diff --git a/app/api/crud.py b/app/api/crud.py
index 6c78412..643ad90 100644
--- a/app/api/crud.py
+++ b/app/api/crud.py
@@ -94,7 +94,7 @@ async def get(
                     dataset=dataset,
                     dataset_name=dataset_name,
                     num_matching_subjects=group["sub_id"].nunique(),
-                    subject_file_paths=list(group["file_path"]),
+                    subject_file_paths=list(group["file_path"].dropna()),
                     image_modals=list(group["image_modal"].unique()),
                 )
             )
diff --git a/app/api/utility.py b/app/api/utility.py
index 15eb481..2c9f6fd 100644
--- a/app/api/utility.py
+++ b/app/api/utility.py
@@ -120,7 +120,7 @@ def create_query(
     SELECT ?dataset ?dataset_name ?sub_id ?file_path ?image_modal
     WHERE {{
     SELECT DISTINCT ?dataset ?dataset_name ?subject ?sub_id ?age ?sex
-    ?diagnosis ?num_sessions ?assessment ?image_modal ?file_path
+    ?diagnosis ?subject_group ?num_sessions ?assessment ?image_modal ?file_path
     WHERE {{
     ?dataset a bg:Dataset;
              bg:label ?dataset_name;
@@ -128,14 +128,27 @@ def create_query(
 
     ?subject a bg:Subject;
             bg:label ?sub_id;
-            bg:age ?age;
-            bg:sex ?sex;
-            bg:diagnosis ?diagnosis;
             bg:hasSession ?session;
-            bg:assessment ?assessment;
             bg:hasSession/bg:hasAcquisition/bg:hasContrastType ?image_modal.
 
-    ?session bg:filePath ?file_path.
+    OPTIONAL {{
+        ?session bg:filePath ?file_path.
+    }}
+    OPTIONAL {{
+        ?subject bg:age ?age.
+    }}
+    OPTIONAL {{
+        ?subject bg:sex ?sex.
+    }}
+    OPTIONAL {{
+        ?subject bg:diagnosis ?diagnosis.
+    }}
+    OPTIONAL {{
+        ?subject bg:isSubjectGroup ?subject_group.
+    }}
+    OPTIONAL {{
+        ?subject bg:assessment ?assessment.
+    }}
 
     {{
     SELECT ?subject (count(distinct ?session) as ?num_sessions)
diff --git a/app/main.py b/app/main.py
index 81af747..1499fe2 100644
--- a/app/main.py
+++ b/app/main.py
@@ -4,10 +4,11 @@
 
 import uvicorn
 from fastapi import FastAPI
+from fastapi.responses import ORJSONResponse
 
 from .api.routers import query
 
-app = FastAPI()
+app = FastAPI(default_response_class=ORJSONResponse)
 
 
 @app.on_event("startup")
diff --git a/requirements.txt b/requirements.txt
index 357c0a7..c8c8cd0 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -15,6 +15,7 @@ identify==2.5.9
 idna==3.4
 iniconfig==1.1.1
 nodeenv==1.7.0
+orjson==3.8.6
 packaging==21.3
 pandas==1.5.2
 platformdirs==2.5.4