Radiation related changes: Demystifying expected from the
unexpected!
Poster No.:
C-2026
Congress:
ECR 2017
Type:
Educational Exhibit
Authors:
A. Chavhan , S. L. Juvekar , M. H. Thakur , S. Gudi , S. Singh ,
1
2
2
1
2
3
3
1 1
N. Jain , N. ARGULWAR , A. Singh ; MUMBAI, Maharashtra/IN,
2
3
Mumbai/IN, Mumbai, ma/IN
Keywords:
Radiation physics, Conventional radiography, CT, MR, Radiation
therapy / Oncology, Radiobiology, Biological effects, Cancer
DOI:
10.1594/ecr2017/C-2026
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Page 1 of 44
Learning objectives
1. Revisiting the concepts of interactions of radiation with the tissue that subsequently
lead to its therapeutic, as well as inadvertent adverse effects
2.System-wise imaging appearance of primary lesion, post treatment changes
suggesting response and changes suggesting adverse effects
Background
Radiotherapy is used for many malignant as well as benign lesions either as curative
or as adjuvant to chemotherapy or surgery. The dark side of radiation therapy
includes a heterogeneous spectrum ranging from mild indolent effects to life threatening
complications.
Radiation related changes impose dilemma to radiologist, making it difficult to distinguish
therapy related changes from residual disease and at times presenting bizarre
These changes are dependent on type of radiation, field of radiation, dose and duration
as well upon the sensitivity of organ systems to radiation
A systemic approach to post radiation scan is essential to differentiate expected versus
the unexpected
Findings and procedure details
BASIC PHYSICS
Radiation therapy is one of the most common treatments for cancer. It uses high-energy
particles or waves
Radiation used for cancer treatment is ionizing radiation because it forms ions
(electrically charged particles) in the cells of the tissues it passes through. This can kill
cells or change genes so that the cells stop growing.
Page 2 of 44
Other forms of radiation such as radio waves, microwaves, and visible light waves are
called nonionizing. These do not form ions.
Ionizing radiation can be classified into two major types:
• Photon radiation: x-rays and gamma rays
• Particle radiation: such as electrons, protons, neutrons, carbon ions, alpha particles,
and beta particles
A high-energy photon beam is by far the most common form of radiation used for
cancer treatment.
A photon is a packet of energy that can be characterized by the equation
E = hv
h is Planck's constant (6.62 × 10
-34
J-sec)
8
v is the frequency of the photon (3 × 10 m/sec)
The high-energy radiations have a short wavelength and a high frequency.
The interaction of a photon beam with matter results in the attenuation of the beam.
Five major types of interactions typically occur:
•
Coherent scattering
•
Photoelectric effect
•
Compton scattering
•
Pair production
Page 3 of 44
•
Photodisintegration
In radiation therapy, the photoelectric effect, the Compton effect, and pair production
are of interest, with the Compton effect being the predominant interaction.
The photoelectric effect involves the interaction of the photon with the inner electrons
and is proportional to the cube power of its atomic number. This interaction is responsible
for the different radiographic densities
Fig. 1: PHOTOELECTRIC EFFECT
References: http://radonc.wikidot.com/local--files/photoelectric-effect/PEE2.png
The Compton effect involves interaction with outer electrons. This effect is related to
electron density and therefore results in much more uniform tissue absorption than lowerenergy photons.
Page 4 of 44
In radiation therapy, the Compton effect predominates; resulting in inferior contrast
than that of diagnostic radiographs.
Fig. 28: COMPTON SCATTERING
References: http://physics.tutorvista.com/modern-physics/compton-scattering
Pair production involves the interaction of the photon with the atomic nuclear
electromagnetic field. This interaction is seen at high energies (> 10 MeV) and is
proportional to the atomic number
Page 5 of 44
Fig. 2: PAIR PRODUCTION
References: http://nuclearpowertraining.tpub.com/h1013v2/css/Gamma-Ray-30
Radiation causes ionisation in tissues which damages DNA (Deoxyribo Nucleic Acid).
Depletion of cancer cells produces the benefit while depletion of normal cells produces
the toxicity. Normal tissues repair radiation injury better than cancer cells as long as the
doses are not "too high" and the gap between doses allows enough time for repair to
take place
Types of radiotherapy
• External beam radiation
• Brachytherapy
• Radiopharmaceuticals
EFFECTS OF IRRADIATION
Common general side effects: Skin changes and fatigue
Page 6 of 44
Side effects specific to where the radiation therapy is given:
Head and neck: Dry mouth, Mucositis, Dysphagia, Trismus, Nausea, lymphedema,
Tooth decay.
Chest: Dysphagia, Shortness of breath, Breast or nipple soreness, Shoulder stiffness
Cough, fever, and fullness of the chest called radiation pneumonitis that happens
between two weeks and six months after radiation therapy.
Radiation fibrosis, which is permanent scarring of the lungs from untreated radiation
pneumonitis
Abdomen: Nausea and vomiting, Diarrhoea, Rectal bleeding, Incontinence, cystitis.
In the liver, an area of low attenuation corresponding to the radiation port or an area of
hyper attenuation if the underlying liver tissue shows fatty change can be seen; Later
the liver may be fibrotic and contracted.
In the stomach, small intestine, and colon, wall thickening and edema are early
manifestations. Ulcers may also be observed. Long-term complications include
strictures and fistulas.
After irradiation of the kidneys, altered attenuation of the renal parenchyma may be
seen at CT. Ureteral strictures, typically involving the distal ureter may be observed
after pelvic irradiation.
The bladder may be small and contracted with a thickened wall after radiation exposure.
Fistulas between the bladder and other pelvic organs sometimes occur.
RADIATION INDUCED CHANGES IN VARIOUS ORGAN SYSTEMS WITH IMAGING
FEATURES
•
BRAIN :
Page 7 of 44
ACUTE: manifests days to weeks after irradiation, seen as transient white matter edema
secondary to changes in vascular permeability. These appear hyperintese on T2/FLAIR.
EARLY DELAYED: Presents 1 to 6 months after RT as abnormal confluent hypodense
areas on NECT (Non enhanced computed tomography) and periventricular white matter
hyperintensities on T2/FLAIR(Fluid Attenuation Inversion Recovery).
LATE DELAYED: Late delayed injury presents as radionecrosis and is usually not
observed until at least six months post irradiation. These late delayed injuries are viewed
as progressive and largely irreversible changes, resulting from loss of glial and vascular
endothelial cells.
Imaging features are described with two terms
1) Soap bubble pattern: an area of contrast enhancement with a heterogenous non
enhancing necrotic centre.
2) Swiss cheese pattern: refers to scattered areas of necrosis of various sizes.
LONG TERM SEQUELAE TO RADIATION INJURY:
•
Radiation-induced vasculopathy leading to ischemic strokes and moyamoyalike disease.
•
Mineralizing microangiopathy is usually seen in patients treated with
combination RT and chemotherapy. It is seen as calcifications in the basal
ganglia and subcortical white matter.
•
Radiation-induced vascular malformations are primarily capillary
telangiectasias or cavernous malformation. T2* (GRE, SWI) sequences
demonstrate "blooming" microhemorrhages.Children under 10 years of age
at the time of irradiation are at higher risk.
•
Radiation-induced neoplasms are rare. Approximately 70% are
meningiomas, 20% malignant astrocytomas or medulloblastomas, and 10%
sarcomas. Meningiomas occur an average of 17-20 years after treatment
whereas gliomas occur at a mean of nine years.
Page 8 of 44
Fig. 3: A
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
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Fig. 4: B
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
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Fig. 5: C
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
A case of right scalp basal cell carcinoma, post craniectomy and post RT.
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The Axial T1(A), T2(B) and T1 post contrast(C) images of follow up MRI showing altered
signal intensity lesion in the right frontal lobe showing irregular peripheral enhancement
(swiss cheese) , associated with diffuse adjacent subcortical white matter hyperintensities
suggestive of edema/gliosis. There is resultant midline shift. The findings are likely s/o
post RT necrosis in given clinical setting.
LUNG:
Acute phase: ground glass opacities/consolidation. Radiation pneumonitis presents as
nodular and focal consolidative opacities within the treatment port. Occasional pleural
effusion with atelectasis might also develop.
Late phase: Radiation fibrosis manifests with consolidation, linear scarring, volume loss
and traction bronchiectasis.
Page 12 of 44
Fig. 6: A
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
Fig. 7: B
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
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Fig. 8: C
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
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Fig. 9: D
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
A case of left hilar primitive neuroectodermal tumour(PNET). Received EBRT to left hilar
region .
A : a well defined mass in the left hilar region with surrounding normal lung parenchyma
B:Regression of the mass with patchy area of consolidation in the left lower lobe
C : pre therapy CT chest of same patient, at higher level (at the level of left pulmonary
artery) showing no significant abnormality in the left lung parenchyma
D : Post RT CT chest at corresponding level as of C, shows changes of fibrosis in left
upper lobe which is in the field of RT port s/o post RT fibrosis.
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Fig. 10: A
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
Page 16 of 44
Fig. 11: B
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
A: CT chest shows a soft tissue mass with calcification within in right hemi-thorax along
right parietal pleura with erosion of right 6th rib.HPR: PNET.
B: Post op, post RT CT chest image showing complete collapse with fibro-bronchiectatic
changes with associated contracture of right hemithorax in the form of crowding of ribs,
ipsilateral mediastinal shift. The findings are suggestive of post radiation changes.
•
BONE:
Changes include growth disturbances, osteoradionecrosis and radiation induced
neoplasia.
Osteoradionecrosis refers to a severe delayed radiation-induced injury and is
characterised by bone tissue necrosis and failure in healing, seen as osteopenia
Page 17 of 44
Mandible is commonly affected due to its superficial location. Manifests as destruction
without sequestration or soft tissue.
Fig. 12: Osteoradionecrosis
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
Known case of carcinoma of right buccal mucosa, post radiotherapy.
Orthopantomogram showing changes of osteoradionecrosis involving the right
hemimandible with extensive destruction and fragmentation of the body, angle and
adjacent vertical ramus of the mandible.
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Fig. 13: Osteoradionecrosis
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
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Operated case of carcinoma right buccal mucosa, post radiotherapy. Axial CT images in
bone window showing erosion of the ramus and visualised body of right hemi-mandible
with associated osteopaenia-osteoradionecrosis.
Avascular necrosis of bone:
Long term complication resulting as a depletion of cellular component due to local
ischemis and microvascular changes.
Vulnerabel bones are femoral head, femoral condyle, head of humerus, capitulum,
scaphoid and talus.
Fig. 14: A
Page 20 of 44
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
Fig. 15: B
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
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Fig. 16: C
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
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Fig. 17: D
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
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Fig. 18: E
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
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Fig. 19: F
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
A case of pelvic fibromatosis.
MR Images A(axial T1 contrast), C( coronal T1 post contrast) and E( coronal STIR) are
pre treatment images showing a large soft tissue mass occupying almost the entire
pelvis.
Page 25 of 44
Images B,D and F showing corresponding images, following RT, showing a decrease in
the size of the pelvic mass. Also seen is cortical irregularity involving articular surface of
head of left femur with subchondral cysts. There is associated mild joint effusion. The
articular cartilage shows altered signal as well. The features are suggestive of avascular
necrosis of left femoral head with secondary early degenerative changes.
•
HEAD AND NECK GLANDS:
Post-RT parotid glands demonstrate loss of gland parenchyma and acinar cell atrophy
seen as heterogeneous, variable hyperechogenicity on ultrasound scan, increase in
signal intensity on T2 and in the late stages gland volume shrinkage.
The changes in thyroid presents with microvascular and parenchymal damage and
fibrosis of the capsule.
Page 26 of 44
Page 27 of 44
Fig. 20: Fatty atrophy of the right parotid
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
Coronal T1 image shows fatty atrophy of the right parotid
Fig. 21: Post RT changes in thyroid gland
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
In a case of carcinoma Tongue,post RT, USG neck shows diffuse Hypoechogenicity and
heterogenous echotexture of the thyroid gland; gland also showed increased vascularity
(not shown). The features represent thyroiditis. The diagnosis of RT induced thyroiditis
is based on temporal relation between completion of RT and onset of clinical symptoms.
•
SPINAL CORD:
Myelomalacia: Refers to increased T2 signal in the cord, and the cord is atrophic and
gliotic as a result of a chronic injury of any form and is irreversible.
Page 28 of 44
Fig. 22: Myelomalacia
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
Page 29 of 44
Fig. 23: Myelomalacia
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
In a case of PNET right paravertebral region ( C7 - D1), post RT, MRI reveals abnormal
high singal intensity in cord at C7- D2 level represting post RT myelomalacia.
residual disease involving the right superior sulcus is seen with pleural infiltration by
residual soft tissue mass.
•
GASTROINTESTINAL COMPLICATIONS:
The rectum and sigmoid colon sustain acute damage to the actively proliferating mucosa,
resulting in proctitis and colitis. The small bowel is more radiosensitive but is usually
less exposed due to its increased mobility
At CT, there is uniform thickening, which can progress to areas of stricture.
Page 30 of 44
At MR imaging there might be bowel wall enhancement on contrast-enhanced T1weighted images with loss of definition of the muscle layers on T1-weighted images.
Chronic: fibrosis leading to stenosis, which may in turn cause bowel obstruction
Fig. 24: Proctocolitis
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
A case of Ca cervix, post RT, with c/o diarrhea. USG pelvis shows thickening involving
distal sigmoid and upper rectum s/o proctocolitis.
Page 31 of 44
Page 32 of 44
Fig. 25: RT induced stricture
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
This is a case of Ca cervix post RT, with intermittent bleeding per rectum.
Spot radiographic image from BARIUM ENEMA showing evidence of smooth luminal
narrowing at the transition of the sigmoid and descending colon. It extends over the length
of approximately 5 cms proximally in the descending colon- RT induced stricture.
RADIATION INDUCED CHANGES IN THE PELVIS:
•
UTERUS AND OVARIES:
Postmenopausal patients: No significant changes
Premenopausal patients: there is loss of distinction between the junctional zone and
outer myometrium. In later stages( 6months after therapy) the endometrium becomes
thin and hypointense. In the ovaries, there is decrease in size and signal intensity and
loss of follicles.
•
URINARY BLADDER:
The bladder is the most radiosensitive organ of the urinary system
ACUTE: manifests as edema and symmetrical thickening of bladder wall. Hematuria
and clot formation due to hemorrhage and necrosis.
USG is very helpful in demonstrating the mobility of clot compared with the tumor and
also for demonstrating non vascular nature of clot.
CHRONIC: The fibrosis leading due to small capacity bladder. Perforation of the bladder
is a rare and late complication
Page 33 of 44
Fig. 26: A
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
Page 34 of 44
Fig. 27: B
References: RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
A : Case of Ca Cervix , post EBRT to pelvis; transabdominal ultrasound images
showing an irregular hyperechoic lesion in the bladder, which was avascular and mobile,
suggestive of a clot.
B: Another such case showing thickening of the bladder wall likely cystitis secondary to
radiation.
Images for this section:
Page 35 of 44
Fig. 5: C
© RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
Page 36 of 44
Fig. 7: B
© RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
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Fig. 11: B
© RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
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Fig. 12: Osteoradionecrosis
© RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
Page 39 of 44
Fig. 17: D
© RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
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Page 41 of 44
Fig. 25: RT induced stricture
© RADIODIAGNOSIS, TATA MEMORIAL CENTRE - MUMBAI/IN
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Conclusion
•
Knowledge of clinical history, therapy planning, biological response of
tissue to radiation etc. can greatly simplify assessment of radiation therapy
changes on imaging.
•
A structured diagnostic approach makes diagnosis and management of
radiationtherapy induced changes quite simplistic
•
Personal information
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