Multicentric Primary Angiosarcoma of Bone Mimicking Metastasis on 18F-FDG PET/CT in a Patient with a History of Sigmoid Colon Cancer: a Case Report

Primary angiosarcoma of the bone (PAB) is a rare and fatal high-grade malignant vascular bone tumor. We report a rare case of multicentric PAB mimicking bone metastasis in a 59-year-old female patient with a history of sigmoid colon cancer. This patient complained of lower back and pelvic pain and presented with multiple osteolytic bone lesions on plain radiography and pelvic computed tomography. First, bone metastasis of sigmoid colon cancer was suspected. However, on the ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) scan, the patient presented unusual multiple hypermetabolic osteolytic bone lesions involving contiguous bones of the lower half of the body. After bone biopsy, these lesions were confirmed to be multicentric PAB. To the best of our knowledge, this is the first case report of an ¹⁸F-FDG PET/CT scan in a patient with multicentric primary bone angiosarcoma.     

Using 18F-FDG PET/CT to Detect an Occult Mesenchymal Tumor Causing Oncogenic Osteomalacia

Oncogenic osteomalacia is a rare paraneoplastic syndrome characterized by renal phosphate excretion, hypophosphatemia, and osteomalacia. This syndrome is often caused by tumors of mesenchymal origin. Patients with oncogenic osteomalacia have abnormal bone mineralization, resulting in a high frequency of fractures. Tumor resection is the treatment of choice, as it will often correct the metabolic imbalance. Although oncogenic osteomalacia is a potentially curable disease, diagnosis is difficult and often delayed because of the small size and sporadic location of the tumor. Bone scintigraphy and radiography best characterize osteomalacia; magnetic resonance imaging findings are nonspecific. Here, we report a case of oncogenic osteomalacia secondary to a phosphaturic mesenchymal tumor that was successfully detected by ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT). This case illustrates the advantages of ¹⁸F-FDG PET/CT in detecting the occult mesenchymal tumor that causes oncogenic osteomalacia.     

Relations Between Pathological Markers and Radioiodine Scan and 18F-FDG PET/CT Findings in Papillary Thyroid Cancer Patients With Recurrent Cervical Nodal Metastases

Purpose

The aim of this study was to investigate relationships between the immunohistochemical results and radioiodine scan and ¹⁸F-FDG PET findings in papillary thyroid cancer (PTC) patients with recurrent cervical nodal metastases.

Methods

A total of 46 PTC patients who had undergone a radioiodine scan and/or ¹⁸F-FDG PET/CT and a subsequent operation on recurrent cervical lymph nodes were enrolled. Twenty-seven patients underwent ¹⁸F-FDG PET/CT, 8 underwent radioiodine scans, and 11 underwent both scans. In all surgical specimens, the immunoexpressions of thyroglobulin (Tg), sodium-iodide symporter (NIS), glucose transporter 1 (Glut-1), and somatostatin receptor 1 and 2A (SSTR1 and SSTR2A) were assessed, and associations between these expressions and radioiodine scan and ¹⁸F-FDG PET findings were evaluated.

Results

Of the 38 patients who underwent ¹⁸F-FDG PET/CT, all patients with weak Tg expression had positive ¹⁸F-FDG uptake, while only 45 % of the patients with moderate or strong Tg expression showed positive uptake (p = 0.01). The proportion of patients with positive ¹⁸F-FDG uptake increased as the degree of Glut-1 expression with luminal accentuation increased. Of the 19 patients who underwent a radioiodine scan, the proportion with positive radioiodine uptake was greater among patients with strong NIS and SSTR2A expression than among patients expressing these markers at weak levels (p = 0.04 for all). All three patients with weak Tg expression were negative for radioiodine uptake.

Conclusion

The ¹⁸F-FDG uptakes of recurrent cervical nodes are related to strong Glut-1 expression with luminal accentuation and weak Tg expression, whereas radioiodine uptake is related to the strong expressions of NIS and SSTR2A.     

Clinical Usefulness of 18F-fluoride Bone PET

Purpose

¹⁸F-fluoride bone positron emission tomography (PET) has been reported as a useful bone imaging modality. However, no clinical bone PET study had been performed previously in Korea. The authors investigated the usefulness of ¹⁸F-fluoride bone PET in Korean patients with malignant or benign bone disease.

Methods

Eighteen consecutive patients (eight women, ten men; mean age, 55 ± 12 years) who had undergone ¹⁸F-fluoride bone PET for the evaluation of bone metastasis (n = 13) or benign bone lesions (n = 5) were included. The interpretation of bone lesions on ¹⁸F-fluoride bone PET was determined by consensus of two nuclear medicine physicians, and final results were confirmed using combination of all imaging studies and/or clinical follow-up. The analysis was performed on the basis of lesion group.

Results

Thirteen patients with malignant disease had 15 lesion groups, among which seven were confirmed as metastatic bone lesions and eight were confirmed as non-metastatic lesions. ¹⁸F-fluoride bone PET correctly identified six of seven metastatic lesions (sensitivity, 86%), and seven of eight non-metastatic lesions (specificity, 88%). On the other hand, five patients with benign conditions had five bone lesion groups; four were confirmed as benign bone diseases and the other one was confirmed as not a bone lesion. ¹⁸F-fluoride bone PET showed correct results in all the five lesion groups.

Conclusions

¹⁸F-fluoride bone PET showed promising potential for bone imaging in Korean patients with malignant diseases as well as with various benign bone conditions. Therefore, further studies are required on the diagnostic performance and cost-effectiveness of ¹⁸F-fluoride bone PET.     

PET/CT in oncology--a major advance

The concept of hardware fusion between positron emission tomography (PET) and computed tomography (CT) has only been introduced commercially in the last 4 years. The advantages of this combined technique over PET alone have become obvious. There is increasing evidence to suggest that PET/CT adds complementary information in staging, re-staging and follow-up in oncology patients, leading to changes in management plans. The present paper is a review of the strengths, weaknesses, current evidence and future directions of this technique.     

18F-FDG PET in children with lymphomas

Purpose The aim of this study was to retrospectively evaluate the performance of positron emission tomography (PET) with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) in children with lymphomas, at various stages of their disease.Methods Twenty-eight children (mean age 12.5 years, 14 girls, 14 boys) with Hodgkins disease (HD, n=17) or non-Hodgkins lymphoma (NHL, n=11) were evaluated. Patients were investigated at initial staging (n=19), early in the course of treatment (n=19), at the end of treatment (n=16) and during long-term follow-up (n=19). A total of 113 whole-body PET studies were performed on dedicated scanners. PET results were compared with the results of conventional methods (CMs) such as physical examination, laboratory studies, chest X-rays, computed tomography, magnetic resonance imaging, ultrasonography and bone scan when available.Results At initial evaluation (group 1), PET changed the disease stage and treatment in 10.5% of the cases. In early evaluation of the response to treatment (group 2), PET failed to predict two relapses and one incomplete response to treatment. In this group, however, PET did not show any false positive results. There were only 4/75 false positive results for PET among patients studied at the end of treatment (group 3, specificity 94%) or during the systematic follow-up (group 4, specificity 95%), as compared with 27/75 for CMs (specificity 54% and 66%, respectively).Conclusion ¹⁸F-FDG-PET is a useful tool for evaluating children with lymphomas. Large prospective studies are needed to appreciate its real impact on patient management.     

The incremental value of <Superscript>18</Superscript>F-FDG PET/CT in paediatric malignancies

PURPOSE: (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography (PET) imaging has been used in the assessment of paediatric malignancies. PET/CT increases the diagnostic accuracy in adult cancer patients. The present study assesses the incremental value of FDG PET/CT in paediatric malignancies. METHODS: A total of 118 (18)FDG PET/CT studies of 46 paediatric patients were reviewed retrospectively. PET and PET/CT results were classified as malignant, equivocal or benign, compared on a site- and study-based analysis, and also compared with the clinical outcome. RESULTS: Three hundred and twenty-four sites of increased FDG uptake were detected. Discordant PET and PET/CT interpretations were found in 97 sites (30%) in 27 studies (22%). PET yielded a statistically significant higher proportion of equivocal and a lower proportion of benign lesion and study results (p<0.001) than PET/CT. With PET there were 153 benign (47%), 84 (26%) equivocal and 87 (27%) malignant sites, while PET/CT detected 226 benign (70%), 10 (3%) equivocal and 88 (27%) malignant lesions. PET/CT mainly improved the characterisation of uptake in brown fat (39%), bowel (17%), muscle (8%) and thymus (7%). The study-based analysis showed that 17 equivocal and seven positive PET studies (20%) were interpreted as benign on PET/CT, while three equivocal studies were interpreted as malignant. The study-based sensitivity and specificity of PET/CT were 92% and 78% respectively. CONCLUSION: PET/CT significantly improved the characterisation of abnormal (18)FDG foci in children with cancer, mainly by excluding the presence of active malignancy in sites of increased tracer activity.     

Pulmonary Actinomycosis Imitating Lung Cancer on 18F-FDG PET/CT: A Case Report and Literature Review

Here we report a case of 41-year-old man with a soft tissue density mass at right upper lung and palpable abscesses at right upper backside and right wrist. ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography demonstrated a 7.8 × 5.0 cm mass with soft-tissue density in the upper lobe of the right lung with high metabolic activity. The infiltrative mass extended to adjacent chest wall soft tissue. Final diagnosis of pulmonary actinomycosis with multiple abscesses was made. The patient responded well to antibiotics treatment.     

18F-FDG和11C-choline PET/CT诊断前列腺良恶性病变的影响因素研究

目的:探讨18F-FDG(18F-脱氧葡萄糖)和11 C-choline(11 C-胆碱)PET/CT显像诊断前列腺良恶性病变的影响因素,以提高PET/CT对前列腺病变的诊断价值。方法:选择可疑前列腺病变患者55例为研究对象,年龄57～82岁,28例为前列腺癌,转移程度不一;其余为前列腺良性病变。所有患者均行全身18 F-FDG和11 C-choline PET/CT检查,分析18 F-FDG和11 C-choline标准摄取值(SUV)与前列病变患者的年龄及病理类型的相互关系和意义。结果:55例前列腺病变患者,18F-FDG和11 C-choline标准摄取值与患者的年龄无统计学差异(P>0.05),18 F-FDG标准摄取值与患者的病理类型亦无统计学差异(P>0.05),而11 C-choline标准摄取值与患者的病理类型有统计学差异(P<0.05)。结论:前列腺病变患者的病理类型是影响11 C-choline标准摄取值的重要因素,11 C-choline PET/CT鉴别诊断前列腺良恶性病变具有重要的价值和意义。     

Evaluation of Bone Metastasis from Hepatocellular Carcinoma Using 18F-FDG PET/CT and 99mTc-HDP Bone Scintigraphy: Characteristics of Soft Tissue Formation

Purpose

Bone metastasis from hepatocellular carcinoma (HCC) can present with soft tissue formation, resulting in oncologic emergency. Contrast-enhanced FDG PET/CT and bone scintigraphy were compared to evaluate characteristics of bone metastases with or without soft tissue formation from HCC.

Methods

Of 4,151 patients with HCC, 263 patients had bone metastases. Eighty-five patients with bone metastasis from HCC underwent contrast-enhanced FDG PET/CT. Fifty-four of the enrolled subjects had recent ^99mTc-HDP bone scintigraphy available for comparison. Metastatic bone lesions were identified with visual inspection on FDG PET/CT, and maximum standardized uptake value (SUV_max) was used for the quantitative analysis. Confirmation of bone metastasis was based on histopathology, combined imaging modalities, or serial follow-up studies.

Results

Forty-seven patients (55%) presented with soft tissue formation, while the remaining 38 patients presented without soft tissue formation. Frequent sites of bone metastases from HCC were the spine (39%), pelvis (19%), and rib cage (14%). The soft-tissue-formation group had more frequent bone pain (77 vs. 37%, p < 0.0001), higher SUV_max (6.02 vs. 3.52, p < 0.007), and higher incidence of photon defect in bone scintigraphy (75 vs. 0%) compared to the non-soft-tissue-formation group. FDG PET/CT had higher detection rate for bone metastasis than bone scintigraphy both in lesion-based analysis (98 vs. 53%, p = 0.0015) and in patient-based analysis (100 vs. 80%, p < 0 .001).

Conclusions

Bone metastasis from HCC showed a high incidence of soft tissue formation requiring emergency treatment. Although the characteristic findings for soft tissue formation such as photon defect in bone scintigraphy are helpful in detection, overall detectability of bone metastasis is higher in FDG PET/CT. Contrast-enhanced PET/CT will be useful in finding and delineating soft-tissue-forming bone metastasis from HCC.     

18F-FDG PET/CT显像用于肺癌诊疗的研究进展

常规¹⁸F-FDG PET/CT静态显像在肺癌的诊断、分期、疗效评估等方面发挥了重要作用,并能通过标准化摄取值等代谢参数进行半定量分析,但静态显像无法提供病变的示踪动力学信息。近年出现的动态显像技术能够连续评估某一时间段内病变的代谢变化过程,并可应用净摄取速率常数等动力学参数进行定量分析,与静态显像相互补充,为肺癌的诊断提供更丰富的信息。就 ¹⁸F-FDG PET/CT静态及动态显像在肺癌诊疗中的研究进展进行综述。     

Evaluation of gross tumor size using CT, 18F-FDG PET, integrated 18F-FDG PET/CT and pathological analysis in non-small cell lung cancer

Purpose

The correlation of gross tumor sizes between combined ¹⁸F-FDG PET/CT images and macroscopic surgical samples has not yet been studied in detail. In the present study, we compared CT, ¹⁸F-FDG PET and combined ¹⁸F-FDG PET/CT for the delineation of gross tumor volume (GTV) and validated the results through examination of the macroscopic surgical specimen.

Methods

Fifty-two operable non-small cell lung cancer (NSCLC) patients had integrated ¹⁸F-FDG PET/CT scans preoperatively and pathological examination post-operation. Four separate maximal tumor sizes at X (lateral direction), Y (ventro-dorsal direction) and Z (cranio-caudal direction) axis were measured on ¹⁸F-FDG PET, CT, combined ¹⁸F-FDG PET/CT and surgical specimen, respectively. Linear regression was calculated for each of the three imaging measurements versus pathological measurement.

Results

No significant differences were observed among the tumor sizes measured by three images and pathological method. Compared with pathological measurement, CT size at X, Y, Z axis was larger, whereas combined ¹⁸F-FDG PET/CT and ¹⁸F-FDG PET size were smaller. Combined ¹⁸F-FDG PET/CT size was more similar to the pathological size than that of ¹⁸F-FDG PET or CT. Results of linear regressions showed that integrated ¹⁸F-FDG PET/CT was the most accurate modality in measuring the size of cancer.

Conclusions

¹⁸F-FDG PET/CT correlates more faithfully with pathological findings than ¹⁸F-FDG PET or CT. Integrated ¹⁸F-FDG PET/CT is an effective tool to define the target of GTV in radiotherapy.     

Lymphadenopathy by Scrub Typhus Mimicking Metastasis on FDG PET/CT in a Patient with a History of Breast Cancer

We report the case of a 60-year-old woman with left-sided breast cancer who showed lymphadenopathy mimicking metastatic lesions. She underwent surveillance ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) after treatment. PET/CT demonstrated multiple lymphadenopathies with increased FDG uptake, most notably in the right axilla. She had an eschar on the right axillary area, and her serologic test was positive for anti-Orientia tsutsugamushi IgM antibody. Ten months after the treatment, follow-up FDG PET/CT and ultrasonography showed improvement in generalized lymphadenopathy.     

18F-氟代脱氧葡萄糖PET及PET-CT在淋巴瘤中的临床应用

PET 在淋巴瘤的分期、再分期、疗效评价及预后判断中具有重要价值,PET-CT则集中了PET的功能显像与CT的解剖显像的双重优势,对淋巴瘤病灶的定位、定性诊断的准确性更高.     

18F-FDG PET in malignant lymphoma: significance of positive findings

Purpose The aim of this study was to evaluate the significance of increased uptake of ¹⁸F-fluorodeoxyglucose (FDG) in patients with malignant lymphoma (ML) studied by positron emission tomography (PET).Methods A total of 1,120 consecutive scans carried out in 848 patients were reviewed; all patients had a diagnosis of ML [574 non-Hodgkins lymphoma (NHL) and 274 Hodgkins disease (HD)] and were studied at completion of therapy, for suspected recurrence or during follow-up. PET was carried out after intravenous injection of 370 MBq of ¹⁸F-FDG; images were recorded after 60–90 min. Patients were selected whose reports indicated areas of increased FDG uptake. PET findings were considered positive for lymphomatous localisation when uptake occurred at sites of previous disease, in asymmetrical lymph nodes or in nodes unlikely to be affected by inflammation (mediastinal, except for hilar, and abdominal). PET findings were adjudged negative for neoplastic localisations in the following instances: physiological uptake (urinary, muscular, thymic or gastrointestinal in patients without MALT), symmetrical nodal uptake, uptake in lesions unrelated to lymphoma that had already been identified by other imaging methods at the time of PET scan, uptake at sites atypical for lymphoma, very low uptake and non-focal uptake. PET findings were compared with the results of other diagnostic procedures (including CT and ultrasound), biopsy findings and follow-up data.Results Overall, 354 scans (in 256 patients) showed increased FDG uptake (244 scans in NHL and 110 in HD): in 286 cases, FDG uptake was considered pathological and indicative of ML, in 41 cases the findings were described as uncertain or equivocal and in 37 cases, FDG uptake was considered unrelated to ML (in ten scans, concurrent findings of abnormal FDG uptake attributed to ML and uptake assigned to other causes were obtained) . Of the 286 patients with positive PET findings, 274 (95.8%) were found to have residual or recurrent ML (i.e. true positives). Four of the 41 patients with inconclusive findings turned out to have ML, while in 13 patients, pathological processes other than ML could be identified as the cause of FDG uptake. ML was excluded in all patients with findings reported as non-pathological (100% true-negative rate). Therefore, the false-positive rate in our series was about 5%. The main cause of increased FDG uptake mimicking ML was inflammation.Conclusion Our data confirm that ¹⁸F-FDG-PET has very high but not absolute specificity for ML. As already suggested, increased FDG uptake may also be observed in patients without active disease; in most cases, however, non-pathological FDG accumulation is properly identified. Less frequently, inconclusive scans are encountered; these cases are usually caused by inflammation, which subsequently resolves.     

Tumor SUVmax Normalized to Liver Uptake on 18F-FDG PET/CT Predicts the Pathologic Complete Response After Neoadjuvant Chemoradiotherapy in Locally Advanced Rectal Cancer

Purpose

This study investigates the feasibility of using ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) to predict the pCR (pathologic complete response) rate after neoadjuvant chemoradiotherapy (NCRT) in patients with locally advanced rectal cancer.

Methods

A total of 88 patients with locally advanced rectal cancer were retrospectively analyzed. All patients were treated with NCRT, followed by radical surgery, and ¹⁸F-FDG PET/CT was performed before and after NCRT. For a semiquantitative assessment, a volume of interest was drawn, including the whole tumor region, and the maximum SUV (SUVmax), SUVmax normalized to liver uptake (SLR), SUVmax normalized to blood pool uptake (SBR), the metabolic tumor volume at SUV 2.0 (MTV[2.0]), SUV 2.5 (MTV[2.5]), and SUV 3.0 (MTV[3.0]) were measured. In addition, their percentage changes after NCRT were assessed. The pCR was verified through a histologic examination of postsurgical specimens. A receiver operating characteristic curve analysis was conducted to predict the pCR by using these PET parameters.

Results

The pCR was predicted in 17 patients (19 %). The values of the area under the curve (AUC) for predicting the pCR were 0.774 for SUVmax after NCRT, 0.826 for SLR after NCRT, 0.815 for SBR after NCRT, 0.724 for MTV(2.5) after NCRT, 0.729 for the percentage change in SUVmax, 0.700 for the percentage change in SLR, and 0.749 for the percentage change in MTV (2.5). Among these PET parameters, SLR after NCRT showed the highest AUC value. The optimal criterion, sensitivity, specificity, and accuracy of SLR after NCRT for predicting the pCR were ≤1.41, 88 %, 65 %, and 68 %, respectively.

Conclusions

F-FDG PET was found to be useful for predicting the pCR after NCRT in patients with locally advanced rectal cancer. Among various PET parameters, SUVmax normalized to liver uptake after NCRT was the best predictor of the pCR.

Electronic supplementary material

The online version of this article (doi:10.1007/s13139-014-0289-x) contains supplementary material, which is available to authorized users.     

Peliosis Hepatis Shows Isometabolism on 18F-FDG PET/CT: Two Case Reports

Peliosis hepatis (PH) is a rare benign disease that is characterized by multiple blood-filled cystic spaces in the hepatic parenchyma. It is also characterized by a range of radiologic findings that might mimic various diseases, including metastatic liver disease and hepatocellular carcinoma. The findings of PH on ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) are not well reported. We here report two cases of biopsy-proven PH. Both patients had been treated for cancer (advanced gastric carcinoma and rectal adenocarcinoma), and follow-up CT of both cases revealed hepatic lesions with the possibility of metastasis. Examination of ¹⁸F-FDG PET/CT images suggested that the lesions were isometabolic, having metabolism similar to that of adjacent hepatic parenchyma. The outcomes of hepatic core-needle biopsies were consistent with peliosis hepatis.     

成人股骨头缺血坏死的X线、CT及静脉造影分析

目的：加深和提高对股骨头缺血性坏死的认识。方法：本组１２例，２３髋做了骨髓静脉造影。结果：Ｘ线、ＣＴ表现０期者，旋股内、外侧静脉显影好，而股骨颈后静脉及臀静脉显影差或不显影，Ⅰ—Ⅳ期者也有少数旋股内、外侧静脉显影好者，表明这两条静脉是主要回流静脉。骨干返流，滋养静脉显影在Ⅱ、Ⅲ期多见，Ⅳ期者少见。造影剂滞流情况，０期者注入造影剂５ｍｉｎ后基本排空，Ⅰ期以上者大部分在１５ｍｉｎ后仍有大量滞流。造影剂进入股骨头毁损区的很难排空。结论：Ｘ线、ＣＴ表现０—Ⅰ期的静脉造影可发现回流障碍，有利于早期诊断。一般分期越重，回流静脉出现越少，滞流越明显，但也有病变较重者，５ｍｉｎ大部分排空，可能与晚期静脉侧枝循环改善有关。造影剂进入骨毁损区很难排空与局部血运有关     

~(18)F-FDG PET/CT在食管癌的应用进展

食管癌恶性程度高、预后差,严重威胁了人类健康,18F-FDG PET/CT集功能和解剖信息于一身,这种医学影像技术在食管癌的应用优势日益受到广大医务工作者的关注。本文综述了18F-FDG PET/CT在食管癌的诊断、分期、复发、疗效和预后评估、放射治疗计划制定等方面的研究进展。     

呋塞米介入对18 F-脱氧葡萄糖正电子发射计算机断层显像的放射防护作用

目的 探讨呋塞米介入¹⁸F-脱氧葡萄糖(¹⁸F-FDG)正电子发射计算机断层显像(PET/CT)的放射防护作用。方法 146例患者按随机数表法随机分为两组,实验组74例,对照组72例。试验组注射前口服呋塞米40 mg,正常对照组未行特殊处理,¹⁸F-FDG注射60、120 min后,分别在其正面前胸、腹水平测量0.5 m处周围剂量当量率。结果 试验组注射¹⁸F-FDG后60 min胸部及腹部、120 min胸部及腹部的周围剂量当量率分别为(30.80±8.61)、(41.38±11.06)、(18.26±4.85)和(24.66±6.50)μSv/h,均低于对照组,差异有统计学意义(t=15.36、13.13、18.73、17.29,P＜0.05)。试验组和对照组的纵隔SUV_max、肝脏SUV_max差异无统计学意义(P＞0.05)。多因素分析显示,是否服用速尿、体表面积是影响周围剂量当量率的主要影响因素(t=-13.52、2.96,P＜0.05),年龄、性别对周围剂量当量率的影响不明显(P＞0.05)。结论 呋塞米介入可促进排尿,在不影响影像质量的前提下有效降低了受检者的体内辐射,有较好的放射防护作用。