2-W single-shot turbo spin echo (TSE) (TR/TE/TSEfactor/NEX:1350/92/281/1). Subsequently, respiratory-triggered IVIM with 16 different b values of 0, 50, 100, 150, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, and 1300 s/mm2 and respiratory-triggered conventional DWI with 3 different b factors of 50, 400, and 800 s/mm2 were obtained with single-shot echo-planar imaging (EPI) sequence. Dynamic T1-W volumetric interpolated breath-hold examination (TR/TE/NEX/FA: 4.86/2.39/1/10.0) were performed after administration of intravenous gadoxetic acid (Primovist, Bayer Schering Pharma, Berlin, Germany) at a dose of 0.025 mmol/kg in all of the patients. Postcontrast arterial phase (25 s), portal venous phase (60 s), and delayed phase (180 s) images were obtained. Fat suppression was acquired with the spectral adiabatic inversion recovery method. All images were obtained with parallel acquisition and a sensitivity encoding (generalized autocalibrating partially parallel acquisitions) technique (R factor of 2). The acquisition time for IVIM sequence and for total upper abdominal MRI were 10 3 minutes and 40 to 45 minutes, respectively. All sequences consisted of a multisection acquisition (slice thickness/ intersection gap: 5 mm/1 mm) with imaging matrix of 115 192. The field of view varied between 240 and 380 mm. Table 2. Correlation of Histologic Grade With ADC and IVIM Parameters IVIM Parameter
ADCcon D f D*
r
P
e0.519 e0.510 0.548 0.184
.011 .026 .007 .40
Abbreviations: ADC, apparent diffusion coefficient; D, true diffusion coefficient; D*, pseudo-diffusion coefficient associated with blood flow; f, perfusion fraction; IVIM, intravoxel incoherent motion.
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Fig 1. Low-grade HCC in a 56-year-old man with cirrhosis. (A) Axial T2 weighted (W) image shows a HCC in the right lobe at segment 8 (white arrow). (B) It shows hyperintensity on diffusion trace image with b value of 1000 s/mm2 (white arrow). (C) ADC is calculated as 1.14 x 103 mm2/s (white arrow). (D) D value is calculated as 1.12 x 103 mm2/s. (E) IVIM parameters were acquired from trace sequences obtained through 16 different b values varying from 0 to 1300 s/mm2, and f value is calculated as 8% consistent with lowgrade HCC.
Histopathologic Assessment All specimens were evaluated by an experienced hepatologist (B.G). Histologic grade was assessed according to the modified Edmondson and Steiner criteria as well-differentiated grade 1, moderately differentiated grade 2, poorly differentiated grade 3, and undifferentiated grade 4 [12]. Pathologic staging was performed according to TNM, 7th edition [12]. Grade 1 and 2 were accepted as low grade (28 HCCs), and grade 3 and 4 were accepted as high grade (14 HCCs).
Image Analysis Quantitative analysis was performed by a work station with dedicated software (AW Volume Share 04, GE Medical Systems, Chicago, Ill, USA) by a radiologist (B.K.S.) who was aware of the pathologic HCC classification but blinded to the histopathologic grade. For quantitative analysis of conventional DWI, an apparent diffusion coefficient (ADC) map was reconstructed automatically from conventional DWI using all b values. For quantitative evaluation of IVIM, the SI was calculated manually from each b value varying between 0 and 1300 s/mm2. Regions of interest (ROIs) were placed by comparing DWI with T2W and postcontrast T1W images. Three ROIs were placed on similar locations in DWI and IVIM images, covering at least two-thirds of the diameter of lesions to prevent interference from the vascular and adjacent structures. The same ROI mask was propagated to all b values. The mean ROI was 60.8 mm2 (range, 33 to 385 mm2). The average of the 3 consecutive measurements was regarded as the final value.
IVIM parameters including D (true diffusion coefficient), D* (pseudo-diffusion coefficient associated with blood flow), and f (perfusion fraction) values were postprocessed using a freely available specific software program based on the website (http:// yamarad.umin.ne.jp/ivim/simplex_en.html) with the following approach according to the IVIM model: SIb/SI0 ¼ (1-f) . exp (-bD) þ fexp(-bD*) Eq. (SI0 ¼ signal intensity at b0; SIb ¼ signal intensity for a given b value.)
Statistical Analysis Histopathology was considered as standard reference for the statistical evaluation. For the statistical evaluation of conventional DWI and IVIM parameters; ADC, D, D*, and f values of the HCCs were compared. The fitness of numeric data set to normal distribution was determined by Kolmogorov-Smirnov test. Subsequently, the differences in those values were analyzed by Student t test. The correlation of conventional DWI and IVIM parameters with HCCs grade were analyzed with Spearman’s correlation test. To evaluate the diagnostic value of parameters for detection of grade and to describe the sensitivity and specificity of the tests, receiver operator characteristic (ROC) analysis was performed. All analyses were reported with SPSS (IBM, Armonk, NY, United States).
RESULTS
The results of quantitative analysis of the conventional DWI and IVIM parameters were reviewed in Table 1. Correlation
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Fig 2. High-grade HCC in a 52-year-old woman with cirrhosis. (A) Axial T2 weighted (W) image shows an HCC in the right lobe at segment 6 (white arrow). (B) It shows hyperintensity on diffusion trace image with b value of 1000 s/mm2 (white arrow). (C) ADC is calculated as 0.72 x 103 mm2/s (white arrow). (D) D value is calculated as 0.68 x 103 mm2/s. (E) IVIM parameters were acquired from trace sequences obtained from 16 different b values varying from 0 to 1300 s/mm2, and f value is calculated as 30% consistent with highgrade HCC.
of histologic grade with ADC and IVIM parameters were reviewed in Table 2. High-grade HCCs had significantly lower ADC and D values than those of the low-grade HCCs (P ¼ .005 and P ¼ .026, retrospectively) (Fig 1). ADC and D values were inversely correlated with tumor grade (r ¼ e0.519, P ¼ .011, r ¼ e0.510, P ¼ .026, respectively). Highgrade HCCs had higher f values in comparison with low grade group (P ¼ .005) (Fig 2). The f values were positively correlated with tumor grade (r ¼ 0.548, P ¼ .007). The best discriminative parameter was f value and the area under the ROC curve was 0.866. With a cut-off value of 32%, f had a sensitivity of 75.6% and a specificity of 73.5% (Table 3). The area under the ROC curve was 0.857 0.109 for ADCcon (P ¼ .032). With a cut-off value 1.10 x 103 mm2/sn, ADC had a sensitivity of 71.4% and a specificity of 67.7% (Table 3). The area under the ROC curve was 0.833 0.152 for D (P ¼ .046). With a cut-off value 1.02 x 103 mm2/sn, D had a sensitivity of 63.6% and a specificity of 66.7% (Table 3).
DISCUSSION
In this study, we found that ADC and D value were significantly lower in high-grade HCC, and ADC and D value were inverse correlate with grade. There are a few studies about the use of DWI for grading of HCCs [13e18]. Most of them reported similar results with us. For example, Nishie et al [4] reported significant difference between ADC values and the histologic grade of HCCs in a series of 85 resection specimen. This reduced diffusion is most likely associated with higher cellular density in higher-grade HCC [19]. Jiang et al [14] evaluated SI of HCCs quantitatively on diffusionweighted imaging instead of ADC values and found a weak negative correlation between SI and HCC grade. We also found that f value was significantly higher in high-grade HCC and that value was positive with grade. The f value reflects increased perfusion and neovascularization of high-grade HCC. During the hepatogenesis (neoangiogenesis, the formation and development of blood vessels, progress), these arteries are present with
Table 3. ROC Analysis
f (%) ADCcon D
Area SD
P
Sensitivity
Specificity
Cut-off
0.866 0.857 0.109 0.833 0.152
.028 .032 .046
75.6% 71.4% 63.6%
73.5% 67.7% 66.7%
32% 1.10 x 103 mm2/sn 1.02 x 103 mm2/sn
Abbreviations: ADC, apparent diffusion coefficient; D, true diffusion coefficient; f, perfusion fraction; ROC, receiver operator characteristic; SD, standard deviation.
INTRAVOXEL INCOHERENT MOTION
increasing size and number in progressed HCCs [20,21]. The results of a study performed by Woo et al [11] revealed significant correlation of f values and arterial contrast enhancement among 42 surgically confirmed cases, similar to our results. As higher arterial enhancement is expected in high-grade HCCs, increased f values detected in our study could be explained by increased vascular perfusion in highgrade groups. We obtained IVIM images with 16 different b values providing higher accuracy of the parameters and optimal signal-to-noise resolution compared with the formerly mentioned study. The main advantage of IVIM technique is underlined by the estimation of the tissue perfusion without administration of contrast agent, and this technique is useful for the evaluation of hypervascular abdominal pathologies such as neuroendocrine tumor, renal cell carcinoma, HCC grading [8,9,21e24], as well as diagnosis of cirrhosis [9]. IVIM can also assess treatment response of antiangiogenic agents for specific tumors (HCC, liver metastases of colon carcinoma) [4]. In our study, ADC showed greater diagnostic accuracy than IVIM parameters in grading HCCs. Statistically insignificancy of f values is thought to be due to restricted number of cases and also lack of grade 4 HCCs among the high-grade group. This result is also compatible with outcomes of a study performed by Granata et al [11] including 62 biopsy-proven HCC series that revealed higher diagnostic performance of ADC compared to f and D values in differentiation of high- and low-grade HCCs. The main limitation of this study is low patient number, necessitating further studies with larger series to provide a consensus on these parameters. The low SNR of the 1.5 T for DWI is another limitation of this study. The EPI sequence obtained in 1.5 T MRI scanner has a relatively low SNR, which results in significant image distortion. Furthermore, EPI has additional anatomic distortion because of susceptibility effects. Also, choice and execution of the mathematic models for IVIM remains a complex issue that might require the development of further sophisticated diffusion quantitative parameters to be applied as biomarkers [6]. In conclusion, conventional DWI in combination with IVIM parameters in addition to the routine MRI protocols can have a potential role in the estimation of HCC grade and can be used for the diagnosis and follow-up of HCC patients with renal or hepatic insufficiency to avoid harmful effects of intravenous contrast agents.
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