MR Diagnosis of Bone Metastases at 1.5 T and 3 T: Can STIR Imaging Be Omitted?

Abstract

Objective: To date, no prospective comparative study of the diagnostic value of STIR versus T1-weighted (T1w) sequences at both 1.5 T and 3 T has been performed with special focus on the detectability of bone metastases.

Materials and Methods: 212 oncological patients had a whole-body MRI at 1.5 T and/or at 3 T. The standard protocol comprised STIR and T1w sequences. All patients who showed typical signs of bone metastases were included in the study. Evaluation of the images was performed by the calculation of the number of metastases by three independent readers and by visual assessment on a 4-point scale.

Results: 86 patients fulfilled the inclusion criteria. The total number of metastases was significantly higher on T1w than on STIR images at both field strengths (p < 0.05). T1w revealed a sensitivity of 99.72 % (3 T) and 100.00 % (1.5 T) versus STIR with 70.99 % (3 T) and 79.34 % (1.5 T). In 53 % (38/72) of all patients, STIR detected fewer bone metastases in comparison with T1w at 3 T. At 1.5 T, STIR showed inferior results in 37.5 % (18/48) of all patients. Qualitative analysis indicated a significantly better lesion conspicuity, lesion delineation and an improved image quality on T1w compared to STIR imaging at both field strengths (p < 0.05) with similar results for T1w at 1.5 T and 3 T, but inferior results for STIR especially at 3 T.

Conclusion: The whole-body MRI protocol for the detection of bone metastases could safely be limited to the T1w sequence in adults, especially at 3 T. There is no need for an additional STIR sequence. These initial results will have a major impact on the department’s workflow if confirmed by larger studies as they will help reduce examination time and therefore save financial resources.

Key points:

• In a routine MR protocol, T1w imaging is sufficient for the detection of bone metastases.

• In case of differential diagnostic problems, other appropriate sequences can be added to the protocol.

• STIR is inferior to T1w in the detection of metastases, especially at 3 T.

Citation Format:

• Ohlmann-Knafo S., Tarnoki A. D., Tarnoki D. L. et al. MR Diagnosis of Bone Metastases at 1.5T and 3T: Can STIR Imaging Be Omitted?. Fortschr Röntgenstr 2015; 187: 924 – 932

Zusammenfassung

Ziel: Bislang gibt es keine prospektive Vergleichsstudie zum diagnostischen Stellenwert der STIR versus T1-gewichteten (T1w) Sequenz sowohl am 1,5 T als auch am 3 T MRT im Hinblick auf die Detektierbarkeit von Knochenmetastasen.

Material und Methoden: 212 onkologische Patienten erhielten eine Ganzkörper-MRT bei 1,5 T und/oder 3 T. Das Standardprotokoll umfasste STIR und T1w-Sequenzen. Alle Patienten, die typische Kriterien von Knochenmetastasen zeigten, wurden in die Studie aufgenommen. Die Bildevaluation erfolgte anhand der Berechnung der Anzahl von Knochenmetastasen durch drei unabhängige Reader und durch visuelle Beurteilung auf einer 4-Punkte-Skala.

Ergebnisse: 86 Patienten erfüllten die Einschlusskriterien. Die Gesamtanzahl der Metastasen war signifikant höher bei T1w als auf den STIR-Bildern bei beiden MRT-Feldstärken (p < 0,05). Die Sensitivität war bei T1w 99,72 % (3 T) und 100,00 % (1,5 T) versus bei STIR 70,99 % (3 T) und 79,34 % (1,5 T). In 53 % (38/72) aller Patienten detektierte die STIR weniger Metastasen im Vergleich zu T1w bei 3 T, bei 1,5 T waren es 37,5 % (18/48) aller Patienten. Die qualitative Analyse ergab eine signifikant bessere Läsionsnachweisbarkeit, Läsionsabgrenzbarkeit und eine verbesserte Bildqualität bei T1w im Vergleich zu STIR an beiden Feldstärken (p < 0,05). Hierbei zeigten sich ähnliche Resultate für T1w bei 1,5 T und 3 T, wohingegen die STIR insbesondere bei 3 T der T1w unterlegen war.

Schlussfolgerung: Besonders bei 3 T kann das Ganzkörper-MRT-Protokoll zur Detektion von Knochenmetastasen bei Erwachsenen auf die T1w-SE-Sequenz beschränkt werden. Eine zusätzliche STIR-Bildgebung ist nicht notwendig. Unsere Studie könnte einen erheblichen Einfluss auf den Workflow einer Abteilung haben, sofern sich die Resultate an einem größeren Patientenkollektiv bestätigen. Insbesondere könnten hierdurch Untersuchungszeiten und Untersuchungskosten reduziert werden.

Kernaussagen:

• Die T1w ist im MRT-Routineprotokoll zur Detektion von Knochenmetastasen ausreichend.

• Bei differentialdiagnostischen Unklarheiten können adäquate Zusatzsequenzen akquiriert werden.

• In der Metastasendetektion ist die STIR der T1w insbesondere bei 3 T deutlich unterlegen.

Key words

skeletal-axial - spine - MR imaging - metastases - technical aspects - staging

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