FDG positron emission tomography in the surveillance of hepatic tumors treated with radiofrequency ablation

PURPOSE: Radiofrequency thermal ablation (RFA) is an emerging technique in the treatment of focal hepatic tumors. Magnetic resonance imaging (MRI) and computed tomography (CT) are currently used to monitor hepatic tumors after RFA for residual disease and recurrence. Fluorodeoxyglucose (FDG) positron emission tomography (PET) is an excellent imaging method for the detection of liver metastases, but it has not been thoroughly evaluated as an alternative to anatomic imaging in the surveillance of liver tumors treated with RFA. The purpose of this investigation was to determine the role of FDG-PET imaging in the surveillance of liver tumors treated with RFA. METHODS: Thirteen patients with histories of malignant tumors of the liver treated with RFA and who had received post-treatment FDG-PET scans were assessed retrospectively. One patient had two post-RFA FDG-PET scans, eight patients had concurrent MRI scans, and six patients had concurrent CT scans. Imaging findings were compared with the results of clinical follow-up. RESULTS: There were either recurrent tumors at the ablation site (8 patients) or new metastases (3 patients) in 11 patients. FDG-PET identified all 11 cases and did not misidentify any cases. Of the seven patients with positive PET findings who received an MRI scan, three were also positive on MRI (42.9%); the other four cases were either negative or equivocal. Of the four patients with positive PET findings who received a CT scan, only two had positive CT scan findings (50%). All recurrences diagnosed by PET were confirmed on clinical follow-up. CONCLUSION: In this preliminary study, FDG-PET was superior to anatomic imaging in the surveillance of patients treated with RFA for malignant hepatic tumors.     

Detection of residual tumor after radiofrequency ablation of liver metastasis with dual-modality PET/CT: initial results

The aim of this study was to determine the accuracy of dual-modality positron emission tomography(PET)/computed tomography (CT) in the detection of residual tumor after radiofrequency ablation (RFA) of liver metastasis of colorectal cancer. Eleven patients with 16 hepatic metastases (mean size 2.9 cm) from colorectal cancer were enrolled in this study, and 19 RFA procedures and 32 PET/CT examinations were performed. The patients had PET/CT before and after RFA using [¹⁸F]-2-fluoro-2-deoxy-D-glucose. CT images alone were read by two radiologists, PET images alone were evaluated by two nuclear physicians. Fused images were read by one physician of each speciality in consensus. The accuracy for detection of residual tumor by the different imaging modalities following RFA was assessed. Eleven patients with a mean age of 63 (range 55–71) years were evaluated. The mean follow-up period was 393 days. The overall procedure-based sensitivity for detection of residual tumor was 65% for PET and PET/CT and 44% for CT alone. The accuracies were 68% and 47%, respectively. Four patients had residual tumor after RFA, six patients total developed local recurrence. PET/CT therefore possibly proved superior to CT alone when assessing the liver for residual tumor after RFA.     

Impact of whole-body imaging on treatment decision to radio-frequency ablation in patients with malignant liver tumors: comparison of [18F]fluorodeoxyglucose-PET/computed tomography, PET and computed tomography

OBJECTIVE: The correct staging of patients with malignant liver tumors before radio-frequency ablation (RFA) is mandatory for successful treatment. Our study aimed to compare the influence on decision to perform RFA of whole-body fluorodeoxyglucose (FDG)-PET/computed tomography (CT) with whole-body contrast-enhanced CT (CE-CT) and PET alone. METHODS: Fifty-eight patients with known hepatic malignancies (23, liver metastases 35) received FDG-PET/CT before RFA planned with curative intention. CT and PET data were each read separately, PET/CT fusion data were read in consensus afterward by a third reader group. The diagnostic accuracy of CE-CT, PET alone, and PET/CT to identify patients eligible for RFA was compared and the impact on decision was analyzed. The McNemar test with Bonferroni correction was used to test for significant differences. RESULTS: The accuracy and sensitivity to detect correctly intrahepatic and extrahepatic tumor were 94 and 97% for CT, 75 and 54% for PET, and 97 and 95% for PET/CT. The differences between CT and PET, as well as between PET/CT and PET, were statistically significant, but there was no significant difference between PET/CT and CT alone (P>0.65). PET alone, CE-CT, and PET/CT correctly identified 32, 55, and 57 patients, respectively. Again, PET/CT showed no significant advantage over CE-CT. Both imaging methods performed significantly better than PET alone (P<0.0001). Forty-three (74%) of 58 patients underwent RFA with curative intention. CONCLUSION: Whole-body imaging changed patient management in 26% of the patients planned for curative intended RFA, yet there was no significant difference between CE-CT and PET/CT.     

Predictive Value of Pattern Classification 24 Hours after Radiofrequency Ablation of Liver Metastases on CT and Positron Emission Tomography/CT

PurposeTo assess a classification scheme for predicting local tumor progression (LTP) after radiofrequency (RF) ablation of liver metastases, using predefined patterns on contrast-enhanced computed tomography (CT) and positron emission tomography (PET) combined with CT (PET/CT) acquired 24 hours after RF ablation.Materials and MethodsThere were 45 metastases in 20 patients treated. After 24 hours, imaging of the ablation zones was performed with contrast-enhanced PET/CT. Three independent radiologists prospectively assessed contrast-enhanced CT and combined PET/CT images to identify three patterns: pattern I, no tissue enhancement or fluorodeoxyglucose uptake between the ablation zone and the liver parenchyma; pattern II, a rimlike pattern; and pattern III, a peripheral nodule. PET/CT images obtained after 8–10 weeks were evaluated for LTP. The patterns were analyzed for their sensitivity, specificity, positive predictive value, and negative predictive value for predicting LTP.ResultsPattern I was most frequently observed (81% for contrast-enhanced CT and 61% for PET/CT) as well as for ablation zones that showed LTP (52% and 37%, respectively). Conversely, pattern II was observed for tumors that were completely ablated (6% and 29%, respectively). Patterns II and III together had the highest sensitivity for predicting LTP (48% and 63%, respectively); pattern III had the highest specificity (94% and 95%, respectively). For nodular patterns, test characteristics were better for PET/CT compared with contrast-enhanced CT, but the difference was not significant. Nodular patterns > 1 cm achieved high positive predictive value (both 100%).ConclusionsInflammation and hyperemia can hinder interpretation on imaging 24 hours after RF ablation, especially on PET/CT. Nodular patterns around the ablation zone on early contrast-enhanced CT and PET/CT have a high predictive value for LTP and should be taken into account for disease management.     

Central lower attenuating lesion in the ablation zone on immediate follow-up CT after percutaneous radiofrequency ablation for hepatocellular carcinoma: Incidence and clinical significance

Purpose

The purpose of this study was to evaluate the incidence of central lower attenuating (CLA) lesion in the ablation zone seen on immediate follow-up CT images after percutaneous radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC), and the correlation of CLA lesions and local tumor progression (LTP).

Subjects and methods

The study group included 146 patients with 167 ablation zones that had undergone follow-up CT examinations for more than 12 months after percutaneous RFA. CLA lesions corresponding to index tumors and ablative margins (safety margins) were evaluated in the ablation zones seen on immediate follow-up CT including coronal and sagittal multiplanar reformatted (MPR) images with narrow window width settings.

Results

CLA lesions were depicted on 48 of 167 ablation zones (28.7%) on immediate follow-up CT images. Among the 48 ablation zones with CLA lesions, 27 (56.3%, 27/48) had ablative margins on all three of the orthogonal MPR images and they showed no LTP (0%) on follow-up CT examinations. Three of the ablation zones with CLA lesions (6.3%, 3/48) having an ablative margin on one plane only also showed no LTP (0%). LTP was observed in 2 of 18 ablation zones (11.1%) that had CLA lesions without ablative margins on all three planes. In the remaining 119 ablation zones without CLA lesions, 5 (4.2%, 5/119) showed LTP.

Conclusion

CLA lesions in ablation zones were occasionally (28.7%) seen on immediate follow-up CT images after RFA for HCCs. The presence of CLA lesions with ablative margins might be a negative predictor of LTP.     

18F-FDG PET/CT与PET/MRI在结直肠癌肝转移诊断中的比较分析

目的 比较18F-氟脱氧葡萄糖（FDG） PET/CT与PET/MRI显像对结直肠癌肝转移的诊断价值。 方法 回顾性分析2018年9月至2019年9月于宁波明州医院行全身18F-FDG PET/CT显像及上腹部18F-FDG PET/MRI显像,并疑似有结直肠癌肝转移的27例患者的临床资料,其中男性19例、女性8例,年龄28~78（60.6±12.2）岁。肝内病灶的最终诊断以组织病理学检查或影像学随访结果为参考标准,分别计算2种检查方法诊断结直肠癌肝转移瘤的灵敏度、特异度、准确率、阳性预测值和阴性预测值。根据肝转移病灶大小分长径≤1 cm、1 cm<长径≤2 cm、长径>2 cm 3组,分别计算各组的2种检查方法的灵敏度。采用McNemar检验比较2种检查方法诊断结直肠癌肝转移瘤的灵敏度、特异度和准确率;采用χ2检验比较2种检查方法诊断结直肠癌肝转移瘤的阳性预测值和阴性预测值。 结果 基于27例结直肠癌患者分析,18F-FDG PET/MRI诊断肝转移瘤的灵敏度、准确率[94%（15/16）、96%（26/27）]均高于PET/CT[81%（13/16）、89%（24/27）],但差异均无统计学意义（McNemar检验,均P>0.05）。基于病灶分析,在27例结直肠癌患者中共发现118个肝内病灶,其中肝转移瘤病灶72个,18F-FDG PET/MRI诊断结直肠癌肝转移瘤病灶的灵敏度、准确率、阴性预测值[85%（61/72）、91%（107/118）、81%（46/57）]均高于PET/CT[63%（45/72）、76%（90/118）、63%（45/72）],且差异均有统计学意义（McNemar检验,χ2=5.072,均P<0.05）。对于长径≤1 cm的肝转移病灶,18F-FDG PET/MRI的诊断灵敏度[63%（17/27）]明显高于PET/CT[7%（2/27）],且差异有统计学意义（McNemar检验,P<0.05）。 结论 与18F-FDG PET/CT相比,18F-FDG PET/MRI在结直肠癌肝转移中具有更高的诊断价值,尤其是在长径≤1 cm的病灶中。     

Contrast-enhanced FDG-PET/CT vs. SPIO-enhanced MRI vs. FDG-PET vs. CT in patients with liver metastases from colorectal cancer: a prospective study with intraoperative confirmation

BACKGROUND: The choice of imaging before liver surgery is debated regarding the use of magnetic resonance (MR) imaging, computed tomography (CT), and positron emission tomography (PET). No studies have compared contrast-enhanced PET/CT with superparamagnetic iron oxide (SPIO)-enhanced MR imaging. PURPOSE: To compare PET/CT with superparamagnetic iron oxide (SPIO)-enhanced MR imaging, PET, and CT in the detection of liver metastases (LM) and extrahepatic tumor from colorectal cancer (CRC). MATERIAL AND METHODS: Thirty-five patients with suspected LM underwent PET/CT with a contrast-enhanced CT protocol and SPIO-enhanced MR imaging. Readers independently analyzed images from MR imaging, PET/CT, and the CT part and PET part of the PET/CT study. Imaging findings were compared with surgical and histological findings. RESULTS: Lesion-by-lesion sensitivity and accuracy for liver lesions was 54% and 77% for PET alone, 66% and 83% for PET/CT, 82% and 82% for SPIO-enhanced MR imaging, and 89% and 77% for CT alone, respectively. CT and SPIO-enhanced MR imaging were less specific but significantly more sensitive than PET (P<0.0001). For extrahepatic tumor, sensitivity and specificity was 83% and 96% for PET/CT and 58% and 87% for CT, respectively. CONCLUSION: CT and SPIO-enhanced MR imaging are more sensitive but less specific than PET in the detection of LM. PET/CT can detect more patients with extrahepatic tumor than CT alone.     

Morphologic and functional changes in nontumorous liver tissue after radiofrequency ablation in an in vivo model: comparison of 18F-FDG PET/CT, MRI, ultrasound, and CT.

Rimlike contrast enhancement on morphologic imaging and increased tracer uptake on (18)F-FDG PET in the periphery of the necrosis can hamper differentiation of residual tumor from regenerative tissue after radiofrequency ablation of liver lesions. This study used MRI, CT, ultrasound, and (18)F-FDG PET/CT to assess the typical appearance of lesions in nontumorous animal liver tissue after radiofrequency ablation. METHODS: Lesions were created by radiofrequency ablation of normal liver parenchyma in 21 minipigs. Follow-up was performed by 3 contrast-enhanced morphologic modalities-MRI, CT, and ultrasound-and by (18)F-FDG PET/CT immediately, 3 and 10 d, and 1, 2, 3, and 6 mo after radiofrequency ablation. Images were evaluated qualitatively for areas of increased enhancement and regions of elevated tracer uptake. Furthermore, all images were assessed quantitatively by determination of ratios comparing enhancement/tracer uptake in the periphery of the necrosis with enhancement/tracer uptake in normal liver parenchyma. Imaging findings were compared with histopathology findings. RESULTS: Immediately after radiofrequency ablation, no increase in (18)F-FDG uptake was visible, whereas elevated enhancement was noticed in the periphery of the necrosis on all morphologic imaging procedures. At further follow-up, an area of rimlike increase in (18)F-FDG uptake surrounding the necrosis was detected on PET/CT. The rimlike pattern of increased enhancement in the arterial phase was present for all liver lesions on CT, MRI, and ultrasound, especially between day 3 and month 1 after the radiofrequency ablation. Both elevated glucose metabolism and enhancement persisted for 6 mo postinterventionally. Histologic examination showed a hemorrhagic border converting into a regeneration capsule. CONCLUSION: If performed immediately after radiofrequency ablation, (18)F-FDG PET/CT probably has benefits over those of morphologic imaging procedures when assessing liver tissue for residual tumor. Later follow-up may be hampered by visualization of peripheral hyperperfusion and tissue regeneration. Further studies on a patient population are essential.     

Radiofrequency Ablation for Treating Liver Metastases from a Non-Colorectal Origin

Objective

We wanted to assess the safety and efficacy of performing radiofrequency ablation (RFA) in patients with non-colorectal liver metastases.

Materials and Methods

In this retrospective study, 25 patients with 40 hepatic metastases (M:F = 17:8; mean age, 57 years; tumor size, 0.5-5.0 cm) from a non-colorectal origin (stomach, biliary, breast, pancreas, kidney and skin) were treated with RFA. The RFA procedures were performed using either an internally cooled electrode or a clustered electrode under ultrasound or CT guidance. Contrast-enhanced CT scans were obtained immediately after RFA and follow-up CT scans were performed within three months after ablation and subsequently at least every six months. The intrahepatic disease-free interval was estimated and the overall survival from the time of the initial RFA was analyzed using the Kaplan-Meier method.

Results

No intraprocedural deaths occurred, but four major complications developed, including abscesses (n = 3) and pneumothorax (n = 1). Technical effectiveness was determined on the initial follow-up images. During the follow-up period (range, 5.9-68.6 months; median time, 18.8 months) for 37 tumors in 22 patients where technical effectiveness was achieved, 12 lesions (32%, 12 of 37) showed local tumor progression and new intrahepatic metastases occurred in 13 patients (59%, 13 of 22). The median intrahepatic disease-free interval was 10.1 months. The 1-year, 3-year and 5-year overall survival rates after RFA were 86%, 39% and 19%, respectively.

Conclusion

RFA showed intermediate therapeutic effectiveness for the treatment of non-colorectal origin liver metastases.     

Comparison of FDG-PET, MRI and CT for post radiofrequency ablation evaluation of hepatic tumors

Purpose

Treatment effect of radiofrequency ablation (RFA) is traditionally accomplished with MRI and/or CT. The aim of the study was to assess the role of FDG-PET in post RFA hepatic tumor evaluation, in comparison with MRI and CT.

Materials and methods

28 patients (33 hepatic RFA lesions) who had post RFA FDG-PET within 8 weeks of abdominopelvic MRI or CT were retrospectively reviewed. Accuracy of FDG-PET on post hepatic RFA evaluation was compared with MRI and/or CT based on clinical and imaging follow-up.

Results

Among total of 33 RFA-treated lesions, 17 had residual or recurrent tumor (positive). PET identified 16 with a sensitivity of 94.1 %. Of these 17 lesions, 12 had concurrent MRI and 8 were positive with a sensitivity of 66.7 %. Similarly, 6 out of the 17 lesions had CT and 4 were positive with a sensitivity of 66.7 %. Sixteen lesions were successfully ablated (negative). Among them FDG-PET was negative in 13 with a specificity of 81.3 %; MRI was performed in 8 and 7 were negative with a specificity of 87.5 %; CT was performed in 8 and 5 were negative with a specificity of 62.5 %. The overall accuracy of PET, MRI and CT was 87.9, 75.0, and 64.3 %, respectively. The average scan numbers for PET, MRI and CT to achieve a final accurate diagnosis were 1.121, 1.316 and 1.250, with a corresponding cost of $1455.2, $1845.8, and $933.8, respectively.

Conclusions

The study suggests that FDG-PET is superior to MRI and/or CT and is more cost-effective in post RFA hepatic tumor assessment.     

Improving liver lesion characterisation using retrospective fusion of FDG PET/CT and MRI

AimTo compare retrospectively fused FDG PET/CT and MRI (PET/MRI) to FDG PET/CT and MRI for characterisation of indeterminate focal liver lesions as malignant or benign in patients with a known primary malignancy.Materials and methodA retrospective review of 70 patients (30 females, 40 males; mean age 56 ± 14 years) with 150 indeterminate lesions after FDG PET/CT and MRI (mean scan time interval 21 ± 11 days). HERMES® software was used to fuse PET/CT and MRI scans which were reviewed by 2 readers using the Likert score (scale 1–5) to characterise lesions as benign (1–3) or malignant (4–5). Final diagnosis was determined by histopathology or follow up imaging. Results for fused PET/MRI were compared to PET/CT and MRI alone.ResultsFor detection, MRI and fused PET/MRI detected all the lesions while PET/CT detected 89.4%. Characterisation of liver lesions as malignant on PET/CT alone yielded sensitivity, specificity, accuracy, PPV and NPV of 55.6%, 83.3%, 66.7%, 83.3%, 55.6% respectively and 67.6%, 92.1%, 80%, 89.3%, 74.5% for MRI, respectively. The sensitivity, specificity, accuracy, PPV and NPV for characterising lesions as malignant increased to 91.9%, 97.4%, 94.7%, 97.1%, 92.5% with PET/MRI fusion. The sensitivity, specificity, accuracy, PPV and NPV of fused PET/MRI for characterising lesions as malignant remained superior to PET/CT and MRI.ConclusionRetrospective fusion of PET with MRI has improved characterisation of indeterminate focal liver lesions compared to MRI or FDG PET/CT alone.     

^18F-FDGPET／CT与超声造影在肝细胞癌复发判断中的对比研究

目的比较18F—FDGPET／CT与超声造影（CEUS）在HCC治疗后复发监测中的效能。方法回顾性分析27例HCC治疗后（15例部分切除术、12例射频消融）患者资料（男22例,女5例;平均年龄47岁）,患者治疗后均行18F．FDGPET／CT及CEUS监测肿瘤复发,2种检查间隔时间在2周内,间隔期间未接受任何治疗。依据病理或随访（〉6个月）结果,计算PET／CT与CEUS诊断HCC复发的灵敏度、特异性及准确性。比较CEUS与PET／CT对CEUS阳性患者和CEUS阴性患者的诊断效能。采用McNemar检验分析数据。结果27例治疗后HCC患者中,25例存在肝内复发,其中11例合并肝外转移;2例肝内未见复发,但有肝外转移。18F-FDGPET／CT及CEUS对肝内病灶检出的灵敏度分别为92．0％（23／25）和60．0％（15／25）,特异性均为2／2,准确性分别为92．6％（25／27）和63．0％（17／27）。15例CEUS阳性患者中,18F．FDGPET／CT及CEUS对肝内病灶检出的灵敏度及准确性均为100％（15／15）;12例CEUS阴性患者中,18F—FDGPET／CT及CEUS对肝内病灶检出的灵敏度分别为8／10和0,特异性均为2／2,准确性分别为83．3％（10／12）和16．7％（2／12）。18F-FDGPET／CT灵敏度及准确性明显高于CEUS,尤其是CEUS阴性组（x2=5．373和5．250,均P〈O．05）。18F-FDGPET／CT对肝外转移病灶的诊断灵敏度为100％（13／13）。结论18F—FDGPET／CT在评估HCC治疗后患者肝内肿瘤复发方面的灵敏度及准确性明显优于CEUS,并能有效发现肝外转移,可作为CEUS阴性而临床高度怀疑复发和转移的HCC患者的有效补充检查手段。     

Sensitivity of PET/MR images in liver metastases from colorectal carcinoma

Our aim was to evaluate the sensitivity of positron emission tomography/magnetic resonance image (PET/MRI) in the detection of liver metastases in patients from colorectal cancer as compared with computed tomography (CT), magnetic resonance imaging (MRI), PET and PET/CT images. From April 2008 to April 2010, twenty-four patients (mean age 56.5±10.5 years) with liver metastases from colorectal cancer diagnosed by pathology were retrospectively studied as above. All image data were respectively collected and fused. PET/CT and PET/MRI fusion images were successfully performed with a PET-MR-CT robot transmission-fusion imaging system. Pathologic findings and clinical follows-up were performed as referenced standards. Images were reviewed independently by at least three experts. We found a total number of 121 metastatic lesions and 35 of them, with a maximum diameter less than 1cm. According to a per-lesion analysis, the sensitivity on liver metastases was 64.5%, 80.2% and 54.5% on CT, MRI and PET, respectively. Based on reconstruction imaging analysis, PET/CT and PET/MRI showed sensitivities of 84.2% and 98.3%. Sensitivity comparison of PET/MRI had superior sensitivity of 98.08%. Paired data analysis (McNemar) resulted a type I error which equated to 0.05. There was a statistically significant difference between CT and MRI or PET for the detection of patients with liver metastatic lesions (P<0.05). However, PET/MRI can efficiently detect more metastatic lesions than PET/CT (P<0.05) among those with diameter <1cm. In conclusion, PET/MRI was a quite efficient diagnostic modality compared to conventional imaging modalities and should be considered the procedure of choice in the detection of liver metastatic lesions from colorectal cancer.     

螺旋CT对射频消融治疗肝脏恶性肿瘤的疗效评价

目的　探讨螺旋CT在肝脏恶性肿瘤射频消融治疗后随访过程中的价值。方法　对 3 6例超声引导下经皮穿刺射频消融治疗的肝脏恶性肿瘤患者 (2 9例原发性肝癌和 7例转移性肝癌 )定期进行螺旋CT双期增强扫描检查 ,观察射频消融的效果及肿瘤复发的情况。结果　肿瘤残留或原位复发的主要征象是消融区的边缘呈带状或结节样强化 ,或在随访CT复查中 ,肿瘤的体积不断增大。在射频消融治疗后的首次CT复查中 ,2 8例 (77.8% )肿瘤出现完全坏死。在随后的CT随访复查中 ,2例 (5.6% )出现肝内原位复发 ,4例 (11.1% )出现肝内异位复发。结论　对于合适的肝脏恶性肿瘤 ,射频消融是一种疗效确切的肿瘤局部治疗方法 ,在其疗效评价和长期随访过程中 ,螺旋CT双期增强扫描是有效的影像检查手段     

Local tumor progression after radiofrequency ablation of colorectal liver metastases: evaluation of ablative margin and three-dimensional volumetric analysis

PURPOSE: Detection of local tumor progression (LTP) after radiofrequency (RF) ablation of colorectal cancer liver metastases may facilitate repeat intervention with potential benefits for patient survival. Ablative margins 1 month after RF ablation may predict LTP, and repeated three-dimensional (3D) volumetric analysis of coagulation volume after ablation may provide earlier detection of LTP versus conventional morphologic criteria. MATERIALS AND METHODS: Seven patients with LTP and four patients without LTP after a follow-up of at least 24 months were identified. Multidetector computed tomography (CT) was performed at 1 and 3 months after RF ablation and then at 3-month intervals until 24 months. Ablative margins were determined from preablation tumor diameter and the corresponding coagulation diameter 1 month after ablation. Postablation coagulation volume was measured from 81 follow-up multidetector CT images using a seeding-based semiautomatic 3D method. RESULTS: LTP was detected at a median of 9 months (range, 6-21 months) after RF ablation. A coagulation diameter smaller than the preoperative tumor diameter was associated with LTP. Increase in coagulation volume was found in six of seven patients at the time of diagnosis of LTP by conventional morphologic criteria. CONCLUSION: Three-dimensional volumetric analysis of postablation coagulation volume is feasible for detection of LTP after RF ablation of colorectal cancer liver metastases. No advantage in early detection of LTP was found for 3D volumetric analysis compared with conventional morphologic criteria in this preliminary study. These findings may reflect a type II error caused by the limited sample size.     

Reproducibility of standardized uptake values of same-day randomized <Superscript>68</Superscript>Ga-PSMA-11 PET/CT and PET/MR scans in recurrent prostate cancer patients

Objective

Positron emission tomography in association with magnetic resonance imaging (PET/MR) and ⁶⁸Ga-PSMA-11 has shown superior detection in recurrent prostate cancer patients as compared to PET/computed tomography (PET/CT). There are, however, several technological differences between PET/CT and PET/MR systems which affect the PET image quality. The objective of this study was to assess the reproducibility of PET/CT and PET/MR SUV’s in recurrent prostate cancer patients. We randomized the patients regarding the order of the PET/CT and PET/MR scans to reduce the influence of tracer uptake as a function of time.

Methods

Thirty patients, all with biochemical recurrence after radical prostatectomy, underwent whole-body PET/CT and PET/MR scans after intravenous injection of a single dose of ⁶⁸Ga-PSMA-11. Fifteen patients underwent PET/CT first and 15 patients underwent PET/MR first. Volumes of interest on tumor lesions were outlined and maximum standardized uptake value (SUVmax) corrected for lean body mass was calculated. Correlation and agreement between scans were assessed by generalized linear mixed-effects models and Bland–Altman analysis. The association between SUV, patient characteristics and imaging parameters was assessed.

Results

Eighteen of the 30 evaluated patients had at least one positive lesion, giving an overall detection rate of 60%. In total, there were 34 visible lesions: 5 local recurrences, 22 lymph node metastases and 7 bone metastases. One group acquired PET/CT and PET/MR at median time points of 63.0 and 159.0 min, while the other group acquired PET/MR and PET/CT at median time points of 92.0 and 149.0 min. SUVmax between scans was linearly correlated, described by the equation Y(PET/CT SUVmax)?=?0.75?+?1.00?×?(PET/MR SUVmax), on average 20% higher on PET/CT than on PET/MR. SUV associated significantly only with type of lesion, scan time post-injection and acquisition time per bed position.

Conclusions

SUVmax from PET/CT and PET/MR are linearly correlated, on average 20% higher on PET/CT than on PET/MR and should, therefore, not be used interchangeably in patient follow-up.

     

Impact of 18F-FDG PET/CT on therapeutic decisions in patients with colorectal cancer and liver metastases

ObjectivesSurgical resection and radio-frequency ablation (RFA) are standard therapeutic procedures for colorectal metastases confined to the liver. The presence of extrahepatic disease has a significant effect on the management of these patients. The goal of this study is to assess the value of positron emission tomography/computed tomography with 18F-fluorodeoxyglucose (18F-FDG PET/CT) in the decision making whether to perform RFA or surgical resection of liver metastases in patients with metastatic colorectal cancer.Material and methodsThirty-five consecutive patients (23 men, 12 women; age range: 46–78 years) with colorectal carcinoma and liver metastases were prospectively enrolled. Nineteen of them were considered candidates for surgical resection and 16 for RFA. All underwent 18F-FDG PET/CT, helical computed tomography of the chest and abdomen and, some of them, magnetic resonance imaging of the abdomen. The 18F-FDG PET/CT studies were performed within 4 weeks from conventional imaging, and additional findings were later confirmed or not, either by histology or follow up.ResultsIn the surgical candidate group, 18F-FDG PET/CT detected extrahepatic disease, missed by conventional imaging, in 9/19 patients (47.3%). These findings directly altered the management in 7 patients (36.8%). In the group of RFA candidates, 18F-FDG PET/CT detected additional extrahepatic disease in 4/16 patients (25%) and directly altered management in all of them. Overall, in 11/35 patients (31.4%), 18F-FDG PET/CT detected extrahepatic metastatic disease.ConclusionIn patients with colorectal cancer and liver metastases, 18F-FDG PET/CT provides relevant additional information that has significant impact on management.     

1.5 T MR导向下肝脏恶性肿瘤射频消融治疗技术初探

目的 探讨1.5 T MR引导下对肝脏恶性肿瘤射频消融治疗的可行性.方法 23例44个经病理证实、不能或不愿手术的肝脏恶性肿瘤病灶,其中11例为原发性肝癌、12例为肝转移癌,肿瘤最大径平均(3.3±1.8)cm,均采用MR兼容多极射频针在1.5 T MR引导下进行射频消融治疗.术后MR扫描观察消融情况,消融灶完全覆盖原病灶、范围超出病灶边缘0.5～1.0 cm为消融完全.结果 所有消融均顺利完成,平均手术时间(93±33)min,消融灶均完全覆盖病灶,无胆瘘、膈肌穿孔、黄疸、气胸等并发症发生.射频电极针在MR图像上呈低信号.消融灶在T2WI序列上呈低信号,周围可见薄层高信号环绕;T1WI序列上消融灶呈明显高信号,边界清晰;DWI上消融灶呈等低信号,周围呈环状稍高信号.结论 1.5 T MR引导下肝脏恶性肿瘤射频消融是安全、有效的技术.     

Fast non-enhanced abdominal examination protocols in PET/MRI for patients with neuroendocrine tumors (NET): comparison to multiphase contrast-enhanced PET/CT

Purpose

To evaluate fast non-enhanced protocols for abdominal PET/MRI in comparison to contrast-enhanced PET/CT with somatostatin receptor (SSR)-specific radiotracers regarding effectiveness of lesion detection in NET patients.

Methods

This was a retrospective analysis of 29 patients (12 male, 57?±?13 years) who underwent PET/CT and subsequently PET/MRI at the same day. Two readers evaluated independently four PET/MRI setups: (I) PET?+?T2 Half Fourier Acquisition Single Shot Turbo Spin Echo (T2 HASTE), (II) PET?+?T2 HASTE?+?T2-weighted spin-echo sequence (T2 TSE), III) PET?+?T2 HASTE?+?Diffusion Weighted Imaging (DWI) and (IV) PET?+?T2 HASTE?+?T2 TSE?+?DWI. A consensus reading of PET/MRI and PET/CT including follow-up examinations served as the reference standard for lesion-based analysis. Lesion sizes were assessed.

Results

Setup IV provided comparable overall detection rates as PET/CT in both readers: PET/MRI 91.5%/92.9% versus 89.7% in PET/CT. In liver and bone lesions (mean diameter: 1.9 and 1.5 cm), PET/MRI was equal or superior to PET/CT: 98%/98% versus 85% in PET/CT; 100%/95% versus 100% in PET/CT, but inferior in pancreatic lesions, small bowel lesions and lymph node metastases (mean diameter: 1.3, 0.5 and 1.8 cm).

Conclusion

A non-enhanced MR protocol comprising T2 HASTE, T2 TSE and DWI for SSR-PET/MRI seems to provide comparable effectiveness in lesions detection as multiphase contrast-enhanced PET/CT. It might, therefore, serve as valid alternative, e.g., for follow-up examinations in patients with unresectable NET and kidney failure.

     

Stereotaxie und Robotik zur Ablation – Spielzeug oder Werkzeug?

CLINICAL AND METHODOLOGICAL ISSUES: Ablative technologies allow local curative tumor treatment by thermal tissue damage. An important prerequisite is the coverage of all tumor cells. Tumor size is the most important limiting factor. STANDARD RADIOLOGICAL METHODS: The drawbacks of conventional computed tomography/ultrasound/magnetic resonance imaging (CT/US/MRI) guided radiofrequency ablation (RFA) are the absence of planning software, imprecise probe placement, imprecise control of probe placement and the ablation zone as well as the lack of reliability and reproducibility. METHODOLOGICAL INNOVATIONS: Stereotactic and robot-assisted systems allow planning of multiple probe positions based on CT/MRI and positron emission tomography (PET) planning data. The probes can be precisely placed according to the coordinates of the image datasets. PERFORMANCE: The 1 and 3 year survival rates after stereotactic RFA (SRFA) of cholangiocellular carcinoma were 91% and 70% respectively and the median overall survival was 60 months. After SRFA of 189 colorectal liver metastases in 63 patients there was no significant difference in local recurrence rates between tumors??5?cm (17.4%). The median overall survival was 33.2 months and the 1, 3, and 5 year overall survival rates after SRFA in patients with resectable colorectal cancer were 92%, 66% and 48%, respectively. ACHIEVEMENTS: In our opinion the excellent and, to a large extent user-independent results justify the increased efforts in time and costs especially for the treatment of patients with large and irregular tumors. PRACTICAL RECOMMENDATIONS: Stereotaxy and robotics are valuable tools for effective tumor ablation especially of large tumors and are likely to gain in importance in the next few years.