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import os
import sys
import numpy as np
import nibabel as nib
import matplotlib.pyplot as plt
from scipy.optimize import curve_fit
# Add src to path
sys.path.append(os.path.join(os.path.dirname(__file__), 'src'))
from ivim_model import calculate_ivim_params, _fit_pixel
def func_qua(x, a0, a1, a2):
return a2 * (x ** 2) + a1 * x + a0
def main():
print("=== Debugging Single Pixel Fit ===")
# Load data
data_dir = os.path.join(os.path.dirname(__file__), 'data', 'CFIN')
nii_file = [f for f in os.listdir(data_dir) if f.endswith('.nii') and 'DTI' in f][0]
bval_file = [f for f in os.listdir(data_dir) if f.endswith('.bval')][0]
img = nib.load(os.path.join(data_dir, nii_file))
data = img.get_fdata()
bvals = np.loadtxt(os.path.join(data_dir, bval_file))
# Preprocess (Average)
unique_b = np.unique(np.round(bvals, -1))
avg_data_list = []
for b_val in unique_b:
idxs = np.where(np.abs(bvals - b_val) < 10)[0]
if len(idxs) > 0:
avg_data_list.append(np.mean(data[:, :, :, idxs], axis=3))
avg_data = np.stack(avg_data_list, axis=3)
# Pick a pixel in the brain
# Slice 9, x=50, y=50 (approx center)
slice_idx = 9
x, y = 48, 48
signal = avg_data[x, y, slice_idx, :]
print(f"Pixel ({x}, {y}, {slice_idx})")
print(f"b-values: {unique_b}")
print(f"Signal: {signal}")
# Run IVIM calculation
print("\n--- Running calculate_ivim_params (Quadratic) ---")
r2, D, f, D_star, K = calculate_ivim_params(unique_b, signal, model_type='quadratic', gof=0.9)
print(f"Result: D={D}, f={f}, D*={D_star}, K={K}, R2={r2}")
# Manual check of the fit
vec_b = unique_b
vec_S = signal / np.max(signal)
vec_S_log = np.log(vec_S + 1e-10)
# Fit high b
limit_dif = 180
idx = np.where(vec_b >= limit_dif)[0][0]
b_high = vec_b[idx:]
S_high = vec_S_log[idx:]
print(f"\nHigh-b data (b >= {limit_dif}):")
print(f"b: {b_high}")
print(f"log(S): {S_high}")
# Try fit
bounds = ([-np.inf, -np.inf, 0], [np.inf, 0, np.inf])
try:
popt, _ = curve_fit(func_qua, b_high, S_high, bounds=bounds)
print(f"Manual Curve Fit params: a0={popt[0]}, a1={popt[1]}, a2={popt[2]}")
print(f"Implied D = {-popt[1]}")
print(f"Implied K = {popt[2] / popt[1]**2 * 6 if popt[1]!=0 else 0}")
except Exception as e:
print(f"Fit failed: {e}")
if __name__ == "__main__":
main()
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