further improvements

atlas/models.py

@@ -392,6 +392,7 @@ def extract_image_dicom_json_from_ds(ds, url, image_index):
             else:
                 d[key] = val
 
+    # Is it worth trying on fake dicom tags?.....
     if d == {}:
         d["SOPInstanceUID"] = f"1.2.840.1111.{image_index}"
         d["SeriesInstanceUID"] = f"1.2.840.1112.1"
@@ -402,7 +403,7 @@ def extract_image_dicom_json_from_ds(ds, url, image_index):
 class SeriesImage(SeriesImageBase):
     image = models.FileField(upload_to=image_directory_path)
     series = models.ForeignKey(
-        "Series", related_name="images", on_delete=models.SET_NULL, null=True
+        "Series", related_name="images", on_delete=models.CASCADE, null=True
     )
 
     def get_dicom_data(self):