MRI Chest Parameters Used in the Assessment of Tumor Response Post Microwave Ablation of Pulmonary Metastases

Zielsetzung:

To determine the value contrast enhanced (CE-MRI) follow-up in the assessment of tumor response of microwave (MW) ablated pulmonary metastases by correlating the results with CE-CT.

Material und Methodik:

This prospective study included 130 ablation sessions for pulmonary metastases in 80 patients. CE-MRI Chest scanning was performed 1week before the ablation and at 24hours, 3, 6, 9 and12months post ablation. Thin section CT Volumetric measurement of the lesions was performed at the same time periods as a second parameter for comparison. The lesion MRI enhancement intensity in each study was estimated, and the ratio to the paraspinal muscle enhancement intensity at the same level was measured (Lesion Muscle Signal (LMS ratio). The correlations between post ablation follow-up CT volume of tumors and CE-MRI LMS ratio at the follow-up periods were assessed.

Ergebnisse:

The preablation tumor volumes range: 0.30 – 6.1 cm (mean: 1.5 cm³, SD:1.3). LMS ratio < 1was associated with post ablation reduction of tumor volume (denoting scaring),while LMS ratio > 1 were noted in: preablation due to high contrast enhancement of the tumor,in24h post ablation due to the inflammatory response associated with the thermal ablation and due to tumor residue or progress. Weak correlation was detected between the LMS-ratios and CT-volumetric changes in 24h post ablation. Strong correlation between the LMS ratios was estimated between the follow up periods of 3 months (SpearmanR: 0.62, p = 0.0021), 6 months (SpearmanR: 0.66, p = 0.001), 9 months (SpearmanR: 0.61, p < 0.001) and 12 months (Spearman R: 0.7, p < 0.00001).

Schlussfolgerungen:

CE-MRI follow up of the MW ablated lung tumors can be used effectively to assess the tumor response to ablation using LMS ratio as a parameter of assessment.

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