Comparison of Coregistration Accuracy of Pelvic Structures Between Sequential and Simultaneous Imaging During Hybrid PET/MRI in Patients with Bladder Cancer

Abstract

Purpose The aim of this study was to compare coregistration of the bladder wall, bladder masses, and pelvic lymph nodes between sequential and simultaneous PET and MRI acquisitions obtained during hybrid 18F-FDG PET/MRI performed using a diuresis protocol in bladder cancer patients. Methods Six bladder cancer patients underwent 18F-FDG hybrid PET/MRI, including IV Lasix administration and oral hydration, before imaging to achieve bladder clearance. Axial T2-weighted imaging (T2WI) was obtained approximately 40 minutes before PET (“sequential”) and concurrently with PET (“simultaneous”). Three-dimensional spatial coordinates of the bladder wall, bladder masses, and pelvic lymph nodes were recorded for PET and T2WI. Distances between these locations on PET and T2WI sequences were computed and used to compare in-plane (x-y plane) and through-plane (z-axis) misregistration relative to PET between T2WI acquisitions. Results The bladder increased in volume between T2WI acquisitions (sequential, 176 [139]mL; simultaneous, 255 [146]mL). Four patients exhibited a bladder mass, all with increased activity (SUV, 9.5–38.4). Seven pelvic lymph nodes in 4 patients showed increased activity (SUV, 2.2–9.9). The bladder wall exhibited substantially less misregistration relative to PET for simultaneous, compared with sequential, acquisitions in in-plane (2.8 [3.1]mm vs 7.4 [9.1]mm) and through-plane (1.7 [2.2]mm vs 5.7 [9.6]mm) dimensions. Bladder masses exhibited slightly decreased misregistration for simultaneous, compared with sequential, acquisitions in in-plane (2.2 [1.4]mm vs 2.6 [1.9]mm) and through-plane (0.0 [0.0]mm vs 0.3 [0.8]mm) dimensions. FDG-avid lymph nodes exhibited slightly decreased in-plane misregistration (1.1 [0.8]mm vs 2.5 [0.6]mm), although identical through-plane misregistration (4.0 [1.9]mm vs 4.0 [2.8]mm). Conclusions Using hybrid PET/MRI, simultaneous imaging substantially improved bladder wall coregistration and slightly improved coregistration of bladder masses and pelvic lymph nodes.

Current Status of Hybrid PET/MRI in Oncologic Imaging

“…An additional study of fluorocholine PET/MRI in patients awaiting radical prostatectomy observed excellent correlation between abnormalities on T2-weighted images and areas of increased uptake and higher accuracy for tumor using PET/MRI compared with MRI alone [64]. We have shown the ability to evaluate prostate cancer using graphic analysis with an image-derived arterial input function based on dynamically acquired PET data obtained immediately after nearly simultaneous injection of both PET and MRI contrast agents as part of a hybrid PET/MRI examination [65]. Our data suggested added potential of the dynamic PET metrics compared with traditional static PET metrics, such as SUV obtained at a delayed equilibrium time point after radiotracer injection.…”

“…6). Preliminary data indicate that simultaneous PET and MRI acquisitions from hybrid PET/MRI achieve substantially improved coregistration of the bladder wall and slightly improved coregistration of bladder masses and pelvic lymph nodes compared with sequential acquisitions [65]. This PET/MRI protocol is being investigated for purposes such as identification of recurrent bladder tumor after transurethral tumor resection as well as prediction and monitoring of response to neoadjuvant chemotherapy.…”

Daily Workflow and Protocol Optimization in Positron Emission Tomography/Magnetic Resonance Imaging Use

“…Benzer biçimde jinekolojik kanserlerde entegre FDG PET/MR görüntüleme lokal tümör yayılımının ve lenf nodu tutulumunun belirlenmesi için kullanışlı bir yöntemdir. MR'ın yüksek yumuşak doku rezolüsyonu ve fonksiyonel görüntüleme özellikleri overlerin, uterusun, prostatın ve mesanenin primer tümör özelliklerinin belirlenmesine ve peritoneal yayılımın araştırılmasına katkıda bulunur (27). Prostat kanserinin tanısında morfolojik (T2 ağırlıklı) ve fonksiyonel (difüzyon ağırlıklı, kontrastlı) multi-parametrik MR görüntülerinden yararlanılır (28).…”

Positron Emission Tomography/Magnetic Resonance Imaging Practices in Oncological Imaging

“…Entegre PET/MR sistemlerinde metabolik ve anatomik bilginin daha iyi registrasyonu, mesane duvarının, lezyonların ve pelvik lenf nodlarının değerlendirilmesinde yarar sağlamaktadır (124). Tüm vücut PET/MR görüntüleme, mesane kanserlerinde primer mesane tümörlerinin değerlendirilmesinin yanı sıra, aynı görüntüleme seansı içerisinde kemik ve yumuşak doku uzak metastaz varlığının araştırılmasında da sağladığı kombine metabolik-fonksiyonel-anatomik verilerle etkili olma potansiyeli taşımaktadır.…”