diff --git a/diffdrr/pose.py b/diffdrr/pose.py
index 482005c9..f8096417 100644
--- a/diffdrr/pose.py
+++ b/diffdrr/pose.py
@@ -8,6 +8,7 @@
 import torch
 
 from einops import rearrange
+from roma import is_orthonormal_matrix
 
 
 class RigidTransform(torch.nn.Module):
@@ -17,11 +18,12 @@ class RigidTransform(torch.nn.Module):
     inversion, and conversions to various representations of SE(3).
     """
 
-    def __init__(self, matrix):
+    def __init__(self, matrix, eps=1e-6):
         super().__init__()
         if matrix.dim() == 2:
             matrix = matrix.unsqueeze(0)
         self.register_buffer("matrix", matrix)
+        self.eps = eps
 
     def __len__(self):
         return len(self.matrix)
@@ -43,11 +45,14 @@ def translation(self):
         return self.matrix[..., :3, 3]
 
     def inverse(self):
-        R = self.matrix[..., :3, :3]
-        t = self.matrix[..., :3, 3]
-        Rinv = R.mT
-        tinv = -torch.einsum("bij, bj -> bi", Rinv, t)
-        matrix = make_matrix(Rinv, tinv)
+        if is_orthonormal_matrix(self.matrix[..., :3, :3], self.eps):
+            R = self.matrix[..., :3, :3]
+            t = self.matrix[..., :3, 3]
+            Rinv = R.mT
+            tinv = -torch.einsum("bij, bj -> bi", Rinv, t)
+            matrix = make_matrix(Rinv, tinv)
+        else:
+            matrix = self.matrix.inverse()
         return RigidTransform(matrix)
 
     def compose(self, T):
diff --git a/environment.yml b/environment.yml
index 89948b86..65fdecac 100644
--- a/environment.yml
+++ b/environment.yml
@@ -20,3 +20,5 @@ dependencies:
   - tqdm
   - pyvista>=0.45.0
   - vtk>9.4.0
+  - pip:
+    - roma
diff --git a/notebooks/api/06_pose.ipynb b/notebooks/api/06_pose.ipynb
index 4db67290..b565ea2e 100644
--- a/notebooks/api/06_pose.ipynb
+++ b/notebooks/api/06_pose.ipynb
@@ -92,6 +92,7 @@
     "import torch\n",
     "\n",
     "from einops import rearrange\n",
+    "from roma import is_orthonormal_matrix\n",
     "\n",
     "\n",
     "class RigidTransform(torch.nn.Module):\n",
@@ -101,11 +102,12 @@
     "    inversion, and conversions to various representations of SE(3).\n",
     "    \"\"\"\n",
     "\n",
-    "    def __init__(self, matrix):\n",
+    "    def __init__(self, matrix, eps=1e-6):\n",
     "        super().__init__()\n",
     "        if matrix.dim() == 2:\n",
     "            matrix = matrix.unsqueeze(0)\n",
     "        self.register_buffer(\"matrix\", matrix)\n",
+    "        self.eps = eps\n",
     "\n",
     "    def __len__(self):\n",
     "        return len(self.matrix)\n",
@@ -127,11 +129,14 @@
     "        return self.matrix[..., :3, 3]\n",
     "\n",
     "    def inverse(self):\n",
-    "        R = self.matrix[..., :3, :3]\n",
-    "        t = self.matrix[..., :3, 3]\n",
-    "        Rinv = R.mT\n",
-    "        tinv = -torch.einsum(\"bij, bj -> bi\", Rinv, t)\n",
-    "        matrix = make_matrix(Rinv, tinv)\n",
+    "        if is_orthonormal_matrix(self.matrix[..., :3, :3], self.eps):\n",
+    "            R = self.matrix[..., :3, :3]\n",
+    "            t = self.matrix[..., :3, 3]\n",
+    "            Rinv = R.mT\n",
+    "            tinv = -torch.einsum(\"bij, bj -> bi\", Rinv, t)\n",
+    "            matrix = make_matrix(Rinv, tinv)\n",
+    "        else:\n",
+    "            matrix = self.matrix.inverse()\n",
     "        return RigidTransform(matrix)\n",
     "\n",
     "    def compose(self, T):\n",
diff --git a/settings.ini b/settings.ini
index 66823fff..89fe1898 100644
--- a/settings.ini
+++ b/settings.ini
@@ -26,8 +26,8 @@ keywords = nbdev jupyter notebook python
 language = English
 status = 3
 user = eigenvivek
-requirements = matplotlib seaborn tqdm imageio fastcore 'pyvista[all]' einops torchvision scipy torchio timm numpy kornia
-pip_requirements = torch
+requirements = matplotlib seaborn tqdm imageio fastcore 'pyvista[all]' einops torchvision scipy torchio timm numpy kornia roma
+pip_requirements = torch roma
 conda_requirements = pytorch
 dev_requirements = nbdev black flake8 ipykernel ipywidgets jupyterlab jupyterlab_execute_time jupyterlab-code-formatter isort
 readme_nb = index.ipynb