diff --git a/foa3d/frangi.py b/foa3d/frangi.py
index f620780..356e3ec 100644
--- a/foa3d/frangi.py
+++ b/foa3d/frangi.py
@@ -304,30 +304,31 @@ def frangi_filter(img, scales_px=1, alpha=0.001, beta=1.0, gamma=None, dark=True
         enhanced_img, fiber_vec, eigenval \
             = compute_scaled_orientation(scales_px[0], img, alpha=alpha, beta=beta, gamma=gamma, dark=dark)
 
-    # parallel scaled vesselness analysis
+    # sequential scaled vesselness analysis
     else:
-        with Parallel(n_jobs=n_scales, backend='threading', max_nbytes=None) as parallel:
-            par_res = \
-                parallel(
-                    delayed(compute_scaled_orientation)(
-                        scales_px[i], img=img,
-                        alpha=alpha, beta=beta, gamma=gamma, dark=dark) for i in range(n_scales))
-
-            # unpack and stack results
-            enhanced_img_tpl, eigenvectors_tpl, eigenvalues_tpl = zip(*par_res)
-            eigenval = np.stack(eigenvalues_tpl, axis=0)
-            eigenvec = np.stack(eigenvectors_tpl, axis=0)
-            enhanced_img = np.stack(enhanced_img_tpl, axis=0)
-
-            # get max scale-wise vesselness
-            best_idx = np.argmax(enhanced_img, axis=0)
-            best_idx = np.expand_dims(best_idx, axis=0)
-            enhanced_img = np.take_along_axis(enhanced_img, best_idx, axis=0).squeeze(axis=0)
-
-            # select fiber orientation vectors (and the associated eigenvalues) among different scales
-            best_idx = np.expand_dims(best_idx, axis=-1)
-            eigenval = np.take_along_axis(eigenval, best_idx, axis=0).squeeze(axis=0)
-            fiber_vec = np.take_along_axis(eigenvec, best_idx, axis=0).squeeze(axis=0)
+        
+        # initialize output arrays
+        scl_shp = (n_scales,) + img.shape
+        enhanced_img = np.zeros(scl_shp)
+
+        eig_shp = scl_shp + img.ndim
+        eigenval = np.zeros(eig_shp)
+        eigenvec = np.zeros(eig_shp)
+
+        # iterate over scales
+        for s in range(n_scales):
+            enhanced_img[s], eigenvec[s], eigenval[s] \
+                = compute_scaled_orientation(scales_px[s], img=img, alpha=alpha, beta=beta, gamma=gamma, dark=dark)
+
+        # get max scale-wise vesselness
+        best_idx = np.argmax(enhanced_img, axis=0)
+        best_idx = np.expand_dims(best_idx, axis=0)
+        enhanced_img = np.take_along_axis(enhanced_img, best_idx, axis=0).squeeze(axis=0)
+
+        # select fiber orientation vectors (and the associated eigenvalues) among different scales
+        best_idx = np.expand_dims(best_idx, axis=-1)
+        eigenval = np.take_along_axis(eigenval, best_idx, axis=0).squeeze(axis=0)
+        fiber_vec = np.take_along_axis(eigenvec, best_idx, axis=0).squeeze(axis=0)
 
     return enhanced_img, fiber_vec, eigenval
 
diff --git a/foa3d/pipeline.py b/foa3d/pipeline.py
index 372aaf6..966da96 100644
--- a/foa3d/pipeline.py
+++ b/foa3d/pipeline.py
@@ -717,8 +717,7 @@ def parallel_frangi_on_slices(img, cli_args, save_dir, tmp_dir, img_name,
         get_image_info(img, px_size, mask_lpf, ch_mye, is_tiled=is_tiled)
 
     # configure batch of basic image slices analyzed in parallel
-    batch_size, max_slice_size = \
-        config_frangi_batch(frangi_sigma_um, ram=ram, jobs=jobs)
+    batch_size, max_slice_size = config_frangi_batch(ram=ram, jobs=jobs)
 
     # get info on the processed image slices
     rng_in_lst, rng_in_lpf_lst, rng_out_lst, pad_lst, \
diff --git a/foa3d/slicing.py b/foa3d/slicing.py
index 360ed8f..3b8a330 100644
--- a/foa3d/slicing.py
+++ b/foa3d/slicing.py
@@ -222,17 +222,13 @@ def compute_overlap_range(smooth_sigma, frangi_sigma, px_rsz_ratio, truncate=2):
         return ovlp
 
 
-def config_frangi_batch(frangi_scales, mem_growth_factor=149.7, mem_fudge_factor=1.0,
-                        min_slice_size=-1, jobs=None, ram=None):
+def config_frangi_batch(mem_growth_factor=149.7, mem_fudge_factor=1.0, min_slice_size=-1, jobs=None, ram=None):
     """
     Compute size and number of the batches of basic microscopy image slices
     analyzed in parallel.
 
     Parameters
     ----------
-    frangi_scales: list (dtype=float)
-        analyzed spatial scales in [μm]
-
     mem_growth_factor: float
         empirical memory growth factor
         of the Frangi filtering stage
@@ -268,19 +264,16 @@ def config_frangi_batch(frangi_scales, mem_growth_factor=149.7, mem_fudge_factor
     if jobs is None:
         jobs = num_cpu
 
-    # number of spatial scales
-    num_scales = len(frangi_scales)
-
     # initialize slice batch size
-    slice_batch_size = np.min([jobs // num_scales, num_cpu]).astype(int)
+    slice_batch_size = np.min([jobs, num_cpu]).astype(int)
     if slice_batch_size == 0:
         slice_batch_size = 1
 
     # get image slice size
-    slice_size = get_slice_size(ram, mem_growth_factor, mem_fudge_factor, slice_batch_size, num_scales)
+    slice_size = get_slice_size(ram, mem_growth_factor, mem_fudge_factor, slice_batch_size)
     while slice_size < min_slice_size:
         slice_batch_size -= 1
-        slice_size = get_slice_size(ram, mem_growth_factor, mem_fudge_factor, slice_batch_size, num_scales)
+        slice_size = get_slice_size(ram, mem_growth_factor, mem_fudge_factor, slice_batch_size)
 
     return slice_batch_size, slice_size