|
|
|||||||||
Clinical Investigations |
Division of Nuclear Medicine, Department of Radiology, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania
| ABSTRACT |
|---|
|
|
|---|
Key Words: adrenal gland tumor 18F-FDG PET
| INTRODUCTION |
|---|
|
|
|---|
With more experience in the evaluation of the adrenal lesions using FDG PET, it has been noted that benign adrenal adenomas can have increased FDG uptake leading to false-positive results on PET (6). In previous studies, the scan was interpreted as positive if the FDG uptake was greater than background or blood-pool activity in the adrenal lesion. Unlike previously published reports, we have adopted different diagnostic criteria to interpret PET studies (6,7). There might be a potential advantage to this approach by increasing the specificity of FDG PET without compromising its sensitivity. This study was undertaken to evaluate the ability of FDG PET and these new criteria in characterizing adrenal lesions in patients with proven or suspected cancers.
| MATERIALS AND METHODS |
|---|
|
|
|---|
PET imaging was performed using a C-PET scanner (ADAC UGM, Philadelphia, PA). This scanner acquires data in 3-dimensional mode without septa. The intrinsic spatial resolution of the system is 5-mm full width at half maximum in the center of the field of view. The patients fasted for at least 4 h and the serum glucose level was < 140 mg/dL in all patients. PET scanning was initiated 60 min after intravenous administration of 2.516 MBq (0.068 mCi)/kg of FDG. Sequential overlapping scans were acquired to cover the neck, chest, abdomen, and pelvis. Transmission scans using a 137Cs point source were interleaved between the multiple emission scans to correct for nonuniform attenuation correction (8). The images were reconstructed using ordered subset expectation maximization, an iterative reconstruction algorithm (9).
FDG PET images were qualitatively evaluated on a high-resolution computer screen by 2 nuclear medicine physicians who were unaware of other clinical or imaging information. Special attention was paid to FDG uptake in the adrenal glands. In cases of disagreement, final decision was made by consensus. The scan was considered negative for malignancy if the degree of FDG uptake in the adrenal region was less than the uptake in the liver at the same coronal section. Conversely, it was considered positive if the uptake in the lesion was equal to or greater than uptake in the liver. On the basis of past experience, we have noted that visual assessment of the suspected lesions may be just as effective as semiquantitative analysis using the standardized uptake value (SUV) in differentiating active from inactive disorder. Therefore, the SUV was not used to differentiate a benign lesion from a malignant adrenal lesion. Furthermore, it was often difficult to generate a region of interest over the lesions that were not visualized on PET scan.
| RESULTS |
|---|
|
|
|---|
|
|
|
|
|
Of 13 lesions in 10 patients on whom MRI was performed for further characterization of indeterminate adrenal lesions on CT, there were 4 true-positives, 6 true-negatives, and 3 false-positives. FDG PET accurately diagnosed all 13 lesions (Table 2). MRI interpretation based on reports from referring physicians had sensitivity, specificity, and accuracy of 67%, 100%, and 77%, respectively, for correctly identifying a benign lesion from a malignant lesion. MRI showed excellent specificity when characterizing a benign lesion. However, MRI criteria for differentiating benign from malignant lesions may differ among institutions. Because of the limited sample size of patients who underwent MRI and the lack of access to magnetic resonance images from different institutions in this study, the performance assessment of MRI might not be as accurate as that of FDG PET.
|
| DISCUSSION |
|---|
|
|
|---|
CT scanning is considered most important in evaluating adrenal masses. Lipid within adenomas causes a low attenuation value on CT, and such an attenuation value has been extremely helpful in differentiating a benign adenoma from a malignant lesion (1619). Delayed enhanced CT could help by analyzing the washout patterns seen in adrenal lesions. Adenomas may show mild enhancement and rapid washout, whereas metastases may show marked, fast enhancement and slower washout (2022). Chemical shift MRI is most commonly used among different magnetic resonance techniques and appears to be highly accurate in the diagnosis of benign adenomas. Any lipid-containing tissue would show a signal loss caused by cancellation of the signal from fat and water. It should be noted, however, that rare adrenal cortical carcinomas or metastases from hepatoma, renal cell carcinoma, or liposarcoma could give the same lipid signal loss seen in adenomas (2325). McNicholas et al. (26) reported excellent diagnostic performance using CT and MRI to identify intracellular lipid. In their study, 36% of adrenal masses were characterized by unenhanced CT scans and 60% more were characterized by MRI using a chemical shift sequence, leaving only 4% of the patients to undergo invasive percutaneous biopsy procedures.
Unlike CT and MRI, FDG PET is based on increased glucose metabolism in malignant lesions. Boland et al. (5) reported that FDG PET distinguished benign adrenal lesions from metastatic lesions with 100% sensitivity and specificity. Erasmus et al. (6) evaluated 33 adrenal masses in 27 patients with bronchogenic carcinomas. PET was interpreted as positive when FDG uptake in the adrenal mass was higher than background activity. The sensitivity for detecting metastasis was 100% and the specificity was 80%. In their prospective study, Maurea et al. (7) considered adrenal FDG uptake to be abnormal when it was higher than blood-pool and background activities. All malignant lesions showed abnormally increased uptake. In benign lesions, no abnormally increased FDG uptake was observed, except for 1 benign pheochromocytoma. It is known that most pheochromocytomas, either benign or malignant, are metabolically active and thus accumulate FDG, although uptake is found in a greater percentage of malignant than in benign pheochromocytomas (27).
We also encountered benign adenomas showing a variable degree of FDG uptake, which could cause false-positive results on PET. Therefore, we decided to use new criteria to interpret scans so that the specificity of FDG PET would improve without compromising sensitivity. Using these criteria, no malignant lesion showed a negative result, giving a sensitivity of 100%. In 5 of 18 malignant lesions, FDG uptake was only equal to or slightly higher than that of the liver. These included 2 metastases from neuroendocrine tumors, 2 early, small metastases, and 1 necrotic metastasis. As previously reported, a neuroendocrine tumor could have lower FDG uptake than typically is seen in a malignant tumor (28). The sizes of the lesions could explain why the early metastases and necrotic metastasis showed relatively less intense FDG uptake than most of the malignant lesions. Of the 32 benign lesions, there were 2 adenomas with uptake equal to or slightly higher than that of the liver. It is unknown why some adenomas show variable FDG uptake. Overall, we achieved the high specificity of FDG PET without compromising sensitivity by using these criteria.
Of the 13 lesions identified by MRI, 3 were false-positives, but FDG PET correctly identified all 3 false-positives as benign. The other 10 adrenal lesions accurately diagnosed by MRI were also characterized as such by PET. Hence, FDG PET can play a role in further differentiation of indeterminate adrenal masses on MRI. MRI was not performed for 2 lesions that were determined by FDG PET as being false-positive. Thus, we were not able to determine whether MRI could have correctly diagnosed these lesions.
Our results indicate that if a lesion shows FDG uptake less than that of the liver, or shows uptake that is significantly higher than the liver, the study can be interpreted with high confidence unless the patient has pheochromocytoma, which can be excluded by biochemical markers. If the lesion in the adrenal gland shows uptake equal to or slightly higher than that of the liver on FDG PET, the study can be read as indeterminate because either benign or malignant lesions can show this degree of FDG uptake. In this situation, an additional imaging study should be performed for further characterization of the lesion, especially when it is the only area of suspicious metastasis identified through an FDG PET scan.
| CONCLUSION |
|---|
|
|
|---|
| FOOTNOTES |
|---|
For correspondence or reprints contact: Abass Alavi, MD, 110 Donner Bldg., Division of Nuclear Medicine, Hospital of the University of Pennsylvania, 3400 Spruce St., Philadelphia, PA 19104.
| REFERENCES |
|---|
|
|
|---|
This article has been cited by other articles:
![]() |
J. R. Strosberg, G. D. Hammer, G. M. Doherty, and K. G. Robinson Management of Adrenocortical Carcinoma J Natl Compr Canc Netw, July 1, 2009; 7(7): 752 - 759. [Abstract] [PDF] |
||||
![]() |
L. Groussin, G. Bonardel, S. Silvera, F. Tissier, J. Coste, G. Abiven, R. Libe, M. Bienvenu, J.-L. Alberini, S. Salenave, et al. 18F-Fluorodeoxyglucose Positron Emission Tomography for the Diagnosis of Adrenocortical Tumors: A Prospective Study in 77 Operated Patients J. Clin. Endocrinol. Metab., May 1, 2009; 94(5): 1713 - 1722. [Abstract] [Full Text] [PDF] |
||||
![]() |
G. W. L. Boland, M. A. Blake, N. S. Holalkere, and P. F. Hahn PET/CT for the Characterization of Adrenal Masses in Patients with Cancer: Qualitative Versus Quantitative Accuracy in 150 Consecutive Patients Am. J. Roentgenol., April 1, 2009; 192(4): 956 - 962. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. J. Brady, J. Thomas, T. Z. Wong, K. M. Franklin, L. M. Ho, and E. K. Paulson Adrenal Nodules at FDG PET/CT in Patients Known to Have or Suspected of Having Lung Cancer: A Proposal for an Efficient Diagnostic Algorithm Radiology, February 1, 2009; 250(2): 523 - 530. [Abstract] [Full Text] [PDF] |
||||
![]() |
G. W. L. Boland, M. A. Blake, P. F. Hahn, and W. W. Mayo-Smith Incidental Adrenal Lesions: Principles, Techniques, and Algorithms for Imaging Characterization Radiology, December 1, 2008; 249(3): 756 - 775. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. Vikram, H. D. W. Yeung, H. A. Macapinlac, and R. B. Iyer Utility of PET/CT in Differentiating Benign from Malignant Adrenal Nodules in Patients with Cancer Am. J. Roentgenol., November 1, 2008; 191(5): 1545 - 1551. [Abstract] [Full Text] [PDF] |
||||
![]() |
P K Singh and H N Buch Adrenal incidentaloma: evaluation and management J. Clin. Pathol., November 1, 2008; 61(11): 1168 - 1173. [Abstract] [Full Text] [PDF] |
||||
![]() |
N K Singh, G J R Cook, V J Lewington, and S C Chua PET/CT assessment of clinically unsuspected, incidental FDG-avid lesions in oncological patients Imaging, September 1, 2008; 20(3): 159 - 168. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. B. Elaini, S. K. Shetty, V. M. Chapman, D. V. Sahani, G. W. Boland, A. T. Sweeney, M. M. Maher, J. T. Slattery, P. R. Mueller, and M. A. Blake Improved Detection and Characterization of Adrenal Disease with PET-CT RadioGraphics, May 1, 2007; 27(3): 755 - 767. [Abstract] [Full Text] [PDF] |
||||
![]() |
W. F. Young Jr. The Incidentally Discovered Adrenal Mass N. Engl. J. Med., February 8, 2007; 356(6): 601 - 610. [Full Text] [PDF] |
||||
![]() |
I. C. Mitchell and F. E. Nwariaku Adrenal Masses in the Cancer Patient: Surveillance or Excision Oncologist, February 1, 2007; 12(2): 168 - 174. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. Chong, K. S. Lee, H. Y. Kim, Y. K. Kim, B.-T. Kim, M. J. Chung, C. A Yi, and G. Y. Kwon Integrated PET-CT for the Characterization of Adrenal Gland Lesions in Cancer Patients: Diagnostic Efficacy and Interpretation Pitfalls RadioGraphics, November 1, 2006; 26(6): 1811 - 1824. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. M. Intenzo, K. S. Lee, and B.-T. Kim Invited Commentary * Authors' Response RadioGraphics, November 1, 2006; 26(6): 1824 - 1826. [Full Text] [PDF] |
||||
![]() |
M. A. Blake, A. Singh, B. N. Setty, J. Slattery, M. Kalra, M. M. Maher, D. V. Sahani, A. J. Fischman, and P. R. Mueller Pearls and Pitfalls in Interpretation of Abdominal and Pelvic PET-CT RadioGraphics, September 1, 2006; 26(5): 1335 - 1353. [Abstract] [Full Text] [PDF] |
||||
![]() |
G. C. Mackie, B. L. Shulkin, R. C. Ribeiro, F. P. Worden, P. G. Gauger, R. J. Mody, L. P. Connolly, G. Kunter, C. Rodriguez-Galindo, J. W. Wallis, et al. Use of [18F]Fluorodeoxyglucose Positron Emission Tomography in Evaluating Locally Recurrent and Metastatic Adrenocortical Carcinoma J. Clin. Endocrinol. Metab., July 1, 2006; 91(7): 2665 - 2671. [Abstract] [Full Text] [PDF] |
||||
![]() |
B. Allolio and M. Fassnacht Adrenocortical Carcinoma: Clinical Update J. Clin. Endocrinol. Metab., June 1, 2006; 91(6): 2027 - 2037. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. Bunyaviroch and R. E. Coleman PET Evaluation of Lung Cancer J. Nucl. Med., March 1, 2006; 47(3): 451 - 469. [Full Text] [PDF] |
||||
![]() |
M. A. Blake, J. M. A. Slattery, M. K. Kalra, E. F. Halpern, A. J. Fischman, P. R. Mueller, and G. W. Boland Adrenal Lesions: Characterization with Fused PET/CT Image in Patients with Proved or Suspected Malignancy--Initial Experience Radiology, March 1, 2006; 238(3): 970 - 977. [Abstract] [Full Text] [PDF] |
||||
![]() |
U. Metser, E. Miller, H. Lerman, G. Lievshitz, S. Avital, and E. Even-Sapir 18F-FDG PET/CT in the Evaluation of Adrenal Masses J. Nucl. Med., January 1, 2006; 47(1): 32 - 37. [Abstract] [Full Text] [PDF] |
||||
![]() |
D E Schteingart, G M Doherty, P G Gauger, T J Giordano, G D Hammer, M Korobkin, and F P Worden Management of patients with adrenal cancer: recommendations of an international consensus conference Endocr. Relat. Cancer, September 1, 2005; 12(3): 667 - 680. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. Thorin-Savoure, F. Tissier-Rible, L. Guignat, A. Pellerin, X. Bertagna, J. Bertherat, and H. Lefebvre Collision/Composite Tumors of the Adrenal Gland: A Pitfall of Scintigraphy Imaging and Hormone Assays in the Detection of Adrenal Metastasis J. Clin. Endocrinol. Metab., August 1, 2005; 90(8): 4924 - 4929. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. Kumar, Y. Xiu, J. Q. Yu, A. Takalkar, G. El-Haddad, S. Potenta, J. Kung, H. Zhuang, and A. Alavi 18F-FDG PET in Evaluation of Adrenal Lesions in Patients with Lung Cancer J. Nucl. Med., December 1, 2004; 45(12): 2058 - 2062. [Abstract] [Full Text] [PDF] |
||||
![]() |
K. Pacak, G. Eisenhofer, and D. S. Goldstein Functional Imaging of Endocrine Tumors: Role of Positron Emission Tomography Endocr. Rev., August 1, 2004; 25(4): 568 - 580. [Abstract] [Full Text] [PDF] |
||||
![]() |
B. Bagheri, A. H. Maurer, L. Cone, M. Doss, and L. Adler Characterization of the Normal Adrenal Gland with 18F-FDG PET/CT J. Nucl. Med., August 1, 2004; 45(8): 1340 - 1343. [Abstract] [Full Text] [PDF] |
||||
![]() |
H. Minn, A. Salonen, J. Friberg, A. Roivainen, T. Viljanen, J. Langsjo, J. Salmi, M. Valimaki, K. Nagren, and P. Nuutila Imaging of Adrenal Incidentalomas with PET Using 11C-Metomidate and 18F-FDG J. Nucl. Med., June 1, 2004; 45(6): 972 - 979. [Abstract] [Full Text] [PDF] |
||||
![]() |
G. Mansmann, J. Lau, E. Balk, M. Rothberg, Y. Miyachi, and S. R. Bornstein The Clinically Inapparent Adrenal Mass: Update in Diagnosis and Management Endocr. Rev., April 1, 2004; 25(2): 309 - 340. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. D. Paulsen, H. V. Nghiem, M. Korobkin, E. M. Caoili, and E. J. Higgins Changing Role of Imaging-Guided Percutaneous Biopsy of Adrenal Masses: Evaluation of 50 Adrenal Biopsies Am. J. Roentgenol., April 1, 2004; 182(4): 1033 - 1037. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. G. Pfister, D. H. Johnson, C. G. Azzoli, W. Sause, T. J. Smith, S. Baker Jr, J. Olak, D. Stover, J. R. Strawn, A. T. Turrisi, et al. American Society of Clinical Oncology Treatment of Unresectable Non-Small-Cell Lung Cancer Guideline: Update 2003 J. Clin. Oncol., January 15, 2004; 22(2): 330 - 353. [Full Text] [PDF] |
||||
![]() |
C. E. Reed, D. H. Harpole, K. E. Posther, S. L. Woolson, R. J. Downey, B. F. Meyers, R. T. Heelan, H. A. MacApinlac, S.-H. Jung, G. A. Silvestri, et al. Results of the American College of Surgeons Oncology Group Z0050 trial: the utility of positron emission tomography in staging potentially operable non-small cell lung cancer J. Thorac. Cardiovasc. Surg., December 1, 2003; 126(6): 1943 - 1951. [Abstract] [Full Text] [PDF] |
||||
![]() |
H. Vesselle, E. Turcotte, L. Wiens, and D. Haynor Application of a Neural Network to Improve Nodal Staging Accuracy with 18F-FDG PET in Non-Small Cell Lung Cancer J. Nucl. Med., December 1, 2003; 44(12): 1918 - 1926. [Abstract] [Full Text] [PDF] |
||||
![]() |
N Khan, N Oriuchi, T Higuchi, H Zhang, and K Endo PET in the follow-up of differentiated thyroid cancer Br. J. Radiol., October 1, 2003; 76(910): 690 - 695. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Paci, G. Sgarbi, G. Ferrari, S. De Franco, and V. Annessi Controversies Over UICC-TNM Classification of Non-small Cell Lung Cancer : Model for a Diagnostic Path Chest, August 1, 2002; 122(2): 754 - 754. [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | RSS | TABLE OF CONTENTS |
| JOURNAL OF NUCLEAR MEDICINE TECHNOLOGY | THE JOURNAL OF NUCLEAR MEDICINE |