Imaging in Stem Cell Transplant and Cell-based Therapy

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in imaging of transplant diseases, especially in the diagnosis and management of
complications associated with stem cell transplantation [ 1 ].
This chapter shall briefly review the history of stem cells and their current status
and applications. We shall also discuss the role of radiology and interventional tech-
niques in administration and monitoring of transplanted stem cells. Recent advances
in stem cell techniques and imaging of the stem cell transplant in various areas shall
be discussed here and in the subsequent chapters.

1.1.1 Stem Cell Types: Definitions and Classification

Stem cells are undifferentiated biological cells that can differentiate into specialized
cells and can undergo mitosis to produce more stem cells. Regardless of their source,
all stem cells have three general properties: they are capable of dividing and renew-
ing themselves for long periods (long term self-renewal); they are unspecialized i.e.,
they lack tissue specific structure and function (plasticity); and they can give rise to
specialized cell types (differentiation) [ 2 , 3 ].
Stem cells are distinguished from one another on the basis of their plasticity. Not
all stem cells have the same degree of plasticity, or developmental versatility. Some
stem cells are more committed to becoming any particular type of cell than others.
The categories into which the various stem cells fall include: the totipotent stem cell,

Table 1.1 Summary of different stem cell imaging strategies with emphasis on the underlying
physiological process and role of different modality in each strategy. A comparative estimate of the
spatial resolution and stem cell detection sensitivity in the direct and indirect labeling of the stem
cells is also provided. (+ least resolution/sensitivity, ++++ maximum resolution/sensitivity). Notice
spatial resolution and stem cell detection sensitivity is not applicable to the direct transfer of stem
cells given on-site delivery of stem cells using interventional techniques. [MRI  =  Magnetic
resonance imaging; PET  =  Positron emission tomography; SPECT  =  Single photon emission
computed tomography). [Adapted from Rodriguez-Porcel M, Wu JC, Gambhir SS.  Molecular
imaging of stem cells. In Stembook. http://www.stembook.org/node/603. Last accessed 03/15/2014.]

Stem cell

imaging strategy

Underlying

physiological

process Imaging modality

Spatial

resolution

Stem cell

detection

sensitivity

Direct stem cell

labeling

1. Early stem cell
   detection


2. Stem cell
   homing
   
   
   1. Fluorescence
   
   
   2. MRI
   
   
   3. SPECT
   
   
   4. PET
   
   
   
   

++

++++

+++

+++

+++

+++

+++

+++

Indirect stem cell

labeling (reporter

gene imaging)

1. Long term
   monitoring of
   cell viability


2. Study stem cell
   biology
   
   
   1. Fluorescence
   
   
   2. Bioluminescence
   
   
   3. SPECT
   
   
   4. PET
   
   
   5. MRI
   
   
   
   

++

++

+++

+++

++++

+++

++++

+++

+++

Not known

Direct transfer of

stem cells

Direct delivery of

stem cells to target

area

1. MR Fluoroscopy


2. Ultrasound

NA NA

T. Pa ndey