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INTERVENTIONAL RADIOLOGY Table of Contents   
Year : 2008  |  Volume : 18  |  Issue : 1  |  Page : 90-91
Technical note: Preprocedural PET/CT guidance for fine needle aspiration cytology of a lung mass


1 Bangalore Institute of Oncology and Health Care Global and Teleradiology Solutions, Bangalore, India
2 Teleradiology Solutions, Bangalore, India
3 Department of Nuclear Medicine, Bangalore Institute of Oncology and Health Care Global, Bangalore, India
4 Bangalore Institute of Oncology and Health Care Global, Bangalore, India

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How to cite this article:
Govindarajan M J, Kalyanpur A, Nagaraj K R, Ravikumar H, Kallur K G, Sridhar P S. Technical note: Preprocedural PET/CT guidance for fine needle aspiration cytology of a lung mass. Indian J Radiol Imaging 2008;18:90-1

How to cite this URL:
Govindarajan M J, Kalyanpur A, Nagaraj K R, Ravikumar H, Kallur K G, Sridhar P S. Technical note: Preprocedural PET/CT guidance for fine needle aspiration cytology of a lung mass. Indian J Radiol Imaging [serial online] 2008 [cited 2017 Sep 25];18:90-1. Available from: http://www.ijri.org/text.asp?2008/18/1/90/38509
When a lung nodule is diagnosed, it is necessary to differentiate a benign lesion from one that is indeterminate/aggressive. Due to the increased possibility of malignancy in patients above the age of 35, with nodules >10 mm in size, immediate, often invasive, workup is required, including contrast-enhanced dynamic CT, positron emission tomography (PET), or biopsy. [1] However, at times, optimal localization of the fine needle aspiration cytology (FNAC)/biopsy site may not be possible as the more easily accessible areas may not necessarily be metabolically active. PET/CT may identify metabolically active areas within the mass and help to optimize the diagnostic tissue yield - PET providing physiological information and CT providing the anatomical details. We present one such case, where a prior CT-guided FNAC was unsuccessful but a subsequent PET/CT allowed proper guidance for correct localization of the FNAC site.


   Case Report Top


A 60-year-old man without a history of smoking, presented with unexplained weight loss and cough with chest pain. A chest radiograph revealed a left mid-zone opacity. CT scan demonstrated a relatively large, predominantly pleural-based mass in the left upper lobe [Figure - 1]. The patient had undergone a percutaneous CT-guided FNAC a few days before but the yield had not been adequate for a confident interpretation. PET/CT was performed using F18 FDG on a 16-slice multi-detector CT scanner (Discovery STE, GE). The PET study showed that the peripheral and inferior portions of the lesion, which were most easily accessible for biopsy, were only minimally metabolically active, while the inner and upper portions of the mass were more active [Figure - 2]. The fused PET/CT images showed the exact area where the FNAC had to be planned [Figure - 3]. FNAC was then performed [Figure - 4] and the histopathologic diagnosis was pleomorphic sarcomatoid carcinoma.


   Discussion Top


The importance of limiting repeat procedures cannot be overemphasized. It is especially important in cases of lung masses, where the chance of significant pneumothorax increases with repeated attempts. [2] In the case of lung lesions, contrast-enhanced CT scans may be able to differentiate between the mass and the adjacent atelectatic lung. However, it is sometimes difficult to do so, especially with peripheral lesions. [3],[4] In our case, intravenous contrast was not administered as the patient had already had a recent diagnostic CT scan, followed by an attempted guided FNAC. The central portions of the mass are often necrotic and a good FNAC/biopsy should avoid these areas. PET scan with FDG helps in delineating metabolically active areas and, along with a CT scan performed at the same time (PET/CT), can help localize the area most likely to give a diagnostic yield during an FNAC/biopsy.

In our case, the peripheral and inferior portions of the lesion, which were more easily accessible percutaneously, were minimally metabolically active and this was probably the reason for the lack of success with the prior CT-guided FNAC.

The literature on the use of PET/CT for interventional guidance is sparse. A recent ex vivo study in pigs showed PET/CT to be more accurate than CT alone for image-guided interventions in liver lesions. [5] PET/CT-guided percutaneous puncture of an infected cyst in a patient with autosomal dominant polycystic kidney disease has also been reported; [6] the exact site/infected cyst could be demonstrated by the PET study. PET/CT has been used for the localization of the electrode tip during radiofrequency ablation of hepatic metastases. [7] PET/CT is also useful in previously treated lesions, where it can differentiate between viable and necrotic areas and guide biopsy/intervention if required. [8]

Logically, with the incorporation of morphological details from CT and MRI and functional details from PET, the ability to guide intervention should improve considerably [9],[10] and, hopefully, properly designed studies may confirm this in the future.

 
   References Top

1.Diederich S, Das M. Solitary pulmonary nodule: Detection and management. Cancer Imaging 2006;6:S42-6.  Back to cited text no. 1    
2.vanSonnenberg E, Casola G, Ho M, Neff CC, Varney RR, Wittich GR, et al . Difficult thoracic lesions: CT guided biopsy experiences in 150 cases. Radiology 1988;167:457-61.  Back to cited text no. 2    
3.Rubens MB, Padley SP. In tumors of the lung. David Sutton's Text book of Radiology and imaging, vol.1, 6 th ed, p. 402-4.  Back to cited text no. 3    
4.Sagel SS, Slone RM. Lung, Airway obstruction, pulmonary collapse, Text book of computed tomography with MRI correlation. Joseph KT Lee, Stuart S Sagel, editors. 3 rd ed, Vol. 1, p. 380.  Back to cited text no. 4    
5.Veit P, Kuehle C, Beyer T, Kuehl H, Bockisch A, Antoch G. Accuracy of combined PET/CT in image-guided interventions of liver lesions: An ex- Vivo study. World J Gastroenterol 2006;12:2388-93.  Back to cited text no. 5    
6.Kaim AH, Burger C, Ganter CC, Goerres GW, Kamel E, Weishaupt D, et al . PET-CT-guided percutaneous puncture of an infected cyst in autosomal dominant polycystic kidney disease: Case report. Radiology 2001;221:818-21.  Back to cited text no. 6    
7.Prior JO, Kosinski M, Delaloye AB, Denys A. Initial report of PET/CT-guided radiofrequency ablation of liver metastases. J Vasc Interv Radiol 2007;18:801-3.  Back to cited text no. 7    
8.Herzog P, Scher B, Helmberger T, Hahn K, Reiser MF, Becker CR. PET-CT interventional tumour therapy. Radiologe 2004;44:1088-95.  Back to cited text no. 8    
9.Yap JT, Camey JP, Hall NC, Townsend DW. Image-guided cancer therapy using PET/CT. Cancer J 2004;10:221-33.  Back to cited text no. 9    
10.Solomon SB. Incorporating CT, MR imaging and positron emission tomography into minimally invasive therapies. J Vasc Interv Radiol 2005;16:445-7.  Back to cited text no. 10    

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Correspondence Address:
M J Govindarajan
No #6, Srinivasa Nilaya, 3rd Cross, LIC Colony, Bima Jyothi, Basaveshwar Nagar, Bangalore - 560 079
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0971-3026.38509

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    Figures

  [Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4]

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