diff --git a/.github/workflows/test_cli.yml b/.github/workflows/test_cli.yml
index 203650d9..bc0b9dc1 100644
--- a/.github/workflows/test_cli.yml
+++ b/.github/workflows/test_cli.yml
@@ -54,6 +54,11 @@ jobs:
         if: always()  # will always run regardless of whether previous step fails - useful to ensure all CLI functions tested
         run: |
           hazen acr_ghosting tests/data/acr/Siemens --report
+          
+      - name: test acr_slice_position
+        if: always()  # will always run regardless of whether previous step fails - useful to ensure all CLI functions tested
+        run: |
+          hazen acr_slice_position tests/data/acr/Siemens --report
 
       - name: test acr_geometric_accuracy
         if: always()  # will always run regardless of whether previous step fails - useful to ensure all CLI functions tested
diff --git a/hazenlib/tasks/acr_slice_position.py b/hazenlib/tasks/acr_slice_position.py
new file mode 100644
index 00000000..bb4bdfaa
--- /dev/null
+++ b/hazenlib/tasks/acr_slice_position.py
@@ -0,0 +1,262 @@
+"""
+ACR Slice Position
+
+https://www.acraccreditation.org/-/media/acraccreditation/documents/mri/largephantomguidance.pdf
+
+Calculates the bar length difference for slices 1 and 11 of the ACR phantom.
+
+This script calculates the bar length difference in accordance with the ACR Guidance. Line profiles are drawn
+vertically through the left and right wedges. The right wedge's line profile is shifted and wrapped round before being
+subtracted from the left wedge's line profile, e.g.:
+
+Right line profile: [1, 2, 3, 4, 5]
+Right line profile wrapped round by 1: [2, 3, 4, 5, 1]
+
+This wrapping process, from hereon referred to as circular shifting, is then used for subtractions.
+
+The shift used to produce the minimum difference between the circularly shifted right line profile and the static left
+one is used to determine the bar length difference, which is twice the slice position displacement.
+The results are also visualised.
+
+Created by Yassine Azma
+yassine.azma@rmh.nhs.uk
+
+28/12/2022
+"""
+
+import sys
+import traceback
+import scipy
+import os
+import numpy as np
+import skimage.morphology
+import skimage.measure
+
+from hazenlib.HazenTask import HazenTask
+
+
+def find_n_peaks(data, n, height=1):
+    peaks = scipy.signal.find_peaks(data, height)
+    pk_heights = peaks[1]['peak_heights']
+    pk_ind = peaks[0]
+    highest_peaks = pk_ind[(-pk_heights).argsort()[:n]]  # find n highest peaks
+
+    return np.sort(highest_peaks)
+
+
+class ACRSlicePosition(HazenTask):
+
+    def __init__(self, **kwargs):
+        super().__init__(**kwargs)
+
+    def run(self) -> dict:
+        results = {}
+        z = []
+        for dcm in self.data:
+            z.append(dcm.ImagePositionPatient[2])
+
+        idx_sort = np.argsort(z)
+
+        for dcm in self.data:
+            curr_z = dcm.ImagePositionPatient[2]
+            if curr_z in (z[idx_sort[0]], z[idx_sort[10]]):
+                try:
+                    result = self.get_slice_position(dcm)
+                except Exception as e:
+                    print(f"Could not calculate the bar length difference for {self.key(dcm)} because of : {e}")
+                    traceback.print_exc(file=sys.stdout)
+                    continue
+
+                results[self.key(dcm)] = result
+
+        results['reports'] = {'images': self.report_files}
+
+        return results
+
+    def centroid_com(self, dcm):
+        # Calculate centroid of object using a centre-of-mass calculation
+        thresh_img = dcm > 0.25 * np.max(dcm)
+        open_img = skimage.morphology.area_opening(thresh_img, area_threshold=500)
+        bhull = skimage.morphology.convex_hull_image(open_img)
+        coords = np.nonzero(bhull)  # row major - first array is columns
+
+        sum_x = np.sum(coords[1])
+        sum_y = np.sum(coords[0])
+        cxy = sum_x / coords[0].shape, sum_y / coords[1].shape
+
+        cxy = [cxy[0].astype(int), cxy[1].astype(int)]
+        return bhull, cxy
+
+    def find_wedges(self, img, mask, res):
+        # X COORDINATES
+        x_investigate_region = np.ceil(35 / res[0]).astype(int)  # define width of region to test (comparable to wedges)
+
+        if np.mod(x_investigate_region, 2) == 0:
+            # we want an odd number to see -N to N points in the x direction
+            x_investigate_region = x_investigate_region + 1
+
+        w_point = np.argwhere(np.sum(mask, 0) > 0)[0].item()  # westmost point of object
+        e_point = np.argwhere(np.sum(mask, 0) > 0)[-1].item()  # eastmost point of object
+        n_point = np.argwhere(np.sum(mask, 1) > 0)[0].item()  # northmost point of object
+
+        invest_x = []
+        for k in range(x_investigate_region):
+            y_loc = n_point + k  # add n_point to ensure in image's coordinate system
+            t = mask[y_loc, np.arange(w_point, e_point + 1, 1)]  # mask for resultant line profile
+            # line profile at varying y positions from west to east
+            line_prof_x = skimage.measure.profile_line(img, (y_loc, w_point),
+                                                       (y_loc, e_point), mode='constant').flatten()
+
+            invest_x.append(t * line_prof_x)  # mask unwanted values out and append
+
+        invest_x = np.array(invest_x).T  # transpose array
+        mean_x_profile = np.mean(invest_x, 1)  # mean of horizontal projections of phantom
+        abs_diff_x_profile = np.abs(np.diff(mean_x_profile))  # absolute first derivative of mean
+
+        x_peaks = find_n_peaks(abs_diff_x_profile, 2)  # find two highest peaks
+        x_locs = w_point + x_peaks  # x coordinates of these peaks in image coordinate system(before diff operation)
+
+        width_pts = [x_locs[0], x_locs[1]]  # width of wedges
+        width = np.max(width_pts) - np.min(width_pts)  # width
+
+        # rough midpoints of wedges
+        x_pts = np.round([np.min(width_pts) + 0.25 * width, np.max(width_pts) - 0.25 * width]).astype(int)
+
+        # Y COORDINATES
+        # define height of region to test (comparable to wedges)
+        y_investigate_region = int(np.ceil(20 / res[1]).item())
+
+        # supposed distance from top of phantom to end of wedges
+        end_point = n_point + np.round(50 / res[1]).astype(int)
+
+        if np.mod(y_investigate_region, 2) == 0:
+            # we want an odd number to see -N to N points in the y direction
+            y_investigate_region = (y_investigate_region + 1)
+
+        invest_y = []
+        for m in range(y_investigate_region):
+            x_loc = (m - np.floor(y_investigate_region / 2) + np.floor(np.mean(x_pts))).astype(int)
+            c = mask[np.arange(n_point, end_point + 1, 1), x_loc]  # mask for resultant line profile
+            line_prof_y = skimage.measure.profile_line(img, (n_point, x_loc), (end_point, x_loc),
+                                                       mode='constant').flatten()
+            invest_y.append(c * line_prof_y)
+
+        invest_y = np.array(invest_y).T  # transpose array
+        mean_y_profile = np.mean(invest_y, 1)  # mean of vertical projections of phantom
+        abs_diff_y_profile = np.abs(np.diff(mean_y_profile))  # absolute first derivative of mean
+
+        y_peaks = find_n_peaks(abs_diff_y_profile, 2)  # find two highest peaks
+        y_locs = w_point + y_peaks - 1  # y coordinates of these peaks in image coordinate system(before diff operation)
+
+        if y_locs[1] - y_locs[0] < 5 / res[1]:
+            y = n_point + round(10 / res[1])  # if peaks too close together, use phantom geometry
+        else:
+            y = np.round(np.min(y_locs) + 0.25 * np.abs(np.diff(y_locs)))  # define y coordinate
+
+        dist_to_y = np.abs(n_point - y[0]) * res[1]  # distance to y from top of phantom
+        y_pts = np.append(y, np.round(y[0] + (47 - dist_to_y) / res[1])).astype(int)  # place 2nd y point 47mm from top of phantom
+
+        return x_pts, y_pts
+
+    def get_slice_position(self, dcm):
+        img = dcm.pixel_array
+        res = dcm.PixelSpacing  # In-plane resolution from metadata
+        mask, cxy = self.centroid_com(img)
+        x_pts, y_pts = self.find_wedges(img, mask, res)
+
+        line_prof_L = skimage.measure.profile_line(img, (y_pts[0], x_pts[0]), (y_pts[1], x_pts[0]),
+                                                   mode='constant').flatten()  # line profile through left wedge
+        line_prof_R = skimage.measure.profile_line(img, (y_pts[0], x_pts[1]), (y_pts[1], x_pts[1]),
+                                                   mode='constant').flatten()  # line profile through right wedge
+
+        interp_factor = 5
+        x = np.arange(1, len(line_prof_L) + 1)
+        new_x = np.arange(1, len(line_prof_L) + (1 / interp_factor), (1 / interp_factor))
+
+        interp_line_prof_L = scipy.interpolate.interp1d(x, line_prof_L)(new_x)  # interpolate left line profile
+        interp_line_prof_R = scipy.interpolate.interp1d(x, line_prof_R)(new_x)  # interpolate right line profile
+
+        delta = interp_line_prof_L - interp_line_prof_R  # difference of line profiles
+        peaks = find_n_peaks(abs(delta), 2, 0.5 * np.max(abs(delta)))  # find two highest peaks
+
+        if len(peaks) == 1:
+            peaks = [peaks[0] - 50, peaks[0] + 50]  # if only one peak, set dummy range
+
+        # set multiplier for right or left shift based on sign of peak
+        pos = 1 if np.max(-delta[peaks[0]:peaks[1]]) < np.max(delta[peaks[0]:peaks[1]]) else -1
+
+        # take line profiles in range of interest
+        static_line_L = interp_line_prof_L[peaks[0]:peaks[1]]
+        static_line_R = interp_line_prof_R[peaks[0]:peaks[1]]
+
+        lag = np.linspace(-50, 50, 101, dtype=int)  # create array of lag values
+        err = np.zeros(len(lag))  # initialise array of errors
+
+        for k in range(len(lag)):
+            temp_lag = lag[k]  # set a shift value
+            difference = static_line_R - np.roll(static_line_L, temp_lag)  # difference of L and circularly shifted R
+            # set wrapped values to nan
+            if temp_lag > 0:
+                difference[:temp_lag] = np.nan
+            else:
+                difference[temp_lag:] = np.nan
+
+            if np.isnan(difference).all():
+                err[k] = 1e10  # filler value to suppress warning when trying to calculate mean of array filled with NaN
+            else:
+                err[k] = np.nanmean(difference)  # calculate mean difference ignoring nan values
+
+        temp = np.argwhere(err == np.min(err[err > 0]))[0]  # find minimum non-zero error
+        shift = -lag[temp][0] if pos == 1 else lag[temp][0]  # find shift corresponding to above error
+
+        dL = np.round(pos * np.abs(shift) * (1 / interp_factor) * res[1], 2)  # calculate bar length difference
+
+        if self.report:
+            import matplotlib.pyplot as plt
+            fig = plt.figure()
+            plt.suptitle('Bar Length Difference = ' + str(np.round(dL, 2)) + 'mm', x=0.5, ha='center')
+            fig.set_size_inches(8, 8)
+
+            plt.subplot(2, 2, (1, 3))
+            plt.imshow(img)
+            plt.plot([x_pts[0], x_pts[0]], [y_pts[0], y_pts[1]], 'b')
+            plt.plot([x_pts[1], x_pts[1]], [y_pts[0], y_pts[1]], 'r')
+            plt.axis('off')
+            plt.tight_layout()
+
+            plt.subplot(2, 2, 2)
+            plt.grid()
+            plt.plot((1 / interp_factor) * np.linspace(1, len(interp_line_prof_L), len(interp_line_prof_L)) * res[1],
+                     interp_line_prof_L, 'b')
+            plt.plot((1 / interp_factor) * np.linspace(1, len(interp_line_prof_R), len(interp_line_prof_R)) * res[1],
+                     interp_line_prof_R, 'r')
+            plt.title('Original Line Profiles')
+            plt.xlabel('Relative Pixel Position (mm)')
+            plt.tight_layout()
+
+            plt.subplot(2, 2, 4)
+            plt.grid()
+            plt.plot((1 / interp_factor) * np.linspace(1, len(interp_line_prof_L), len(interp_line_prof_L)) * res[1],
+                     interp_line_prof_L, 'b')
+
+            shift_line = np.roll(interp_line_prof_R, pos * shift)
+            if shift < 0 and pos == -1:
+                shift_line[0:np.abs(shift)] = np.nan
+            elif shift < 0 and pos == 1:
+                shift_line[pos * shift:] = np.nan
+            elif shift > 0 and pos == -1:
+                shift_line[pos * shift:] = np.nan
+            else:
+                shift_line[0:np.abs(pos) * shift] = np.nan
+
+            plt.plot((1 / interp_factor) * np.linspace(1, len(interp_line_prof_L), len(interp_line_prof_L)) * res[1],
+                     shift_line, 'r')
+            plt.title('Shifted Line Profiles')
+            plt.xlabel('Relative Pixel Position (mm)')
+            plt.tight_layout()
+
+            img_path = os.path.realpath(os.path.join(self.report_path, f'{self.key(dcm)}.png'))
+            fig.savefig(img_path)
+            self.report_files.append(img_path)
+
+        return dL
diff --git a/tests/test_acr_slice_position.py b/tests/test_acr_slice_position.py
new file mode 100644
index 00000000..2097808d
--- /dev/null
+++ b/tests/test_acr_slice_position.py
@@ -0,0 +1,85 @@
+import os
+import unittest
+import pathlib
+import pydicom
+
+from hazenlib.tasks.acr_slice_position import ACRSlicePosition
+from tests import TEST_DATA_DIR
+
+
+class TestACRSlicePositionSiemens(unittest.TestCase):
+    ACR_SLICE_POSITION_DATA = pathlib.Path(TEST_DATA_DIR / 'acr')
+    centre = [128, 129]
+    x_pts = [(123, 129), (123, 129)]
+    y_pts = [(40, 83), (44, 82)]
+    dL = -0.59, -1.56
+
+    def setUp(self):
+        self.acr_slice_position_task = ACRSlicePosition(data_paths=[os.path.join(TEST_DATA_DIR, 'acr')])
+        self.dcm_1 = pydicom.read_file(os.path.join(TEST_DATA_DIR, 'acr', 'Siemens', '0.dcm'))
+        self.dcm_11 = pydicom.read_file(os.path.join(TEST_DATA_DIR, 'acr', 'Siemens', '10.dcm'))
+
+    def test_object_centre(self):
+        assert self.acr_slice_position_task.centroid_com(self.dcm_1.pixel_array)[1] == self.centre
+
+    def test_wedge_find(self):
+        # IMAGE 1
+        res = self.dcm_1.PixelSpacing
+        mask, _ = self.acr_slice_position_task.centroid_com(self.dcm_1.pixel_array)
+        assert (self.acr_slice_position_task.find_wedges(self.dcm_1.pixel_array, mask, res)[0] ==
+                self.x_pts[0]).all() == True
+
+        assert (self.acr_slice_position_task.find_wedges(self.dcm_1.pixel_array, mask, res)[1] ==
+                self.y_pts[0]).all() == True
+
+        # IMAGE 11
+        res = self.dcm_11.PixelSpacing
+        mask, _ = self.acr_slice_position_task.centroid_com(self.dcm_11.pixel_array)
+        assert (self.acr_slice_position_task.find_wedges(self.dcm_11.pixel_array, mask, res)[0] ==
+                self.x_pts[1]).all() == True
+
+        assert (self.acr_slice_position_task.find_wedges(self.dcm_11.pixel_array, mask, res)[1] ==
+                self.y_pts[1]).all() == True
+
+    def test_slice_position(self):
+        assert round(self.acr_slice_position_task.get_slice_position(self.dcm_1), 2) == self.dL[0]
+        assert round(self.acr_slice_position_task.get_slice_position(self.dcm_11), 2) == self.dL[1]
+
+
+class TestACRSlicePositionGE(unittest.TestCase):
+    ACR_SLICE_POSITION_DATA = pathlib.Path(TEST_DATA_DIR / 'acr')
+    centre = [253, 257]
+    x_pts = [(246, 257), (246, 257)]
+    y_pts = [(82, 163), (85, 165)]
+    dL = 0.3, 0.41
+
+    def setUp(self):
+        self.acr_slice_position_task = ACRSlicePosition(data_paths=[os.path.join(TEST_DATA_DIR, 'acr')])
+        self.dcm_1 = pydicom.read_file(os.path.join(TEST_DATA_DIR, 'acr', 'GE', '0.dcm'))
+        self.dcm_11 = pydicom.read_file(os.path.join(TEST_DATA_DIR, 'acr', 'GE', '10.dcm'))
+
+    def test_object_centre(self):
+        assert self.acr_slice_position_task.centroid_com(self.dcm_1.pixel_array)[1] == self.centre
+
+    def test_wedge_find(self):
+        # IMAGE 1
+        res = self.dcm_1.PixelSpacing
+        mask, _ = self.acr_slice_position_task.centroid_com(self.dcm_1.pixel_array)
+        assert (self.acr_slice_position_task.find_wedges(self.dcm_1.pixel_array, mask, res)[0] ==
+                self.x_pts[0]).all() == True
+
+        assert (self.acr_slice_position_task.find_wedges(self.dcm_1.pixel_array, mask, res)[1] ==
+                self.y_pts[0]).all() == True
+
+        # IMAGE 11
+        res = self.dcm_11.PixelSpacing
+        mask, _ = self.acr_slice_position_task.centroid_com(self.dcm_11.pixel_array)
+        assert (self.acr_slice_position_task.find_wedges(self.dcm_11.pixel_array, mask, res)[0] ==
+                self.x_pts[1]).all() == True
+
+        assert (self.acr_slice_position_task.find_wedges(self.dcm_11.pixel_array, mask, res)[1] ==
+                self.y_pts[1]).all() == True
+
+    def test_slice_position(self):
+        assert round(self.acr_slice_position_task.get_slice_position(self.dcm_1), 2) == self.dL[0]
+        assert round(self.acr_slice_position_task.get_slice_position(self.dcm_11), 2) == self.dL[1]
\ No newline at end of file