the future of medical imaging

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A T e c h n i c a l R

e v i e w / R e p o r t o f t h e J o u r n a l

A r t i c l e

b y A . D . A . M a i d m e n t

T H E F U T U R

E O F M E D I C A L I M A G I N G

S u b m

i t t e d b y :

D h e e r a j N o s i n a

P r a m e y T

h i r k a t e h

P r i t h i S J

CITATION:

THE FUTURE OF MEDICAL IMAGINGA.D.A. [email protected] Radiation Protection Dosimetry (2010), Vol. 139, No. 1±3, pp. 3±7

Advance Access publication 18 March 2010Department of Radiology, University of Pennsylvania, 3400 Spruce Street, Philadelphia,

PA 19104, USA

Journal article downloaded from rpd.oxfordjournals.org at Western Michigan University

on October 31, 2010



Introduction

The author examines the future of medical imaging informed by his own research

directions. The results presented are specific to the field of breast imaging. An

analysis is made over the general advantages of Computed Tomography and the

edge it holds over Projected Radiography in the foreseeable future. A summary is

made in accordance with three broad trends:

(1) Increased prevalence of low-dose tomographic X-ray imaging;

(2) Continuing advances in functional and molecular X-ray imaging; and

(3) Novel image-based biomarker discovery

I. TOMOGRAPHIC IMAGING:

It is inferred that, with the development of digital tomosynthesis and low-dose

computed tomography(CT), projection radiography will not be preferred unless

the time, effort or radiation risk associated with tomographic imaging seem to be

unjustified.

We are now introduced to two different existing technologies for Breast Imaging;Digital Breast Tomosynthesis (DBT) and dedicated Breast Computed Tomography

(BCT).

Breast Computed Tomography (BCT):

In this system, a woman lies on a table with the breast positioned through a

central hole on the table. X-ray radiations are shot at the target and an opposing

detector rotates around the breast capturing images which are then reconstructed

and displayed. The total dose to the breast is comparably low.

Digital Breast Tomosynthesis (DBT):

This is an alternative competing technology to BCT. In this DBT system, the breast

is compressed between a movable compression paddle and a stationary breast

support containing the detector array. X-rays are passed through the breast and



projection images are acquired while the breast is immobile. These images are

reconstructed using filtered back-projection into a set of images that are aligned

perpendicular to the central ray of the central projection.

The author has further discussed the differences between the respective images

from BCT and DBT:

y DBT images are characterized by high in-plane spatial resolution, while

spatial resolution of BCT images is poorer in-plane. Accordingly, DBT

images have virtually no resolution out of plane while BCT images have

good resolution in orthogonal planes.

y Consequently, in DBT images the tumors stand out clearly because

overlying tissue is not imaged.

y DBT images require lower amounts of dose compared to BCT.y The figure below depicts how the tumor stands out more clearly in a DBT

image(b) when compared to a digital mammogram(a).



II. FUNCTION AL A ND MOLECULAR IMAGING:

Traditional X-ray imaging relies on detecting the abnormal structure of a tissue

(Morphologic information). In molecular imaging, an external molecule isintroduced and its behavior is studied inside the body. There are two emerging

technologies in this type of imaging:

1. Contrast Enhanced Digital Breast Tomosynthesis (CE-DBT)

2. Contrast Enhanced Breast Computed Tomography (CE-BCT)

CE-DBT:

The author is an active researcher in the field of CE-DBT. Initially, a regular DBT

image of the breast is captured which later acts as a mask for subtraction from the

contrast enhanced image . With the breast still held in compression a radiographic

agent (the agent used by the author is Visipaque-320, in a dosage of 1 ml/kg) is

administered to the body and the contrast enhanced image is thus obtained. This

image is then subtracted from the mask to create one or more difference images.

It has two basic approaches:

a. Temporal Subtraction

b. Dual Energy Subtraction

Temporal Subtraction:

A filtered X-ray beam is used whose energy is matched to the K-edge of Iodine.

This reduces the overall dose received by the subject but it has the inherent

disadvantage of motion artifacts.

Dual Energy Subtraction:

In this technique, a pair of images is obtained, one with energy just below the K-line of Iodine and the other with energy just above. This helps in elimination of

motion artifacts resulting in a more accurate diagnosis. Also, the radiographic

substance can be injected before the breast is compressed.



III. IMAGE-B A SED BIOMARKER S:

Biomarkers are quantitative metrics of a disease which help in determining

disease risk or presence. They can also be used to tailor treatments to the patient

and monitor the course of treatment. Research has shown that increased

Parenchymal Density (PD) is associated with increased risk of breast cancer. Also,

retro-areolar texture is indicative of breast cancer gene expression. The author has

expanded on this research and arrived at the following conclusions:

y Texture is inherent to a woman

y Texture can provide information about risk of breast cancer

y Texture indicates the quality of the image

The above assumptions hold good even to digital mammography, but have more

prominence in DBT. This is due to the fact that a digital mammography image

shows a combination of skin texture and parenchymal texture, while they can be

separately imaged in DBT.

The above figure shows (a) Traditional digital mammogram, (b) DBT image of skin

and (c) Midline DBT image of breast.

the future of medical imaging

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