Washout ratio on contrast-enhanced CT for adrenal lesion: A comparison of 5 min and 10 min delay after IV contrast injection

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1 Washout ratio on contrast-enhanced CT for adrenal lesion: A comparison of 5 min and 10 min delay after IV contrast injection Poster No.: C-1165 Congress: ECR 2010 Type: Topic: Scientific Exhibit Genitourinary Authors: Y. Kumagae, Y. Fukukura, T. Kamiyama, K. Takumi, T. Shindo, A. Tateyama, M. Sato, M. Nakajo; Kagoshima/JP Keywords: DOI: adrenal adenoma, CT, delayed scan /ecr2010/C-1165 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 13

2 Purpose It is well known that the majority of adrenal adenomas contain as much as % cytoplasmic lipid, and many adrenal adenomas have low attenuation on unenhanced CT scans [2-3,8-9,12-18]. Therefore, unenhanced CT densitometry may differentiate some adenomas from nonadenomas because nearly all the other nonadenomas (metastases in particular) are lipid poor. However, 10-40% of all adenomas contain small amounts of lipid, and cannot be characterized on the basis of unenhanced attenuation values. Several articles have described that delayed enhanced CT images are highly accurate in distinguishing adrenal adenomas from nonadenomas [1,4-5,7-9,12,14-15,17-19], because adenomas lose enhancement more rapidly than malignant masses do. In general, a min delay was recommended by most authors [1,4-5,7-9,12,14-15,17-19]. However, a shorter delayed enhanced CT protocol to facilitate the differentiation of these lesions would be desirable. In this study, we evaluated the usefulness of 5-min delayed phase compared with 10-min delayed phase in distinguishing adenomas from nonadenomas. Methods and Materials Patient Population From March 2005 to March 2009, 206 patients were consecutively examined with multidetector-helical CT for evaluation of suspected adrenal diseases. Their clinical records were reviewed. The patients with followings were excluded from the study (Fig 1): normal findings (n=49), adenomas treated by transcatheter arterial embolization (n=5), expansive necrosis or cystic change of pheochoromocytoma and metastasis(n=2), calcification (n=2), cystic lesion (n=2), hyperplesia (n=3), myelolipoma (n=5), extra adrenal lesion (n=4), and uncertain diagnosis (n=40). The final study group comprised 94 patients (51 men and 43; age range, years; mean age, 63 years) with 101 masses comprising 75 adenomas and 26 nonadenomas. Fig 2 shows the clinical data of individual adenoma and nonadenoma groups. Seventy- Page 2 of 13

3 two patients had 75 adenomas which were diagnosed by pathologic examination (n = 11) or by size stability on previous or follow-up at least a 6-months (29 months ± 14 [standard deviation]; range, 6 to 136 months) CT examinations (n = 64). Three patients had an adenoma in each of the bilateral adrenal glands. Thus, three of 72 patients had 2 adenomas. Twenty-two patients had 26 nonadenomas including 8 metastases (two from lung cancer in one patients who had bilateral adrenal metastases, one from hepatocellular carcinoma, one from gastric carcinoma, one from renal cell carcinoma, one from malignant melanoma,and two from primary-unknown tumor), 9 pheochromocytomas, 2 cortical carcinomas, 5 malignant lymphomas in three patient in whom two had bilateral adrenal malignant lymphomas, and 2 neurofibromas. One patient had a pheochromocytoma in left adrenal gland and a neurofibroma in right adrenal gland. Thus, four of 22 patients had two nonadenomas in each of bilateral adrenal gland. Fifteen of 26 nonadenomas were diagnosed by pathologic examination (two metastases, four pheochromocytomas, two cortical carcinoma, five malignant lymphoma, and two neurofibromas). Six metastases were diagnosed by other clinical examination or change of the mass on the follow-up CT examinations within 6 months after chemotherapy. Five pheochromocytomas were diagnosed by radionuclide imaging. No statistically significant difference was evident among the two groups in the distribution of following: sex (P =.118; #2 test), or side (P =.757; #2 test). CT Protocols All imaging was performed with multi-detector row CT scanner (Aquilion, Toshiba Medical Systems). The CT parameters was follows: tube voltage of 120 kvp, tube current of ma, detector row configuration of 16 x 1 mm, gantry rotation speed of 0.5 seconds, and table increment of 15 mm/rotation in the cephalocaudal direction. The reconstruction section and interval thickness was 3.0 mm. The dose of 2 ml per kilogram of body weight of nonionic contrast material with an iodine concentration of 300 mg I/mL was injected over a fixed duration of 30 seconds, and 20 ml of saline was injected at the same rate immediately after the end of contrast material injection through a 20-gauge plastic intravenous catheter sited in an upper extremity vein, typically an antecubital vein. Unenhanced CT scans and three phase enhanced CT scans were successively performed. The early phase was initiated automatically 20 seconds after a bolus-tracking program detected the threshold enhancement of 50 HU in the aorta at the level of the celiac axis. The scan delay from the administration of contrast material to the start of delayed scans were fixed at 5 and 10 minutes, respectively. Data Analysis The diagnostic parameter measurements were retrospectively performed on a workstation (SYNAPSE; Fujifilm, Tokyo, Japan). The size of adrenal mass was recorded with the CT distance cursor to measure the largest diameter in the axial plane on the unenhanced CT. A circular or ovoid region-of-interest (ROI) cursor was used to measure CT attenuation values. The cursor covered at least one-half to two-thirds of the mass, Page 3 of 13

4 excluding cystic, calcified, or necrotic regions. To reduce partial volume effects, the cursor was placed to avoid the edge of the mass. We did not use a standard deviation range or cut off value for our measurements of HU on the lesions we studied. From the data acquired, we calculated the CT attenuation of the masses on unenhanced, early, and delayed (5- and 10-min) enhanced CT. From these, we calculated the following diagnostic parameters: wash-in (= early attenuation - unenhanced attenuation), washout attenutation (WO) (= early attenuation - delayed attenuation) of 5- (WO5) and 10- min (WO10), percentage enhancement washout ratio (PEW) = (washout attenuation / wash-in attenuation) x 100 of 5- (PEW5) and 10-min (PEW10), and relative percentage enhancement washout ratio (RPEW) = (washout attenuation / early attenuation) x 100 of 5- (RPEW5) and 10-min (RPEW10). Statistical Analysis From the data acquired, the differences in the mean values of 12 parameters (The size, unenhanced attenuation, early enhanced attenuation, enhanced attenuation of 5- and 10-min, values of wash-in, WO of 5- and 10-min, PEW of 5- and 10-min, and RPEW of 5- min and 10-min) between adenoma group and nonadenoma group were examined using Mann-Whitney U test. We generated receiver operating characteristic (ROC) curves using the Medcalc Statistical Software to assess the ability of the size, unenhanced attenuation, enhanced attenuation of 5- and10-min, and values of wash-in, WO of 5- and 10-min, PEW of 5- and 10-min, and RPEW of 5- and 10-min to discriminate between adenomas and nonadenomas. Diagnositic accuracy was measured by using the area under the binomial ROC curve (Az) value. In addition, we determined the optimal cut-off point of these parameters for the best accuracy to distinguish adrenal adenomas from nonadenomas. We also compared the accuracy for adenomas between 5- and 10-min delayed scan in regard to enhanced attenuation, WO, PEW, and RPEW. Statistical analysis was performed using SPSS version 14.0 software for Windows (SPSS, Chicago, Ill). P values of less than.05 were considered to indicate statistically significant differences. Images for this section: Page 4 of 13

5 Fig. 1 Page 5 of 13

6 Fig. 2 Page 6 of 13

7 Results The mean values of adenomas and nonadenomas on the unenhanced attenuation, early enhanced attenuation, 5-min-enhanced attenuation, 10-min-enhanced attenuation, wash-in, WO of 5- and 10-min, PEW of 5- and 10-min, and RPEW of 5- and 10-min were showed in Fig 1. There were statistically significant differences in all parameters between the individual adenomas and nonadenoma groups except for early enhanced attenuation. Az values of the CT parameters for the diagnosis of adenomas were showed in Fig 2. There was no significant difference between 5- and 10-min in Az values of delayed attenuation (5-min, Az=0.885; 10-min, Az=0.914; P=0.084), WO (5min, Az=0.783; 10min, Az=0.775; P=0.567), PEW (5min, Az=0.836; 10min, Az=0.856; P=0.266), or RPEW (5min, Az=0.863; 10min, Az=0.882; P=0.253) (Fig 3). The sensitively, specificity, and accuracy values at the cut-off point of the CT parameters were given in Fig 2. In comparison of accuracy at the cut-off point between 5- and 10-min, there was no significant difference with regard to enhanced attenuation (p=0.69; McNemar test), WO (P=1.00; McNemar test ), PEW (P=1.00; McNemar test ), RPEW5, or RPEW10 (P=0.69; McNemar test ). Images for this section: Page 7 of 13

8 Fig. 1 Page 8 of 13

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11 Conclusion Five-minute contrast material-enhanced CT would be useful in the differentiation between adrenal adenomas and nonadenomas as those at 10-min contrast material-enhanced CT. References 1. Boland GW, Hahn PF, Peña C, Mueller PR. masses: characterization with delayed contrast-enhanced CT. Radiology 1997;202: Boland GW, Lee MJ, Gazelle GS, Halpern EF, McNicholas MMJ, Mueller PR. Characterization of adrenal masses using unenhanced CT: an analysis of the CT literature. AJR Am J Roentgenol 1998;171: Korobkin M, Giordano TJ, Brodeur FJ, et al. adenomas: relationship between histologic lipid and CT and MR findings. Radiology 1996;200: Korobkin M, Brodeur FJ, Francis IR, Quint LE, Dunnick NR, Londy F. CT timeattenuation washout curves of adenomas and nonadenomas. AJR Am J Roentgenol 1998;170: Szolar DH, Kammerhuber FH. Adrenal adenomas and nonadenomas: assessment of washout at delayed contrast-enhanced CT. Radiology 1998;207: Peña CS, Boland GW, Hahn PF, Lee MJ, Mueller PR. Characterization of indeterminate (lipid-poor) adrenal masses: use of washout characteristics at contrastenhanced CT. Radiology 2000;217: Caoili EM, Korobkin M, Francis IR, Cohan RH, Dunnick NR. Delayed enhanced CT of lipid-poor adenomas. AJR Am J Roentgenol 2000;175: Caoili EM, Korobkin M, Francis IR, et al. Adrenal masses: characterization with combined unenhanced and delayed enhanced CT. Radiology 2002;222: Blake MA, Kalra MK, Sweeney AT, et al. Distinguishing benign from malignant a masses: multi-detector row CT protocol with 10-minute delay. Radiology 2005;238(2): Akobeng AK: Understanding diagnostic tests 3: Receiver operating curves. Acta Paediatr 2007;96: Page 11 of 13

12 11. Pamela T.Johnson, Karen M. Horton, Ellito K. Fishman, et al. Adrenal Mass Imaging with Multidetector CT: Pathologic Conditions Pearls, and Pitfalls. Radiographics 2009; 29: Pamela T.Johnson, Karen M. Horton, Ellito K. Fishman, et al. Adrenal imaging with Multidetector CT: Evidence-based Protocol Optimization and Interpretative Practice. Radiographics 2009; 29: N.Reed Dunnick and Melvyn Korobkin, Imaging of Adrenal Incidentalomas: Current Status 14. Dieter H. Szolar,, Melvyn Korobkin, Pia Reittner, et al. Adrenocortical Carcinomas and Adrenal Pheochoromocytomas: Mass and Enhancement Loss Evaluation at Delayed Contrast-enhanced CT. Radiology 2005; 234: Ersin Ozturk, H. Onur Sldiroglu, Mecit Kantarci, et al. Computed tomography findings in diseases of the adrenal gland. Wien Klin Wochenschr (2009) 121: Ioannis Ilias, Anju Sahdev, Rodney H Reznek, Ashley B Grossman and Karel Pacak et al. The optimal imaging of adrenal tumors: a comparison of different methods. Endocrine- Related Cancer 2007;14: Takuro Kamiyama, Yoshihiko Fukukura,Tomohide Yoneyama, et al. Distinguishing Adrenal Adenomas from Nonadenomas: Combined Use of Diagnositic Parameters of Unenhanced and Short 5-minute Dynamic Enhanced CT protocol. Radiology 2009; 250 : 18. M.Kebapci, T.Kaya, E.Gurbuz, et al. Differentiation of adrenal adenomas (lipid rich and lipid poor) from nonadenomas by use of washout characteristics on delayed enhanced CT. Abdom Imaging 2003;28: Szolar DH, Kammerhuber F et al. Quantiative CT evaluation of adremal gland masses: a step forward in the differentiation between adenomas and nonadenomas. Radiology 1997;202(2): Personal Information Address: Department of Radiology, Kagoshima University Graduate School of Medical and Dental Sciences, Sakuragaoka, Kagoshima , Japan Corresponding author: Page 12 of 13

13 Yuichi Kumagae, Department of Radiology, Kagoshima University Graduate School of Medical and Dental Sciences, Sakuragaoka, Kagoshima , Japan Tel: , Fax: , Page 13 of 13