Written by Brian Hulela
Updated at 20 Jun 2025, 16:32
5 min read
Kidney Stone Detection on an image from Kaggle
Object detection is a fundamental task in computer vision that enables machines not only to recognize objects within an image but also to identify their exact locations. This capability is crucial for numerous real-world applications, from autonomous vehicles to medical diagnostics. In this article, we’ll explore the key concepts of object detection, its distinction from image classification, its impact on medical imaging, and the role of bounding boxes in the detection process.
Before diving into object detection, it’s important to distinguish it from image classification, a related but distinct task.
Image classification focuses on identifying the category of an entire image. For example, a classification model might analyze an image and determine whether it contains a “cat” or a “dog.” However, it doesn’t provide any information on where in the image the cat or dog is located. The goal is purely to identify the presence of an object, not its position.
If you're interested in image classification, check out Training a Convolutional Neural Network for Binary Classification: Cats vs. Dogs for a deeper dive.
Images of cats and dogs classified with a CNN classifier
Object detection, on the other hand, goes beyond classification by identifying both the object’s presence and its precise location. For instance, a model might detect a “cat” in an image and draw a rectangular box around it, pinpointing its exact position. This means object detection combines classification (what the object is) with localization (where the object is).
Because of this added complexity, object detection is more challenging than image classification. It requires not only recognizing objects but also understanding their spatial relationships within the image.
Cat and Dog Detection with YOLO11 on an Image by Jimmy Ku on Kaggle
In medical imaging, object detection plays a vital role in identifying and diagnosing conditions with greater accuracy and efficiency. One key application is the detection of kidney stones, which can be difficult to spot in medical scans, especially for less experienced doctors.
Medical images—such as X-rays, CT scans, and ultrasounds—are often complex, containing various anatomical structures and potential anomalies. Traditionally, radiologists manually inspect these images to detect abnormalities, a process that can be time-consuming and susceptible to human error.
Object detection automates and improves this process by allowing trained AI models to scan medical images and accurately pinpoint abnormalities like kidney stones or brain tumors. These models not only detect the presence of an abnormality but also highlight its exact location using a bounding box. This automation helps doctors:
Identify even small abnormalities that might be difficult to detect manually.
Assess the size, position, and severity of the abnormalities more quickly.
Provide faster and more accurate diagnoses, leading to better treatment outcomes for patients.
Kidney Stone Detection using a Convolutional Neural Network
A fundamental element of object detection is the use of bounding boxes—rectangular boxes that outline detected objects in an image. These boxes provide both positional and size information about the detected object.
Illustration of an Object Detection Bounding Box
Bounding boxes are typically represented by four coordinates:
(x1, y1) – the top-left corner of the bounding box.
(x2, y2) – the bottom-right corner of the bounding box.
These coordinates define the area where the object is located.
Bounding boxes serve two key functions:
Object Classification – Determining what the object is (e.g., a kidney stone, a cat, or a car).
Object Localization – Accurately predicting the object's position and size within the image.
For example, in medical imaging, an object detection model may detect a kidney stone and precisely mark its location with a bounding box. This spatial information is critical for doctors, allowing them to make informed decisions about treatment.
Without bounding boxes, object detection would lack the crucial ability to pinpoint where objects appear in an image, making the results far less actionable—especially in fields like medicine, where precision can mean the difference between early detection and a missed diagnosis.
Object detection is a powerful extension of image classification that enables both recognition and localization of objects in an image. Bounding boxes play a crucial role in this process, allowing AI models to visually highlight objects, providing critical insights in applications ranging from self-driving cars to medical diagnostics.
In the healthcare sector, object detection has already shown its value by improving accuracy in diagnosing conditions such as kidney stones, reducing human error, and accelerating the diagnostic process. As AI continues to evolve, its impact on object detection and medical imaging will only grow, leading to more advanced and reliable automation.
