| Objective: Nasopharyngeal carcinoma(NPC) is one of the most common malignant tumors of the head and neck in southern China. It has a unique biological behavior and epidemiological features. It is important for staging and management to judge the skull base bone invasion of nasopharyngeal carcinoma. The aim of this study was to evaluate the comparative value of 18F-sodium fluoride(18F-Na F) positron emission tomography(PET)/computed tomography(CT) versus magnetic resonance imaging(MRI) in the diagnosis of skull-base bone invasion in patients with nasopharyngeal carcinoma. Methods: Sixty-three patients(45 male and 18 female), between the ages of 23 and 72 years(average, 48.49±11.46 years), had nasopharyngeal carcinoma confirmed by biopsy. Patients were examined with 18F-Na F PET/CT and MRI within 20 days, without any treatment between scans. Studies were interpreted by 2 nuclear medicine physicians and 2 radiologists with more than 10 years working experience, blinded to the diagnosis and to the results of the other imaging studies. There are 6 steps in this study.(1) Judging whether the skull base was invaded through 18F-Na F PET/CT and MRI imaging. Skullbase bone invasion was defined as positive and normal was defined as negative.(2) Recording the uptake of 18F-Na F on PET, signal changing on MRI and bone invasion type( no obvious bone destruction, osteosclerosis, osteolysis and mixed bone destruction) on low dose CT of patient who was defined as positive.(3) The reference standard was skull-base bone destruction on 6-month follow up imaging(18F-Na F PET/CT, MRI and enhanced CT), to judge whether patients was skull base bone invasion.(4) Counting true positive, true negative, false positive and false negative of 18F-Na F PET/CT and MRI.(5) Calculating sensitivity, specificity, positive predictive value, negative predictive value and accuracy of the two imaging methods. Chi-square test was used to evaluate the difference.(6) Record the differences of diagnosis results in various bone invasion types of the two imaging in the diagnosis of skull base bone invasion of nasopharyngeal carcinoma. During the 20 days, patient did not receive any treatment. Results:(1) 34 patients(24 male and 10 female) demonstrated skull-base bone invasion on 6 months follow-up imaging. 18F-Na F PET/CT produced true positive in 33 patients, true negative in 26 patients, false positive in 3 patients and false negative in 1 patient. MRI produced true positive in 31 patients, true negative in 25 patients, false positive in 4 patients and false negative in 3 patients.(2) Of the 34 patients initially diagnosed with skull-base bone invasion by follow-up imaging, 30 had positive findings both on 18F-Na F PET/CT and MRI. Onepatient was missed diagnosis by 18F-Na F PET/CT and 3 patients was missed diagnosis by MRI.(3) The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 18F-Na F PET/CT were 97.1%( 33/ 34), 89.7%( 26/ 29), 91.7%( 33/ 36), 96.3%( 26/ 27), and 93.7%( 59/ 63), respectively; for MRI, these values were 91.2%( 31/ 34), 86.2%( 25/ 29), 88.6%( 31/ 35), 89.3%( 25/ 28), and 88.9%( 56/ 63).(4) Chi-square test shows that sensitivity(X2=1.062, P=0.303), specificity(X2=0.162, P=0.687), positive predictive value(X2=0.191, P=0.662), negative predictive value(X2=1.002, P=0.317), and accuracy(X2=0.896, P=0.344) did not differ between 18F-Na F PET/CT and MRI. There is no obvious difference between the two materials in the diagnosis of skull base bone invasion.(5) This study changed 7 patients’ T staging, 18F-Na F PET/CT and MRI could both effected T staging in nasopharyngeal carcinoma patients with skull base bone invasion.(6) 13 of the 34 patients demonstrated osteosclerosis on low dose CT. 8 of the 34 patients with osteolysis at the skull base. 6 of the 34 patients were mixed bone destruction. 7 of the 34 patients lacked overt bony destruction on low dose CT. 11 of the 34 patients showed high 18F-Na F concentrations on PET and abnormal signals on MRI at the same sites.(7) Of the 34 patients, 18F-Na F PET/CT detected 133 lesions and MRI detected 97 lesions at skull base bone. Clivus is the most common site in skull base bone invasion. Conclusion: Case analysis: 18F-Na F PET/CT and MRI bothhave high sensitivity, specificity, positive predictive value, negative predictive value, and accuracy. 18F-Na F PET/CT and MRI both have advantages and disadvantages. We should combine the two imaging methods, in order to improve the diagnostic accuracy of skull base bone invasion for nasopharyngeal carcinoma. In addition, 18F-Na F PET/CT and MRI can both change the patient’s T staging, which is positive significance for the treatment of NPC patients. Lesion analysis: 18F-Na F PET/CT and MRI demonstrate clivus is the most common site in skull base bone invasion of nasopharyngeal carcinoma. 18F-Na F PET/CT detected more lesions than MRI in each type of bone invasion. 18F-Na F PET/CT, combining anatomic and metabolic information, has potential advantage for diagnosing tiny bone lesions in the skull base. It is insufficient to detect tiny bony lesion on skull base for MRI. |
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