diff --git a/dap/algos/forcesend.py b/dap/algos/forcesend.py
index 73d19c2..1c243b4 100644
--- a/dap/algos/forcesend.py
+++ b/dap/algos/forcesend.py
@@ -4,30 +4,29 @@ from .mask import calc_mask_pixels
 from .thresh import threshold
 
 
-def calc_force_send(results, data, pixel_mask_pf, image, data_summed, n_aggregated_images):
+def calc_force_send(results, data, pixel_mask_pf, image, aggregator):
     force_send_visualisation = False
 
     if data.dtype == np.uint16:
-        return data, force_send_visualisation, data_summed, n_aggregated_images
+        return data, force_send_visualisation, aggregator
 
     apply_aggregation = results.get("apply_aggregation", False)
     apply_threshold   = results.get("apply_threshold", False)
 
     if not apply_aggregation:
-        data_summed = None
-        n_aggregated_images = 0
+        aggregator.reset()
 
     if not apply_aggregation and not apply_threshold:
         data = image
-        return data, force_send_visualisation, data_summed, n_aggregated_images
+        return data, force_send_visualisation, aggregator
 
     calc_apply_threshold(results, data) # changes data in place
 
-    data, force_send_visualisation, data_summed, n_aggregated_images = calc_apply_aggregation(results, data, data_summed, n_aggregated_images)
+    data, force_send_visualisation, aggregator = calc_apply_aggregation(results, data, aggregator)
 
     calc_mask_pixels(data, pixel_mask_pf) # changes data in place
 
-    return data, force_send_visualisation, data_summed, n_aggregated_images
+    return data, force_send_visualisation, aggregator
 
 
 
@@ -48,34 +47,29 @@ def calc_apply_threshold(results, data):
 
 
 
-def calc_apply_aggregation(results, data, data_summed, n_aggregated_images):
+def calc_apply_aggregation(results, data, aggregator):
     force_send_visualisation = False
 
     apply_aggregation = results.get("apply_aggregation", False)
     if not apply_aggregation:
-        return data, force_send_visualisation, data_summed, n_aggregated_images
+        return data, force_send_visualisation, aggregator
 
     if "aggregation_max" not in results:
-        return data, force_send_visualisation, data_summed, n_aggregated_images
+        return data, force_send_visualisation, aggregator
 
-    if data_summed is None:
-        data_summed = data.copy()
-        n_aggregated_images = 1
-    else:
-        data_summed += data
-        n_aggregated_images += 1
+    aggregator += data
 
-    data = data_summed
+    data = aggregator.data
+    n_aggregated_images = aggregator.counter
 
     results["aggregated_images"] = n_aggregated_images
     results["worker"] = 1 #TODO: keep this for backwards compatibility?
 
     if n_aggregated_images >= results["aggregation_max"]:
         force_send_visualisation = True
-        data_summed = None
-        n_aggregated_images = 0
+        aggregator.reset()
 
-    return data, force_send_visualisation, data_summed, n_aggregated_images
+    return data, force_send_visualisation, aggregator
 
 
 
diff --git a/dap/utils/__init__.py b/dap/utils/__init__.py
index 4474c56..45f8cbe 100644
--- a/dap/utils/__init__.py
+++ b/dap/utils/__init__.py
@@ -1,4 +1,5 @@
 
+from .aggregator import Aggregator
 from .bits import read_bit
 from .bufjson import BufferedJSON
 
diff --git a/dap/utils/aggregator.py b/dap/utils/aggregator.py
new file mode 100644
index 0000000..bd6d315
--- /dev/null
+++ b/dap/utils/aggregator.py
@@ -0,0 +1,26 @@
+
+class Aggregator:
+
+    def __init__(self):
+        self.reset()
+
+    def reset(self):
+        self.data = None
+        self.counter = 0
+
+    def add(self, item):
+        if self.data is None:
+            self.data = item.copy()
+            self.counter = 1
+        else:
+            self.data += item
+            self.counter += 1
+        return self
+
+    __iadd__ = add
+
+    def __repr__(self):
+        return f"{self.data!r} / {self.counter}"
+
+
+
diff --git a/dap/worker.py b/dap/worker.py
index 3919c33..9f8c9f1 100644
--- a/dap/worker.py
+++ b/dap/worker.py
@@ -4,7 +4,7 @@ from random import randint
 import numpy as np
 
 from algos import calc_apply_threshold, calc_force_send, calc_mask_pixels, calc_peakfinder_analysis, calc_radial_integration, calc_roi, calc_spi_analysis, JFData
-from utils import BufferedJSON, read_bit
+from utils import Aggregator, BufferedJSON, read_bit
 from zmqsocks import ZMQSockets
 
 
@@ -43,9 +43,7 @@ def work(backend_address, accumulator_host, accumulator_port, visualisation_host
 
     zmq_socks = ZMQSockets(backend_address, accumulator_host, accumulator_port, visualisation_host, visualisation_port)
 
-
-    data_summed = None
-    n_aggregated_images = 0
+    aggregator = Aggregator()
 
 
     while True:
@@ -118,7 +116,7 @@ def work(backend_address, accumulator_host, accumulator_port, visualisation_host
         calc_peakfinder_analysis(results, pfdata, pixel_mask_pf)
 
 # ???
-        data, force_send_visualisation, data_summed, n_aggregated_images = calc_force_send(results, data, pixel_mask_pf, image, data_summed, n_aggregated_images)
+        data, force_send_visualisation, aggregator = calc_force_send(results, data, pixel_mask_pf, image, aggregator)
 
         results["type"]  = str(data.dtype)
         results["shape"] = data.shape