涙腺部MRI計測による悪性リンパ腫とIgG4関連疾患の鑑別

Differentiation of malignant lymphoma and IgG4-related disease based on by MRI measurements

要約　目的：悪性リンパ腫（ML）とIgG4関連疾患（IgG4RD）の鑑別における涙腺部MRI計測の有用性について検討する。

対象と方法：2016年10月〜2021年11月に日本医科大学付属病院眼科外来を初診し，涙腺生検で診断が確定した8例（ML 3例，IgG4RD 5例）を後ろ向きに調査した。術前MRI T1強調画像中，涙腺が最大に描出された断面を用い，眼球を中心に，冠状断では上側を0度，耳側を90度とし，軸位断では前側を0度，耳側を90度として眼窩部涙腺の範囲および中心角度を計測し，涙腺の範囲指数（冠状断と軸位断の涙腺範囲を乗算値），涙腺の左右差指数を算出して，t検定を用いて疾患別に比較した。

結果：涙腺範囲は，冠状断・軸位断ともにML（冠状断 平均177.2度，軸位断 平均154.0度）がIgG4RD（冠状断 平均109.8度，軸位断 平均116.4度）に比べて有意に大きかった。涙腺の範囲指数はMLがIgG4RDに比べて有意に大きかった。左右差指数は，ML（冠状断0.52，軸位断0.58）がIgG4RD（冠状断0.90　軸位断0.85）に比べて左右差が大きかった。

結論：MLはIgG4RDに比べて涙腺は大きく左右差を生じやすい。涙腺部のMRI計測は両者の鑑別に有用である。

Abstract　Purpose：In this study, we investigated the usefulness of lacrimal magnetic resonance imaging（MRI）in differentiating between malignant lymphoma（ML）and IgG4-related disease（IgG4RD）.

Methods：Eight patients with ML（three patients）and IgG4（five patients）whose diagnoses were confirmed by lacrimal gland biopsy, who first visited Nippon Medical School Hospital between October 2016 and November 2021, were reviewed retrospectively. On the preoperative MRI T1-weighted image, the range and central angle of the orbital lacrimal gland were measured based on the cross-section with the lacrimal gland maximally depicted, centered on the eyeball, with the upper side at 0° on the upper side at 90° and the anterior side at 0° on the axial section and 90° on the anterior side in the axial section. These values were compared by disease using the t-test. In addition, the “range index”, a value obtained by multiplying the lacrimal gland range of the coronal and axial slices and “lateral difference index”, the ratio of the right and left lacrimal gland range on the coronal and axial slices, were also calculated and compared by disease using the t-test.

Results：ML（mean coronal section：177.2°, mean axial section：154.0°）was significantly larger in the lacrimal region of the lacrimal gland（mean coronary section：109.8°, mean axial section：116.4°）. The range index of the ML lacrimal gland was significantly greater than that of IgG4RD. The left-right difference index was greater in ML（coronal cross section 0.52, axial cross section 0.58）than in IgG4RD（coronal cross section 0.90, axial cross section 0.85）.

Conclusion：In ML, the lacrimal gland is more likely to cause a left-right difference than that in IgG4RD. MRI measurement of the lacrimal gland is useful for differentiating between ML and IgG4RD.