Comparison of 18F-FDG-PET/CT and 18F-FDG-PET/MR imaging in oncology: a systematic review

Objective

The aim of this study was to systematically review the literature to evaluate the clinical performance of integrated ¹⁸F-FDG PET/MR as compared with ¹⁸F-FDG PET/CT in oncologic imaging.

Methods

The literature was searched using MEDLINE and EMBASE via OVID. Studies comparing the diagnostic accuracy of integrated ¹⁸F-FDG PET/MR and ¹⁸F-FDG PET/CT in the diagnosis, staging/restaging, assessment of treatment response, or evaluation of metastasis in patients with suspected or diagnosed cancers were deemed eligible for inclusion. Risk of bias and applicability concerns were assessed using the QUADAS-2 tool.

Results

Twenty studies met the inclusion criteria. The overall quality of the studies was rated favorably with bias or applicability concerns in a few studies. Our review suggests that ¹⁸F-FDG PET/MR performs comparably to ¹⁸F-FDG PET/CT in the detection of local lymph node and distant metastases and superiorly in determining the local extent of tumor. SUV obtained from ¹⁸F-FDG PET/MR correlated highly with those obtained from ¹⁸F-FDG PET/CT.

Conclusions

Based on early evidence, ¹⁸F-FDG PET/MR is comparable to ¹⁸F-FDG PET/CT in the clinical scenarios examined in this review. The potential for interchangeability of ¹⁸F-FDG PET/MR with ¹⁸F-FDG PET/CT will vary by indication and the body site that is being imaged, with PET scanners integrated with MRI predicted to provide greater detail in the evaluation of local tumor extent, where ¹⁸F-FDG PET/CT can be limited.

     

Multicentre study of 18F-FDG-PET/CT prostate incidental uptake

Aim

The purpose of our study was to establish the prevalence and pathological nature of fluorine-18-fluorodeoxyglucose (18F-FDG) prostate incidental uptake (PIU) among patients studied for non-prostate-malignant purposes in three nuclear medicine centres.

Methods

We retrospectively evaluated 20,422 scans performed on male patients; all patients underwent 18F-FDG-PET/CT for purposes not related to prostate disease.

Results

Among 20,422 patients PIU was identified for 280 (1.4 %) with an average age of 70 ± 10.7 years. Sixty-three of the 280 patients with PIU (22.5 %) underwent PSA dosage and biopsy to determine the nature of the incidental uptake. Thirty-five of the 63 (55.5 %) PIU were malignant whereas 28/63 (44.5 %) were benign. The average value of PSA for patients with benign PIU was 3.7 ± 2.8 ng/ml whereas it was 7.8 ± 8.2 ng/ml in patients with malignant PIU; this difference was statistically significant. For malignant lesions, the average lesion-to-liver SUVmax ratio was 2.9 ± 2.5 and the average lesion-to-blood-pool SUVmax ratio was 3.7 ± 2.5. For benign lesions, the average lesion-to-liver SUVmax ratio was 2.5 ± 1.7 and the average lesion-to-blood-pool SUVmax ratio was 3.5 ± 2.4; there was no statistically significant difference between lesion-to-liver and lesion-to-blood-pool SUVmax ratios for benign and malignant lesions.

Conclusion

Because PIU values are indicative of malignancy for a substantial percentage of patients, further investigation is required.

     

肺外结核18F-FDG-PET/CT误诊分析

目的 探讨肺外结核的18F-FDG-PET/CT表现并分析肺外结核误诊原因.方法 回顾性分析25例18F-FDG-PET/CT误诊为恶性肿瘤的肺外结核患者资料.结果 25例18F-FDG-PET/CT误诊恶性肿瘤中23例经病理证实结核,2例经临床诊断性治疗最终诊断为结核,包括8例骨关节结核,10例胸腹膜结核,7例淋巴结结核.8例骨关节结核中4例为胸椎结核,2例关节结核,另2例全身骨骼广泛受侵.4例胸椎结核呈溶骨性破坏,邻近软组织肿胀及软组织肿块,18F-FDG-PET示病变椎体呈明显放射性浓聚影,标准摄取最大值(SUVmax)=3.56 ～ 12.58.2例全身广泛骨质破坏,CT示全身多发骨质破坏,软组织肿块不明显,PET是全身骨骼弥漫性放射性浓聚影.关节软组织结核2例:CT示左侧腰大肌脓肿,1例左侧腰大肌脓肿向下延伸至左侧髋关节,骨盆左侧及左侧髋关节软组织肿块,PET呈大片状不均放射性浓聚影,SUVmax=4.36～ 8.23.胸膜腹膜结核10例中有1例为胸膜腹膜结核,9例为腹膜结核,CT表现为腹膜及胸膜均匀增厚并伴有不同程度的胸腹腔积液.增厚的腹膜及胸膜呈条状放射性浓聚影,SUVmax=2.56 ～ 6.23,9例腹膜结核患者肠系膜内可见多发软组织密度结节及小斑片影,即“污秽征”.淋巴结结核7例:CT表现为对称性两侧纵隔、肺门多发淋巴结增大,最大径1.5 ～8.0 cm,SUVmax=10.5.结论 肺外结核的18F-FDG-PET/CT表现没有特征性,与恶性肿瘤鉴别困难.在充分分析PET/CT征象的基础上结合临床及实验室检查,才能最大限度地减少肺外结核的误诊.     

18F-FDG-PET/CT predicts survival in hypopharyngeal squamous cell carcinoma

Objectives

We investigated the relationship between overall survival of patients and pretreatment [¹⁸F]-2-fluorodeoxyglucose (¹⁸F-FDG) uptake, assessed by positron emission tomography combined with computed tomography (PET/CT) in hypopharyngeal squamous cell carcinoma.

Methods

Thirty-one patients who were newly diagnosed as resectable hypopharyngeal squamous cell carcinoma underwent pretreatment ¹⁸F-FDG-PET/CT. We used the maximum standardized uptake value (SUVmax) as ¹⁸F-FDG uptake. Overall survival rate was calculated by the Kaplan–Meier method.

Results

The median SUVmax was 11.53 (range 2.49–22.33). Patients with SUVmax ≥ 13 significantly exhibited shorter overall survival in univariate analysis (p < 0.01). Moreover, by Cox proportional hazards model of multivariate analysis, SUVmax ≥ 13 was a significant prognostic factor independent of clinical T and N classification, and treatment group (p < 0.02).

Conclusions

These results suggested that SUVmax obtained by pretreatment ¹⁸F-FDG PET/CT assessment is an important prognostic factor in patients with hypopharyngeal squamous cell carcinoma.     

18F-FDG-PET/CT findings of retroperitoneal tumors: a pictorial essay

A variety of different tumors can arise from any of the tissues present in the retroperitoneum, and they exhibit a wide range of pathologic types. Although computed tomography (CT) and magnetic resonance imaging (MRI) can demonstrate important characteristics of these tumors, diagnosis is often challenging for radiologists. The purpose of this pictorial essay is to review ¹⁸F-fluorodeoxyglucose positron emission tomography/CT (FDG-PET/CT) features of different kinds of benign and malignant retroperitoneal tumors in comparison with CT or MRI findings alone and to become familiar with the wide variety of imaging characteristics.     

The effect of 18F-FDG-PET/CT respiratory gating on detected metabolic activity in lung lesions

Objective  Respiratory gated PET/CT (positron emission tomography/computed tomography) of the lung is expected to increase the accuracy of quantitative determinations in lesional activities, regardless of the gating method used; reasonably, respiratory gating should increase standard uptake value (SUV; and possibly decrease lesional size), on the basis of the reduction of the “smearing effect.” However, literature data are very limited, particularly for in vivo studies. The objective of this article is to test the SUV variations in a large group of lung lesion studies. Methods  A group of 26 consecutive positive studies (21 men, 5 women, age 36-84, mean 68), performed on patients referred to our institution for known or suspected lung cancer, are examined. All studies were performed both with conventional PET/CT total body scan and with Real-Time Position Management (RPM) triggered selective gated study of the thorax. Four studies were considered technically unsatisfactory and were discarded; the remaining 22 studies are the object of this work. Max lesional SUVs were evaluated in both settings by semi-automated algorithms; for the gated studies, both values of the bin that showed more relevant variations from the clinical routinary study (“best bin”) and an average value that was calculated over all bins were determined. Results were compared on a one-to-one basis. Results  In conventional, SUV showed a mean ± standard deviation (SD) value of 9.2 ± 6.9 (range 0.9–26). In the averaged gated studies, the mean ± SD value was 13.4 ± 11.7 (range 1.4–47); in the “best bin” dataset the mean ± SD was 14.9 ± 12.9, ranging from 1.6 to 53.1. In general, the use of respiratory trigger induced rather variable but overall consistent increases in SUV. If the percentage variations in the average trigger dataset are considered, there is an average increase of +60%, SD ± 97 (P < 0.05). Similar results are found in the “best bin” dataset, the average percentage increase in SUV values being +77.2% (SD ± 04.6). Conclusions  In lung cancer, triggering procedures increase the signal to noise ratio. The increase in SUV determined by gating is very variable, but generally relevant. This could lead to an SUV values cut-off revision, and may have an impact on smaller lesions detection.     

18F-FDG-PET/MRI in lymphoma patients

The introduction of hybrid PET/MRI imaging using integrated systems into clinical practice has opened up the possibility of reducing the radiation dose from hybrid imaging by eliminating the contribution from computed tomography. Studies comparing the possibilities of PET/CT and PET/MRI imaging demonstrated it is possible to use the advantages of the high contrast resolution of magnetic resonance for soft tissue and bone marrow along with PET records in a quality comparable to PET/CT imaging. The significant feature for PET imaging in Hodgkińs lymphoma is that it is a tissue with high levels of radiopharmaceutical accumulation, which decreases proportionally after successful therapeutic effect, the effect of therapy is assessed using Deauville score system on interim examinations. While the efficacy of prognosis determined using the Deauville scale in HL is widely accepted, it turns out that in DLBCL, the prognostic value of PET imaging is bound to the evaluation of subtypes. PET/MRI scanning can be used to evaluate a relapse if follicular lymphoma has already been treated, or to confirm transformation into more aggressive forms. In children and adults with Burkitt's lymphoma, negative findings after induction therapy have a high negative predictive value for relapse prognosis.     

18F-FDG-PET/CT findings in primary pulmonary mixed squamous cell and glandular papilloma

A 55-year-old female had an abnormal shadow on chest radiograph. Computed tomography (CT) revealed a 26-mm tumor mass in the left upper lobe. No malignant findings were obtained by bronchoscopic cytology or histopathological diagnostics, but on positron emission tomography with 18F-fluorodeoxyglucose (FDG-PET) examination the maximum SUV was 9.01 in accordance with the tumor mass shadow on CT. Video-assisted thoracoscopic surgery was performed as clinically suspected of lung cancer, and the diagnosis was pulmonary mixed squamous cell and glandular papilloma (PMSGP). Primary PMSGP is extremely rare, and this is the first to describe the PET findings of this disease.     

18F-FDG-PET/CT in the diagnosis of paraneoplastic neurological syndromes: a retrospective analysis

Objectives

Paraneoplastic neurological syndromes (PNS) constitute a challenging diagnostic problem, as the underlying tumour often remains unidentified for a long time, even with frequent conventional diagnostic procedures. For appropriate patient management timely identification of the tumour is critical. We evaluated the value of ¹⁸F-FDG-PET/CT in the investigation of PNS.

Methods

The case notes of 46 consecutive patients with clinically suspected PNS who underwent ¹⁸F-FDG-PET/CT were reviewed retrospectively and the performance of PET/CT for detecting underlying tumours was assessed.

Results

PET/CT detected foci of increased ¹⁸F-FDG uptake in 10 out of 46 patients. In six of these 10 patients combined PET/CT identified the underlying disease: four patients suffered from PNS; vasculitic and local metastatic disease was detected in two other patients.

Conclusions

Based on our results, we believe that the role of positron emission tomography in the detection of occult neoplasms in patients with PNS has been overestimated in the past. In clinical practice, PNS is far more often suspected than proven. In our study combined PET/CT identified malignancy as the underlying cause of suspected PNS in only 8.7% (4/46). We believe that combined PET/CT should be reserved for stringently selected patients with a high clinical index of suspicion for PNS and after conventional imaging techniques fail to detect a tumour.