Significance of 18F—FDG PET / CT imaging in the evaluation of the efficacy of lymphoma

CHEN+Chengcheng,+WANG+Zhengguang,+CHENG+Nan

Abstract To evaluate the 18F-labeled deoxyglucose （18F-FDG） PET /CT imaging in the evaluation of the efficacy of lymphoma significance.Methods： 42 cases of our hospital patients with malignant lymphoma for 2-5 times 18F-FDG PET / CT imaging results in the treatment process， and the treatment process simple CT results were compared and analyzed， the final results were confirmed by pathology and clinical. Results： The lesions were found in153，including 141 malignant， benign 12， sensitivity， specificity， and accuracy evaluating of lymphoma treatment effect of 18F-FDG PET / CT were， 99.30%， 91.67%， 98.70%， were significantly better than CT examination （P

Key words lymphoma； Tomography； Emission computed； Single photon； Fluorine-18 deoxyglucose positron emission tomography.

中圖分類號：R319 文獻標識碼：A

Lymphoma is a common malignancy of lymphoid tissue. The current conventional clinical imaging methods are mainly x-ray， B ultrasound， CT， MRI etc. These methods mainly reflect the size， density and other anatomical information， there are some limitations. While the 18F-labeled deoxyglucose （18F-fluorodeoxyglucose， 18F-FDG） PET/ CT imaging can be the perfect fusion of anatomical information and molecular metabolic information with lesions [2] . through a retrospective analysis of the treatment of patients with lymphoma after18F-FDG PET / CT imaging in the study， and the results were compared with CT alone， 18F-FDG PET / CT evaluation of the significance of lymphoma.

Objects and methods

General information 42 patients with pathologically confirmed malignant lymphoma， 30 males and 12 females， with average age of 41 years. All patients before treatment were pathologically diagnosed or lymph node biopsy， including non-Hodgkin's lymphoma （NHL） in 33 cases， and 9 cases of Hodgkin lymphoma （HL）. The nearest 18F-FDG PET/CT examination was made after the end of treatment 1 to 2 months.

Imaging methods 42 patients included in this study before treatment line CT， MRI， 18F-FDG PET / CT in at least one imaging， and take 18F-FDG PET/CT examination in the treatment underwent. Imaging PET / CT scanner for the U.S. company GE's Discovery VCT. 18F-FDG imaging agent produced by the Japanese company Sumitomo cyclotron and synthesis by automated synthesis module automatically radiochemical purity of > 95% ， the radioactivity concentration > 370MBq/ml， PH value of 4 to 8 ， the drug half-life of 105 to 115 minutes. Before the examination， the patients take 4 to 6 hours of fasting .check routine before the fasting blood glucose， blood glucose concentration within 8.0mmol/l guarantee. Quiet ， dark 10min after injection of 18F-FDG， injected a dose of 0.15 ～ 0.18mCi/kg. After intravenous injection of repose about 50 minutes ， after urination take routine checks . Scan including CT scans and PET scans， scan range from the parietal to the upper thigh. Spiral CT scan first perspective acquisition conditions， voltage 120KVP， current 110mA， rotation speed 0.7s /circuit， bed-speed 29.46cm/s， matrix 512 * 512. PET emission scanning using ordinary scan matrix 128 * 128， each bed collecting 1.5-3min. Image after image obtained by the attenuation correction ， iterative reconstruction method ， the image is transferred to a workstation for digital convergence and reconstruction.

PET/CT image analysis By 3 years of experience with image doctor diagnosis information， they read the pieces together， comprehensive analysis the CT images shown metabolic lesions， size， shape， density， and the corresponding parts of PET lesions displayed. PET images of the lesions in uptake as positive， select the most obvious level， the lesion uptake 18F-FDG outlined ROIs （region of interest， ROI）， measuring the maximum standardized uptake value （maximum standard uptake value SUVmax）， SUVmax ≥ 2.5 as a diagnostic criterion positive lesions. Bone marrow infiltration with 18F-FDG uptake is equal to or higher than the liver as positive.

Conventional inspection methods and image processing 64-slice spiral CT （Brilliance CT 64， Philip） routine collection neck， chest， abdomen， pelvic CT images （plain）， thickness of 5mm， if necessary， enhanced scan； with lymph node diameter ≥ 1.0cm lymphoma invasion diagnostic criteria. By three experienced imaging doctors reading the pieces to determine.

Imaging evaluation criteria ①PET/CT imaging of benign and malignant judgment criteria after treatment： see the lesions after treatment is still unusually high metabolism， or the primary site of the lesion， lymph nodes before treatment increases， considered malignant ； if the primary site of the lesion， increasing lymph nodes disappeared， there is still residual lesions or show partial PET corresponding parts but no abnormalities on CT images of high metabolic， considered benign. ②purely CT judged benign and malignant standard： The original site of the lesion， compared with pre-treatment increases lymph nodes， or still residual lesions after topical treatment， considered malignant； increased after treatment or lymph node lesions disappeared， or lymph nodes down to normal size， considered benign. ③ increased lymph criteria： lower paratracheal mediastinal group （4R area） and subcarinal （Area 7） lymph node diameter> 1.5cm， lymph nodes in other parts of the body diameter> 1cm.

Statistical Methods using SPSS17.0 software， computing data to€盨 said. T test and X2 test. With P <0.05 was considered statistically significant.

Result

Final diagnosis The final diagnosis results of 42 cases of lymphoma， 35 cases were proven by clinical follow up， 7 cases were confirmed by operation and pathology.Lesions were found in 153， including 141 malignant lesions， 12 benign lesions. Malignant lesions invaded parts：126 lymph nodes （lymph node 37 which， Mediastinal lymph nodes 29，qbdominal and pelvic lymph nodes 19，axillary lymph nodes 16，retroperitoneal lymph nodes 12， and inguinal lymph nodes 9 supraclavicular lymph node 6），lung 7，skin 5，bone 7，pharyngeal lymphoid tissue， nasal cavity， stomach， intestine the two .Benign disease distribution： Pulmonary inflammatory lesions 3，Chronic inflammation of lymph node 5，Inflammatory polyps in the nasal cavity and pharynx each 1.endprint

18F-FDG PET / CT evaluation 18F-FDG PET /CT for 98.70% （151/153） of the lesions were accurately evaluated. False negative one， diffuse large B lymphoma after multiple courses of chemotherapy， 18F-FDG PET/CT showed no abnormal corresponding parts of high metabolism， but the corresponding parts of the nodule CT image shows abnormal signal changes for recurrent lesions， lesions after chemotherapy disappear. False positive one for supraclavicular. Soft tissue density and showed a high metabolism， consider lymph node involvement， anti-infection treatment lesions disappeared， the final diagnosis of chronic lymphadenitis. 18F-FDG PET/CT evaluation of the efficacy of lymphoma， the sensitivity， specificity， accuracy， positive predictive value and negative predictive value was 99.30% （140/141）， 91.67%% （11/12）， 98.70% （151 / 153）， 99.30% （140/141）， 91.67% （11/12）.

Evaluation of the efficacy of CT pure CT pure for 85.81% （121/14） of the lesions was accurately evaluated. False negative 10， which normal lymph node size （diameter <1 cm） 7， CT diagnosis of negative， but follow-up confirmed as positive； infringement of three， the corresponding CT images showed no bone abnormalities. False-positive 20， still visible after treatment of localized lymph node 10 increases， but the follow-up of residual lesions considered negative； still see the nasal pharyngeal soft tissue mass， but considering the local residual lesions and a negative follow-up； lung inflammatory lesions considered violation of a lung； still see after treatment， follow-up in addition to high metabolic bone negative 7. Evaluation of the efficacy of CT pure lymphoma sensitivity， specificity， accuracy， positive predictive value and negative predictive value were 85.21% （121/142）， 9.10% （2/22）， 85.21% （121/142）， 85.82% （121/141）， 16.67% （2/12）.

Comparative efficacy evaluation about 18F-FDG PET / CT and purely CT， Both compared in sensitivity， accuracy， positive predictive value and negative predictive value. The differences were statistically significant ，specific differences were also statistically significant （P <0.01）.

Discuss

Lymphoma is one of the common malignant tumors， it can achieve high cure rate and treatment by radiotherapy （or） chemotherapy[3]， while accurate， timely， and effective monitoring of the efficacy of the measures necessary to improve the cure rate. Conventional imaging methods （CT， MRI， etc） high image resolution， clear display of subtle lesions， can be used for routine diagnosis of lymphoma， but not for efficacy monitoring[4-5]. 18F-FDG PET/CT will organize and diseased organs， the function of molecular information and accurate anatomical structure information integration， and has important value for lymphoma tumor residual detection， evaluation of curative effect[6-8].endprint

18F-FDG PET / CT examination can fully reflect systemic conditions after the treatment of malignant lymphoma .Especially early， objective characteristics， it has obvious advantages in clinical work. Due to the wide distribution of the human lymphoid tissue lymphoma can occur in any part of the body. Conventional imaging methods are often not comprehensive response to the disease situation. The 18F-FDG PET/CT has high sensitivity， high specificity， functional imaging and whole body imaging， one examination can reflect a systemic disease involving the case. There is a good response to treatment of lymphoma， their growth slows or stops， decreased metabolic activity of tumor cells， the performance of 18F-FDG uptake reduce or disappear. In this study， CT false-positive lesions （such as radiotherapy and chemotherapy are still increasing residual lymph nodes and local organizations）， 18F-FDG PET/CT were carried out qualitatively accurate， allowing patients to avoid unnecessary treatment.

Many times of 18F-FDG PET / CT imaging before and after the treatment to determine the efficacy of malignant lymphoma has a unique value， early detection of residual and recurrent lesions after surgery to help clinical monitoring efficacy and timely correction treatment.

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