Delineation and agreement of FET PET biological volumes in glioblastoma: results of the nuclear medicine credentialing program from the prospective, multi-centre trial evaluating FET PET In Glioblastoma (FIG) study-TROG 18.06.

PURPOSE: The O-(2-[18F]-fluoroethyl)-L-tyrosine (FET) PET in Glioblastoma (FIG) trial is an Australian prospective, multi-centre study evaluating FET PET for glioblastoma patient management. FET PET imaging timepoints are pre-chemoradiotherapy (FET1), 1-month post-chemoradiotherapy (FET2), and at suspected progression (FET3). Before participant recruitment, site nuclear medicine physicians (NMPs) underwent credentialing of FET PET delineation and image interpretation. METHODS: Sites were required to complete contouring and dynamic analysis by ≥ 2 NMPs on benchmarking cases (n = 6) assessing biological tumour volume (BTV) delineation (3 × FET1) and image interpretation (3 × FET3). Data was reviewed by experts and violations noted. BTV definition includes tumour-to-background ratio (TBR) threshold of 1.6 with crescent-shaped background contour in the contralateral normal brain. Recurrence/pseudoprogression interpretation (FET3) required assessment of maximum TBR (TBRmax), dynamic analysis (time activity curve [TAC] type, time to peak), and qualitative assessment. Intraclass correlation coefficient (ICC) assessed volume agreement, coefficient of variation (CoV) compared maximum/mean TBR (TBRmax/TBRmean) across cases, and pairwise analysis assessed spatial (Dice similarity coefficient [DSC]) and boundary agreement (Hausdorff distance [HD], mean absolute surface distance [MASD]). RESULTS: Data was accrued from 21 NMPs (10 centres, n ≥ 2 each) and 20 underwent review. The initial pass rate was 93/119 (78.2%) and 27/30 requested resubmissions were completed. Violations were found in 25/72 (34.7%; 13/12 minor/major) of FET1 and 22/74 (29.7%; 14/8 minor/major) of FET3 reports. The primary reasons for resubmission were as follows: BTV over-contour (15/30, 50.0%), background placement (8/30, 26.7%), TAC classification (9/30, 30.0%), and image interpretation (7/30, 23.3%). CoV median and range for BTV, TBRmax, and TBRmean were 21.53% (12.00-30.10%), 5.89% (5.01-6.68%), and 5.01% (3.37-6.34%), respectively. BTV agreement was moderate to excellent (ICC = 0.82; 95% CI, 0.63-0.97) with good spatial (DSC = 0.84 ± 0.09) and boundary (HD = 15.78 ± 8.30 mm; MASD = 1.47 ± 1.36 mm) agreement. CONCLUSION: The FIG study credentialing program has increased expertise across study sites. TBRmax and TBRmean were robust, with considerable variability in BTV delineation and image interpretation observed.

The clinical challenge of relapsed diffuse large B-cell lymphoma with disseminated infection.

Fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) is an essential tool in the diagnosis, staging, and assessment of treatment response in the management of lymphoma. Diffuse large B-cell lymphoma (DLBCL) represents the most common type of non-Hodgkin lymphoma (NHL). Although the curability rate is high, there are around 40% of patients exhibit relapse and present a therapeutic challenge. As important as 18F-FDG PET/CT is in the management of DLBCL, there are several limitations and potential pitfalls in assessing treatment response or relapse in patients who are also affected by active infectious disease concurrently. Hence, the knowledge of variable physiologic and altered physiologic uptake is of incredible essence when it comes to interpreting a complex scan. In this case report, we present a patient with relapsed DLBCL complicated by disseminated infection.

Vertebral Body Osteonecrosis Mimicking Malignant Disease on 18F-FDG PET.

ABSTRACT: We report a case of vertebral osteonecrosis after chemotherapy in a 24-year-old man with non-Hodgkin lymphoma, with transient avidity on 18F-FDG PET initially misinterpreted as recurrent extranodal disease. The patient demonstrated a partial metabolic response on midtreatment restaging PET; however, posttreatment PET showed an increase in uptake in T4 and T5 vertebrae, interpreted as recurrent vertebral disease. Repeat PET performed 9 days later showed resolution of thoracic vertebral uptake without interval treatment. On follow-up PET study, thoracic vertebrae demonstrated photopenia with sclerosis on CT, concerning for osteonecrosis. MRI features were concordant with this diagnosis.

Discrepancies between positron emission tomography/magnetic resonance imaging and positron emission tomography/computed tomography in a cohort of oncological patients.

INTRODUCTION: This study aims to evaluate discrepant findings between positron emission tomography/magnetic resonance imaging (PET/MRI) and positron emission tomography/computed tomography (PET/CT) in a cohort of oncological patients and to undertake a phantom study to assess the potential for extended PET acquisitions to lead to false-positive findings on PET/MRI. METHODS: Discrepant findings from a series of 106 patients undergoing same-day 18 F-fluorodeoxyglucose (FDG)-PET/CT and PET/MRI were reviewed. Phantom studies explored the potential for PET acquisition time to contribute to discrepancy. RESULTS: There were 14 discrepant cases, 5 (35.7%) of which related to PET/MRI acquisitions that had been extended to 10 min. Three of these five cases proved to be falsely positive. Phantom studies showed greater contrast recovery and signal to noise ratio for 10-min PET/MRI acquisitions compared to 2-min acquisitions using PET/CT. There were no discrepancies when PET/CT showed disseminated disease (P = 0.036). CONCLUSIONS: Extended PET/MRI acquisitions used to accommodate multiple MRI sequences may be associated with false-positive findings compared to PET/CT. PET/MRI is more likely to have incremental value when the prior probability for disseminated disease is low.

Imaging and Right Ventricular Pacing Lead Position: A Comparison of CT, MRI, and Echocardiography.

BACKGROUND: Right ventricular nonapical (RVNA) pacing may reduce the risk of heart failure. Fluoroscopy is the standard approach to determine lead tip position, but is inaccurate. We compared cardiac computed tomography (CT), magnetic resonance imaging (MRI), two-dimensional and three-dimensional transthoracic echocardiography (TTE), and chest x-ray (CXR) to assess which provides the optimal assessment of right ventricular (RV) lead tip position. METHODS: Eighteen patients with MRI-conditional pacemakers (10 RVNA and eight apical [RVA] leads) underwent contrast CT, MRI, TTE, and a standard postimplant posteroanterior and lateral CXR. To compare images, the RV was arbitrarily partitioned into three long-axis segments (right ventricular outflow tract, middle, and apex), and two short-axis segments (septal and nonseptal). Agreement between modalities was assessed. RESULTS: RV lead tip position was identified in all patients on CT, TTE, and CXR, but was not identified in seven (39%) patients on MRI due to device-related artifact. Of 10 leads deemed to be nonapical/septal during implant, 70% were identified as nonapical on CXR, 60% on CT, 60% on MRI, and 80% on TTE. On CT imaging only 10% were truly septal, 20% on MRI, 30% on CXR, and 80% on TTE. Agreement was better between modalities when assessing position of the designated RVA leads. CONCLUSION: During implant leads intended for the septum are not confirmed as such on subsequent imaging, and marked heterogeneity is apparent between modalities. MRI is limited by artifact, and discrepancy exists between TTE and CT in identifying septal lead position. CT gave the clearest definition of lead tip position.

Evidence-based medicine and clinical fluorodeoxyglucose PET/MRI in oncology.

Positron Emission Tomography/Magnetic Resonance Imaging (PET/MRI) is a hybrid of two technologies each with its own evidence for clinical effectiveness. This article amalgamates evidence for clinical effectiveness of fluorodeoxyglucose (FDG) PET/CT and MRI as separate modalities with current evidence for hybrid PET/MRI and considers whether such an approach might provide a stronger case for the clinical use of PET/MRI at an earlier stage.Because links between diagnostic accuracy and health outcomes have already been established for FDG-PET/CT in the investigation of suspected residual or recurrent malignancies, evidence showing improved diagnostic performance and therapeutic impact from the use of PET/MRI as an alternative would imply clinical effectiveness of this modality for this application. A meta-analysis of studies comparing FDG-PET/CT to MRI in patients with suspected residual disease or recurrence of tumours indicates complementary roles for these modalities. PET demonstrates greater sensitivity for recurrence within lymph nodes whereas MRI is more effective that PET/CT in the detection of skeletal and hepatic recurrence. A review of studies assessing therapeutic impact of PET/MRI suggests a greater likelihood for change in clinical management when PET/MRI is used for assessment of suspected residual or recurrent disease rather than tumour staging.Supplementing the evidence-base for FDG-PET/MRI with studies that compare the components of this hybrid technology deployed separately indicates that FDG-PET/MRI is likely to be clinical effective for the investigation of patients with a range of suspected residual or recurrent cancers. This indication should therefore be prioritised for further health technology assessment.

Peri-aortofemoral prosthesis urinoma: diagnosis by Tc-99m MAG3 SPECT/CT and differentiation from simultaneous hepatobiliary excretion.

A 75-year-old woman developed renal failure 1 week after elective aortobifemoral bypass surgery. Postoperative computed tomography showed right hydronephrosis. Tc-99m mercaptoacetyltriglycerine (MAG3) scintigraphy was performed to exclude renal obstruction or acute tubular necrosis. Planar MAG3 images demonstrated right hydronephrosis and unusual accumulation of tracer between the kidneys and the right upper quadrant of abdomen, with new areas of activity in the right lower quadrant on delayed images. SPECT/CT demonstrated MAG3 activity within fluid collections adjacent to the aorta and right iliac/inguinal arteries, consistent with a urine leak. The right upper quadrant activity represented MAG3 accumulation within the gallbladder.

Prediction of long-term renal transplant allograft function from day 3 post-transplant Tc-99m MAG3 scintigraphy.

PURPOSE: Serum creatinine (sCr) levels of >1.5mg/dL or >130 ummol/L at 1 year after renal transplantation were strongly predictive of long-term allograft survival. A Tc-99m MAG3 study with a Hilson's perfusion index (PI) is routinely performed on day 3 post-transplantation at Princess Alexandra Hospital, Australia. The predictive power of day 3 post-transplantation Hilson's PI for long-term sCr levels; and early sCr levels (at 1 or 3 months) to predict sCr levels at 12 months post-transplantation were studied. MATERIALS AND METHODS: One hundred eight patients receiving renal transplantation from April 2001 to March 2002 were retrospectively analyzed. sCr levels at 1, 3, and12 months, and 5 years after renal transplantation were recorded and compared with the day 3 post-transplantation Hilson's PI. RESULTS: Accuracy of 72% to 74%, and 90% sensitivity were recorded between Hilson's PIs and sCr levels up to 12-month post-transplantation. Spearman's correlation shows a significant relationship (R = 0.32-0.39, P = 0.00002-0.003). However, the association seems to have low specificity. A significant relationship was found for early sCr levels (at 1 or 3 months) to predict sCr levels at 12-month post-transplantation, with a Spearman correlation coefficient (R = 0.68-0.85, P < 0.000001). CONCLUSION: There is a strong relationship between the day 3 Hilson's PIs and serial sCr levels post-transplantation, and between the early sCr levels (1 and 3 months), and the 12 months sCr levels post-transplantation. A composite index integrating these 2 markers to predict long-term renal allograft survival remains to be investigated.