Design a deep learning model to classify X-ray images as "Pneumonia" or "No Pneumonia" with high accuracy.

Sure, here is a step-by-step guide to design a deep learning model for classifying X-ray images as "Pneumonia" or "No Pneumonia":

1. Data Collection: The first step is to collect a large number of X-ray images that have been labeled as "Pneumonia" or "No Pneumonia". This could be done by collaborating with hospitals or using publicly available datasets.

2. Data Preprocessing: The collected images need to be preprocessed before they can be used for training. This could involve resizing the images to a standard size, normalizing the pixel values, and splitting the dataset into a training set and a validation set.

3. Model Selection: For this task, a Convolutional Neural Network (CNN) would be a good choice as they have proven to be effective for image classification tasks. You could start with a simple architecture with a few convolutional layers followed by max pooling and fully connected layers.

4. Training: The model can be trained using the training set. During training, the model's weights are adjusted to minimize the difference between the predicted labels and the true labels. This could be done using a suitable optimization algorithm like Stochastic Gradient Descent (SGD) or Adam.

5. Evaluation: The trained model can be evaluated on the validation set. The performance of the model can be measured using appropriate metrics like accuracy, precision, recall, and F1 score.

6. Hyperparameter Tuning: If the performance of the model is not satisfactory, you can tune the hyperparameters of the model and the training process. This could involve adjusting the learning rate, the batch size, the number of layers in the model, etc.

7. Testing: Once you are satisfied with the performance of the model on the validation set, you can test it on a separate test set to get an unbiased estimate of its performance.

8. Deployment: The final step is to deploy the model in a suitable environment where it can be used to classify new X-ray images.

Remember, deep learning models require a lot of computational resources for training, especially when dealing with large images. Therefore, it might be necessary to use a machine with a powerful GPU or a cloud-based platform.