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- Angel Mironov
- Department of Neuroradiology
- Kantonsspital Aarau, Switzerland
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- Radiation creates ionized oxygen species (free radicals) that react with
cellular DNA
- Therapeutic effects of radiation therapy may derail and generate some
undesirable sequels. The adverse effects of radiation therapy are
generally related to total radiation doses and fractionation size. A
total dose of 5500 cGy have a 3-5 % occurrence of radiation necrosis
- The adverse effects of radiation therapy occur in a distinct chronologic
order and have characteristic pathophysiology
- In clinical situation the adverse effects of radiation therapy present
always a diagnostic dilemma
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- Does the mass recurrence consist of original tumor regrowth, of non
tumorous adverse effects of radiation therapy, or of the both?
- Does this mass recurrence requires a treatment of patients neurologic
function?
- What therapy may be appropriate?
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- Conventional MRI signal changes in radiation necrosis cannot be
differentiated from tumor related changes sufficiently
- Recurrent tumor - high metabolic activity
- Radiation necrosis - inactive metabolically
- Functional imaging techniques:
- PET, SPECT,
CBV-mapping, MRS
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- Therapy lead to increased metabolism and thus to diagnostic limitation
of functional techniques:
- @ increased glucose transport
- @ energy consumption for repair
- @ metabolically-active inflammatory elements
- @ energy consumption for apoptosis
- @ active metabolismus in surviving normal tissue
- In cases with proven necrosis by imaging:
- 70 % mixture of
necrosis & tumor
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- To analyze by reason of nonrandomized sampling of serial MR imaging data
the chronological change of morphology in cases of recurrent mass after
radiation therapy
- To determine by expertise in an unbiased way the nature, significance,
and chronological relationship of various MR signal changes and
morphology concerning the tumorous and non tumorous mass in cases of
recurrent mass after radiation therapy
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- 45 patients have been retrospectively studied over a period of 10 years
after treatment for brain tumors by surgery followed by radiation
therapy & chemotherapy
- The patients underwent serial follow up MR imaging in different time
sequences over a period up to 10 years
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- Brain Edema:
- @early & delayed reaction,
possible manifestation unpredictable;
- @usually vasogenic edema
- Blood-brain barrier disruption:
- @early (direct cellular injury),
or delayed (small vessels injury or radiation necrosis) features;
- @may persist intermittent for
long time – from months to many years;
- @the configuration and intensity
of Gd enhancement may change;
- @festoon-like or facet-like very
bright appearance with progress in centrifugal direction and
inappropriate small mass effect are typical;
- @involvement of white matter, the
gyral surface and the subependymal periventricular space
- Demyelination:
- @Early delayed & late delayed reaction - few weeks to many years
after irradiation
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- Brain atrophy, reactive gliosis:
- @early (direct) or late delayed (associated with necrosis)
- Small vessels injury, Necrosis:
- @Late delayed reaction – 6 months to several months & years after
irradiation
- @Often fulminant development after long period of inactivity
- @Depending on vasogenic edema may be without or with (inappropriate
small) mass effect
- @Responsive on steroid & anticoagulant therapy
- Diffuse axonal injury:
- @Radiation neuropathy (Wallerian degeneration) reaching its appearance
with a latency of few months to many years after irradiation
- @Pathognomonic feature for radiation injury of brain manifested as
demyelination & degeneration of ipsilateral long tracts
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- In a separated peripheral nerve
the nerve fibers of the distal stump degenerate while those of proximal
stump survive: nerve fibers need to be connected to the cell body as
their nutritive centre
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- The radiation - induced effects are in terms of morphology and time
presentation unpredictable
- The radiation - induced effects imply change of tumor mass and surrounding
area in different ratio
- The inductive analysis of sequential MR imaging may provide valuable
differential diagnostic
- The therapeutic options for radiation - induced effects include: observation,
steroid & anticoagulants treatment, or surgery for mass resection
- The pathophysiological base of differentiating of tumor recurrence from
radiation necrosis is not enough known, but well comprehensible
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Notes
