主题：PET-CT相关资料 -- xtqntd

Journal of Nuclear Medicine Vol. 48 No. 1 (Suppl) 4S-18S

2007 by Society of Nuclear Medicine

Screening for Cancer with PET and PET/CT: Potential and Limitations

Heiko Schder1 and Mithat Gnen2

1 Department of Radiology/Nuclear Medicine, Memorial Sloan-Kettering Cancer Center, New York, New York; and 2 Department of Biostatistics and Epidemiology, Memorial Sloan-Kettering Cancer Center, New York, New York

Screening for cancer remains a very emotional and hotly debated issue in contemporary medical practice. An analysis of published data reveals a multitude of opinions based on a limited amount of reliable data. Even for breast cancer screening, which is now widely practiced in the United States and many European countries, there is continuing controversy regarding the appropriate age limits for screening mammography and, in fact, concerning the value of mammography itself. Similarly, there is no agreement as to whether screening for lung or prostate cancer is meaningful as currently practiced. Recommendations and decisions regarding cancer screening should be based on reliable data, not good intention, assumptions, or speculation. Therefore, we first explain the underlying principles and premises of screening and then briefly discuss current controversies regarding screening for breast, prostate, and lung cancers. Recently, some authors advocated CT, PET, or PET/CT for whole-body screening without support from reliable data. We discuss the potential financial, legal, and radiation safety implications associated with whole-body CT or PET cancer screening. We conclude from the available data that neither CT nor PET/CT cancer screening is currently warranted. Far from providing a desirable binary answer (presence of absence of cancer), in nonselected populations the procedures frequently yield equivocal or indeterminate findings that require further evaluation, with associated costs and potential complications. The clinical and statistical relevance of occasionally detected cancers is likely too low to justify population-wide screening efforts with these 2 imaging modalities. Ultimately, the true utility, or lack thereof, of PET and PET/CT for cancer screening can be assessed only in a prospective randomized trial. Because of prohibitive costs and the required length of follow-up, it is unlikely that such a trial will ever be conducted. Rather than spending time and resources on screening studies, medical practitioners should continue using whole-body PET/CT for diagnosing, staging, and restaging cancer and for monitoring treatment effects. Researchers should also investigate the utility of whole-body PET/CT for the surveillance of selected groups of patients who have cancer, who have completed curative treatment, but who remain at high risk for recurrent disease.

Asian Pac J Cancer Prev. 2007 Jan-Mar;8(1):93-7.

Cancer screening with whole-body PET/CT for healthy asymptomatic people in Japan: re-evaluation of its test validity and radiation exposure.

Ghotbi N, Iwanaga M, Ohtsuru A, Ogawa Y, Yamashita S.

Takashi Nagai Memorial International Hibakusha Medical Center, Nagasaki University Hospital, Nagasaki City, Japan.

Abstract

The use of Positron Emission Tomography (PET) or PET/CT for voluntary cancer screening of asymptomatic individuals is becoming common in Japan, though the utility of such screening is still controversial. This study estimated the general test validity and effective radiation dose for PET/CT cancer screening of healthy Japanese people by evaluating four standard indices (sensitivity, specificity, positive/negative predictive values), and predictive values with including prevalence for published literature and simulation-based Japanese data. CT and FDG-related dosage data were gathered from the literature and then extrapolated to the scan parameters at a model PET center. We estimated that the positive predictive value was only 3.3% in the use of PET/CT for voluntary cancer screening of asymptomatic Japanese individuals aged 50-59 years old, whose average cancer prevalence was 0.5%. The total effective radiation dose of a single whole-body PET/CT scan was estimated to be 6.34 to 9.48 mSv for the average Japanese individual, at 60 kg body weight. With PET/CT cancer screening in Japan, many healthy volunteers screened as false positive are exposed to at least 6.34 mSv without getting any real benefit. More evaluation concerning the justification of applying PET/CT for healthy people is necessary.

翻译：在50－59岁的一般日本人群中，目前癌症患病率为0。5％，由此阳性预测值为3。3％，即PET－CT发现100例“癌症”／“阳性”只有3到4例是真的。

Journal of Nuclear Medicine Vol. 46 No. 6 930-935

2005 by Society of Nuclear Medicine

Clinical Investigations

Integrated PET/CT for the Assessment of Coronary Artery Disease: A Feasibility Study

Mehdi Namdar, MD1, Thomas F. Hany, MD2, Pascal Koepfli, MD1, Patrick T. Siegrist, MD1, Cyrill Burger, PhD2, Christophe A. Wyss, MD1, Thomas F. Luscher, MD1, Gustav K. von Schulthess, MD, PhD2 and Philipp A. Kaufmann, MD1

1 Nuclear Cardiology Section, Division of Cardiology, University Hospital, Zurich, Switzerland

2 Division of Nuclear Medicine, University Hospital, Zurich, Switzerland

An accurate, noninvasive technique for the diagnosis of coronary artery disease (CAD) should provide complementary information on coronary anatomy and pathophysiologic lesion severity. We present, what is to our knowledge, the first clinical evaluation of integrated PET/CT for combined acquisition of coronary anatomy and perfusion. Methods: On an integrated PET/CT scanner, contrast-enhanced CT angiography (CTA) and rest/adenosine-stress myocardial perfusion scanning with 13N-ammonia were performed on 25 patients [COLOR=blue]with CAD documented by coronary angiography.[/COLOR] Contrast-enhanced CTA was performed with retrospective electrocardiography gating after injection of 150 mL of intravenous contrast medium. Decisions on whether to treat with revascularization (anatomic lesion plus ischemia) or conservatively (no lesion or no ischemia) based on PET/CT were compared with those based on PET plus coronary angiography. Results: Of the 100 coronary artery segments (left main, left anterior descending, left circumflex, and right in 25 patients), 7 (in 5 patients) were considered impossible to evaluate by CT because of rapid vessel movement but were correctly categorized by PET alone. In the remaining 93 segments, the sensitivity and specificity of PET/CT versus PET plus coronary angiography were 90% and 98%, respectively. Positive and negative predictive values were 82% and 99%, and accuracy was 97%. Conclusion: The data of this preliminary study suggest that PET/CT allows accurate noninvasive clinical decision making about CAD. Because of its high negative predictive value, PET/CT may play an important role in noninvasive selection of CAD patients for revascularization. Integration of higher-performance multislice spiral CT scanners into PET/CT hybrids will accelerate the clinical implementation of this technique.

在已经确诊CAD的病人诊断病情用，而不是什么在一般人群里筛检早期冠心病

False-Positive FDG PET Uptakethe Role of PET/CT

Sandra J. Rosenbaum1 Contact Information, Thomas Lind1, Gerald Antoch2 and Andreas Bockisch1

(1) Department of Nuclear Medicine, University of Essen, Hufelandstrasse 55, 45122 Essen, Germany

(2) Department of Radiology, University of Essen, Hufelandstrasse 55, 45122 Essen, Germany

Received: 6 September 2005 Revised: 27 October 2005 Accepted: 18 November 2005 Published online: 17 December 2005

Abstract Positron emission tomography (PET) is a powerful molecular imaging technique for the human body-imaging applications currently available. As altered glucose metabolism is characteristic for many malignancies, FDG-PET is mostly used in oncology for staging and therapy control. Although PET is a [COLOR=blue]sensitive tool for detecting malignancy, FDG uptake is not tumor specific. It can also be seen in healthy tissue or in benign disease as inflammation or posttraumatic repair and could be mistaken for cancer. [/COLOR]The experienced nuclear medicine physician mostly manages to differentiate malignant from non-malignant FDG uptake, but some findings may remain ambiguous. In these cases, the difficulties in differentiating physiologic variants or benign causes of FDG uptake from tumor tissue can often be overcome by combined PET and CT (PET/CT) as anatomic information is added to the metabolic data. Thus, PET/CT improves the diagnostic accuracy compared to PET alone and helps to avoid unnecessary surgery/therapy. However, PET/CT involves other sources of artifacts that may occur when using CT for attenuation correction of PET or by patient motion caused by respiration or bowel movements.

PET-CT较单纯的PET特异性有所提高。但是PET的缺陷并未被完全消除。

http://www.who.int/cancer/detection/en/

Early detection of cancer greatly increases the chances for successful treatment.

There are two major components of early detection of cancer: education to promote early diagnosis and screening.

Recognizing possible warning signs of cancer and taking prompt action leads to early diagnosis. Increased awareness of possible warning signs of cancer, among physicians, nurses and other health care providers as well as among the general public, can have a great impact on the disease. Some early signs of cancer include lumps, sores that fail to heal, abnormal bleeding, persistent indigestion, and chronic hoarseness. Early diagnosis is particularly relevant for cancers of the breast, cervix, mouth, larynx, colon and rectum, and skin.

Screening refers to the use of simple tests across a healthy population in order to identify individuals who have disease, but do not yet have symptoms. Examples include breast cancer screening using mammography and cervical cancer screening using cytology screening methods, including Pap smears. Screening programmes should be undertaken only when their effectiveness has been demonstrated, when resources (personnel, equipment, etc.) are sufficient to cover nearly all of the target group, when facilities exist for confirming diagnoses and for treatment and follow-up of those with abnormal results, and when prevalence of the disease is high enough to justify the effort and costs of screening.

Based on the existing evidence, mass population screening can be advocated only for breast and cervical cancer, using mammography screening and cytology screening, in countries where resources are available for wide coverage of the population. Several ongoings studies are currently evaluating low cost approaches to screening that can be implemented and sustained in low-resource settings. For example visual inspection with acetic acid may prove to be an effective screening method for cervical cancer in the near future. More studies that evaluate low cost alternative methods to mammography screening, such as clinical breast examination, are needed.

Is whole-body FDG-PET valuable for health screening?

Matthias Weckesser1 Contact Information and Otmar Schober1

(1) Department of Nuclear Medicine, Münster University, Albert-Schweitzer-Strasse 33, 48149 Münster, Germany

Published online: 22 February 2005

The idea of using imaging for whole-body cancer screening is alluring. Every nuclear medicine physician working with 18F-fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) has observed patients with malignancies unrelated to the referral diagnosis. In a series of such clinically unexpected results, Agress and Cooper showed that lsquoincidentalrsquo does not mean lsquonegligiblersquo; considerable pathology, especially in the colon, may be detected [1]. These observations suggest the use of FDG-PET for health screening. The justification for such an approach, however, is far from clear, and many prerequisites will have to be met before FDG-PET can be recommended for this purpose.

Bayesian theorem这就是之前反复强调的条件概率

The following considerations with respect to screening programmes have been published on the WHO homepage (http://www.who.int/cancer/detection/en/): A screening test aims to be sure that as few as possible with the disease get through undetected (high sensitivity) and as few as possible without the disease are subject to further diagnostic tests (high specificity). Given high sensitivity and specificity, the likelihood that a positive screening test will give a correct result (positive predictive value) strongly depends on the prevalence of the disease within the population.这就是我在之前几天的讨论中反复强调的患病率问题 If the prevalence of the disease is very low, even the best screening test will not be an effective public health programme [2]. For example, if a diagnostic test has a sensitivity and specificity of 90% but the prevalence of a disease is as low as 1%, only one out of ten positive test results will be cancer related. The mathematical basis for these considerations was introduced by Bayes more than 200 years ago [3]. It is far from proven that FDG-PET has a 90% accuracy in patients with asymptomatic neoplastic disease. Even in malignancies in which FDG-PET has a well-defined role, the results in the early detection of disease are less favourable. For example in colon cancer, FDG-PET regularly fails to detect small precancerous or malignant lesions and specificity is limited by the presence of inflammatory or unspecific bowel disease [4, 5]. It is, however, the resection of small lesions which may decrease cancer-related mortality.

Eligibility for FDG-PET screening

The definition of populations at risk is a major issue in developing screening programmes. Furthermore, it has to be proved that cancer is not only diagnosed at earlier stages but that specific cancer mortality of the screened population decreases. Prospective randomised trials on FDG-PET as a screening tool are not yet available. Potential sources of bias in such studies have been discussed elsewhere [6]. The data that are available suggest positive FDG-PET findings in about 1–2% of the screened population [7–9]. Thus, on average, 50–100 FDG-PET scans have to be performed to identify one patient with malignancy. Furthermore, in some of these studies the authors do not state whether the patients had participated in other screening programmes (e.g. patient history, faecal occult blood testing, colonoscopy and mammography). So it is unclear whether or not the FDG-PET-positive lesions would have been missed by routine diagnostic techniques. Clinical follow-up for 6–10 months is a gold standard for negative findings in these studies. This period is too short to exclude the presence of small malignant lesions, e.g. in the colon. Inclusion criteria have not been reported in detail in the aforementioned studies, and results may be more favourable in well-defined populations. The definition of subjects at risk by use of a simple questionnaire has been studied in much detail in cardiovascular disease (e.g. [10]). It is, however, more difficult to identify high-risk patients when assessing cancer in general.

Cost-effectiveness is another issue in this context, which will not be addressed in detail since there are no substantial data for FDG-PET in the setting of screening. Data on secondary expenses caused by false positive findings are also not available.

FDG-PET-negative tumours

As FDG-PET holds promise for whole-body tumour screening, subjects who have been screened may have a confidence which is not substantiated. It is well known that some common tumours may be negative on FDG-PET. Patients might regard further screening tests as unnecessary and early-stage malignancy might be missed. Prostate cancer in male subjects and breast cancer in women are examples of such tumours. An FDG-PET scan is not a substitute for the respective screening programmes for these cancers, although FDG-PET may provide valuable information in restaging breast cancer [11]. Recent data on the Japanese screening programme were reported in the ldquoNews and Viewsrdquo section of this journal. A total of 253 malignancies were detected within 10 years. Half of these tumours did not show increased glucose metabolism but were detected by ultrasound, CT, MRI or laboratory tests. A total of 21,804 FDG-PET studies were performed in 8,615 persons to achieve this rate of detection [12].

The WHO has published further prerequisites for establishing a screening programme. These include the definition of guidelines addressing eligibility for participation in the programme, well-defined criteria for image interpretation and defined mechanisms for the treatment of abnormalities. Quality control mechanisms and expenses are other topics dealt with by the WHO. These questions have not yet been addressed sufficiently for FDG-PET in screening.

Radiation protection

While radiation exposure due to FDG-PET is regarded as negligible in patients with proven cancers or a high probability of malignancy, the use of FDG-PET in the general population is a different matter. The effective dose of FDG-PET can be estimated at about 10 mSv, when 370 MBq is injected [13]. According to the International Commission on Radiation Protection (ICRP), the risk of radiation-induced cancer is as high as 5/10,000 for an effective dose of 10 mSv [14]. Although these figures are estimates only, they are widely used in radiation protection. Applying these data to FDG-PET screening, one radiation-induced cancer is to be expected with 2,000 FDG-PET studies. If only 1–2% of these studies are positive, this means one additional cancer for the detection of cancer in 20–40 patients. This risk can only be accepted if a benefit for the majority of patients has clearly been demonstrated.

Regulatory restrictions in many countries, e.g. in Germany, prohibit the use of ionising radiation without a legitimate indication. The use of FDG-PET in normal examinees may only be legally approved after a formal application for a scientific project. Thus performing FDG-PET as a screening test in healthy persons is legally not possible in many countries.

Conclusion

In summary, the authors believe that it is too early to recommend FDG-PET as a screening tool. General reflections on sensitivity and specificity, on cost-effectiveness and on radiation protection support scepticism about the future introduction of FDG-PET in this setting. The authors advocate extending research on the use of FDG-PET in well-defined clinical situations when malignancy is known or is strongly suspected to be present. This may include clinical studies on the use of FDG-PET as a second-line diagnostic tool in a screened population, as reported by Pastorino et al. [15].

Is whole-body FDG-PET valuable for health screening?

Michiru Ide1 Contact Information and Yutaka Suzuki1

(1) HIMEDIC Imaging Center at Lake Yamanaka, Hirano 562-12, Yamanakako-mura, Minamitsuru-gun, Yamanashi 401-0502, Japan

Published online: 22 February 2005

The survival of patients with various cancers, such as colorectal, breast and prostate carcinomas, has improved significantly since the 1970s [1], but unfortunately cancer remains the first or second most common cause of death among both men and women in developed countries. Present-day medical practice generally assumes that early detection of cancer offers the best chance of a good outcome. Finding a cancer in an asymptomatic person provides more treatment options, offers a better prognosis and cuts down on expenses compared with the cost incurred when cancers are detected at later stages. To detect cancers at an early stage, self-referral for mammography, routine or virtual colonoscopy, sigmoidoscopy, Pap smear screening, prostate-specific antigen testing and measurements of other tumour-specific markers have been actively recommended by consensual medical opinion, despite some continuing debate as to the value of these measures. With improvements in the standard of living and ready access to medical information via the internet and other mass media, more and more healthy lay persons are willing to undergo cancer screening. In Far Eastern countries (especially Japan), this tendency is strongly evident.

Tumour screening can be defined as the application of diagnostic tests or procedures to asymptomatic people for the purpose of dividing them into two groups: those who have a condition that would benefit from early intervention and those who do not. The intention of traditional or conventional cancer screening has been the early detection of cancer in a target organ, but an ideal cancer screening test would be a non-invasive and painless procedure that can (a) [COLOR=blue]simultaneously detect various cancers, regardless of the organ or site involved at a time when they are curable, [/COLOR],and (b) yield a high sensitivity and specificity [2].

不晓得作者的筛检是跟谁学的，总之蓝字部分在我见过的中英文教科书里都没有这种牺牲特异性的筛检策略。恰恰相反，在原文给出的引用文献里恰恰在Screening Test Detects Little Pseudodisease一节里强调了特异性的重要性。引文［2］为 Obuchowski NA, Grham RJ, Baker ME, Powell KA. Ten criteria for effective screening for pulmonary and colon cancers. Am J Roentgenol 2001;176:1357–62. 日本这位作者在这里完全是想当然了。

Whole-body FDG-PET

Warburg first reported that tumours are characterised by abnormally increased glucose metabolism, with increased production of lactate (caused by glycolysis) [3]. This is a basic principle underlying cancer detection by the glucose analogue 18F-fluoro-2-deoxy-d-glucose (FDG). Increased FDG accumulation in neoplastic tissues is a function of increased expression and activity of glucose transporter proteins and the glucose phosphorylating enzyme hexokinase, which result from increased anaerobic metabolism in cancer cells, as well as metabolic trapping of FDG within tumour cells due to the lack of further metabolic pathways for FDG [4]. FDG positron emission tomography (PET) is currently widely used as a way of examining virtually any part of the body in order to detect tumours, e.g. lung, breast, colorectal, pancreatic and head and neck cancer, malignant lymphoma and malignant melanoma [5, 6]. It can also be used successfully in patients with unknown primary tumours [7].

引文5 Hustinx R, Benard F, Alavi A. Whole-body PET imaging in the management of patients with cancer. Semin Nucl Med 2002;32:35–46.

6. Rohren EM, Turkington TG, Coleman RE. Clinical application of PET in oncology. Radiology 2004;231:305–32.

7. Rades D, Kuhnel G, Wildfang A, Borner AR, Chmoll HJ, Knapp W. Localised disease in cancer of unknown primary (CUP): the value of positron emission tomography (PET) for individual therapeutic management. Ann Oncol 2001;12:1605–9.

全部都是在肿瘤病人里进行疾病病程控制的文章。完全不涉及一般人群。

The advantage of whole-body FDG-PET in comparison with other imaging modalities is that it allows the entire body to be surveyed seamlessly within a reasonably short period ; furthermore, most metabolically active cancers can be detected at an early stage. State-of-the-art dedicated PET cameras offer high sensitivity and spatial resolution [8]. Using a contemporary PET camera, whole-body images can be obtained within 10 min with an administered dose of 185 MBq.可以跟德国人的那篇文章里提到的辐射潜在致癌剂量向比较一下

The characteristics of whole-body FDG-PET seem to satisfy the requirements for cancer screening [9, 10]. Whole-body FDG-PET comes close to being an ideal modality for the purpose of cancer screening in that it achieves high sensitivity without any apparent hazard. 非常重要的两点，1，高敏感度，没有提及特异度（很快就要提了）2，作者认为“无害”，显然我并不同意，大家可以自己查一下辐射剂量方面的资料。It also provides information on the extension of the cancer, because the primary tumour and metastatic foci can be detected simultaneously. Whole-body FDG-PET appeals to many people who are concerned about possibly harbouring a threat to their health and can afford the cost. Further development of PET hardware and software will lead to further reductions in the administered dose and scanning times, and will improve the throughput of the examination.

The most crucial limitation of whole-body FDG-PET is the possible[COLOR=red]low specificity in the diagnosis of cancer.[/COLOR] A number of benign processes, particularly inflammation, show higher uptake of FDG than background tissues. There is also physiological uptake. Recognition of physiological uptake of FDG and unusual patterns of FDG biodistribution is important in order to avoid misinterpretation of PET [11, 12]. False positive interpretations that lead to unnecessary biopsy or surgery can be largely avoided if the potential sites and characteristics of non-malignant lesions and physiological accumulation are recognised when evaluating the PET images. We nuclear physicians should be familiar with patterns of FDG uptake due to factors other than malignant tumours. 还是要主观判断啊Delayed images have been reported to be useful for differentiation between tumoural and non-tumoural uptake: in cases of non-tumoural uptake, the activity decreases in the delayed images [13, 14]. Recently, PET/CT has been advocated as a tool for improvement of diagnosis by FDG-PET [15]. Hybrid imaging can precisely localise and improve the characterisation of foci of increased FDG uptake, with the consequence that false positive rates will decrease. PET/CT has not been adopted for the purpose of cancer screening. If it were to be used for cancer screening, the radiation dose due to CT would have to be taken in consideration.

Japanese experience in cancer screening

In Japan, we have 10 years experience in the performance of whole-body FDG-PET, in addition to conventional modalities, for the purpose of cancer screening [9, 10, 16]. In April 2004, a questionnaire survey不是病例报告，而是病例调查－追查由此引发的偏倚不是临床医生的专长了吧 on cancer screening with whole-body FDG-PET was carried out. At the 11 PET facilities, 39,785 applicants (23,431 male and 16,354 female, average age 53.6 years) participated in cancer screening. The screening modalities other than whole-body PET differed between the facilities. All participants were asymptomatic with regard to cancer. For cancer screening, the administered dose of FDG was 3.7 MBq/kg and whole-body PET scanning generally was performed 60 min after tracer injection, from the neck to the upper third of the thigh. Whole-body FDG-PET images were evaluated by visual inspection. The results are presented in Tables 1 and 2.

Table 1 Cancers detected by cancer screening with whole-body FDG-PET in Japan

没法贴数据表格。请查阅http://www.springerlink.com/content/l5butvbyj30qjl53/fulltext.html

表中给出了526例肿瘤患者，其中358例PET-CT阳性，168例PET－CT阴性。但是，作者没有给出假阳性和假阴性的数字，这在评估任何一种检测方法时都是必需的。可以这么说，缺少了这两个数字，本文所有结论都无法得到证明，PET－CT的敏感度、特异度、阴／阳性预测值无一能被计算出来

Overall, malignant tumours were discovered in 526 participants (1.35%). This discovery rate is much higher than that achieved with conventional cancer screening in Japan (0.10%). In descending order of frequency, the most commonly detected cancers were thyroid, lung, colon, prostate and breast cancers. All these cancers were found in the early stages. There were 358 PET-positive cases and 168 PET-negative cases. Most of the thyroid, lung, colon and breast cancers were PET positive, but the prostate, renal and bladder cancers were generally PET negative. PET-negative cancers were detected by the conventional methods: computed tomography, ultrasound, magnetic resonance imaging and tumour-specific markers. Overall, there were more PET-negative cases among males than females, because of the many PET-negative cases of prostate cancer (Table 1).

The PET-negative cases can be attributed to the following four reasons: (1) high urinary tract activity, (2) cancers of low cell density (signet ring cell cancer of the stomach and the scirrhous type of breast cancer), (3) hypometabolic or FDG-negative cancers (lung cancer and malignant hepatoma) and (4) small cancers. 这一段实际是在说PET－CT假阴性的可能原因Renal excretion of FDG may hamper the detection of urological cancers and lesions in the pelvic cavity [17]. Most well-differentiated lung adenocarcinomas have been reported to be PET negative [18]. Malignant hepatoma is also PET negative due to the high activity of glucose-6-phosphatase [19]. The spatial resolution of the PET camera is around 6 mm [8], and in tumours smaller than twice the resolution, the sensitivity is decreased due to partial volume effects. Tumours smaller than 10 mm in diameter are, therefore, difficult to detect, although detection of much smaller cancers by FDG-PET has been reported [10]. In order to minimise the number of false negative cases, it is important that conventional examinations are performed conjointly.

In the application of PET for cancer screening, radiation exposure should be taken seriously. Radiation absorbed doses have been measured and the effective dose equivalent of 18F-FDG was estimated at 2.1×10–2 mSv/MBq [20]. In cancer screening we administer 185 MBq, so the radiation dose is 3.9 mSv. If screening is limited to the older generation, the additional radiation dose at this level will not be a big issue.

Needless to say, the quality of screening should be kept to a high standard. To this end, the Clinical PET Promotion Council and the Japanese Society of Nuclear Medicine have worked hard together to produce guidelines for mass screening with whole-body FDG-PET. These guidelines were published last year [21] and are now available at http://www.jsnm.org/report/FDG-PET_gaidorain2004_part3.pdf 这应该就是某位河友贴出来的日文版的指南吧出处吧The guidelines describe the nature of an appropriate facility and offer an outline of cancer screening. Data acquisition and analysis methods are fully described, and the guidelines also refer to the other screening modalities that may be used in conjunction with whole-body FDG-PET. In addition it is explained which tumours are easy and which are difficult to detect by FDG-PET; in the latter cases, effective alternative modalities are recommended. A new edition will be published yearly. When whole-body FDG-PET cancer screening is performed on the basis of these guidelines, the quality of cancer screening will be much improved.

Conclusion

Cancer is still the leading cause of death in developing countries. The success of cancer treatment is highly dependent on early detection. There is a need for a highly accurate screening method that is easy to perform and non-invasive or minimally invasive. Whole-body FDG-PET may fulfil this need. Based on experience in Japan, we believe that it has the potential to detect a wide variety of cancers at potentially curable stages in asymptomatic individuals, provided the data are evaluated by radiologists or oncologists who are highly trained in the interpretation of PET images. Whole-body FDG-PET might be the most powerful tool for cancer detection when it is used in combination with tumour markers and other imaging modalities.

此文发表2年后，综合日本各地数据的文献发表，其阳性预测值仅3。3％，该文附后

不是学医的那位请不必再花力气去写“系统性”的文章了，您不可能比下文中的日本临床家更加系统全面地了解PET－CT，这样的脏活累活还是交由我们医界的人来完成吧。而对于结果的解释，我个人认为谨慎是必要的。您难道愿意找一个马虎潦草吹牛吹到天上去的医生给您看病么？

对另一位医生河友，很佩服您孜孜不倦的精神，为河里贡献了一些资料。只是资料的组织和比对上稍欠严谨，没有理出其后应有的脉络。

行文至此，关于PET－CT在一般人群中应用的各方面专家意见（正方＋反方）均已在本系列中。如果您有不同意见，大可一条条反驳，深入考证。