Diffusion-weighted MRI in a liver protocol: Its role in focal lesion detection

Abstract

AIM:To evaluate the role of diffusion-weighted imaging (�WI) in the detection of focal liver lesions (FLLs), using a conventional magnetic resonance imaging (MRI) protocol. METHODS:Fifty-two patients (22 males, average age 55.6 years, range: 25-82 years), studied using a 1.5 Tesla magnetic resonance scanner, were retrospectively analyzed; detection of FLLs was evaluated by considering the number of lesions observed with the following sequences: (1) respiratory-triggered diffusion-weighted single-shot echo-planar (�W SS-EP) sequences; (2) fat-suppressed fast spin-echo (fs-FSE) T2 weighted sequences; (3) steady-state free precession (SSFP) images; and (4) dynamic triphasic gadolinium-enhanced images, acquired with three-dimensional fast spoiled gradient-echo (3� FSPGR). Two radiologists independently reviewed the images: they were blinded to their respective reports. �W SS-EP sequences were compared to fs-FSE, SSFP and dynamic gadolinium-enhanced acquisitions using a t -test. Pairs were compared for the detection of: (1) all FLLs; (2) benign FLLs; (3) malignant FLLs; (4) metastases; and (5) hepatocellular carcinoma (HCC). RESULTS:Interobserver agreement was very good (weighted k = 0.926, CI = 0.880-0.971); on the consensus reading, 277 FLLs were detected. In the comparison with fs-FSE, DW SS-EP sequences had a significantly higher score in the detection of all FLLs, benign FLLs, malignant FLLs and metastases; no statistical difference was observed in the detection of hepatocellular carcinoma (HCCs). In the comparison with SSFP sequences, DW SS-EP had significantly higher scores (P < 0.05) in the detection of all lesions, benign lesions, malignant lesions, metastases and HCC. All FLLs were better detected by dynamic 3� FSGR enhanced acquisition, with P = 0.0023 for reader 1 and P = 0.0086 for reader 2 in the comparison with �W SS-EP sequences; with reference to benign FLLs, �W SS-EP showed lower values than 3� FSPGR enhanced acquisition (P < 0.05). No statistical differences were observed in the detection of malignant lesions and metastases; considering HCCs, a very slight difference was reported by reader 1 (P = 0.049), whereas no difference was found by reader 2 (P = 0.06). CONCLUSION:In lesion detection, �WI had higher scores than T2 sequences; considering malignant FLLs, no statistical difference was observed between �WI and dynamic gadolinium images.

Technical advancements and protocol optimization of diffusion-weighted imaging (DWI) in liver

“…Based on a long gradient echo train, the EPI sequence is inherently sensitivity to B0 inhomogeneity or magnetic susceptibility artifacts caused by tissue and air interface in the abdominal region, especially at higher field such as 3T [3,43]. The most effective way to minimize such artifact is by reducing the echo train length in EPI.…”

“…For the detection of focal liver lesions, DWI performs better than T2 weighted sequences but is generally inferior to T1 weighted dynamic gadolinium enhanced (DCE) images [3,[14][15][16]. Therefore, DWI can be complementary to standard MR protocol for imaging focal liver lesion, especially for patients who has renal dysfunction or other contraindications to gadolinium based contrast agents.…”

“…The ability to probe tissue microstructure makes DWI a powerful tool in clinical diagnosis of abdominal diseases and differentiation of different types of lesions. In last few years, DWI has become of routine part of abdominal MRI [3].…”

Extra-Neuroradiologic Applications of Diffusion-Weighted Imaging in Pediatric Patients: Review

“…fokal karaciğer lezyonlarının MRG ile saptanması üzerinde yaptıkları bir çalışmada, bütün fokal karaciğer lezyonları incelendiğinde DAG'lerin yağ baskılı T2 ağırlıklı konvansiyonel sekanstan istatistiksel olarak anlamlı düzeyde daha iyi lezyon tespiti yaptığı ortaya konulmuştur. 19 Yalnızca hepatoselüler kanser olgularında iki yöntemin lezyon saptama konusunda anlamlı düzeyde bir farklılığı göze çarpmamıştır. DAG bütün lezyonları "steadystate free precession (SSFP)" imajlardan daha iyi saptamıştır.…”

“…Bütün fokal karaciğer lezyonlarına bir arada bakıldığında dinamik kontrastlı üç boyutlu (3B) görüntülerin DAG'lerden daha iyi lezyon tespiti yaptığı, ancak malign fokal karaciğer lezyonlarında ve metastazlarda DAG ile kontrastlı 3B dinamik görüntüler arasında lezyonun saptanması açısından istatistiksel olarak anlamlı düzeyde bir farklılığın bulunmadığı rapor edilmiştir. 19 Yu ve ark., yaptıkları çalışmada DAG ile özellikle 1 cm'nin altındaki lezyonlarda kontrastlı dinamik incelemelere göre daha fazla sayıda lezyonun saptandığını, ancak 1 cm'nin üzerindeki lezyonlarda ise iki yöntem arasında istatistiksel olarak anlamlı düzeyde bir farklılık olmadığını bildirmiş-lerdir. 20 Çocukluk çağı nöroblastomlarının değerlendi-rilmesinde DAG ile başta T2 ağırlıklı MRG sekansı olmak üzere diğer MRG sekanslarının karşılaştırıl-masında DAG'nin tümörü saptamada, sınırlarının ortaya konulmasında daha üstün olduğu rapor edilmiştir.…”