Objective      To explore the possibility of detecting the transcriptional activity of human telomerase reverse transcriptase (hTERT) promoter with MR imaging (MRI).        Methods      The Lenti-hTERT-Fth-flag-Puro vector was constructed and transfected into telomerase-positive human lung carcinoma A549 cells and telomerase-negative primary human periodontal ligament fibroblasts (HPDLFs)

with Lenti-CMV-Fth-flag-Puro vector used as control. Immunofluorescent staining and Western blotting were used to detect Fth-flag protein expression. Prussian blue iron staining was used for assaying iron accumulation. MRI was performed to determine the changes of T

*

2

WI signal intensity and T

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2

value of cells in vitro.        Results      After transfected with Lenti-hTERT-Fth-flag-Puro vector

Fth-flag protein overexpression and iron accumulation increase were observed in transfected A549 cells but not in untransfected cells. MRI showed that the T

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2

WI signal intensity and T

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2

value of transfected A549 cells (SI: 1 340.86±49.21

T

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2

value: 12.10±0.92) were significantly decreased as compared to untransfected A549 cells (SI: 2 049.08±87.58

T

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2

value: 21.44±1.15) (

P

0.05). However

Fth-flag protein overexpression and iron accumulation increase were not observed in HPDLFs cells after transfected with Lenti-hTERT-Fth-flag-Puro vector. Accordingly

no significant difference of the T

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2

WI signal intensity and T

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2

value were observed between transfected HPDLFs cells (SI: 2 225.42±73.43

T

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2

value: 24.01±1.13) and untransfected HPDLFs cells (SI: 2 148.48±54.74

T

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2

value: 23.39±1.72) (P0.05).  While transfected with Lenti-CMV-Fth-flag-Puro vector

A549 and HPDLFs cells both showed Fth-flag protein overexpression an

d iron accumulation increase

and the T

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2

WI signal intensity and T

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2

value of transfected cells (A549: 1 137.38±60.59

9.61±1.17; HPDLFs: 1 299.16±53.42

11.54±0.74) were both significantly decreased as compared to untransfected ones (

P

0.05).       Conclusion      It is achievable to detect transcriptional activity of hTERT promoter using MRI technology. The reporter gene imaging system used in this study may become a new prognostic method for cancer.