18F-FDG符合线路显像对食管癌术后复发转移的诊断价值

目的 探讨^18F-脱氧葡萄糖（FDG）符合线路显像对食管癌术后复发转移的诊断价值。方法 对29例临床怀疑复发转移的食管鳞状细胞癌术后患者行^18F-FDG符合线路显像，计算其诊断复发转移灶的灵敏度、特异性和准确性，并与CT诊断结果比较。结果 29例患者中符合线路显像真阳性19例，真阴性6例，假阳性、假阴性各2例，其诊断食管癌术后复发转移的灵敏度、特异性和准确性分别为90．5％（19／21例）、75．0％（6／8例）和86．2％（25／29例）；而CT诊断的灵敏度、特异性和准确性分别为71．4％（15／21例）、87．5％（7／8例）和75．9％（22／29例）。在符合线路显像与CT检查均阳性的13例患者中，CT检出病灶20个；而符合线路显像检出27个，比CT多检出的病灶包括食管癌复发，锁骨上、纵隔和肺门淋巴结及骨转移。结论 ^18F-FDG符合线路显像对食管癌术后复发转移的诊断具有较高的临床价值，尤其在临床疑有复发转移而常规影像学检查阴性时有重要意义。     

18F-FDG符合线路SPECT显像联合CT、B超、MRI在结直肠癌术后复发及转移中的诊断价值

目的探讨18F-FDG 符合线路 SPECT 显像联合传统显像(CT、B 超、MRI)在结直肠癌术后复发及转移中的诊断价值.资料与方法107例结直肠癌术后患者行18F-FDG 符合线路 SPECT 显像,并联合 CT、B 超、MRI 诊断结直肠癌术后复发及转移.结果107例患者最终确定复发及转移共29例.18F-FDG 符合线路 SPECT 显像与传统显像诊断均为阳性的15例患者中,传统显像检出病灶20个,符合线路 SPECT 显像检出病灶26个.传统显像检出3个符合线路 SPECT 显像未发现的转移病灶,而符合线路 SPECT 显像检出9个传统显像未发现的病灶.18F-FDG 符合线路 SPECT 显像诊断结直肠癌术后复发及转移的灵敏度、特异性和准确率分别为79.3%、89.7%和86.9%;传统显像的诊断效能分别为62.1%、88.5%和81.3%;二者联合的诊断效能分别为89.7%、92.3%和91.6%.二者联合诊断结直肠癌术后复发及转移的灵敏度和准确率明显优于传统显像(P <0.05).结论18F-FDG 符合线路 SPECT 显像联合 CT、B 超、MRI 在监测结直肠癌术后复发及转移中具有重要临床价值.     

18F-FDG符合线路显像在结直肠癌术后随访中的应用

本研究对43例结直肠癌术后怀疑复发或转移的患者行^18F-脱氧葡萄糖（FDG）双探头符合线路显像，并对比同期CT或B超检查，以评价^18F-FDG显像在结直肠癌术后随访中的价值，现报道如下。     

18F-FDG符合线路显像在食管癌术前分期中的价值

目的 探讨^18F-FDG符合线路显像在食管癌术前分期中的价值。方法 35例食管癌患者术前行^18F—FDG符合线路显像及CT检查，其中30例行手术治疗，以术后病理检查结果作为“金标准”，比较^18F—FDG符合线路显像及CT检查对原发肿瘤、淋巴结及远处转移（TNM）分期的价值；另5例发现远处转移，放弃手术治疗。结果 ^18F-FDG符合线路显像T分期与病理T分期比较符合率为63％（19／30）；^18F-FDG与CT探测淋巴结病变的灵敏度为60．00％和54．28％，特异性为94．44％和77．77％，准确性为84．80％和71．20％，阴性预测值为85．86％和81．39％，阳性预测值为80．77％和48．72％，其中特异性、准确性及阳性预测值差异有统计学意义。^18F—FDG符合线路显像发现5例远处转移，改变了其治疗方案。结论 ^18F-FDG符合线路显像对食管癌的术前分期、治疗方案的制定有临床应用价值。     

^18F-FDG PET／CT及增强CT诊断原发性肝癌及肝癌术后复发的价值

目的比较^18F-脱氧葡萄糖（FDG）PET／CT与增强CT对原发性肝癌或肝癌术后复发的诊断价值。方法回顾性分析诊断为原发性肝癌或肝癌术后复发且进行^18F-FDG PET／CT与增强CT检查的病例共25例,2种检查间隔时间在1周内。其中原发性肝癌经手术或穿刺证实,肝癌术后复发经临床随访证实。结果25例患者中,确诊为原发性肝癌14例,其中肝细胞肝痛13例,胆管细胞癌1例;肝癌术后复发11例。^18F-FDG PET／CT对原发性肝癌的诊断阳性率为78．6％（11／14）,增强CT阳性率为92．9％（13／14）。在肝癌术后复发中,^18F-FDGPET／CT诊断阳性牢为100．0％（11／11）,增强CT阳性率为63．6％（7／11）。结论在原发性肝癌诊断中,增强CT优于^18F-FDG PET／CT,^18F-FDG PET／CT显像联合增强CT可明显提高诊断率。而在肝癌术后复发检测中,^18F-FDG PET／CT优于增强CT。     

18F-FDG hPET/CT显像在腹部消化系肿瘤的应用

目的 评价^18F-脱氧葡萄糖(FDG)符合线路显像结合图像融合(hPET/CT)探测可疑腹部消化系恶性肿瘤或肿瘤复发的临床价值。方法 对51例临床怀疑为腹部消化系恶性肿瘤或肿瘤复发患者行^18F-FDG符合线路显像，经迭代法处理和重建，获得经检查衰减校正后的断层图像和融合图像，以目测双盲阅片进行诊断分析，并与手术病理检查或CT和(或）MRI、临床随访作出的最后诊断结果进行对比。结果 ^18F—FDG符合线路显像对腹部消化系肿瘤诊断的灵敏度、特异性和准确性分别为94．1％，76．5％和88．2％；对结直肠癌复发的诊断灵敏度为94．1％，特异性为83．3％，准确性为91．3％。结论 ^18F—FDG符合线路显像对腹部消化系恶性肿瘤或肿瘤复发的诊断具有较高的灵敏度和准确性。     

^18F-FDGPET／CT多次显像在监测和预测非小细胞肺癌术后复发和转移中的价值

目的探讨^18F-FDGPET／CT多次显像在监测和预测NSCLC术后复发和转移中的价值。方法NSCLC患者85例（男64例,女21例;平均年龄58．0岁）,分别于术前1周内和术后3个月接受多次全身^18F—FDGPET／CT显像。肿瘤复发和转移的诊断经病理学确诊或经多种影像学综合诊断并经临床随访证实。计算^18F—FDGPET／CT显像的诊断效能,统计学分析采用疋。检验和两独立样本t检验。结果85例患者中,肿瘤复发和转移43例,无复发和转移42例。PET／CT在半年内检出率为9.3％（4／43）,1年内为30．2％（13／43）,2年内为76．7％（33／43）,2年以上为97．7％（42／43）,未检出2。3％（1／43）。18F-FDGPET／CT对NSCLC复发和转移的诊断灵敏度、特异性、准确性分别为97．7％（42／43）、95．2％（40／42）和96．5％（82／85）。术前肿瘤分期、原发灶大小和原发灶SUVmax是2年内肿瘤复发和转移的影响因素似。12．360,t=3．281和2．465,均P〈0．05）,而性别、年龄和病理类型对其则均无明显影响。0．639、0．012和3．800,均P〉0．05）。结论^18F—FDGPET／CT多次显像有助于监测NSCLC术后复发和转移;术前肿瘤分期、原发灶大小及原发灶SUV。为2年内发生肿瘤复发和转移的影响因素。     

^18F-FDG PET／CT显像监测胃癌术后复发转移的价值

目的评价^18F-脱氧葡萄糖（FDG）PET／CT监测胃癌术后复发及转移的临床价值。方法回顾性分析胃癌术后临床疑复发或转移而行^18F-FDG PET／CT检查的45例患者临床资料,根据细胞学、病理或随访结果分析PET／CT检查结果,计算残胃及转移灶最大标准摄取值（SUVmax）。采用SPSS11．5软件进行数据处理,SUVmax两样本均数比较采用t检验。结果（1）45例中22例临床疑残胃复发,12例患者最终确定残胃复发,^18F-FDG PET／CT诊断残胃复发的灵敏度、特异性及准确性分别为100．0％（12／12）、70．0％（7／10）和86．4％（19／22）,12例复发病灶SUVmax为6．27±3．42（其中2例低分化腺癌的SUVmax较低,分别为2．5和3．3）,另10例无复发的残胃SUVmax为3．92±2．24（其中3例吻合口炎性病灶局部SUVmax较高,分别为8．3,5．2和6．3）,差异无统计学意义（t=1．862,P〉0．05）。（2）对残胃以外转移灶的检出：PET／CT灵敏度、特异性、准确性在区域淋巴结转移中分别为78．9％（15／19）、92．3％（24／26）和86．7％（39／45）,在腹膜转移中分别为6／9、97．2％（35／36）和91．1％（41／45）,在远处转移中分别为86．7％（13／15）、93．3％（28／30）和91．1％（41／45）。（3）PET／CT假阳性8处为炎性或肠管摄取,假阴性9处多为直径〈1．0cm的转移灶和低分化腺癌及印戒细胞癌的转移灶。结论^18F-FDG PET／CT虽然检测胃癌术后区域淋巴结和腹膜转移的灵敏度较低,但仍是监测其术后复发转移的有效手段。     

^18F-FDG PET／CT显像诊断妇科肿瘤复发、转移的价值

目的探讨^18F-脱氧葡萄糖（FDG）PET／CT显像诊断妇科肿瘤复发、转移的价值,并评价其对临床再分期及治疗决策的影响。方法对47例临床可疑复发、转移的妇科肿瘤患者行^18F—FDG PET／CT显像,对PET、CT及PET／CT图像进行对比分析。采用SPSS12．0软件,对数据行∥检验、校正的,检验及确切概率法分析。结果47例患者中共发现病灶158处,其中恶性病灶149处,良性病灶9处。^18F-FDG PET／CT诊断妇科肿瘤复发、转移的灵敏度、特异性、准确性、阳性预测值及阴性预测值分别为95．97％（143／149）,6／9,94．30％（149／158）,97．95％（143／146）及50．00％（6／12）。PET／CT在诊断妇科肿瘤复发、转移的灵敏度、准确性及阴性预测值方面明显优于单纯CT（χ^2=18．198,18．890,6．825,P均〈0．05）;^18F-FDG PET／CT和单纯PET在各项诊断效能指标间差异无统计学意义（χ^2=0．632,0．000,0．459,0．000,0．150,P均〉0．05）,但PET／CT使33．54％（53／158）的单纯PET无法准确定位的病灶得到了准确定位。同单纯CT及PET相比,PET／CT分别使44．68％（21／47）和31．91％（15／47）的患者TNM分期改变,对T分期的影响最明显;共有19．15％（9／47）的患者临床分期改变,并改变相应的治疗决策。结论^18F—FDG PET／CT显像诊断妇科肿瘤复发、转移准确而全面,对临床再分期及治疗决策有重要影响。     

18F-FDG符合线路显像在不明原发灶肿瘤中的临床价值

目的评价^18F-脱氧葡萄糖(FDG)符合线路显像在不明原发灶肿瘤(UPT)中的临床价值。方法UPT患者36例，在^18F-FDG符合线路显像后4周内进行常规影像学检查。结果^18F-FDG符合线路显像对原发灶的检出灵敏度为42％(15／36例)；1例原发灶仅被^18F-FDG显像发现，3例首先被^18F-FDG显像发现，后在^18F-FDG显像结果的提示下被其他影像学检查发现，11例同时分别被^18F-FDG显像和常规影像学检查发现；14％(5／36例)患者因找到原发灶而改变了治疗方案；53％(19／36例)患者发现新的转移灶。结论^18F-FDG符合线路显像是寻找UPT原发灶的一种有效方法，并可同时评价患者的全身转移情况，可为选择最佳治疗方案和预后评价提供依据。     

Accuracy of integrated FDG-PET/contrast-enhanced CT in detecting pelvic and paraaortic lymph node metastasis in patients with uterine cancer

The purpose is to evaluate the accuracy of integrated ¹⁸F-fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography ((CT) with intravenous contrast medium in detecting pelvic and paraaortic lymph node metastasis in patients with uterine cancer, with surgical and histopathological findings used as the reference standard. Forty-five patients with endometrial or uterine cervical cancer underwent radical hysterectomy, including pelvic lymphadenectomy with or without paraaortic lymphadenectomy, after PET/CT. PET/CT findings were interpreted by two experienced radiologists in consensus. The criterion for malignancy on PET/CT images was increased tracer uptake by the lymph node, independent of node size. The overall node-based sensitivity, specificity, PPV, NPV and accuracy of PET/CT for detecting nodal metastases were 51.1% (23/45), 99.8% (1,927/1,931), 85.2% (23/27), 98.9% (1,927/1,949) and 98.7% (1,950/1,976), respectively. The sensitivity for detecting metastatic lesions 4 mm or less in short-axis diameter was 12.5% (2/16), that for between 5 and 9 mm was 66.7% (16/24), and that for 10 mm or larger was 100.0% (5/5). The overall patient-based sensitivity, specificity, positive predictive value ((PPV), negative predictive value (NPV), and accuracy were 50% (6/12), 90.9% (30/33), 66.7% (6/9), 83.3% (30/36) and 80.0% (36/45), respectively. Integrated FDG-PET/contrast-enhanced CT is superior to conventional imaging, but only moderately sensitive in predicting lymph node metastasis preoperatively in patients with uterine cancer.     

Correlation between serum CEA level and metabolic volume as determined by FDG PET in postoperative patients with recurrent colorectal cancer

To determine the correlation between serum CEA level and the metabolic volume by FDG PET in postoperative patients with recurrent colorectal cancer, FDG PET was performed in 29 consecutive patients with recurrent or metastatic colorectal cancer whose CEA levels were higher than 5 ng/ml. A whole body emission scan was performed 60 minutes after injecting 370-555 MBq of F-18 FDG. "PET volume" and "PET metabolic volume" of tumors were measured on FDG PET images. Based on an isocontour plot of tumor mass at 2.5 SUV (standardized uptake value), the metabolically active tumor "PET volume" was calculated. "PET metabolic volume" was obtained by multiplying the "PET volume" by the mean SUV of the tumor. All recurrent or metastatic lesions were single or multiple lesions of measurable size (axial diameter > 1 cm, minimum "PET volume" 3.5 cm3), and were verified by operation or by other imaging modalities (CT or MRI). There was a linear associations between "PET volume" and serum CEA level. Further regression analysis by least squares showed a highly significant model with an equation of volume = 41.2 + 0.471 x CEA (r2 = 0.629). However, no such association was found between "PET metabolic volume" and serum CEA level according to the residual normality test. In conclusion, "PET volume" measured by FDG PET and serum CEA level in colorectal cancer are significantly correlated. Tumor volume determined by FDG PET can be used as an effective marker of tumor burden in postoperative patients with colorectal carcinoma.     

Usefulness of intraoperative sonography for revealing hepatic metastases from colorectal cancer in patients selected for surgery after undergoing FDG PET.

OBJECTIVE: The purpose of this study was to compare the diagnostic performance of preoperative positron emission tomography (PET) with FDG and intraoperative sonography with the standard of histologic examination of resected liver specimens in evaluating patients for curative resection of liver metastases from colorectal cancer. MATERIALS AND METHODS: We retrospectively identified 47 patients with recurrent colorectal cancer who underwent surgical exploration for possible curative resection of hepatic metastases. All patients underwent CT or MR imaging and FDG PET preoperatively and intraoperative sonography. The performance of the imaging techniques was evaluated through review of the radiologic reports and correlation with surgical and histopathologic findings. RESULTS: Eighty-seven malignant hepatic lesions were identified by histopathologic analysis of liver specimens, and 23 benign hepatic abnormalities were documented histopathologically or by uroradiologic imaging. For hepatic sections characterized as containing metastases by radiologic imaging, the positive predictive value for FDG PET was 93% (54/58); for intraoperative sonography, 87% (52/60); and for conventional imaging, 83% (43/52). For individual lesions characterized as probably malignant, the positive predictive value for FDG PET was 93% (62/68); for intraoperative sonography, 89% (63/71); and for conventional imaging, 78% (46/59). The findings at intraoperative sonography led to a change in the clinical treatment of only one patient (2%). CONCLUSION: The results indicate that FDG PET effectively screens potential candidates for curative liver resection. Although intraoperative sonography helps to determine the anatomic location of metastases thus facilitating surgical resection, its adjunctive use in patients screened preoperatively by FDG PET has limited impact on treatment selection.     

Role of (18)F-FDG dual-head gamma-camera coincidence imaging in recurrent or metastatic colorectal carcinoma.

(18)F-FDG PET has been shown to be of high diagnostic accuracy for the evaluation of recurrent colorectal cancer. However, the limited availability of PET scanners precludes (18)F-FDG assessment of many patients for whom the study is indicated. An alternative is the SPECT system in coincidence mode. The aim of this study was to determine the role of dual-head camera (18)F-FDG coincidence imaging (DHC (18)F-FDG) in patients with recurrent colorectal cancer. METHODS: Sixty-seven DHC (18)F-FDG studies were performed on 62 patients with suspected recurrent colorectal cancer. Reports of contemporary CT were available for the purpose of correlation for 61 of the studies. The final diagnosis of the imaging findings was based on histology or clinical and imaging follow-up of at least 6 mo. RESULTS: In lesion-based analysis, 103 tumor sites were suspected on DHC (18)F-FDG, CT, or colonoscopy. Ninety-three of them were found to be true tumor sites. For DHC (18)F-FDG, the sensitivity was 88%, specificity was 80%, positive predictive value (PPV) was 98%, negative predictive value (NPV) was 42%, and accuracy was 87%. For CT, the sensitivity was 63%, specificity was 10%, PPV was 85%, NPV was 3%, and accuracy was 57%. In patient-based analysis, DHC (18)F-FDG differentiated patients with recurrent cancer from disease-free patients with a sensitivity of 91%, specificity of 73%, PPV of 94%, NPV of 62%, and accuracy of 88%. DHC (18)F-FDG detected tumor sites in 12 (67%) of 18 patients with elevated carcinoembryonic antigen and negative CT findings. CONCLUSION: DHC (18)F-FDG is an adequate readily available technique for assessment of recurrent colorectal cancer and has a diagnostic accuracy better than that of CT.     

Value of 2-[18F]-fluoro-2-deoxy-D-glucose imaging with dual-head gamma camera in coincidence mode: comparison with computed tomography/magnetic resonance imaging in patients with suspected recurrent head and neck cancers

OBJECTIVE: The aim of the present study was to assess the value of dual-head gamma-camera (DHGC) imaging in the coincidence mode using 2-[18F]-fluoro-2-deoxy-D-glucose in differentiating recurrent tumor from posttreatment changes in previously treated head and neck cancer. METHODS: This was a single-center prospective study performed with the approval of our Institutional Review Board. Twenty-nine patients with suspected recurrent head and neck cancers were prospectively enrolled in this study. Dual-head gamma-camera imaging in the coincidence mode followed computed tomography (CT; n = 24)/magnetic resonance imaging (MRI; n = 5) within a period of 1 week (mean = 3.5 days) in all patients. Thirteen patients had definite pathologic confirmation of recurrence by undergoing a biopsy. Sixteen patients, however, did not have a definite pathologic confirmation and were followed clinically. The mean duration of follow-up for the subgroup of patients who were followed clinically was 22.8 months (range: 4-48 months). Sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) for CT/MRI and DHGC imaging in the coincidence mode were calculated. RESULTS: The sensitivity, specificity, PPV, NPV, and accuracy of CT/MRI in the detection of recurrent cancer were 76.5%, 58.3%, 72.2%, 63.6%, and 69%, respectively. In contrast, the sensitivity (100%), NPV (100%), and accuracy (82.8%) of DHGC imaging in the coincidence mode were superior to that of CT/MRI. Dual-head gamma-camera imaging in the coincidence mode had a specificity (58.3%) and PPV (77.3%) comparable to those of CT/MRI. CONCLUSION: Our data suggest that modified positron emission tomography with DHGC imaging in the coincidence mode is a useful tool in the assessment of recurrent head and neck cancer.     

符合线路SPECT在消化系统肿瘤术后复发转移中的应用研究

探讨18F-FDG符合线路SPECT在消化系统肿瘤术后复发转移中的临床应用价值.材料和方法:对35例临床怀疑复发转移的消化系统肿瘤术后患者行18F-FDG符合线路SPECT显像,对其显像结果进行分析,计算其诊断的准确率、灵敏度、特异性、阳性预测值、阴性预测值及其95%可信区间,并与B超、CT、MRI的诊断结果相比较.结果:在35例消化系统肿瘤术后患者中,其诊断的准确率、灵敏度、特异性、阳性预测值、阴性预测值分别为91.4%、88.9%、100%、100%、72.7%;其95%可信区间分别为77%～98%、71%～98%、63%～100%、86%～100%、39%～94%.符合线路SPECT的诊断准确率、灵敏度明显高于B超,与CT和MRI的比较尚无显著性差异;95%可信区间分析,结果显示符合线路SPECT高于B超、CT和MRI;18F-FDG符合线路SPECT和B超、CT、MRI联合应用在某些病例的诊断中具有互补性.结论:18F-FDG SPECT/PET显像在消化系统肿瘤术后复发转移的诊断中具有较高的临床应用价值.     

18F-FDG PET/CT在宫颈癌诊断中的应用

目的 探讨18F-脱氧葡萄糖(FDG) PET/CT在宫颈癌诊断及其复发、转移灶探测中的应用价值.方法 88例患者行腹部或全身18F-FDG PET/CT显像,其中初诊者30例(宫颈良性病变11例,宫颈癌19例),宫颈癌治疗后58例.病灶根据病理检查、多种影像诊断技术及临床随访确诊,随访时间均为6个月～3年.结果 30例初诊者中,PET/CT诊断宫颈癌的灵敏度、特异性和准确性分别为17/19,10/11和27/30(90.0%).58例治疗后患者中,11例存在肿瘤复发或残余,PET/CT诊断肿瘤复发、残余的灵敏度、特异性和准确性分别为10/11,47/47(100.0%)和57/58(98.3%).41例有肿瘤转移,PET/CT诊断转移灶的灵敏度、特异性和准确性分别为92.7%,88.9%和90.9%;转移灶以盆腹腔淋巴结为主,39.0%有盆腔淋巴结转移,27.3%有腹膜后淋巴结转移,所有淋巴结转移患者中PET/CT发现26.8%病灶直径＜1.0cm.28.6%(22/77)的患者PET/CT发现腹腔外远处转移灶.18例输尿管梗阻患者中,16例PET/CT发现为肿瘤侵犯压迫所致.结论 18F-FDG PET/CT显像在宫颈癌的诊断及其复发、转移灶探测中有良好的应用价值,尤其是对远处转移灶和小淋巴结转移灶的检测,可使临床分期更准确.     

PET-CT显像在结肠直肠癌术后复查的临床应用

目的:评价18F-脱氧葡萄糖(FDG)PET-CT显像与CT扫描在诊断结肠直肠癌术后转移与否的准确性。方法:20例临床可疑(血清癌胚抗原(CEA)升高或CT显像阳性或可疑)结肠直肠癌术后转移的患者行全身18F-FDG PET-CT显像,PET-CT显像结果与CT扫描结果对比分析。结果:20例患者共有病灶27个,病理组织学结果及临床随访结果证实,20个恶性病灶,7个良性病灶。PET-CT显像的阳性预测值为94.7%,阴性预测值为75%,CT扫描结果的阳性预测值为81.3%,阴性预测值为36.3%,两者有显著性差异。结论:全身18F-FDG PET-CT显像在诊断结肠直肠癌术后转移与否的准确性高于比CT扫描结果。     

Value of radioimmunoscintigraphy with technetium-99m labelled anti-CEA monoclonal antibody (BW431/26) in the detection of colorectal cancer

This study was undertaken as part of a Coordinated Research Programme initiated by the International Atomic Energy Agency to evaluate the usefulness of radioimmunoscintigraphy (RIS) in the management of patients with colorectal cancer. Technetium-99m labelled BW431/26, a monoclonal antibody against carcino-embryonic antigen (CEA), was used. The study included 73 patients (31 females and 42 males). Sixty-eight patients were suspected of having recurrent colorectal adenocarcinoma while another five were suspected to have primary colorectal cancer. Images were acquired at 10 min and 4 and 24 h following the injection of radioantibody. The efficacy of RIS in tumour detection was evaluated by the findings at surgery, histological investigation and/or other diagnostic modalities and clinical follow-up. Four of five patients with suspected primary colorectal cancer gave true-positive results (three at primary sites, one at the site of a metastatic lesion) while one was false-positive. The overall accuracy of RIS in the diagnosis of recurrent colorectal cancer was 87%. Its sensitivity in the detection of locoregional or abdominal recurrence and liver metastases was 97% and 89% respectively. RIS was more accurate than computed tomography (CT) scan in the detection of pelvic recurrence and liver metastases while CT scan was far superior to RIS in detecting lung metastases. RIS proved most useful in patents who had rising CEA levels on clinical follow-up but in whom other work-up, including CT scan, was negative. The advantages of RIS include the ability to detect tumour recurrence prior to other investigations and to identify tumour recurrence in areas such as the pelvis, where CT and magnetic resonance imaging have their greatest weaknesses in diagnosing recurrent disease. The imaging accuracy is significantly increased when combined CT and antibody imaging is performed.