Commentary on Article

Here is a brief review on a recent article posted in the RSNA journal "Radiology" on December 2011. It was made by these authors:

Anwar R. Padhani, MB, BS, FRCP, FRCR,
Dow-Mu Koh, MD, MRCP, FRCRand
David J. Collins, BA, MInstP

And it was made in The Royal Mardsen Hospital, Sutton Surey, England. Here are some pictures of the Hospital:





So, the purpose of the article was to show how the whole body sequence Diffusion Weighted Image (DWI) used in Magenetic Resonance Imaging (MRI) can be used as a important tool for oncologic patients in every step of the stages either diagnostic, response to treatment or in resolution period.

The DWI sequence is not a novelty itself and it's use in MRI is widely known. It was developed in the 80´s and the main use of this sequence has been detecting brain isquemia or also called acute stroke. The physics of DWI is that allows the mapping of the diffusion process of molecules, mainly water in biological tissues in vivo  called the Brownian motion of particles so when there is a restriction of the motion of particles (suchs as stroke) it is represented as a bright signal. In the past decade there has been several advances in the use of DWI in several other entities and in other parts of the body. Special interest has been shown in tumoral processes because hypercelularity and packed tissues as in a tumor has briht signal in DWI. Several other benefits are that there are NO use of ionizing radiation, NO use of any intravenous or oral contrast, relatively short time adquisition of images, NO use of radioactive material, more availability of MRI than PET or SPECT.  Right now worldwide there are several investigations published and more yet to come how this sequence is used in several parts of the body but none (to my knowledge) that uses a complete whole body scan in DWI.

The technical aspects of this article are a bit complex and it is not my intention to describe those but is important to say that they use mainly 1.5 Tesla with a body coil. 3 Tesla magnets are not ase useful because they lack of fat supression in wide body areas and are more susceptible to artifacts.

One of the great tools we have in monitoring tumoral disease is positron emmision thomography (PET) so here I share to you the comparision of DWI and PET screening in a 23 y/o patient with Hodgkin Lymphoma pre and post quemotherapy treatment.

The images in A. are DWI coronal images that show a wide tumor in mediastinum with several lymph nodes in supraclavicular and axilar region and some of spleen involment too, but post treatment they were almost gone. In B. we see the PET scanning of the same patient pre and post quemotherapy with almost the same conclusion. Arrow shows the spleen involment also seen in DWI. The black spots in thorax and in pelvis are the radionuclide IV contrast that in the heart there is a increased uptake wich is normal and in pelvis represents the urinary bladder filled with the IV contrast. See kidneys are still eliminating it.

There is also in the article a recomendation to be familiar with the normal intensity of signal in all organs because some of them have physiologic more water concentration. Also there has to be an ADC map wich is comparative and usefull in depicting celularity but it's still a complex technique that requieres some expertise training.

It's a promising tool that we have to check into..



Here is the link to the abstract:

http://radiology.rsna.org/content/261/3/700.abstract