Adrenal masses: characterization with in vivo proton MR spectroscopy--initial experience.
OBJECTIVE
To prospectively determine the accuracy of in vivo proton ((1)H) magnetic resonance (MR) spectroscopy in distinguishing adrenal adenomas, pheochromocytomas, adrenocortical carcinomas, and metastases, with histologic or computed tomographic findings and follow-up data as the reference standards.


METHODS
This study was approved by the institutional ethics committee, and informed consent was obtained. Sixty consecutive patients (24 male and 36 female patients; mean age, 53 years) harboring adrenal tumors larger than 2 cm in diameter (mean diameter, 4.6 cm +/- 3.4 [standard deviation]) entered the study and were examined with a 1.5-T MR imaging system and point-resolved multivoxel (1)H MR spectroscopy. Thirty-eight patients had adenomas; 10, pheochromocytomas; five, carcinomas; and seven, metastases. Amplitude values for choline, creatine, lipid, and a metabolite peak at precession frequency of 4.0-4.3 ppm were measured. Metabolite ratios (choline-creatine, choline-lipid, lipid-creatine, and 4.0-4.3 ppm/creatine) and cutoff values (obtained by using receiver operating characteristic analyses) were obtained and compared for each type of adrenal mass, which was identified previously on the basis of clinical, hormonal, and pathologic evidence. Results were evaluated with chi(2) and Student t tests. Significance was inferred at P < .05.


RESULTS
Cutoff values of 1.20 for the choline-creatine ratio (92% sensitivity, 96% specificity; P < .01), 0.38 for the choline-lipid ratio (92% sensitivity, 90% specificity; P < .01), and 2.10 for the lipid-creatine ratio (45% sensitivity, 100% specificity) enabled adenomas and pheochromocytomas to be distinguished from carcinomas and metastases. A 4.0-4.3 ppm/creatine ratio greater than 1.50 enabled distinction of pheochromocytomas and carcinomas from adenomas and metastases (87% sensitivity, 98% specificity; P < .01). The best distinction was obtained by comparing choline-creatine and 4.0-4.3 ppm/creatine ratios.


CONCLUSIONS
(1)H MR spectroscopy can be used to characterize adrenal masses on the basis of spectral findings for benign adenomas, carcinomas, pheochromocytomas, and metastases.
Faria
Juliano F
JF
Department of Diagnostic Imaging, Federal University of São Paulo, Napoleão de Barros, 800, Vila Clementino, São Paulo, SP, Brazil 04024-002. drjulianounifesp@hotmail.com
Goldman
Suzan M
SM
Szejnfeld
Jacob
J
Melo
Homero
H
Kater
Cláudio
C
Kenney
Philip
P
Huayllas
Martha P
MP
Demarchi
Guilherme
G
Francisco
Viviane V
VV
Andreoni
Cássio
C
Srougi
Miguel
M
Ortiz
Valdemar
V
Abdalla
Nitamar
N
D000236:Adenoma / Q000175:diagnosis* / Q000378:metabolism; D000310:Adrenal Gland Neoplasms / Q000175:diagnosis* / Q000378:metabolism / Q000556:secondary; D018268:Adrenocortical Carcinoma / Q000175:diagnosis* / Q000378:metabolism; D000328:Adult; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D010673:Pheochromocytoma / Q000175:diagnosis* / Q000378:metabolism; D011446:Prospective Studies; D015203:Reproducibility of Results