” قالوا سبحانك لا علم لنا إلا ما علمتنا إنك أنت العليم الحكيم“ بسم الله الرحمن الرحيم

OUTLINE Principle of Tomotherapy. CT scan similarity. Tomotherapy idea. Serial and Spiral. Clinical Application and Overview.

Tomotherapy Tomotherapy is intensity-modulated rotational radiotherapy utilizing a photon fan beam. Tomotherapy is intensity-modulated rotational radiotherapy utilizing a photon fan beam. Radiation therapy device designed on a CT scanner-based platform. Radiation therapy device designed on a CT scanner-based platform. Tomotherapy means slice therapy coined to describe IMRT using fan beam. Tomotherapy means slice therapy coined to describe IMRT using fan beam.

Computer Tomography CT

Prospective Gating

Retrospective Gating

Types of CT Scanner Serial Helical (Spiral)

Two Flavor SerialHelical (Spiral)

Medco, a company formed by neurosurgeon Mark Carol began developing the serial tomotherapy concept. Medco, a company formed by neurosurgeon Mark Carol began developing the serial tomotherapy concept. Their first presentation was in 1992 (Carol et al. 1993) and their first patient was treated with tomotherapy in 1994 Their first presentation was in 1992 (Carol et al. 1993) and their first patient was treated with tomotherapy in 1994

Basic Principle Rotation therapy is relatively insensitive to the energy of the beam (Johns and Cunningham 1983). Rotation therapy is relatively insensitive to the energy of the beam (Johns and Cunningham 1983). Before megavoltage beams were developed, rotation therapy was used to deliver x-radiation deep within the body. Before megavoltage beams were developed, rotation therapy was used to deliver x-radiation deep within the body. The lower exit dose of orthovoltage photon beams approximately compensated for the high entrance dose. The lower exit dose of orthovoltage photon beams approximately compensated for the high entrance dose. of megavoltage beams, rotational delivery fell into disfavor because skin-sparing of megavoltage beams, rotational delivery fell into disfavor because skin-sparing could be achieved even for single fields of radiation. could be achieved even for single fields of radiation.

Intensity Modulation The linac output can be varied. The linac output can be varied. The jaw opening can be changed. The jaw opening can be changed. The gantry speed can be altered. The gantry speed can be altered. The couch speed can be modified. The couch speed can be modified. The leaf states can be changed. The leaf states can be changed.

Tomotherapy Information The primary collimator and jaws are fabricated from an alloy containing 95% tungsten. The primary collimator and jaws are fabricated from an alloy containing 95% tungsten. The thickness of the clamshell is about 22 cm, which reduces the leakage for IMRT with high numbers of monitor units to values typical for conventional delivery with conventional monitor units. The thickness of the clamshell is about 22 cm, which reduces the leakage for IMRT with high numbers of monitor units to values typical for conventional delivery with conventional monitor units.

At the axis of rotation, the leaf thickness is cm and the leaf height is 10 cm of 95% tungsten. The leaves have a tongue- and-groove design that results in an inter- leaf leakage less than 0.5% of its open intensity, which makes it the best-shielded radiotherapy unit used for IMRT. At the axis of rotation, the leaf thickness is cm and the leaf height is 10 cm of 95% tungsten. The leaves have a tongue- and-groove design that results in an inter- leaf leakage less than 0.5% of its open intensity, which makes it the best-shielded radiotherapy unit used for IMRT.

can irradiate up to a 160 cm long field. can irradiate up to a 160 cm long field. The Tomotherapy unit has instead a set of uniform thickness filters before and after the monitor chamber to provide buildup to the monitor chamber, to shield the monitor chamber from the jaws, and to remove extremely low-energy photons. The Tomotherapy unit has instead a set of uniform thickness filters before and after the monitor chamber to provide buildup to the monitor chamber, to shield the monitor chamber from the jaws, and to remove extremely low-energy photons.

The rate of fall-off at a plane through the machine axis is about 2.5% to 3% per cm so that by the edge of the field (20 cm from the central axis) the output is 40% to 50% of its value at the center of the beam. The intensity variation leaf-to-leaf is about 2%,but this small discretization cannot be discerned dosimetrically. The rate of fall-off at a plane through the machine axis is about 2.5% to 3% per cm so that by the edge of the field (20 cm from the central axis) the output is 40% to 50% of its value at the center of the beam. The intensity variation leaf-to-leaf is about 2%,but this small discretization cannot be discerned dosimetrically.

The major advantage of a lack of a field- flattening filter is the beam quality. The thin set of filters produces far less head scatter than a conventional linac equipped with a field-flattening filter. The major advantage of a lack of a field- flattening filter is the beam quality. The thin set of filters produces far less head scatter than a conventional linac equipped with a field-flattening filter.

This also improves the imaging characteristics of the beam. The energy spectrum at the center of the field is not significantly harder than the spectrum at the edge of the field. This means that the beam is easier to characterize with model- based dose calculation systems This also improves the imaging characteristics of the beam. The energy spectrum at the center of the field is not significantly harder than the spectrum at the edge of the field. This means that the beam is easier to characterize with model- based dose calculation systems

The helical tomotherapy has a conventional xenon ion chamber CT detec- tor system on board the system that acquires a transmission signal from the linac beam. The parameters of the linac radiofrequency system are adjusted for imaging from those for treatment so that the beam has a lower energy (about 3.5 MV),lower pulse repe- tition frequency,and smaller output. The helical tomotherapy has a conventional xenon ion chamber CT detec- tor system on board the system that acquires a transmission signal from the linac beam. The parameters of the linac radiofrequency system are adjusted for imaging from those for treatment so that the beam has a lower energy (about 3.5 MV),lower pulse repe- tition frequency,and smaller output.

Absence Of Metal Artifacts Metal artifacts arise in conventional CT scanners because the attenuation of the metal is non-linear due to the photoelectric effect. In helical CT, the beam is penetrating enough to eliminate metal artifacts arising from hip prostheses and dental filings. Absence Of Metal Artifacts Metal artifacts arise in conventional CT scanners because the attenuation of the metal is non-linear due to the photoelectric effect. In helical CT, the beam is penetrating enough to eliminate metal artifacts arising from hip prostheses and dental filings.

This means that a verification CT could be a more reliable CT system for prostate patients with hip replacements and head and neck patients with cancer of the tongue. This means that a verification CT could be a more reliable CT system for prostate patients with hip replacements and head and neck patients with cancer of the tongue.

For a typical 30-fraction treat- ment schedule, daily imaging delivers a total exposure dose to the imaged volume of less than 1 Gy. For a typical 30-fraction treat- ment schedule, daily imaging delivers a total exposure dose to the imaged volume of less than 1 Gy. For a typical 30-fraction treatment schedule, daily imaging delivers a total exposure dose to the imaged volume of less than 1 Gy. For a typical 30-fraction treatment schedule, daily imaging delivers a total exposure dose to the imaged volume of less than 1 Gy.

Nonetheless, MV CT images are far superior to planar images (either kV or MV) for the verification of correct patient setup. Moreover, helical MV CT imaging is a slow CT imaging technique that allows for the encoding of target motion in the resulting MV CT data set (see fig. 10, 11 ), and therefore the pretreatment verification of a motion envelope defined from four-dimensional CT. Nonetheless, MV CT images are far superior to planar images (either kV or MV) for the verification of correct patient setup. Moreover, helical MV CT imaging is a slow CT imaging technique that allows for the encoding of target motion in the resulting MV CT data set (see fig. 10, 11 ), and therefore the pretreatment verification of a motion envelope defined from four-dimensional CT.

Tungsten MLC 2cm in width

CRANE

Rock Mackie with the University of Wisconsin Tomotherapy Research Unit

Tomotherapy

Hi - ART

Tomos ’Universal’ Signature

Tomotherapy And Adaptive Radiotherapy

instead of simply delivering the intended treatment plan, one would take an exit dose measurement during treatment and reconstruct the dose distribution that has been delivered. Using any of a number of metrics, one could then compare this actually delivered dose dis- tribution with the intended one. instead of simply delivering the intended treatment plan, one would take an exit dose measurement during treatment and reconstruct the dose distribution that has been delivered. Using any of a number of metrics, one could then compare this actually delivered dose dis- tribution with the intended one.

the pretreatment dose guidance that is currently possible with tomotherapy. The overlaid isodose cloud can be used to visually verify that the intended targets lie within the high-dose region and that organs at risk lie outside the high-dose region. the pretreatment dose guidance that is currently possible with tomotherapy. The overlaid isodose cloud can be used to visually verify that the intended targets lie within the high-dose region and that organs at risk lie outside the high-dose region.

Positioning Verification However, placing a slippery polyethylene sheet with handholds between the couch top and mattress can easily effect lateral movements. The next generation of couches on helical tomotherapy units has lateral adjustments. Tomotherapy comes equipped with a set of moveable CT- simulator lasers so that the modified position of the patient can be confirmed. However, placing a slippery polyethylene sheet with handholds between the couch top and mattress can easily effect lateral movements. The next generation of couches on helical tomotherapy units has lateral adjustments. Tomotherapy comes equipped with a set of moveable CT- simulator lasers so that the modified position of the patient can be confirmed.

The process is not accurate unless a CT of the patient at the time of treatment is used. Dose reconstruc- tion has been tested using the UW tomotherapy benchtop unit but not yet implemented on the UW clinical unit. The process is not accurate unless a CT of the patient at the time of treatment is used. Dose reconstruc- tion has been tested using the UW tomotherapy benchtop unit but not yet implemented on the UW clinical unit.

Deformable Registration And Autocontouring

Deformable registration algorithms typically use common features such as contours or points that are identified automatically in both images (Blake and Isard 1998). The intervening space between identifiable features is deformed according to finite element methods using established elastic property parameters ( Deformable registration algorithms typically use common features such as contours or points that are identified automatically in both images (Blake and Isard 1998). The intervening space between identifiable features is deformed according to finite element methods using established elastic property parameters (

Re-optimization is the modification of subsequent treatment fractions on the basis of the dose reconstruction and deformable registration of the regions of interest and the dose distribution (Wu 2002) Re-optimization is the modification of subsequent treatment fractions on the basis of the dose reconstruction and deformable registration of the regions of interest and the dose distribution (Wu 2002)

While it is not possible to remove the excess dose delivered to a sensitive structure, it may be possible to take this into account in re-optimization so that the dose delivered in the whole course of therapy might be the same or only marginally higher. While it is not possible to remove the excess dose delivered to a sensitive structure, it may be possible to take this into account in re-optimization so that the dose delivered in the whole course of therapy might be the same or only marginally higher.

Re-optimization might also be done if it is decided that the target volume needs to change part way through the course of ther- apy. Re-optimization is a research topic and not yet being tested on the UW clinical unit Re-optimization might also be done if it is decided that the target volume needs to change part way through the course of ther- apy. Re-optimization is a research topic and not yet being tested on the UW clinical unit

Disadvantage Ring gantry are minimal since few patients are treated with non-coplanar radiation fields and IMRT diminishes the need for these types of field arrangements. Ring gantry are minimal since few patients are treated with non-coplanar radiation fields and IMRT diminishes the need for these types of field arrangements.

Clinical Appliaction Image-Guided Stereotactic Body Radiotherapy of Non-Small-Cell Lung Cancer. Image-Guided Stereotactic Body Radiotherapy of Non-Small-Cell Lung Cancer.

Treatment of Multiple Metastasis

Future

Needs to be able to calculate the dose actually delivered during therapy. Needs to be able to calculate the dose actually delivered during therapy. The actually delivered dose can be calculated from collected exit dose measurements during treatment using back-projection The actually delivered dose can be calculated from collected exit dose measurements during treatment using back-projection has to have the ability to reliably track four-dimensional target motion envelopes since tomotherapy is a fully dynamic therapy has to have the ability to reliably track four-dimensional target motion envelopes since tomotherapy is a fully dynamic therapy

reliably contour changes in the target and to quantify organ deformation. Target variation and organ deformation can be handled using deformable image registration and projecting the contours from the old data set onto the new data set using nonlinear transformation reliably contour changes in the target and to quantify organ deformation. Target variation and organ deformation can be handled using deformable image registration and projecting the contours from the old data set onto the new data set using nonlinear transformation

MRIgRT

Tomotherapy With MRI

Against

“There are no non- violent revolutions…” Malcolm X

WITH!

EORTC 22922/ MA20

Highly Arched Chest Wall More than conventional: 3 fields Conventional: 2 tangential fields 50% 70% 90% 120% IMRT

Spare Time on the treatment Machine. Single Plan reduce planning work Load. Reduced work on Linac. Reduces treatment time from 7 to 5 weeks

Herceptin Anthracyclin Taxanes Radiotherapy

Cramp? Better