Korean J Radiol.  2018 Feb;19(1):40-46. 10.3348/kjr.2018.19.1.40.

Diffusion-Weighted MRI for the Initial Viability Evaluation of Parasites in Hepatic Alveolar Echinococcosis: Comparison with Positron Emission Tomography

• Zheng J
• Wang J
• Zhao J
• Meng X

• KMID: 2425107
• DOI: http://doi.org/10.3348/kjr.2018.19.1.40

Abstract

OBJECTIVE
More than 70% of hepatic alveolar echinococcosis (HAE) are inoperable. Thus, long-term, or even life-long, pharmacological treatment with benzimidazoles is necessary. For effective treatment, it is of great importance to employ imaging techniques to detect and monitor the non-resectable parasitic viability. Therefore, this study aimed to evaluate diffusion-weighted imaging (DWI) in assessing the viability of HAE in comparison to 18-fluoro-deoxyglucose (18F-FDG) positron emission tomography, combined with computed tomography (PET/CT).
MATERIALS AND METHODS
Positron emission tomography, computed tomography and DWI (b-values: 0, 800 s/mm2) were retrospectively analysed in eight patients with clinically-verified HAE to, generate the apparent diffusion coefficient (ADC) map. The activity of HAE lesions in both techniques were determined independently by two radiologists according to the following standard: (+), marked focally or perilesionally increased FDG uptake/high signal intensity; (−), a hepatic defect without FDG uptake/no high signal intensity. Every lesion's maximum standardized uptake value (SUV(max)) on the PET/CT images and mean ADC values on the parametric ADC maps were measured respectively. Results of PET/CT and DWI were compared on a per-lesion-basis. Pearson's correlation coefficient was assessed for statistical analysis.
RESULTS
A total of 14 HAE lesions were detected. Eight lesions (diameter 3-15 cm) showed perilesional hyper-signal intensity on DWI. This was visualised on PET/CT as increased FDG uptake. They mainly existed in the lesion's border with normal liver parenchyma. Five lesions (diameter < 2 cm) were detected as nodular hyperintensity on DWI and a "˜hot spot' on PET/CT in the same distribution. One patient, who had received oral drug therapy for three years showed significantly decreased perilesional hyperintensity on the DWI and a hepatic defect without any FDG uptake on PET/CT. Pearson's correlation coefficient indicated a significant inverse correlation of the ADC and the SUV(max) (r = −0.67, p < 0.001).
CONCLUSION
Diffusion-weighted imaging is capable of offering information on visually detecting the HAE lesions' viability and may be useful for routine application in the initial diagnosis of HAE.

Keyword

Echinococcosis; Liver; MRI; Diffusion-weighted imaging; PET/CT

MeSH Terms

Benzimidazoles
Diagnosis
Diffusion
Drug Therapy
Echinococcosis
Echinococcosis, Hepatic*
Electrons*
Humans
Liver
Magnetic Resonance Imaging*
Parasites*
Positron-Emission Tomography and Computed Tomography
Positron-Emission Tomography*
Retrospective Studies
Benzimidazoles

Figure

• 

  Fig. 1 37-year-old female with HAE.Axial T1WI (A) and T2WI (B), and fat-suppressed DWI (C) (b-value = 800 s/mm2) SS-EPI MRI images depict HAE lesion (arrows) involving inferior vena cava. Lesion consists of multiple small round cysts with solid component (A, B). Relative to surrounding liver parenchyma, lesion remains hypointense, while it has hyperintense ring (at lesion's border with normal liver parenchyma) on high b-value DWI (C), which cannot be detected on T1WI or T2WI. PET/CT (D) demonstrated lesion with internal filling defect and peripheral increased FDG uptake, with same distribution as on DWI. DWI = diffusion-weighted imaging, FDG = fluoro-deoxyglucose, HAE = hepatic alveolar echinococcosis, PET-CT = positron emission tomography, combined with computed tomography, T1WI = T1-weighted images, T2WI = T2-weighted images

• 

  Fig. 2 50-year-old man suffering from HAE and CE.(A) On MR-T2WI, HAE lesions are displayed as multiple high-signal-intensity nodular lesions (arrows) in right lobe of liver while CE is oval cystic lesion within cyst wall contained daughter cysts in caudate lobe (arrowheads). Note also, there is low-signal-intensity nodule in splenic hilum, which also is degenerated CE lesion (open arrow). HAE lesions were detected as nodular hyper-signal intensity in DWI (B) and “hot spot” in PET/CT in same distribution (C), CE lesions presented with low-signal intensity on DWI (B) and non-activity on PET/CT (C). CE = cystic echinococcosis

• 

  Fig. 3 Comparison of DWI images obtained from 43-year-old male patient with HAE before and after oral drug therapy for three years.A. In initial diagnosis, DWI demonstrated perilesional high-signal intensity existing in lesion's border with normal liver parenchyma (arrows). B. After oral drug therapy for three years, DWI showed reduced but persisted perilesional high-signal intensity (arrows). C, D. Post-therapy PET and PET/CT showed hepatic defect without any FDG uptake.

• 

  Fig. 4 Scatter plots of SUVmax and ADC including regression line for 14 HAE lesions in 8 patients.There was significant inverse correlation between ADC and SUVmax (Pearson's correlation coefficient, r = −0.67, p < 0.001). ADC = apparent diffusion coefficient, SUVmax = maximum standardized uptake value

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