diff --git a/sybil/model.py b/sybil/model.py
index 10fb857..c6899ac 100644
--- a/sybil/model.py
+++ b/sybil/model.py
@@ -227,8 +227,6 @@ def _calibrate(self, scores: np.ndarray) -> np.ndarray:
 
         Parameters
         ----------
-        calibrator: Optional[dict]
-            Dictionary of sklearn.calibration.CalibratedClassifierCV for each year, otherwise None.
         scores: np.ndarray
             risk scores as numpy array
 
diff --git a/sybil/serie.py b/sybil/serie.py
index 6151313..e159b2b 100644
--- a/sybil/serie.py
+++ b/sybil/serie.py
@@ -1,3 +1,4 @@
+import functools
 from typing import List, Optional, NamedTuple, Literal
 from argparse import Namespace
 
@@ -137,6 +138,7 @@ def get_raw_images(self) -> List[np.ndarray]:
         images = [i["input"] for i in input_dicts]
         return images
 
+    @functools.cache
     def get_volume(self) -> torch.Tensor:
         """
         Load loaded 3D CT volume