Scintimetric Characterization of metastatic lymph nodes in various primary malignancies by Dual Phase PETCT study.
Dr.V Sivasubramaniyan 1&2, 1 Senior Consultant PETCT & Molecular imaging, Professor of Nuclear Medicine, Sri Aurobindo Institute of Medical Sciences, Indore, Madhyapradesh, India & 2 DR.Scholar, Sri Sathya Sai Institute of Higher Learning, Puttaparthi, india 1 DR. ViNOD BHANDARI Chairman, Sri Aurobindo Institute of Medical sciences, Indore, Madhyapradesh, India. 2 DR.K.Venkataramaniah, Senior Professor & Doctoral Research guide,Sri Sathya Sai Institute of Higher Learning, Puttaparthi, India.
Abstract: This retrospective analysis of the dual phase PETCT scans thrives to assess the utility of Scintimetric Characterization of the metastatic lymph nodes in various primary malignancies. Methods: In the proven cases of various primary malignancies like Ca.Breast, Ca.Prostate, Lymphomas and alveolar tumors the SUV max values of the metastatic lymph nodes were calculated in both the Early and Delayed phase scans. The PETCT study was performed using the GE Discovery IQ PETCT in those patients with positive lymph node uptake. The early scan was done One hour post injection of 5 to 10 mCi of F18-FDG tracer in the fasting state with their informed consent with optimal serum blood sugar level of 150 mg/dl. The delayed PETCT was done Four hours after the post injection time with voluntary consent of the patients without any additional injection of the tracer or contrast medium.The SUV max values were obtained utilizing the Advantage 4.4 software provided by the GE. Total of Forty eight lymph nodes at various locations were included in the study. The calculated SUV max values were used to arrive at the Rong’s Retention Ratio and the Dr.V.Siva’s modification of RRI. The results were tabulated and analyzed.
Results: The Rong’s Retention Ratio values arrived at by subtracting the early phase value from the delayed phase value and then dividing it by the early phase value and multiplying it with 100. The Rong’s retention ratio in the Metastatic lymph nodes group showed the mean value of 37.2 +/- 16.5. The Dr.V.Siva’s modification of the Rong’s Ratio was arrived at by dividing the Delayed Phase value by the Early phase value and multiplying it with 100. The omission of subtraction of the early phase value in the Rong’s Retention ratio showed the mean value of 132.7 +/- 19.3. The Dr.V.Siva’a modification of Rong’s Retention ratio resulted in the increase in value by 100 with no significant overlap (Fig.1). The definitive cut of value of 100 and above could be assigned to indicate the malignant and metastatic lesions in the Dual Phase PETCT scans. Conclusion: The Scintimetric Characterization of the lymph node tracer uptake by Dual phase PETCT provides a definitive proof of malignant process occurring at the metastatic lymph nodes. This will be more useful in differentiating the infective lymph node enlargement in the midst of the metastatic lymph nodes and vice versa. Further evaluation of this concept is warranted as this is a single institutional study of short duration and small number of cases.
Keywords: Dual Phase PETCT scans, Scintimetric Characterization, Rong’s Retention Ratio and Dr.V.Siva’s modification of Rong’s Retention Ratio.
Introduction
The accumulation of the tracer in the lymph nodes results in focal hot spot in the PETCT scans of various primary
malignancies like carcinoma breast, Prostate etc. Whether this is due to secondary metastatic involvement from the primary or a mere infective or inflammatory origin plays a vital role in the staging of the disease process. The mere calculation of SUV max values in the hot spot areas was not useful in this regard. Hence the necessity and utility of Dual Phase PETCT evaluation tumor detection was reported by Kuboto K et.al (1).
The optimal time interval between the early and delayed scans was discussed and determined to be the maximum of 4 hr from the time of injection of F18 FDG by Chen Y M et.al (2). Rong Tian et al have documented the utility of Dual Phase PETCT in the differentiation of benign and malignant bone lesions (3). In this Rong had defined a Retention Ratio based on the SUV max values in the early and delayed PETCT scans as follows Rong’s Retention Ratio = D SUVmax – E SUVmax / E SUVmax X 100 Where D SUV max = SUV max value of the lymph node in
the delayed PETCT and E SUV max = SUV max value of the lymph node in the early PETCT scans. The utility and the advantage of dual time point based quantitative evaluation of metabolic uptake rates by dual phase PETCT scans have been highlighted by De hoff j et al (4) and Jones C et al (5).
The usefulness of the scintimateric characterization of the hot spots in the evaluation of Primary malignancies had been reported by Dr..V.Siva et al (6). In this the original Rong’s Retention Ratio was modified as follows DR.V.Siva’s modification of Rong’s Ratio = D SUVmax /E SUVmax X 100 Materials and Method: In the proven cases of various primary malignancies like Ca.Breast, Ca.Prostate, Lymphomas and alveolar tumors the SUV max values of the metastatic lymph nodes were calculated in both the Early and Delayed phase scans.
The PETCT study was performed using the GE Discovery IQ PETCT in those patients with positive lymph
node uptake. The early scan was done One hour post injection of 5 to 10 mCi of F18-FDG tracer in the fasting state with their informed consent with optimal serum blood sugar level of 150 mg/dl. The delayed PETCT was done Four hours after the post injection time with voluntary consent of the patients without any additional injection of the tracer or contrast medium. The SUV max values were obtained utilizing the Advantage 4.4 software provided by the GE. Total of Forty eight lymph nodes at various locations were included in the study. The calculated SUV max values were used to arrive at the Rong’s Retention Ratio and the Dr.V.Siva’s modification of RRI.
Results : The results were tabulated in the table as shown below
lymph nodes group showed the mean value of 37.2 +/- 17.0. The Dr.V.Siva’s modification of the Rong’s Ratio showed the mean value of 132.7 +/- 19.8. The Dr.V.Siva’a modification of Rong’s Retention ratio resulted in the increase in value by 100 with no significant overlap (Fig.1).
In the previous study of dual PETCT scintimentric characterization of the various primary malignancies the Rong’s Retention ratio showed the mean value of 35.8 +/- 8 and the Dr.V.Siva’s modification of RRI showed the mean value of 135 +/- 8.1 as reported confirming that the definitive cut of value of 100 and above could be assigned to indicate the malignant and metastatic lesions in the Dual Phase PETCT scans in the Dr.V.Siva’s modification method. By eliminating the subtraction of early SUV max value from the delayed SUV max value the negative values were avoided. The statistical analysis of the data using student t test evaluation showed that there is clear cut demarcation between the original Rong’s Retention Ratio values and the Dr.V.Siva’s modification of Rong’s Ratio as shown in the Figure 2.
The p value is < 0.0001 indicating the validity of the Dr.V.Siva’s modification of Rong’s Ratio in the scintimetric characterization of the metastatic lymph nodes of various primary cancers. However the homogeneous population of cancer patients and non inclusion of the benign lymph nodal enlargement is a definitive limitation of this study. Further evaluation of this concept is warranted as this is a single institutional study of short duration and small number of cases.
Conclusion :
It can be concluded that the Scintimetric Characterization of the lymph node tracer uptake by Dual phase PETCT provides a definitive proof of malignant process occurring at the metastatic lymph nodes. This will be more useful in identifying the infective lymph node enlargement in the midst of the metastatic lymph nodes and vice versa. REFERENCES:
- Kubota K, Itoh M, Ozaki et al. Advantage of delayed whole body FDG-PET imaging for tumor detection, Eur J Nucl Med.2001;28;693 – 703.
- Chen YM, Huang G, Sun XG et al. Optimizing delayed scan time for FDG PET: comparison of the early and late delayed scan, NuclMed Communications, 2008;29;425 – 430.
- Rong Jian & Minggang Su & Ye lian& Fanglan Li & Anren Kuang & Jiancheng Zeng , Dual- Time point PET/CT with F-18 FDG for the differentiation of malignant and benign bone lesions, Skeletal Radiology (2009) 38: 451- 458.
- Den Hott J, Hotheinz P, Oehme L et al. Dual time point base quantification of metabolic uptake rates 18F-FDG PET, EJNMMI Res. 2013;3: 1-6
- Jones C, Badger S, Lynch I, A potential diagnostic role of dual phase 18F-FDG PET/CT scanning, Ulster Med J, 2014;83;52-54.
- Dr.V.Sivasubramaniyan, Sai Shivnarayan, Dr.K.Venkataramaniah, Scintimetric Characterization of Primary Tumors by Dual Phase PETCT study, INDIAN JOURNAL OF APPLIED RESEARCH, Feb.2020. Volume 10/ Issue 2/ 61-62