This document discusses the role of imaging in radiotherapy and outlines several key points: 1. Imaging has evolved from basic x-rays to cross-sectional imaging like CT and MRI to better define tumor volumes and organs at risk. 2. Modern radiotherapy relies on accurate tumor delineation using imaging for treatment planning, simulation, delivery, verification and monitoring. 3. Emerging technologies like PET and functional MRI provide complementary anatomical and biological information that can further improve radiotherapy outcomes. 4. Greater collaboration between radiology and radiation oncology departments, including dedicated imaging units and personnel, can help maximize the benefits of modern imaging for radiotherapy.

3. The Incremental Journey So
Far
1. Visual determination and/or physical palpation of
abnormal masses to guide radiotherapy target.
2. Plain x-rays and anatomical landmarks
3. Crossectional imaging
4. Medical technology advances in delivery of
radiotherapy.

4. Steps of Radiotherapy Process
1. Cancer staging
2. Target volume determination
3. Treatment planning
4. Simulation
5. Radiotherapy delivery
6. Radiotherapy verification
7. Patient monitoring
8. Patient follow up

5. Imaging needs in each step

6. Cancer Staging
0 To determine the extent of disease
0 To determine the intent of radiotherapy- curative,
high dose local control, palliative.

7. Target volume determination
0 To define the treatment volumes of the tumour for
treatment planning
0 To identify the relevant organs-at-risk for treatment
planning

8. Treatment Planning
0 To evaluate the defined 3-D target volumes and
organs-at-risk for selection of the number of beams,
the orientation of the beams, design of the treatment
plan, selection of the plan technique, use of intensity
modulation or image guided strategy and computing
plan distributions.
0 To review plan dosimetry in 3D and permit creation of
dose-volume histograms.
0 To provide opportunity for plan optimization

9. Simulation
0 To determine patient positioning and set up in 3D
0 To assess position and use of radiation immobilization
aids or anatomical markers.

10. Radiotherapy Delivery
0 To provide accuracy and reliability of treatment
delivery
0 To offer opportunity for image guided radiotherapy
such as adaptive or predictive treatments
0 To permit options for target tracking and target gating

11. Radiotherapy Verification
0 To confirm placement of treatment fields or delivery
of radiotherapy
0 To evaluate in vivo dosimetry
(EPIDs)

12. Patient Monitoring
0 To assess uncertainties in patient tolerance to
treatment

13. Patient Follow up
0 To determine tumour response
0 To assess treatment related side effects
0 To evaluate disease recurrence

14. 0 From as early as the 1970s research on how crossesctional
imaging can contribute to RTP was ongoing especially after
the introduction of CT in medical science. For example
Gotein et al concluded that improved tumor delineation
and target coverage using CT could result in an increase in
local tumor control probability by an average of 6% with
the chance of five-year survival increasing by an average of
3.5% ⋆. With advances in CT technology now it is possible
to provide 3D spatial volumes for better tumour definition
and reduce geographical miss during RT.
⋆Goitein M. The utility of computed tomography in radiation therapy; an estimate of
outcome. Int J Radiat Oncol Biol Phys 1979; 5: 1799–807.

15. An example of a lung
radiotherapy case where
the anterior treatment
field was planned using
conventional radiotherapy
planning methods with a
simple chest radiograph
image and (B–D) the same
lung case planned using
CT simulation planning
where the anterior
treatment field in shown
in B and the
corresponding coronal and
sagittal views are shown
in C and D, respectively.
Note that shaping of the treatment field for A is crude and does not provide estimation of
the tumor shape. By using CT scanning, the 3D shape of the tumor can be determined. The
treatment fields can then be shaped to the profile of the tumor using multileaf collimation
and taking into account the surrounding organs-at-risk such as the heart, esophagus, and
lung tissue as demonstrated in B. (Source: Husband and Reznek's Imaging in Oncology ).

16. Improving Therapeutic Ratios
0 Radiotherapy planning studies have outlined that the
volume of irradiated tissue can be reduced by 30% to 50%
using CFRT compared to conventional planning techniques
⋆.
0 IMRT is an improvement of CRFT in reducing dose to OAR
in concave structures e.g the rectum during RT of prostatic
cancer.
0 IGRT addresses the temporal and spatial variations that
may lead to geographical misses of the target volume and
OAR to increase therapeutic ratios.
⋆ Robinson MH, Bidmead AM, Harmer CL. Value of conformal planning in the
radiotherapy of soft tissue sarcoma. Clin Oncol (R Coll Radiol) 1992; 4: 290–3

17. Necessary imaging information
for target volume delineation
1. Patient
2. The tumour
3. Nodal regions
4. Organs at risk
(Structured reporting is gaining popularity all over the
world as an effective tool of communication between
the radiologist and clinician).

18. Patient
0 Position – has to be the same during imaging and
treatment delivery.
0 Any devices that will be used during therapy must
also be included during the treatment planning scan.
0 Specific conditions needed during treatment must
also be reproduced during the RTP scan eg.
Breathhold technique or full bladder

19. The tumour
0 Spatial location
0 3D shape and size
0 Details of the edge where it forms a border with adjacent
normal tissue
0 Details of the adjacent anatomy where no clear boundaries
are defined
0 Details of any potential microscopic extension
0 Functional tumour activity in relation to anatomical and
morphological status
0 Details of spatial variation that may be associated with the
tumour.

20. Nodal regions
0 Mention of the known locoregional nodal sites
0 Abnormal size and suspicious features
Organs at risk (OAR)
0 Anatomical details including normal variants.
0 Potential temporal spatial variation

21. Radiologist’s Forte
0 Staging
0 Follow up
0 Monitoring

22. Radio-oncologist’s Field
0 Target delineation
0 Treatment planning
0 Simulation
0 Delivery
0 Verification

23. What will drive more
partnership?
Multimodality imaging.
0Multimodality imaging will include not only
anatomic but also functional descriptions.
0 Imaging biomarkers are becoming more established.
0 Moreover, multimodality imaging aims to combine
the benefits from different imaging modalities, often
providing complementary information to aid target
volume delineation.

24. Multimodality Imaging
CT
0 CT is the current mainstay imaging modality used in RTP.
0 It provides geometrically accurate and reliable cross-sectional
images with 3D external contours of the patient.
0 Tissue or electron density information available from the
Hounsfield units on the CT slices can be directly used, after
applying correction factors, to calculate radiation absorbed
doses for planning dosimetry.
0 Limitations in certain anatomical areas such as brain and
pelvis

25. Multimodality Imaging
MRI
0 MRI is replacing CT as the diagnostic imaging modality of
choice for many regions in the body.
0 Better soft tissue characterisation and multiple sequences
detail the tumour characteristics as well as the OAR.
0 Its application in RTP has been gaining recognition since
the turn of the millennium⋆.
0 It has a superb role in differentiating tumour
recurrence/residue vs post radiation fibrosis.
0 Has complementary role with CT in some cases
⋆Khoo VS. MRI-"magic radiotherapy imaging” for treatment planning? Br J Radiol
2000; 73: 229–33.

26. Multimodality Imaging
MRI
0 Some centres are using MRI for both external beam
therapy and brachytherapy
0 Cine MRI can be used to resolve temporo-spatial
uncertainties (IGRT).
0 USPIO agents can be used for nodal mapping sometimes in
conjunction with PET.
0 Already MR has been integrated with LINAC machine⋆.
0 Functional MRI has a role in IMRT and IGRT.
0 Oncologists must have necessary training to comprehend
MR images.
⋆Lagendijk JJ, Raaymakers BW, Raaijmakers AJ, et al. MRI/linac integration. Radiother
Oncol 2008; 86: 25–9.

27. Multimodality Imaging
PET
0 It has been documented that PET can change cancer
patient management in over a third of cases⋆.
0 FDG PET is the most used modality. Combination with
MR and/or CT yields better fusion for morphological
and functional imaging.
0 Progress is being reported in RTP of cases involving
head and neck, lungs, GIT and gynaecological cancers.
⋆Gambhir SS, Czernin J, Schwimmer J, et al. A tabulated summary of the FDG
PET literature. J Nucl Med 2001; 42(Suppl 5): 1S–93S.

28. Conclusion
0 Staging of cancer and follow up have a well
established partnership between imaging and
radiotherapy departments in Kenya currently .
0 Target volume delineation , treatment planning,
simulation, radiation delivery, verification and
monitoring are areas showing potential for more
partnership between the two disciplines.

29. Way Forward
0 Dedicated imaging units within radiotherapy
departments.
0 Dedicated radiological team within the radiotherapy
department.
0 Personnel training.
0 Multidisciplinary teams.

30. Asanteni