**6. MRI and the newer 3D technology**

As in all areas of life, knowledge and experience are also the key to success in dealing with technology. One of these new technologies that deserves application and experience is "high resolution 3D imaging". Perhaps, it will even change the way we scan in MRI in the future.

3D imaging does not mean, as the term might suggest, image representation in spatial form, but rather the generation of images by means of 3-dimensional data sets.

3D imaging provides numerous benefits for experienced surgeons, from the facilitated planning of complex operations to the use of realistic models. The latter provides effective solutions for one of the greatest challenges in any academic surgical department: training young surgeons in practical techniques without the negative impact of the learning curve on the patient.

Since 2019, radiologists working in MRI have been using extremely fast, high-resolution 3D data sets. These make even the smallest lesions visible and allow viewing from a variety of perspectives. The "isotropic resolution" (less than 1 mm) ensures excellent display of the tumor's characteristics and its relation to the surroundings and neighboring organs – and in the shortest possible time. A relevant surgical area can often be measured in only 5 minutes, which saves time and reduces movement artifacts. The "3D high-resolution compressed SENSE pelvic program" converts layered 2D measurements into a single 3D volume scan (**Figure 11**), plane by plane. It allows easily reformatting of isotropic 3D volume data in the range below 0.5 mm in any plane, without gaps, and with the same resolution as the "native" plane. The SNR-rich, ultra-thin 3D volume allows visualization of even subtle lesions without the partial volume averaging effect. Moreover, tissue structures that are best seen in oblique view can be viewed easily.

The new, self-calibrating technique with parallel imaging and compressed scanning significantly speeds up the MRI examination. As a result, scanning times can be reduced by up to 50% compared with those of conventional examination without "compressed SENSE" – all while providing exquisite tissue contrast.

The advantage of 3D imaging in surgical and radiotherapy planning is obvious: multiplanar images with excellent soft tissue contrast. This allows exact delineation of the tumor and healthy tissue, which is of decisive importance for RCT planning.

Furthermore, during follow-up, e.g. after RCT, changes in anatomy and tumor biology can be better visualized, thus permitting improved adaptation of treatment plans.

### **Figure 11.**

*A 3D volume of pelvis acquires contiguous, sub-millimeter, isotropic 3D data sets that can be easily reformatted into any plane, without losing its resolution. The SNR-rich, ultra-thin slices can provide help to visualize even small and subtle lesions without partial volume averaging effect. This will change the way we scan in the future. Muscularis propria with rectal tumor (red dashed line), mesorectum (yellow arrow), FMR = CRM (green arrow). Source: F. Bauer, Radiology, Kaufbeuren.*

**93**

*Imaging and Diagnosis for Planning the Surgical Procedure*

Our own experience shows that high resolution in 3D has clear advantages with regard to the assessment of the mesorectal fascia. 3D volume scans allow very clear and seamless visualization of the MRF/CRM at any desired level — even in critical areas, such as ventrally or around the junctional zone, where there is very little to no fat tissue. Another advantage we see is in the use of arbitrary angulation (adapted to the tumor level) in real time, which permits any possibly unfavorable 2D angulation to

Our current results contradict our own older experience as well as the common opinion in the literature regarding the reliability of 3D MRI. The new technology is very stable and can be implemented quickly if given the prerequisite of using 3 T systems with the latest hardware and software technology. **Localization** certainly plays an important role here. In the small pelvis we have no respiratory or pulsation artifacts and the intestinal peristalsis can be exposed very effectively with Buscopan. Of course, we do not have all these unique local conditions in the area of the parenchymatous upper abdominal organs. I can only encourage every user to include this 3D measurement of the pelvis (if 3 T devices are available) in the

The surgical department has particularly appreciated this 3-dimensional, high quality, multiplanar real-time imaging. We, radiologists, we are especially pleased that the correct orthogonal planning to the tumor can be done very accurately and now in real time, but retrospectively. In the past, incorrect angulation has often produced incorrect readings, resulting in over or underestimation to the distance to the mesorectal fascia. If our measurements are to agree with the histological result, this evaluation must be extremely precise. We see a further advantage in tumors with a strong curvature or in double carcinomas, where multiple angulation is required for precise axial layers. We can now perform all these transformations from one acquired 3D data set. We see no real argument against this 3D volume measurement of the pelvis, which supplements the current standard protocol with an additional

CT cannot be recommended for the local staging of rectal cancer.

node prediction accuracy of CT is lower than with MRI.

The decisive advantage of MRI over CT is that it displays much better the morphology of the tumor and its topographical relationship to the border lamella of the mesorectum and to neighboring structures (prostate, seminal vesicle, vagina, uterus, os sacrum and os coccygeum as well as bladder and sphincter apparatus). As we have shown above, the relationship of the tumor to the neighboring structures is just as important as the TNM classification scheme [17, 18]. In addition, the lymph

For the detection of distant metastases, however, contrast-enhanced CT (CECT)

is currently the method of choice due to its high availability and supported by current guidelines [19]. In most cases, it consists of a combined examination of the thorax and abdomen, which is a routine protocol both preoperatively for staging

We do not routinely use PET-CT in our center for primary staging, nor for restaging after CRT, as complete remission can be evaluated much better with MRI.

be checked quickly and, if necessary, to be corrected accordingly.

*DOI: http://dx.doi.org/10.5772/intechopen.93873*

standard protocol of the rectal examination.

5-minute measurement.

**7.1 MRI vs. CT**

and in follow-up.

**7.2 MRI vs. PET-CT**

**7. Other imaging modalities**

*Colorectal Cancer*

provides effective solutions for one of the greatest challenges in any academic surgical department: training young surgeons in practical techniques without the

Since 2019, radiologists working in MRI have been using extremely fast, high-resolution 3D data sets. These make even the smallest lesions visible and allow viewing from a variety of perspectives. The "isotropic resolution" (less than 1 mm) ensures excellent display of the tumor's characteristics and its relation to the surroundings and neighboring organs – and in the shortest possible time. A relevant surgical area can often be measured in only 5 minutes, which saves time and reduces movement artifacts. The "3D high-resolution compressed SENSE pelvic program" converts layered 2D measurements into a single 3D volume scan (**Figure 11**), plane by plane. It allows easily reformatting of isotropic 3D volume data in the range below 0.5 mm in any plane, without gaps, and with the same resolution as the "native" plane. The SNR-rich, ultra-thin 3D volume allows visualization of even subtle lesions without the partial volume averaging effect. Moreover, tissue structures that are best seen in

The new, self-calibrating technique with parallel imaging and compressed scanning significantly speeds up the MRI examination. As a result, scanning times can be reduced by up to 50% compared with those of conventional examination without

The advantage of 3D imaging in surgical and radiotherapy planning is obvious: multiplanar images with excellent soft tissue contrast. This allows exact delineation of the tumor and healthy tissue, which is of decisive importance for RCT planning. Furthermore, during follow-up, e.g. after RCT, changes in anatomy and tumor biology can be better visualized, thus permitting improved adaptation of treat-

*A 3D volume of pelvis acquires contiguous, sub-millimeter, isotropic 3D data sets that can be easily reformatted into any plane, without losing its resolution. The SNR-rich, ultra-thin slices can provide help to visualize even small and subtle lesions without partial volume averaging effect. This will change the way we scan in the future. Muscularis propria with rectal tumor (red dashed line), mesorectum (yellow arrow), FMR = CRM (green* 

"compressed SENSE" – all while providing exquisite tissue contrast.

negative impact of the learning curve on the patient.

oblique view can be viewed easily.

ment plans.

**92**

**Figure 11.**

*arrow). Source: F. Bauer, Radiology, Kaufbeuren.*

Our own experience shows that high resolution in 3D has clear advantages with regard to the assessment of the mesorectal fascia. 3D volume scans allow very clear and seamless visualization of the MRF/CRM at any desired level — even in critical areas, such as ventrally or around the junctional zone, where there is very little to no fat tissue.

Another advantage we see is in the use of arbitrary angulation (adapted to the tumor level) in real time, which permits any possibly unfavorable 2D angulation to be checked quickly and, if necessary, to be corrected accordingly.

Our current results contradict our own older experience as well as the common opinion in the literature regarding the reliability of 3D MRI. The new technology is very stable and can be implemented quickly if given the prerequisite of using 3 T systems with the latest hardware and software technology. **Localization** certainly plays an important role here. In the small pelvis we have no respiratory or pulsation artifacts and the intestinal peristalsis can be exposed very effectively with Buscopan. Of course, we do not have all these unique local conditions in the area of the parenchymatous upper abdominal organs. I can only encourage every user to include this 3D measurement of the pelvis (if 3 T devices are available) in the standard protocol of the rectal examination.

The surgical department has particularly appreciated this 3-dimensional, high quality, multiplanar real-time imaging. We, radiologists, we are especially pleased that the correct orthogonal planning to the tumor can be done very accurately and now in real time, but retrospectively. In the past, incorrect angulation has often produced incorrect readings, resulting in over or underestimation to the distance to the mesorectal fascia. If our measurements are to agree with the histological result, this evaluation must be extremely precise. We see a further advantage in tumors with a strong curvature or in double carcinomas, where multiple angulation is required for precise axial layers. We can now perform all these transformations from one acquired 3D data set. We see no real argument against this 3D volume measurement of the pelvis, which supplements the current standard protocol with an additional 5-minute measurement.
