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Prostate Cancer
Figure 3: Exclusion of Beam Entrance Through Artificial Figure 5: Typical Image Guidance Procedure With
Femoral Heads to Avoid Unwanted ‘High-intensity’ Orthogonal kV and MV Views for a Prostatic Patient
Through Metal Treated with RapidArc
Figure 4: Typical Set-up for Image Guidance with
The method allows fast and accurate detection of position shifts and main daily patient
features with almost radiological quality.
Orthogonal kV and MV Views for a Prostatic Patient
Treated with RapidArc
Figure 6: Typical Image Guidance Procedure with
3D Cone Beam Computed Tomography for a Prostatic
Patient Treated with RapidArc
After having approved or eventually corrected the position of the
The method allows to directly compare planning computed tomography (CT) and treatment
CT on a weekly or more frequent basis detecting detailed anatomical features of patient,
patient, normally with accuracy greater than 2mm, treatment can
organ deformation, tumour or target characteristics in 3D.
start after retraction of the imaging arms. Figure 5 shows a typical
verification of patient positioning through 2D–2D kV–MV imaging. The Treatment of IOSI is still in the learning phase. Image guidance
MV images are acquired with minimal patient exposure (less than procedures, mixing both 2D–2D and CBCT processes, have been
1MU). Patient position with this first level procedure is verified mainly performed with an average time of 7’37”±2’43”. These times include
via anatomical landmarks, such as bony structures. More quantitative image acquisition, online analysis, eventual repositioning of patients
measurements, tailored to the position of the target mass, can be and approval for treatment. The longest component of this sequence
carried out using internal gold markers implanted either in the tumour is analysis and approval for treatment, which requires the intervention
mass (or cavity for post-operative patients) or in its proximity. This last of clinicians from time to time.
approach is still under investigation in our department with the active
collaboration of urologists. Conclusions
At IOSI RapidArc is now offered to all prostate patients. Treatments are
The second level of imaging, to be scheduled at weekly intervals, carried out with single arcs and with a total treatment time, inclusive
requires the acquisition of a CBCT scan. In this case, the kV of imaging procedures, of less than 10 minutes. Of that time, the actual
source performs a complete rotation around the patient and treatment only takes 74 seconds. The rest is spent in image guidance
volumetric images are reconstructed online with a delay of few and improving the clinician’s relationship with the patient. This
seconds, generating a 3D data set equivalent to a normal CT scan. treatment and protocol has increased our treatment capability from
Figure 6 shows a typical CBCT image set overlaid on a standard three to four high-quality treatments without RapidArc to treating six
computed tomography scan (acquired on a 16-slice radiological to eight patients per hour with RapidArc. In addition to the logistical
scanner). The quality of images, the spatial and contrast resolution features, dosimetric preliminary findings suggest that this innovative
allows the precise and accurate assessment of global patient technology can open new investigational strategies, particularly in
positioning as well as a detailed investigation on individual organs accelerated hypofractionated treatments, dose escalation and
at risk or even target mass. The aim of this 3D imaging protocol is adaptive treatments. Although the preliminary clinical data are
to promptly react to any potential change in the patient’s anatomy encouraging, experimental and clinical studies are needed and are
that would require modification or adaptation of treatments to being performed to determine the volume/time/dose/fractionation
guarantee that the high degree of conformal avoidance granted by relationships of this novel delivery technique on the control of the
RapidArc is maintained. tumours and on reduction of damage to normal tissue. n
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