Medical image segmentation basics in Computer Vision - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the library used for image segmentation.

Computer Vision

import [1] as cv

Drag options to blanks, or click blank then click option'

Atensorflow

Bcv2

Cnumpy

Dmatplotlib

Attempts:

3 left

💡 Hint

Common Mistakes

Importing unrelated libraries like numpy or matplotlib for segmentation.

Using tensorflow which is for deep learning but not direct image processing here.

We use cv2 (OpenCV) for image processing tasks including segmentation.

2fill in blank

medium

Complete the code to read a medical image from a file.

Computer Vision

image = cv.[1]('scan.png', cv.IMREAD_GRAYSCALE)

Drag options to blanks, or click blank then click option'

Aimread

Bimshow

Cimwrite

Dresize

Attempts:

3 left

💡 Hint

Common Mistakes

Using imshow which displays images but does not read files.

Using imwrite which saves images instead of reading.

imread reads an image file into memory. We use grayscale mode for medical scans.

3fill in blank

hard

Fix the error in the thresholding step to segment the image.

Computer Vision

_, segmented = cv.threshold(image, [1], 255, cv.THRESH_BINARY)

Drag options to blanks, or click blank then click option'

A128

B256

C-1

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using 256 which is out of range for pixel values.

Using negative or zero values which do not segment properly.

The threshold value must be between 0 and 255 for 8-bit images. 128 is a common middle value.

4fill in blank

hard

Fill both blanks to create a mask and apply it to the image.

Computer Vision

mask = segmented [1] 255
result = cv.bitwise_and(image, image, mask=[2])

Drag options to blanks, or click blank then click option'

A==

Bmask

C128

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!=' instead of '==' which inverts the mask.

Using incorrect mask values like 128.

The mask is created by checking where segmented equals 255. Then we apply this mask to the original image.

5fill in blank

hard

Fill all three blanks to calculate Dice coefficient for segmentation evaluation.

Computer Vision

intersection = (predicted_mask [1] true_mask).sum()
dice = (2 * intersection) / (predicted_mask.sum() [2] true_mask.sum())
print('Dice coefficient:', [3])

Drag options to blanks, or click blank then click option'

A&

B+

Cdice

D|

Attempts:

3 left

💡 Hint

Common Mistakes

Using bitwise OR (|) instead of AND (&) for intersection.

Adding intersection instead of predicted and true sums in denominator.

Printing a wrong variable instead of dice.

Dice coefficient uses intersection with bitwise AND (&), sums added (+), and prints the calculated dice value.

Practice

1. What is the main goal of medical image segmentation?

easy

A. To separate important parts of an image pixel by pixel

B. To classify the whole image into categories

C. To enhance the brightness of medical images

D. To compress the image for storage

Solution

1. Step 1: Understand segmentation purpose

   Medical image segmentation aims to identify and separate regions of interest within an image at the pixel level.

2. Step 2: Compare options

   Only To separate important parts of an image pixel by pixel describes pixel-level separation, which matches segmentation. Other options describe different tasks.

3. Final Answer:

   To separate important parts of an image pixel by pixel -> Option A

4. Quick Check:

   Segmentation = pixel-level separation [OK]

Hint: Segmentation means pixel-level separation of image parts [OK]

Common Mistakes:

• Confusing segmentation with image classification
• Thinking segmentation enhances image brightness
• Mixing segmentation with image compression

2. Which of the following is the correct way to describe the input and output of a segmentation model?

easy

A. Input: Image; Output: Class label

B. Input: Mask; Output: Image

C. Input: Image; Output: Mask showing segmented regions

D. Input: Text; Output: Image

Solution

1. Step 1: Identify model inputs and outputs

   Segmentation models take images as input and output masks that highlight segmented areas pixel-wise.

2. Step 2: Match options to this understanding

   Input: Image; Output: Mask showing segmented regions correctly states input as image and output as mask. Others mismatch input/output types.

3. Final Answer:

   Input: Image; Output: Mask showing segmented regions -> Option C

4. Quick Check:

   Segmentation model output = mask [OK]

Hint: Segmentation outputs masks, not class labels [OK]

Common Mistakes:

• Confusing segmentation output with classification labels
• Swapping input and output roles
• Assuming text input for image tasks

3. Given this Python snippet using a UNet model for segmentation:

pred_mask = unet_model.predict(test_image)
print(pred_mask.shape)

What does pred_mask.shape represent?

medium

A. The dimensions of the predicted segmentation mask

B. The training loss value

C. The number of classes in the dataset

D. The dimensions of the input image

Solution

1. Step 1: Understand prediction output

   The predict method returns the segmentation mask predicted by the model for the input image.

2. Step 2: Interpret shape attribute

   The shape shows the size (dimensions) of this predicted mask, matching the input image size and channels.

3. Final Answer:

   The dimensions of the predicted segmentation mask -> Option A

4. Quick Check:

   pred_mask.shape = mask size [OK]

Hint: Model.predict returns mask; shape shows mask size [OK]

Common Mistakes:

• Thinking shape shows input image size
• Confusing shape with number of classes
• Mixing shape with loss or metric values

4. You wrote this code to train a segmentation model but get an error:

model.fit(images, masks, epochs=10)

What is a likely cause of the error?

medium

A. The model does not support segmentation

B. The images are grayscale but masks are color

C. The epochs parameter is missing

D. The masks are not the same size as the images

Solution

1. Step 1: Check input-output size requirements

   Segmentation training requires masks to have the same spatial size as input images for pixel-wise comparison.

2. Step 2: Identify common error

   If masks differ in size, model.fit will raise an error due to shape mismatch.

3. Final Answer:

   The masks are not the same size as the images -> Option D

4. Quick Check:

   Mask size must match image size [OK]

Hint: Masks must match image size for training [OK]

Common Mistakes:

• Ignoring mask-image size mismatch
• Assuming epochs parameter causes error
• Thinking color difference causes training error

5. You want to improve segmentation accuracy on small tumors in medical images. Which approach is best?

hard

A. Train only on images without tumors

B. Use a UNet model with skip connections to capture fine details

C. Reduce image resolution to speed up training

D. Use a simple linear model without convolution layers

Solution

1. Step 1: Understand model choice for fine details

   UNet with skip connections preserves spatial details, helping segment small structures like tumors.

2. Step 2: Evaluate other options

   Reducing resolution loses detail; training without tumors ignores target; linear models lack spatial understanding.

3. Final Answer:

   Use a UNet model with skip connections to capture fine details -> Option B

4. Quick Check:

   UNet + skip connections = better small object segmentation [OK]

Hint: UNet skip connections help segment small details [OK]

Common Mistakes:

• Reducing resolution loses important details
• Ignoring tumor images during training
• Using non-convolutional models for images