Value of retrospective image fusion of F-FDG PET and MRI for preoperative staging of head and neck cancer: Comparison with PET/CT and contrast-enhanced neck MRI

Purpose

To assess the clinical value of retrospective image fusion of neck MRI and ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) PET for locoregional extension and nodal staging of neck cancer.

Materials and methods

Thirty patients with carcinoma of the oral cavity or hypopharynx underwent PET/CT and contrast-enhanced neck MRI for initial staging before surgery including primary tumor resection and neck dissection. Diagnostic performance of PET/CT, MRI, and retrospective image fusion of PET and MRI (fused PET/MRI) for assessment of the extent of the primary tumor (T stage) and metastasis to regional lymph nodes (N stage) was evaluated.

Results

Accuracy for T status was 87% for fused PET/MRI and 90% for MRI, thus proving significantly superior to PET/CT, which had an accuracy of 67% (p = 0.041 and p = 0.023, respectively). Accuracy for N status was 77% for both fused PET/MRI and PET/CT, being superior to MRI, which had an accuracy of 63%, although the difference was not significant (p = 0.13). On a per-level basis, the sensitivity, specificity and accuracy for detection of nodal metastasis were 77%, 96% and 93% for both fused PET/MRI and PET/CT, compared with 49%, 99% and 91% for MRI, respectively. The differences for sensitivity (p = 0.0026) and accuracy (p = 0.041) were significant.

Conclusion

Fused PET/MRI combining the individual advantages of MRI and PET is a valuable technique for assessment of staging neck cancer.     

Prospective evaluation of MRI,C-acetate PET/CT and contrast-enhanced CT for staging of bladder cancer

Purpose

To prospectively evaluate the diagnostic performance of magnetic resonance imaging (MRI), ¹¹C-acetate positron emission tomography/computed tomography (PET/CT) and contrast-enhanced CT for bladder cancer staging, using whole-mount pathologic review of radical cystectomy and pelvic lymph node specimens as the reference standard.

Materials and methods

The institutional review board approved this prospective study, which was compliant with the Health Insurance Portability and Accountability Act. Written informed consent was obtained from 16 patients with histologically confirmed bladder cancer who underwent MRI, ¹¹C-acetate PET/CT and contrast-enhanced CT before radical cystectomy and pelvic lymph node dissection. Before imaging 4/16 patients had received intravesical Bacillus Calmette-Guérin treatment, 6 had received systemic chemotherapy, 3 had received both and 3 had received neither. Measures of diagnostic performance including accuracy, sensitivity and specificity were estimated separately for each imaging modality.

Results

MRI correctly staged 56% of patients (9/16), overstaged 38% (6/16) and understaged 6% (1/16). CT correctly staged 50% of patients (8/16), overstaged 44% (7/16) and understaged 6% (1/16). In 9 patients, ¹¹C-acetate PET/CT showed uptake within the bladder wall; the uptake was true-positive in 7 patients and false-positive in 2 patients. Of the remaining 7 patients, 5 had true-negative and 2 had false-negative PET/CT results for cancer in the bladder wall. For all modalities, staging accuracy was reduced in patients with a history of prior intravesical and/or systemic chemotherapy.

Conclusion

In staging bladder cancer, MRI, ¹¹C-acetate PET/CT and CT displayed similar levels of accuracy. For all modalities, a history of intravesical and/or systemic chemotherapy affected staging accuracy.     

Value of fusion of PET and MRI in the detection of intra-pelvic recurrence of gynecological tumor: comparison with 18F-FDG contrast-enhanced PET/CT and pelvic MRI

Background

To evaluate the diagnostic value of retrospective image fusion from pelvic magnetic resonance imaging (MRI) and ¹⁸F-fluorodeoxyglucose positron emission tomography (PET) in detecting intra-pelvic recurrence of gynecological tumor.

Methods

Thirty patients with a suspicion of recurrence of gynecological malignancy underwent inline contrast-enhanced PET/computed tomography (CT) and pelvic contrast-enhanced MRI for restaging. Diagnostic performance about the local recurrence, pelvic lymph node and bone metastasis and peritoneal lesion of PET/low-dose non-enhanced CT (PET/ldCT), PET/full-dose contrast-enhanced CT (PET/ceCT), contrast-enhanced MRI, and retrospective image fusion from PET and MRI (fused PET/MRI) were evaluated by two experienced readers. Final diagnoses were obtained by histopathological examinations, radiological imaging and clinical follow-up for at least 6 months. McNemar test was employed for statistical analysis.

Results

Documented positive locally recurrent disease, pelvic lymph node and bone metastases, and peritoneal dissemination were present in 53.3, 26.7, 10.0, and 16.7 %, respectively. Patient-based sensitivity for detecting local recurrence, pelvic lymph node and bone metastasis and peritoneal lesion were 87.5, 87.5, 100 and 80.0 %, respectively, for fused PET/MRI, 87.5, 62.5, 66.7 and 60.0 %, respectively, for contrast-enhanced MRI, 62.5, 87.5, 66.7 and 80.0 %, respectively, for PET/ceCT, and 50.0, 87.5, 66.7 and 60.0 %, respectively, for PET/ldCT. The sensitivity of diagnosing local recurrence by fused PET/MRI was significantly better than that of PET/ldCT (p = 0.041). The patient-based sensitivity, specificity and accuracy for the detection of intra-pelvic recurrence/metastasis were 91.3, 100 and 93.3 % for fused PET/MRI, 82.6, 100 and 86.7 % for contrast-enhanced MRI, 82.6, 100 and 86.7 % for PET/ceCT and 78.3, 85.7 and 80.0 % for PET/ldCT.

Conclusion

Fused PET/MRI combines the individual advantages of MRI and PET, and is a valuable technique for assessment of intra-pelvic recurrence of gynecological cancers.     

Depiction and characterization of liver lesions in whole body [F]-FDG PET/MRI

Objectives

To assess the value of PET/MRI with [¹⁸F]-FDG using a whole body protocol for the depiction and characterization of liver lesions in comparison to PET/CT.

Methods

70 patients (31 women, 39 men) with solid tumors underwent [¹⁸F]-FDG PET/CT and followed by an additional PET/MRI using an integrated scanner. Two readers rated the datasets (PET/CT; PET/MRI) regarding conspicuity of hepatic lesions (4-point ordinal scale) and diagnostic confidence (5-point ordinal scale). Median scores for lesion conspicuity and diagnostic confidence were compared using Wilcoxon's rank sum test. Prior examinations, histopathology and clinical follow-up (116 ± 54 days) served as standard of reference.

Results

36 of 70 (51%) patients showed liver lesions. Using PET/CT and PET/MRI all patients with liver metastases could correctly be identified. A total of 97 lesions were found (malignant n = 26; benign n = 71). For lesion conspicuity significantly higher scores were obtained for PET/MRI in comparison to PET/CT (p < 0.001). Significantly better performance for diagnostic confidence was observed in PET/MRI, both for malignant as for benign lesions (p < 0.001).

Conclusions

PET/MRI, even in the setting of a whole body approach, provides higher lesion conspicuity and diagnostic confidence compared to PET/CT and may therefore evolve as an attractive alternative in oncologic imaging.     

Fusion of PET and MRI for staging of uterine cervical cancer: comparison with contrast-enhanced 18F-FDG PET/CT and pelvic MRI

PurposeTo investigate the fusion of pelvic magnetic resonance imaging (MRI) and fluorodeoxyglucose positron emission tomography (PET) for assessment of locoregional extension and nodal staging of cervical cancer.MethodsPET/computed tomography (CT), MRI, and non-fused and fusion of PET and MRI for assessing the extent of the primary tumor and metastasis to nodes were evaluated.ResultsAccuracy for T-status was 83.3% for fused and non-fused PET/MRI and MRI proved significantly more accurate than PET/CT (53.3%) (P= .0077). Sensitivity, specificity, and accuracy for nodal metastasis were 92.3%, 88.2%, and 90.0% for fused PET/MRI and PET/contrast-enhanced CT; 84.6%, 94.1%, and 90.0% for non-fused PET/MRI; and 69.2%, 100%, and 86.7% for MRI.ConclusionFused PET/MRI combines the individual advantages of MRI and PET.     

Low-dose non-enhanced CT versus full-dose contrast-enhanced CT in integrated PET/CT scans for diagnosing ovarian cancer recurrence

Objective

To evaluate low-dose non-enhanced CT (ldCT) and full-dose contrast-enhanced CT (ceCT) in integrated ¹⁸F-fluorodeoxyglucose (FDG)-PET/CT studies for restaging of ovarian cancer.

Materials and methods

One hundred and twenty women who had undergone treatment for ovarian cancer underwent a conventional PET/CT scans with ldCT, and then ceCT. Two observers interpreted and decided in consensus on the PET/ldCT and PET/ceCT images by a 3-point scale (N: negative, E: equivocal, P: positive) per patient and lesion site. Final diagnoses were obtained by histopathological examinations, or clinical follow-up for at least 6 months.

Results

Patient-based analysis showed that the sensitivity, specificity, and accuracy of PET/ceCT was 86.9% (40/46), 95.9% (71/74), and 92.5% (111/120), respectively, whereas those of PET/ldCT were 78.3% (36/46), 95.0% (70/74), and 88.3% (106/120), respectively. All sensitivity, specificity, and accuracy significantly differed between two methods (McNemar test, p < 0.0005, p = 0.023, and p < 0.0001, respectively). The scales of detecting 104 recurrent lesion sites were N:14, E:6, P:84 for PET/ceCT, and N:15, E:17, P:72 for PET/ldCT, respectively. Eleven equivocal and one negative regions by PET/ldCT were correctly interpreted as positive by PET/ceCT.

Conclusion

PET/ceCT is a more accurate imaging modality with higher confidence for assessing ovarian cancer recurrence than PET/ldCT.     

Improved detection of localized prostate cancer using co-registered MRI and (11)C-acetate PET/CT

Objectives

We aimed to study the ability of contrast enhanced MRI at 1.5 T and ¹¹C-acetate PET/CT, both individually and using fused data, to detect localized prostate cancer.

Methods

Thirty-six men with untreated prostate cancer and negative for metastatic disease on pelvic CT and bone scan were prospectively enrolled. A pelvic ¹¹C-acetate PET/CT scan was performed in all patients, and a contrast enhanced MRI scan in 33 patients (6 examinations using both endorectal coil and surface coils, and 27 examinations using surface coils only). After the imaging studies 10 patients underwent prostatectomy and 26 were treated by image guided external beam radiation treatment. Image fusion of co-registered PET and MRI data was performed based on anatomical landmarks visible on CT and MRI using an advanced in-house developed software package. PET/CT, MRI and fused PET/MRI data were evaluated visually and compared with biopsy findings on a lobar level, while a sextant approach was used for patients undergoing prostatectomy.

Results

When using biopsy samples as method of reference, the sensitivity, specificity and accuracy for visual detection of prostate cancer on a lobar level by contrast enhanced MRI was 85%, 37%, 73% and that of ¹¹C-acetate PET/CT 88%, 41%, 74%, respectively. Fusion of PET with MRI data increased sensitivity, specificity and accuracy to 90%, 72% and 85%, respectively.

Conclusions

Fusion of sequentially obtained PET/CT and MRI data for the localization of prostate cancer is feasible and superior to the performance of each individual modality alone.     

Potential impact of PET/CT on the initial staging of lymphoma

Purpose

The aim of this study was to investigate the potential impact of PET/CT on the initial staging of lymphoma with comparison to each of the PET and CT components alone.

Materials and methods

PET/CTs from 37 patients with lymphoma undergoing initial staging were studied. Review of PET, CT and PET/CT images were done and staging of each patient by each modality was assigned and compared together. Clinical follow-up, additional imaging and histology served as the standard of reference.

Results

PET/CT correctly diagnosed 83 nodal regions as positive for lymphomatous involvement versus 61 and 57 detected by PET and CT respectively. The respective sensitivities, specificities, and accuracies for the detection of nodal involvement were: PET: 88.4%, 65%, 94%, CT 89.1%, 60.1%, 96.1%, PET/CT 96.3%, 88.3%, 98.2%. PET/CT also correctly identified more extra-nodal lesions (n = 24) than CT (n = 16) and PET (n = 15). Correct staging was more accurate at PET/CT (n = 31) in comparison to PET alone (n = 23) and CT alone (n = 21).

Conclusions

PET/CT was superior to PET and CT in the initial staging of lymphoma with significant better performance compared to PET and CT to clarify nodal and extra-nodal involved sites. The application of PET/CT rather than CT or PET is likely to be more beneficial.     

Staging accuracy of pancreatic cancer: Comparison between non-contrast-enhanced and contrast-enhanced PET/CT

Purpose

Our aim was to clarify the diagnostic impact of contrast-enhanced (CE) ¹⁸F-fluorodeoxyglucose (FDG)–positron emission tomography (PET)/computed tomography (CT) for staging of pancreatic cancer compared to non-CE PET/CT.

Method and materials

Between April 2006 and November 2009, a total of 95 patients (age range, 36–83 years [mean age, 67]) with primary pancreatic cancer underwent ¹⁸F-FDG PET/CT examinations. Diagnostic accuracy was compared between non-CE PET/CT and CE PET/CT. Images were analyzed visually and quantitatively by two blinded reviewers. Reference standard was histological examination in 48 patients (51%) and/or confirmation of an obvious progression in number and/or size of the lesions on follow-up CT examinations in 47 patients (49%).

Results

For T-staging, invasion of duodenum (n = 20, 21%), mesentery (n = 12, 13%), and retroperitoneum (n = 13, 14%) was correctly diagnosed by both modalities. The ROC analyses revealed that the Az values of celiac artery (CA), common hepatic artery (CHA), splenic artery (SV), and superior mesenteric vein (SMV) invasion were significantly higher in the CE PET/CT group for both readers. Nodal metastasis was correctly diagnosed by CE PET/CT in 38 patients (88%) and by non-CE PET/CT in 45 patients (87%). Diagnostic accuracies of nodal metastasis in two modalities were similar. Using CE PET/CT, distant metastasis, scalene node metastasis, and peritoneal dissemination were correctly assigned in 39 patients (91%), while interpretation based on non-CE PET/CT revealed distant metastasis, scalene node metastasis, and peritoneal dissemination in 42 patients (81%). Diagnostic accuracy of distant metastasis, scalene node metastasis, and peritoneal dissemination with CE PET/CT was significantly higher than that of non-CE PET/CT (p < 0.05).

Conclusion

CE PET/CT allows a more precise assessment of distant metastasis, scalene node metastasis, and peritoneal dissemination in patients with pancreatic cancer.     

Comparison of whole-body PET/CT and PET/MRI in breast cancer patients: Lesion detection and quantitation of 18F-deoxyglucose uptake in lesions and in normal organ tissues

Purpose

To compare the performance of PET/MRI imaging using MR attenuation correction (MRAC) (DIXON-based 4-segment -map) in breast cancer patients with that of PET/CT using CT-based attenuation correction and to compare the quantification accuracy in lesions and in normal organ tissues.

Methods

A total of 36 patients underwent a whole-body PET/CT scan 1 h after injection and an average of 62 min later a second scan using a hybrid PET/MRI system. PET/MRI and PET/CT were compared visually by rating anatomic allocation and image contrast. Regional tracer uptake in lesions was quantified using volumes of interest, and maximal and mean standardized uptake values (SUVmax and SUVmean, respectively) were calculated. Metabolic tumor volume (MTV) of each lesion was computed on PET/MRI and PET/CT. Tracer uptake in normal organ tissue was assessed as SUVmax and SUVmean in liver, spleen, left ventricular myocardium, lung, and muscle.

Results

Overall 74 FDG positive lesions were visualized by both PET/CT and PET/MRI. No significant differences in anatomic allocation scores were found between PET/CT and PERT/MRI, while contrast score of lesions on PET/MRI was significantly higher. Both SUVmax and SUVmean of lesions were significantly higher on PET/MRI than on PET/CT, with strong correlations between PET/MRI and PET/CT data (ρ = 0.71–0.88). MTVs of all lesions were 4% lower on PET/MRI than on PET/CT, but no statistically significant difference was observed, and an excellent correlation between measurements of MTV with PET/MRI and PET/CT was found (ρ = 0.95–0.97; p < 0.0001). Both SUVmax and SUVmean were significantly lower by PET/MRI than by PET/CT for lung, liver and muscle, no significant difference was observed for spleen, while either SUVmax and SUVmean of myocardium were significantly higher by PET/MRI. High correlations were found between PET/MRI and PET/CT for both SUVmax and SUVmean of the left ventricular myocardium (ρ = 0.91; p < 0.0001), while moderate correlations were found for the other normal organ tissues (ρ = 0.36–0.61; p < 0.05).

Conclusions

PET/MRI showed equivalent performance in terms of qualitative lesion detection to PET/CT. Despite significant differences in tracer uptake quantification, due to either methodological and biological factors, PET/MRI and PET/CT measurements in lesions and normal organ tissues correlated well. This study demonstrates that integrated whole-body PET/MRI is feasible in a clinical setting with high quality and in a short examination time.