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Extra-Oral Roentgenographic Technics, Using the Casette Table
EXTRA-ORAL ROENTGENOGRAPHIC TECHNICS, USING THE CASETTE TABLE B y D. W.
L ovett,
D.D .S.,* Iowa City, Iowa
X T R A -O R A L roentgenography is an important part o f both medical and dental roentgenography. It has often been neglected by both pro fessions, because of lack o f a simple, convenient and workable technic. T h e casette table, shown in Figure i, has been developed for the purpose o f perfecting such a technic. T h e casette table technic has been developed for the use of the roentgenologist and general practitioner, to obtain conveniently and satisfactorily diagnostic extra-oral roentgenograms, and not for scientific research. It also affords much positional comfort to the patient. T he technic is not new, but is a great improvement over those used at present, for both the operator and the patient. T h e casette table, a “ glorified” angle board, is simple o f construction, easy to manipulate, efficient in operation and a nice-appearing piece o f equipment. The general dimensions are as follow s: height, 36 inches; width, 25^ inches; over-all thickness, 10 inches for table top; for base, 14 inches. This table can be used w ith either a dental chair or an ordinary straight chair. A dental chair is prefer able because the elevation o f the patient when seated can be varied. This change in elevation, the only adjustment neces sary, with the chair, is to compensate for the difference in height of the various patients. The table is so designed as to be freely moved to any position in front or on either side of the chair; which gives free access to every position
E
•Instructor, Department of Radiology, State University of Iowa College of Dentistry. Jour. A .D .A ., V o l. 28, Septem ber 1941
necessary raphy.
for
extra-oral
roentgenog
TE C H N IC
The steps in the extra-oral technic are as follows: 1. The table is moved into position. 2. T h e casette is placed (with markers). 3. T h e height o f the chair is adjusted. 4. The table top is positioned to the patient’s head. 5. T h e table read ing is made. 6. The angulation is ad justed. 7. Exposure is made. M A X ILL A R Y SIN U S TECH N IC
The patient is seated in an upright position in the chair and the table is moved into position in front o f the pa tient. (Fig. 3.) T h e edge of the table top will be approximately parallel with a line drawn through the front tips of both arm rests o f the chair. The casette is placed on the adjustable table top (marked L and R for left and right, respectively). T h e chair height is ad justed to a position in which the pa tient’s chin is about 4 or 5 inches above the table top. T h e patient’s arms are placed over the ends of the stationary table top, for comfort and stability, and the head is tipped forward in a comfortable position. T h e table top is raised to fit the nose and chin of the patient snugly. (The mouth can be either closed or open.) T h e adjustable table top will autom atically lock in any position desired. The necessary adjust ments are made for the patient’s com fort. T h e table reading is taken and, by consulting Chart 1, the tube angulation is set. For example, if the table reading
L o v e t t — R o e n t g e n o g r a p h ic T e c h n i c s , U s in g C a s e t t e T a b l e
is 65°, the vertical tube angulation will be 450. T he long axis o f the tube, or horizontal angulation, will be parallel with the edge of the tablé top. T he cen tral ray is directed parallel with the sagittal plane to pass directly between the m axillary sinuses. A film target dis tance of from 24 to 30 inches should be used. The exposure time for adults, us ing ultra-speed screens, will be from five to eight seconds, depending on the size of the head and the age o f the patient. These tables (1-4) are computed for
r473
as that for the m axillary sinus except for step 4. T h e patient’ s head is bowed slightly more and the table top and casette are adjusted to fit the patient’s nose and forehead. T h e same angulation chart, film target distance and exposure time are used. L A T E R A L JA W (R A M U S AND M OLAR REGION) RECORD
The patient is seated in an upright position in the chair and the casette table moved to a diagonal position at the side of the patient. (Fig. 2.) T h e chair is adjusted so that the top o f the table is approximately 6 inches below the top of the patient’s shoulder. T h e patient’s
Fig. 2.— Casette table in position at side of chair, adjusted to patient for lateral temporomandibular record.
Fig. 1.— Extra-oral casette table.
the ordinary or normal cases. T he an gulation m ay have to be changed slightly for varied cases. Also, the angulation may have to be varied when the opera tor wishes a specific area recorded and is not especially interested in the rest of the entire field. FRO N TAL SINUS (N O SE , T U R B IN A TE S AND E T H N O ID s) RECORD
T h e frontal sinus technic is the same
arm (the one next to the table) is placed on the table as shown in Figure 2. T he head is tipped sideways toward the table and the table top and casette are adjusted to the side of the head. The ear should be snugly against the casette and the nose about 2-|- inches from the casette. This should put the patient in a comfortable position. I f not, the angle of the table top is changed to a com fortable position, care being observed to keep the head in the correct relation to the casette after the change is made. The table reading is taken and, from Table
1474
T h e J o u r n a l o f t h e A m e r ic a n D e n t a l A s s o c ia t io n
2, the correct vertical tube angulation is m ade. W ith a 4 to 6 inch skin target distance, the central ra y is directed to pass abou t on e-h alf inch below the angle o f the ja w and through the area that is to be of the m ost vital interest in the roentgenogram . T h is w ill m ake the lon g axis o f the tube approxim ately parallel to the plane o f the casette. T h e exposure time w ith double intensifying screens w ill be one to one and oneh a lf seconds w ith ou t screens, but w ith super speed films, from six to seven seconds. T h e same technic and table applies to both right and left sides.
T h e table is set against the side of the chair on the side of the patient on which the articulation is to be recorded. T he chair is adjusted so that the top of the patient’s shoulder is from 4 to 5 inches above the top of the table. The patient leans toward the table and places the arm next to the table upon the sta tionary top, as shown in Figure 2. The head is tipped slightly toward the table and the casette adjusted to fit against the side of the patient’s head. T h e ear and the temple should be snug against the casette. The table reading is taken and, from Table 3, the tube angulation
Fig. 3.— Casette table in position in front of chair, adjusted to patient for anteroposte rior temporomandibular record.
Fig. 4.— Casette table in position in front of chair, positioned to patient for bregmamentum record.
LA T E R A L JA W (B IC U SPID AND M OLAR REGION) RECORD
T h e technic for the bicuspid and molar region is very much the same as for the molar and ramus region except for the position of the head in relation to the casette. The head is tilted in the same manner. The table top and casette are adjusted to the head so that the cheek is flat against the casette and the nose touching or almost touching the casette. T h e same film target distance, angulation chart and exposure time are used.
l a t e r a l t e m p o r o m a n d ib u l a r r e c o r d
is set. T h e central ray should be directed through a point 2 inches above and onehalf inch anteriorly from the external auditory meatus. T h e long axis of the tube should be parallel with the sagittal plane. W ith the tube in this position and the designated angulation toward the inferior aspect, the central ray will emanate at the temporomandibular ar ticulation next to the film. T h e film target distance should be 20 inches and the time of exposure with double in tensifying screens, for adults, from three and one-half to four and one-half seconds.
L o v e t t — R o e n t g e n o g r a p h ic T e c h n ic s , U sin g C a s e t t e T a b l e
AN TE R O PO STE RIO R TE M PO RO M A N D IBU LAR RE C O R D
The patient is seated in the upright position in the chair. The table is posi tioned in front of the patient as for the m axillary sinus technic. The chair is adjusted so that the top of the patient’s shoulders is about 6 inches above the top of the table. T h e patient’s arms are
'475
under the chin and forehead for support. (Fig. 3.) This support will afford a com fortable position for the patient. The table reading is taken and the angulation of the tube set from T able 4. T h e cen tral ray is directed through the head m idway between the ears and to pass just below the nose. T h e film target dis tance should be 24 inches and the expo sure time with double intensifying
T a b l e 1.— M a x i l l a r y S i n u s ; F o r e h e a d a n d N o s e ; N o s e a n d C h in
Table Reading
T a b l e 3.— L a t e r a l T e m p o r o m a n d i b u l a r
Tube Angulation
20....... ................................................9 0 2 5 ....... ................................................ 8 5 3 0 ....... ................................................ 8 0 3 5 ....... ................................................ 7 5 4 0 ___ ................................................ 7 0 4 5 .. .. ................................................6 5 5 0 ....... .............................................. 6 0 5 5 .... ................................................5 5 6 0 ....... ................................................5 0 6 5 .... ................................................4 5 7 0 .... ................................................4 0 7 5 .. .. ................................................3 5 8 0 ... . ........................................ 3 0 8 5 ... . ................................................2 5 9 0 ........................................................ 20 T able
Table
Reading
2 .—
L ater al Jaw
Tube Angulation
9 0 ....... ..................................... — 8 8 5 . . . . ........................................ — 3 8 0 ... . ................................................. 2 7 5 ................................................................ 7 7 0 .. .. ................................................. 1 3 6 5 ... . ................................................. 1 8 6 0 . ... .......................................... 2 3 5 5 . . . . .......................................... 2 8 5 0 . . . . ............................................................................. 3 3 placed over the stationary part o f the table as in the m axillary sinus position. T h e head is tipped forward and the table top and casette are adjusted to the head so that the nose touches the casette at about the center. The chin and fore head should be equally distance from the casette. This positioning can best be carried out by placing small cork blocks
R ecord T able
Tube
R ea d in g
A ngulation
9 0 ...
......................1 5
8 5 ...
.........................20
8 0 ...
.........................2 5
7 5 ...
........................ 3 0
7 0 ...
.........................3 5
6 5 ...
.........................4 0
6 0 ...
.........................4 5
55 ...
........................ 50
SO. ..
.........................5 5
4 5 ...
.........................60
T a b l e 4.— A n t e r o p o s t e r i o r T em por om an d ibu lar R ecord
T able
Tube
Reading
A ngulation
4 0 ...
.........................5 0
4 5 ...
.........................45
5 0 ...
.........................40
5 5 ...
.........................3 5
6 0 ...
.........................3 0
6 5 ...
.........................2 5
7 0 ...
.........................20
75 ...
.........................1 5
8 0 ...
.........................1 0
8 5 ...
.........................
9 0 ...
5
............. 0
screens for adults from six to seven seconds. LA TE R A L H EAD RECORD
For the lateral head record, the chair and table positions are the same as those used for the lateral temporomandibular procedure. T h e table top and casette are adjusted to fit snugly against the ears,
1476
T h e J o u r n a l o f t h e A m e r ic a n D e n t a l A s s o c ia t io n
with the sagittal plane parallel with the plane of the casette. T h e table reading is taken and the angulation determined from Table 4. T h e central ray is directed to pass through the head at a point one and one-half inches anteriorly from the external auditory meatus and perpen dicular to the sagittal plane. T h e film target distance should be 24 inches. The exposure time with double intensifying screens is, for adults, from seven to eight seconds. PRO FILE RECORD
T h e table position, head position, table setting and angulation for the profile technic are the same as that used for the lateral head procedures, with the ex ception that a film target distance of 72 inches should be used. For conveni ence in setting the correct tube angula tion, the table top and casette should be set at 90°, so that difficuties will not be encountered in using a 72-inch film target distance. The exposure time with double intensifying screens is from one and one-half to two seconds. BREGM A-M EN TU M RECORD
Films taken by this technic give ex cellent views o f the heads o f the con dyles, the coronoid processes and the rami. T h e bregma is that point formed by the fibrous articulation o f the two. parietal bones and the frontal bone. T h e mentum is the anterior-inferior border o f the synthesis of the mandible. T h e table is positioned in front of the patient in the same manner as in the m axillary sinus procedure. T he chair is
adjusted so that the top of the patient’s shoulders is approxim ately 6 inches above the table top. T h e table top read ing is set at o for this technic. W ith the patient’s chin in the mento-anterior position, the chin should touch the casette at a point about two-thirds the distance to the opposite border and m idway be tween the lateral borders. T h e near border o f the casette should touch the clavicle region at approximately its superior border. (Fig. 4.) T h e central ray should be directed to pass through the bregm a and mentum. This will give a tube angulation o f approximately io°. The film target distance should be 24 inches and the exposure time for adults, using double intensifying screens, will be from seven to nine seconds. TA B LE M ODIFICATION S
The adjustable table top can be modi fied to suit many purposes. A change tunnel can be incorporated for stereo scopic roentgenography. Also, a com pression band can be added to help in stabilization during stereoscopic proce dures, bu t it is not generally necessary for regular extra-oral work. CO N CLU SIO N
This technic adequately serves the purpose o f general diagnostic extra-oral roentgenography. It affords comfort and ease for the patient in all necessary extra oral positions. T h e technics for the operator are easy, simple and efficient. Most im portant o f all, satisfactory diag nostic extra-oral roentgenograms are obtained. 501 O akland Avenue.
L ovett,
D.D .S.,* Iowa City, Iowa
X T R A -O R A L roentgenography is an important part o f both medical and dental roentgenography. It has often been neglected by both pro fessions, because of lack o f a simple, convenient and workable technic. T h e casette table, shown in Figure i, has been developed for the purpose o f perfecting such a technic. T h e casette table technic has been developed for the use of the roentgenologist and general practitioner, to obtain conveniently and satisfactorily diagnostic extra-oral roentgenograms, and not for scientific research. It also affords much positional comfort to the patient. T he technic is not new, but is a great improvement over those used at present, for both the operator and the patient. T h e casette table, a “ glorified” angle board, is simple o f construction, easy to manipulate, efficient in operation and a nice-appearing piece o f equipment. The general dimensions are as follow s: height, 36 inches; width, 25^ inches; over-all thickness, 10 inches for table top; for base, 14 inches. This table can be used w ith either a dental chair or an ordinary straight chair. A dental chair is prefer able because the elevation o f the patient when seated can be varied. This change in elevation, the only adjustment neces sary, with the chair, is to compensate for the difference in height of the various patients. The table is so designed as to be freely moved to any position in front or on either side of the chair; which gives free access to every position
E
•Instructor, Department of Radiology, State University of Iowa College of Dentistry. Jour. A .D .A ., V o l. 28, Septem ber 1941
necessary raphy.
for
extra-oral
roentgenog
TE C H N IC
The steps in the extra-oral technic are as follows: 1. The table is moved into position. 2. T h e casette is placed (with markers). 3. T h e height o f the chair is adjusted. 4. The table top is positioned to the patient’s head. 5. T h e table read ing is made. 6. The angulation is ad justed. 7. Exposure is made. M A X ILL A R Y SIN U S TECH N IC
The patient is seated in an upright position in the chair and the table is moved into position in front o f the pa tient. (Fig. 3.) T h e edge of the table top will be approximately parallel with a line drawn through the front tips of both arm rests o f the chair. The casette is placed on the adjustable table top (marked L and R for left and right, respectively). T h e chair height is ad justed to a position in which the pa tient’s chin is about 4 or 5 inches above the table top. T h e patient’s arms are placed over the ends of the stationary table top, for comfort and stability, and the head is tipped forward in a comfortable position. T h e table top is raised to fit the nose and chin of the patient snugly. (The mouth can be either closed or open.) T h e adjustable table top will autom atically lock in any position desired. The necessary adjust ments are made for the patient’s com fort. T h e table reading is taken and, by consulting Chart 1, the tube angulation is set. For example, if the table reading
L o v e t t — R o e n t g e n o g r a p h ic T e c h n i c s , U s in g C a s e t t e T a b l e
is 65°, the vertical tube angulation will be 450. T he long axis o f the tube, or horizontal angulation, will be parallel with the edge of the tablé top. T he cen tral ray is directed parallel with the sagittal plane to pass directly between the m axillary sinuses. A film target dis tance of from 24 to 30 inches should be used. The exposure time for adults, us ing ultra-speed screens, will be from five to eight seconds, depending on the size of the head and the age o f the patient. These tables (1-4) are computed for
r473
as that for the m axillary sinus except for step 4. T h e patient’ s head is bowed slightly more and the table top and casette are adjusted to fit the patient’s nose and forehead. T h e same angulation chart, film target distance and exposure time are used. L A T E R A L JA W (R A M U S AND M OLAR REGION) RECORD
The patient is seated in an upright position in the chair and the casette table moved to a diagonal position at the side of the patient. (Fig. 2.) T h e chair is adjusted so that the top o f the table is approximately 6 inches below the top of the patient’s shoulder. T h e patient’s
Fig. 2.— Casette table in position at side of chair, adjusted to patient for lateral temporomandibular record.
Fig. 1.— Extra-oral casette table.
the ordinary or normal cases. T he an gulation m ay have to be changed slightly for varied cases. Also, the angulation may have to be varied when the opera tor wishes a specific area recorded and is not especially interested in the rest of the entire field. FRO N TAL SINUS (N O SE , T U R B IN A TE S AND E T H N O ID s) RECORD
T h e frontal sinus technic is the same
arm (the one next to the table) is placed on the table as shown in Figure 2. T he head is tipped sideways toward the table and the table top and casette are adjusted to the side of the head. The ear should be snugly against the casette and the nose about 2-|- inches from the casette. This should put the patient in a comfortable position. I f not, the angle of the table top is changed to a com fortable position, care being observed to keep the head in the correct relation to the casette after the change is made. The table reading is taken and, from Table
1474
T h e J o u r n a l o f t h e A m e r ic a n D e n t a l A s s o c ia t io n
2, the correct vertical tube angulation is m ade. W ith a 4 to 6 inch skin target distance, the central ra y is directed to pass abou t on e-h alf inch below the angle o f the ja w and through the area that is to be of the m ost vital interest in the roentgenogram . T h is w ill m ake the lon g axis o f the tube approxim ately parallel to the plane o f the casette. T h e exposure time w ith double intensifying screens w ill be one to one and oneh a lf seconds w ith ou t screens, but w ith super speed films, from six to seven seconds. T h e same technic and table applies to both right and left sides.
T h e table is set against the side of the chair on the side of the patient on which the articulation is to be recorded. T he chair is adjusted so that the top of the patient’s shoulder is from 4 to 5 inches above the top of the table. The patient leans toward the table and places the arm next to the table upon the sta tionary top, as shown in Figure 2. The head is tipped slightly toward the table and the casette adjusted to fit against the side of the patient’s head. T h e ear and the temple should be snug against the casette. The table reading is taken and, from Table 3, the tube angulation
Fig. 3.— Casette table in position in front of chair, adjusted to patient for anteroposte rior temporomandibular record.
Fig. 4.— Casette table in position in front of chair, positioned to patient for bregmamentum record.
LA T E R A L JA W (B IC U SPID AND M OLAR REGION) RECORD
T h e technic for the bicuspid and molar region is very much the same as for the molar and ramus region except for the position of the head in relation to the casette. The head is tilted in the same manner. The table top and casette are adjusted to the head so that the cheek is flat against the casette and the nose touching or almost touching the casette. T h e same film target distance, angulation chart and exposure time are used.
l a t e r a l t e m p o r o m a n d ib u l a r r e c o r d
is set. T h e central ray should be directed through a point 2 inches above and onehalf inch anteriorly from the external auditory meatus. T h e long axis of the tube should be parallel with the sagittal plane. W ith the tube in this position and the designated angulation toward the inferior aspect, the central ray will emanate at the temporomandibular ar ticulation next to the film. T h e film target distance should be 20 inches and the time of exposure with double in tensifying screens, for adults, from three and one-half to four and one-half seconds.
L o v e t t — R o e n t g e n o g r a p h ic T e c h n ic s , U sin g C a s e t t e T a b l e
AN TE R O PO STE RIO R TE M PO RO M A N D IBU LAR RE C O R D
The patient is seated in the upright position in the chair. The table is posi tioned in front of the patient as for the m axillary sinus technic. The chair is adjusted so that the top of the patient’s shoulders is about 6 inches above the top of the table. T h e patient’s arms are
'475
under the chin and forehead for support. (Fig. 3.) This support will afford a com fortable position for the patient. The table reading is taken and the angulation of the tube set from T able 4. T h e cen tral ray is directed through the head m idway between the ears and to pass just below the nose. T h e film target dis tance should be 24 inches and the expo sure time with double intensifying
T a b l e 1.— M a x i l l a r y S i n u s ; F o r e h e a d a n d N o s e ; N o s e a n d C h in
Table Reading
T a b l e 3.— L a t e r a l T e m p o r o m a n d i b u l a r
Tube Angulation
20....... ................................................9 0 2 5 ....... ................................................ 8 5 3 0 ....... ................................................ 8 0 3 5 ....... ................................................ 7 5 4 0 ___ ................................................ 7 0 4 5 .. .. ................................................6 5 5 0 ....... .............................................. 6 0 5 5 .... ................................................5 5 6 0 ....... ................................................5 0 6 5 .... ................................................4 5 7 0 .... ................................................4 0 7 5 .. .. ................................................3 5 8 0 ... . ........................................ 3 0 8 5 ... . ................................................2 5 9 0 ........................................................ 20 T able
Table
Reading
2 .—
L ater al Jaw
Tube Angulation
9 0 ....... ..................................... — 8 8 5 . . . . ........................................ — 3 8 0 ... . ................................................. 2 7 5 ................................................................ 7 7 0 .. .. ................................................. 1 3 6 5 ... . ................................................. 1 8 6 0 . ... .......................................... 2 3 5 5 . . . . .......................................... 2 8 5 0 . . . . ............................................................................. 3 3 placed over the stationary part o f the table as in the m axillary sinus position. T h e head is tipped forward and the table top and casette are adjusted to the head so that the nose touches the casette at about the center. The chin and fore head should be equally distance from the casette. This positioning can best be carried out by placing small cork blocks
R ecord T able
Tube
R ea d in g
A ngulation
9 0 ...
......................1 5
8 5 ...
.........................20
8 0 ...
.........................2 5
7 5 ...
........................ 3 0
7 0 ...
.........................3 5
6 5 ...
.........................4 0
6 0 ...
.........................4 5
55 ...
........................ 50
SO. ..
.........................5 5
4 5 ...
.........................60
T a b l e 4.— A n t e r o p o s t e r i o r T em por om an d ibu lar R ecord
T able
Tube
Reading
A ngulation
4 0 ...
.........................5 0
4 5 ...
.........................45
5 0 ...
.........................40
5 5 ...
.........................3 5
6 0 ...
.........................3 0
6 5 ...
.........................2 5
7 0 ...
.........................20
75 ...
.........................1 5
8 0 ...
.........................1 0
8 5 ...
.........................
9 0 ...
5
............. 0
screens for adults from six to seven seconds. LA TE R A L H EAD RECORD
For the lateral head record, the chair and table positions are the same as those used for the lateral temporomandibular procedure. T h e table top and casette are adjusted to fit snugly against the ears,
1476
T h e J o u r n a l o f t h e A m e r ic a n D e n t a l A s s o c ia t io n
with the sagittal plane parallel with the plane of the casette. T h e table reading is taken and the angulation determined from Table 4. T h e central ray is directed to pass through the head at a point one and one-half inches anteriorly from the external auditory meatus and perpen dicular to the sagittal plane. T h e film target distance should be 24 inches. The exposure time with double intensifying screens is, for adults, from seven to eight seconds. PRO FILE RECORD
T h e table position, head position, table setting and angulation for the profile technic are the same as that used for the lateral head procedures, with the ex ception that a film target distance of 72 inches should be used. For conveni ence in setting the correct tube angula tion, the table top and casette should be set at 90°, so that difficuties will not be encountered in using a 72-inch film target distance. The exposure time with double intensifying screens is from one and one-half to two seconds. BREGM A-M EN TU M RECORD
Films taken by this technic give ex cellent views o f the heads o f the con dyles, the coronoid processes and the rami. T h e bregma is that point formed by the fibrous articulation o f the two. parietal bones and the frontal bone. T h e mentum is the anterior-inferior border o f the synthesis of the mandible. T h e table is positioned in front of the patient in the same manner as in the m axillary sinus procedure. T he chair is
adjusted so that the top of the patient’s shoulders is approxim ately 6 inches above the table top. T h e table top read ing is set at o for this technic. W ith the patient’s chin in the mento-anterior position, the chin should touch the casette at a point about two-thirds the distance to the opposite border and m idway be tween the lateral borders. T h e near border o f the casette should touch the clavicle region at approximately its superior border. (Fig. 4.) T h e central ray should be directed to pass through the bregm a and mentum. This will give a tube angulation o f approximately io°. The film target distance should be 24 inches and the exposure time for adults, using double intensifying screens, will be from seven to nine seconds. TA B LE M ODIFICATION S
The adjustable table top can be modi fied to suit many purposes. A change tunnel can be incorporated for stereo scopic roentgenography. Also, a com pression band can be added to help in stabilization during stereoscopic proce dures, bu t it is not generally necessary for regular extra-oral work. CO N CLU SIO N
This technic adequately serves the purpose o f general diagnostic extra-oral roentgenography. It affords comfort and ease for the patient in all necessary extra oral positions. T h e technics for the operator are easy, simple and efficient. Most im portant o f all, satisfactory diag nostic extra-oral roentgenograms are obtained. 501 O akland Avenue.