- Email: [email protected]
Couch Rotation Technique for Treatment of Head and Neck Cancer
.Mr&a/ Pnnted
Dosrnw~v, Vol. 17. pp. 57-60 m the U.S.4. All rights reserved
Copyright
0
1992 Amencan
0739-021 l/92 Associatmn of Medical
$5.00 + .OO Doskmetrists
COUCH ROTATION TECHNIQUE FOR TREATMENT OF HEAD AND NECK CANCER V. RAO
DEVINENI,M.D. and MARTIN
E. KEISCH,
M.D.
Radiation Oncology Center, Mallinckrodt Institute of Radiology, Washington University Medical Center, 4939 Audubon, Suite 5500, St. Louis, MO 63110, U.S.A. Abstract-This paper reviews a technique for patients with head and neck cancer that achieves adequate inferior margins on the lateral ports by rotating the treatment couch. This technique has the advantage of avoiding multiple ports in an area of high risk or over a tumor mass. Key Words: Head and neck cancer, Treatment technique.
technique may be needed since there is some reduction in the volume covered when this technique is used. In our institution, cerrobend blocks are prepared after outlining the target area on a simulation film taken in treatment position. With a rotation of the couch it is necessary to outline the inferior border of the clavicles with a wire prior to obtaining the simula-
INTRODUCI’ION
Radiotherapy techniques in head and neck cancer have become more standardized at the present time. In most situations, radiation therapy to head and neck tumors is delivered with right and left lateral parallel opposed techniques, both for definitive therapy and for postoperative situations. This assures adequate cranial and caudal coverage. In patients with tumor or an area of risk in the lower part of the neck, an anterior low neck port is usually used to cover nodes to the level of the clavicle. When this is done, the inferior border of the lateral port may cut across the tumor causing nonhomogeneous distribution of the dose in this junction area. We review an option for treating head and neck cancers with a couch rotation technique when disease is present in the lower cervical region. MATERIALS
AND
METHODS
Under normal circumstances in a true lateral setup, the head of the table is at 180”. The gantry is rotated to 90” for a right lateral and 270” for a left lateral treatment. The treatment setup is isocentric to the midplane of the transverse diameter. With this technique the inferior border, normally placed a few centimeters above the shoulder, adequately covers most of the lymphatics. However, in situations where there is a lymph node in the lower part of the neck or when the shoulders are somewhat high, as is noted in some patients, the inferior border may be overlying the lymph node or the area of tumor tissue. In such circumstances, rotating the foot of the couch 5’ away from the side of the gantry (i.e., 175” when the right lateral is being treated and 185” when the left lateral is being treated) will increase the coverage of the low neck and will include the inferior border of the clavicle in the treatment volume, thus eliminating the need for an AP low neck field. A superior margin slightly higher than that used in the straight lateral
Fig. 1. Left lateral simulation film showing the position of the enlarged low cervical node as well as the wires marking the clavicles (right-sided wire is thin, left-sided wire is thick). (Simulator film). 57
58
Medical Dosimetry
Fig. 2. Port film for setu@shown in Fig. 1. (Treatment
Volume 17, Number 2, 1992
verifi-
cation film).
Fig. 3. Skin lines for same patient in Fig. 1: note coverage of supraclavicular fossa and enlarged low cervical node. (Clinical photograph).
film since the clavicles are no longer superimposed. By using different diameter wires under each clavicle, the right and left sides may be identified on
the simulation films for the purpose of drawing the blocks (Fig. 1). Figures 2 and 3 show the port film and clinical photograph for one patient’s setup.
tion
\
\-I-~-
_-------f-y
Fig. 4. Transverse plan through upper cervical region is similar to that seen in lateral techniques without couch angulation. (Transverse plan).
Couch rotation technique 0 V. R. DEVINENIand M. E. KEISCH
Left
Right
59
only 1000 cGy. Figures 4 and 5 show the transverse and coronal plans obtained with this technique. The transverse plan is through the level of the central axis. The coronal plan is located just anterior to the spinal canal (off-cord) on a plane that coincides with the middle of the supraclavicular fossa in the AP/PA dimension. The transverse plan is very similar in dose distribution to that seen without inferior angulation of the lateral port. The coronal plan, however, shows the coverage of the supraclavicular fossa with an adequate dose (N 5000 cGy). Additionally, it can be seen that the jugulodigastric nodal area receives 60006500 cGy. Figure 6 shows the same coronal plan superimposed on a magnetic resonance image to further demonstrate coverage of these anatomical regions. DISCUSSION
Fig. 5. Coronal plan through the plane of the jugulodigastric node as well as the middle of the supraclavicular fossa. (Coronal plan).
DOSIMETRY The details of treatment are: (Using 6 MV photons and three-dimensional compensating filters) 4000 cGy to the large on-cord field, 2000 cGy offcord, and 1000 cGy to the off-cord boost volume. In addition, the ipsilateral neck receives 2000 cGy using 9 MeV electrons, while the contralateral neck receives
In this paper we describe a technique for treating head and neck cancers with disease in the lower cervical region when a conventional combination of parallel opposed laterals and an AP low neck field would meet at an area of known disease. One alternative is to treat with a single large AP photon field to cord tolerance, and then boost with AP electrons.’ It has been noted that this technique may inadequately treat the jugulodigastric region due to electron absorption by the mandible.‘v2 The couch rotation technique described here eliminates underdosing low neck disease due to field junctions over involved lymph nodes and also delivers adequate doses to the jugulodigastric region. This technique has been used in the treatment of laryngeal cancer and described previously.3x4T5Initially
Fig. 6. Same as in Fig. 5, overlying a coronal MR image to clarify coverage of the cervical and supraclavicular regions. (Coronal plan over MR).
60
Medical Dosimetry
described, by Cunningham and Van Dyk,3 with a more acute angulation (12”) and 15” wedge filters, this was suggested as a technique for treating early neck disease with better coverage inferiorly from an equal-sized field. In their technique the patient sat upright in a plaster mold making simulation impossible and verification difficult. The inferior angulation resulted from gantry rotation, rather than couch rotation. In a later report, Harwood et al4 analyzed the results in supraglottic laryngeal carcinoma at Princess Margaret Hospital when the technique as described by Cunningham3 was used. The reported results are comparable to those in other published series,4 supporting the adequacy of the technique. Andrew, Eapen, and Kulkam? described a refinement ofthis technique in which the patient is supine and the inferior angulation is made by couch rotation as we describe here. This modification allows simulation and potentially improves immobilization and reproducibility. Dose calculation was experimentally verified with the measured data from water phantoms and agreed within 2% of calculated isodose curves. In our variation of this technique, the use of custom cerrobend blocks and careful delineation of the inferior extent of
Volume 17, Number 2, 1992
the target volume by using wires below the clavicles allows further assurance of the adequacy of target coverage and sparing of normal tissues. The degree of couch rotation can be considerably minimized by using wires as described rather than a 12” angulation in all cases as described in previous reports.3,4s5
REFERENCES 1. Marks, J.E.; Lee, F. Irradiation techniques for head and neck cancer. In: Levitt, S.H.; Tapley, N.D.V., editors. Technological basis of radiation therapy: practical clinical applications. Philadelohia: Lea and Febiaer, 1984: 116- 137. 2. M-arks, J.E.; Silverm&, C.L.; Devineni, V.R. Success of elective irradiation of occult lymphatic metastases from cancers of the larynx and pyriform sinus. Head Neck Surg. 9:77-8 1; 1986. 3. Cunningham, J.R.; Van Dyk, J. Laryngeal cancer: Practical problems in effective dose delivery. Laryngoscope 85:10291038; 1975. 4. Harwood, A.R.; Beale, F.A.; Cummings, B.J.; Keane, T.J.; Payne, D.G.; Rider, W.D.; Rawlinson, E.; Elhakim, T. Supraglottic laryngeal carcinoma: An analysis of dose-time-volume factors in 4 10 patients. ht. J. Radiat. Oncol. Biol. Phys. 9:3 I l319; 1983. 5. Andrew, J.W.; Eapen, L.; Kulkami, N.S. Homogeneous irradiation of the “short-necked” laryngeal cancer patient. Int. J. Radiat. Oncol. Biol. Phys. 10~549-553; 1984.
Dosrnw~v, Vol. 17. pp. 57-60 m the U.S.4. All rights reserved
Copyright
0
1992 Amencan
0739-021 l/92 Associatmn of Medical
$5.00 + .OO Doskmetrists
COUCH ROTATION TECHNIQUE FOR TREATMENT OF HEAD AND NECK CANCER V. RAO
DEVINENI,M.D. and MARTIN
E. KEISCH,
M.D.
Radiation Oncology Center, Mallinckrodt Institute of Radiology, Washington University Medical Center, 4939 Audubon, Suite 5500, St. Louis, MO 63110, U.S.A. Abstract-This paper reviews a technique for patients with head and neck cancer that achieves adequate inferior margins on the lateral ports by rotating the treatment couch. This technique has the advantage of avoiding multiple ports in an area of high risk or over a tumor mass. Key Words: Head and neck cancer, Treatment technique.
technique may be needed since there is some reduction in the volume covered when this technique is used. In our institution, cerrobend blocks are prepared after outlining the target area on a simulation film taken in treatment position. With a rotation of the couch it is necessary to outline the inferior border of the clavicles with a wire prior to obtaining the simula-
INTRODUCI’ION
Radiotherapy techniques in head and neck cancer have become more standardized at the present time. In most situations, radiation therapy to head and neck tumors is delivered with right and left lateral parallel opposed techniques, both for definitive therapy and for postoperative situations. This assures adequate cranial and caudal coverage. In patients with tumor or an area of risk in the lower part of the neck, an anterior low neck port is usually used to cover nodes to the level of the clavicle. When this is done, the inferior border of the lateral port may cut across the tumor causing nonhomogeneous distribution of the dose in this junction area. We review an option for treating head and neck cancers with a couch rotation technique when disease is present in the lower cervical region. MATERIALS
AND
METHODS
Under normal circumstances in a true lateral setup, the head of the table is at 180”. The gantry is rotated to 90” for a right lateral and 270” for a left lateral treatment. The treatment setup is isocentric to the midplane of the transverse diameter. With this technique the inferior border, normally placed a few centimeters above the shoulder, adequately covers most of the lymphatics. However, in situations where there is a lymph node in the lower part of the neck or when the shoulders are somewhat high, as is noted in some patients, the inferior border may be overlying the lymph node or the area of tumor tissue. In such circumstances, rotating the foot of the couch 5’ away from the side of the gantry (i.e., 175” when the right lateral is being treated and 185” when the left lateral is being treated) will increase the coverage of the low neck and will include the inferior border of the clavicle in the treatment volume, thus eliminating the need for an AP low neck field. A superior margin slightly higher than that used in the straight lateral
Fig. 1. Left lateral simulation film showing the position of the enlarged low cervical node as well as the wires marking the clavicles (right-sided wire is thin, left-sided wire is thick). (Simulator film). 57
58
Medical Dosimetry
Fig. 2. Port film for setu@shown in Fig. 1. (Treatment
Volume 17, Number 2, 1992
verifi-
cation film).
Fig. 3. Skin lines for same patient in Fig. 1: note coverage of supraclavicular fossa and enlarged low cervical node. (Clinical photograph).
film since the clavicles are no longer superimposed. By using different diameter wires under each clavicle, the right and left sides may be identified on
the simulation films for the purpose of drawing the blocks (Fig. 1). Figures 2 and 3 show the port film and clinical photograph for one patient’s setup.
tion
\
\-I-~-
_-------f-y
Fig. 4. Transverse plan through upper cervical region is similar to that seen in lateral techniques without couch angulation. (Transverse plan).
Couch rotation technique 0 V. R. DEVINENIand M. E. KEISCH
Left
Right
59
only 1000 cGy. Figures 4 and 5 show the transverse and coronal plans obtained with this technique. The transverse plan is through the level of the central axis. The coronal plan is located just anterior to the spinal canal (off-cord) on a plane that coincides with the middle of the supraclavicular fossa in the AP/PA dimension. The transverse plan is very similar in dose distribution to that seen without inferior angulation of the lateral port. The coronal plan, however, shows the coverage of the supraclavicular fossa with an adequate dose (N 5000 cGy). Additionally, it can be seen that the jugulodigastric nodal area receives 60006500 cGy. Figure 6 shows the same coronal plan superimposed on a magnetic resonance image to further demonstrate coverage of these anatomical regions. DISCUSSION
Fig. 5. Coronal plan through the plane of the jugulodigastric node as well as the middle of the supraclavicular fossa. (Coronal plan).
DOSIMETRY The details of treatment are: (Using 6 MV photons and three-dimensional compensating filters) 4000 cGy to the large on-cord field, 2000 cGy offcord, and 1000 cGy to the off-cord boost volume. In addition, the ipsilateral neck receives 2000 cGy using 9 MeV electrons, while the contralateral neck receives
In this paper we describe a technique for treating head and neck cancers with disease in the lower cervical region when a conventional combination of parallel opposed laterals and an AP low neck field would meet at an area of known disease. One alternative is to treat with a single large AP photon field to cord tolerance, and then boost with AP electrons.’ It has been noted that this technique may inadequately treat the jugulodigastric region due to electron absorption by the mandible.‘v2 The couch rotation technique described here eliminates underdosing low neck disease due to field junctions over involved lymph nodes and also delivers adequate doses to the jugulodigastric region. This technique has been used in the treatment of laryngeal cancer and described previously.3x4T5Initially
Fig. 6. Same as in Fig. 5, overlying a coronal MR image to clarify coverage of the cervical and supraclavicular regions. (Coronal plan over MR).
60
Medical Dosimetry
described, by Cunningham and Van Dyk,3 with a more acute angulation (12”) and 15” wedge filters, this was suggested as a technique for treating early neck disease with better coverage inferiorly from an equal-sized field. In their technique the patient sat upright in a plaster mold making simulation impossible and verification difficult. The inferior angulation resulted from gantry rotation, rather than couch rotation. In a later report, Harwood et al4 analyzed the results in supraglottic laryngeal carcinoma at Princess Margaret Hospital when the technique as described by Cunningham3 was used. The reported results are comparable to those in other published series,4 supporting the adequacy of the technique. Andrew, Eapen, and Kulkam? described a refinement ofthis technique in which the patient is supine and the inferior angulation is made by couch rotation as we describe here. This modification allows simulation and potentially improves immobilization and reproducibility. Dose calculation was experimentally verified with the measured data from water phantoms and agreed within 2% of calculated isodose curves. In our variation of this technique, the use of custom cerrobend blocks and careful delineation of the inferior extent of
Volume 17, Number 2, 1992
the target volume by using wires below the clavicles allows further assurance of the adequacy of target coverage and sparing of normal tissues. The degree of couch rotation can be considerably minimized by using wires as described rather than a 12” angulation in all cases as described in previous reports.3,4s5
REFERENCES 1. Marks, J.E.; Lee, F. Irradiation techniques for head and neck cancer. In: Levitt, S.H.; Tapley, N.D.V., editors. Technological basis of radiation therapy: practical clinical applications. Philadelohia: Lea and Febiaer, 1984: 116- 137. 2. M-arks, J.E.; Silverm&, C.L.; Devineni, V.R. Success of elective irradiation of occult lymphatic metastases from cancers of the larynx and pyriform sinus. Head Neck Surg. 9:77-8 1; 1986. 3. Cunningham, J.R.; Van Dyk, J. Laryngeal cancer: Practical problems in effective dose delivery. Laryngoscope 85:10291038; 1975. 4. Harwood, A.R.; Beale, F.A.; Cummings, B.J.; Keane, T.J.; Payne, D.G.; Rider, W.D.; Rawlinson, E.; Elhakim, T. Supraglottic laryngeal carcinoma: An analysis of dose-time-volume factors in 4 10 patients. ht. J. Radiat. Oncol. Biol. Phys. 9:3 I l319; 1983. 5. Andrew, J.W.; Eapen, L.; Kulkami, N.S. Homogeneous irradiation of the “short-necked” laryngeal cancer patient. Int. J. Radiat. Oncol. Biol. Phys. 10~549-553; 1984.