MRI can be difficult for patients, particularly elderly and claustrophobic ones. They may feel uncomfortable lying in a large, tube-shaped magnet that makes loud knocking noises.

In addition, longer scan times can cause staff to work overtime, which isn’t good for their health. Thankfully, innovations such as Philips Compressed SENSE enable MR sequences and full exams to be conducted in much shorter time without compromising quality.

Reduced Field of View (FOV)

In MRI, the field of view (FOV) determines the specific area of the patient’s body that will be captured in the final image. This is an important parameter in MRI scanning, as it can reduce scan times and eliminate unnecessary areas of the body from being included in the final images. However, it is also important to maintain a high level of image quality and ensure that all necessary data is acquired.

The FOV of an MRI scan can be reduced without affecting image quality by using a variety of techniques. Some of these techniques require additional hardware, while others are purely computational and can be used with current MRI scanners. The key to these techniques is the use of a small area of interest. By acquiring only a very small region of the body, scans can be significantly shortened without sacrificing imaging resolution or diagnostic confidence.

Traditionally, a larger FOV is acquired during an MRI scan to enable full coverage of the subject’s anatomy. This is often inefficient, as much of the data is unnecessarily wasted on areas of the body that are not displaying any signal or contain no useful information. However, the geometry of the object to be imaged can be used to optimize the FOV for a particular scan, reducing the scan time and improving image quality.

A number of different FOV-sensing methods have been developed and used at low fields for diffusion tensor imaging (DTI) and localization of cardiac structures. However, their application at higher fields has not been widely explored.

Implementing a reduced-FOV technique at 7 T poses many challenges, including the need to compensate for high B1 inhomogeneities, and to limit distortion of the spinal cord geometry in diffusion images. To overcome these challenges, the authors have designed a sequence with selective inner-volume imaging and outer-volume suppression (rFOV).

The method works by identifying an initial survey scan that is used for spatially-selective RF excitation. Then, the FOV of each slice that will be acquired during the main MRI scan is optimized based on the measurements from the survey scan. This approach allows a significant reduction in scan time without compromising image quality and is compatible with SENSE or ZOOM-SENSE reconstructions.

Reduced Slew Rate

For an MRI scan to work correctly, the patient needs to remain completely still, which can be difficult for some patients. The clicks and jolts of the machine can also be unnerving for younger children and people with neurodegenerative conditions. To help these patients and others who can’t hold still for long, researchers at Boston University have designed a new device that reduces the MRI scanning time while boosting image quality.

The MRI device uses a combination of technologies to enhance the signal-to-noise ratio (SNR) in the imaging volume, which is then used to reconstruct images. The new technique, called “smooth gradient mode,” works by lowering the frequency of the gradient waveform to reduce the slew rate and improve image resolution and contrast. This method can be applied to any MRI scanner and requires no additional hardware, making it a cost-effective solution for increasing the efficiency of MRI systems.

There are a variety of methods to shorten the scan times of MRI, such as rectangular field-of-view (RFOV) and partial Fourier imaging, but these techniques typically result in a lower SNR or less resolution. Another option is phase oversampling, which increases the number of phases in the imaging volume to increase image quality and decrease scan time. However, this approach can negatively impact other scan parameters, such as phase-encoding efficiency and spatial resolution.

Scanner manufacturers have developed software to compensate for patient motion and reduce scan time by utilizing the advantages of a faster phase-encoding process. These systems are based on the AIR (Attenuated Inversion Recovery) reconstruction engine with an adaptive gradient system that automatically adjusts the phase-encoding frequency based on the geometry of the target region and corresponding rFOV. This new technology, which is compatible with existing MRI equipment, can reduce MRI scan time by 9-14% without the need for additional hardware and can achieve comparable image quality compared to traditional CS acquisitions.

A shorter scan time can enable hospitals to fit more MRIs into a day, which is important for high-risk patients and those living in remote areas where access to diagnostic services may be limited. It can also allow technicians to spend more time with each patient, explaining the exam step-by-step and helping to calm them, which is especially beneficial for children and other nervous patients.

Reduced Noise

The MRI scan, inclusive of a BIOMED SCAN Bucharest, process involves lying down while the machine takes images of the body. This requires the patient to stay very still, and they may hear clicking or thumping noises from the scanner. These sounds are caused by short bursts of radio waves that knock the protons in the body out of alignment, and this sends off signals that can be picked up by receiver coils. This information is then used to create a picture of the body. The patient may need to wear earplugs or headphones during this process.

Acoustic noise in MRI has long been a problem, and many different methods have been proposed to reduce it. These include modifying the gradient coil structure to limit sound transmission or using “quiet” sequences to eliminate the need for pulsing currents. However, the acoustic impedance of the MR scanner bore and the interaction between the gradient coil structure and outside air can limit the effectiveness of these strategies.

Another method for reducing noise is to increase the phase oversampling. This reduces the image data, but it also increases the SNR and, therefore, the scan time. However, this technique has a limited effect on image quality.

Other solutions to reduce noise include increasing the slew rate and optimizing sequences. Developing quieter gradient coils has also proved successful. In one study, a mechanically rotating gradient coil was used to minimize the effects of the gradient pulsing, and this resulted in a noise reduction of 20.7 dB.

This reduction in acoustic noise can lead to shorter scan times and, as a result, a greater number of patients that can be served in a day. This is especially important for high-risk patients who must be diagnosed quickly, as well as those living in rural areas where access to diagnostic services is limited.

Advanced acceleration techniques can shorten MRI sequences and whole exams by up to 50 percent without compromising image quality.1 This frees up valuable time to address other priorities, such as improving productivity in the imaging department or reducing staff overtime. RWJBarnabas Health is an example of a healthcare system that has benefited from this type of technology. By accelerating their scans with Philips Compressed SENSE, they were able to cut their scanning time from an hour to thirty minutes, and this allowed them to double the number of patients they could serve in a day.

Optimized Protocols

One of the challenges in optimizing MRI scanners and protocols is transforming improvements in attributes like image quality into improved diagnostic performance. For example, longer scan times may result in better signal-to-noise ratios (SNR) and higher resolution, but these features don’t necessarily translate into improved lesion visibility or diagnostic confidence. To convert attributes into clinical performance, the MRI protocol needs to be optimized for a specific set of tissue parameters.

To do this, the natural variability of these tissue parameters must be taken into account. This requires a figure of merit that is based on the separability of tissues rather than on MRI image quality. The best way to define such a figure of merit is by analyzing the natural distribution of tissue parameter values in S-space. To do this, the TPDFs are mapped to S-space, and a risk function is then calculated that relates the probability of observing a particular sequence with the TPDFs in the S-space. Then, a search is conducted in S-space for a mapping that maximizes the integral in Eq. [4a].

The mapping that maximizes this integral must be chosen such that it minimizes the time spent acquiring the data needed to detect a particular type of lesion in a given region of interest. The resulting protocol is then tested to ensure that it achieves this goal. This approach is known as stochastic gradient descent optimization.

Another way to optimize MRI scanning protocols is to improve the efficiency of the workflow. For example, reengineering the facility layout to use dockable tables can allow a scanner to accommodate more patients in the same amount of scanning time. This can help reduce patient wait times, which can be a major source of frustration for many people seeking medical care.

Fortunately, a combination of strategies can significantly shorten scan times without sacrificing MRI image quality. By using Compressed SENSE, researchers have found that it is possible to reduce scan times by up to 32% for spinal, brain, and joint imaging. This can enable hospitals to screen more patients per day within the same number of scanning hours, and it can also reduce the costs associated with a shortened MRI session.