- Email: [email protected]
Ultrasonic grey scale visualization of the thyroid gland
Ulrrasoundin
Med.
& Biol., Vol.
I, pp. 405410.
ULTRASONIC
J. JELLINS*,
Pergamon
Press, 1975. Printed
GREY SCALE THYROID G. KOSSOFF*,
m Great
Britam
VISUALIZATION GLAND
J. WISEMAN?,
T.
(Receiced 23 July 1974; and in$nalf&w
REEVEI
OF THE
and I. HALES?
11 October 1974)
Abstract-Ultrasonic examination of the thyroid provides an accurate method of differentiating between solid and cystic lesions. With grey scale echography contents of many solid lesions give rise to a characteristic echo pattern which may eventually allow the ultrasonic classification of these lesions. This preliminary study of 40 patients presents the echograms associated with some of the more common pathological conditions of the thyroid gland. Key words: Acoustic, Ultrasonics, Ultrasonic
Goitre, Graves’ disease, Thyroid scanning, Grey Scale technique.
gland situated just below the skin with no overlaying air or bony structure is a soft tissue organ amenable to ultrasonic examination (Rasmussen et al., 1971; Blum et (I[., 1971 ; Thijs et al., 1972; Miskin et al., 1973). The main emphasis has been on the differentiation between solid and cystic lesions as either of these may be present in a “cold” isotope scan and the distinction aids in the clinical management of the patient. Grey scale echography is particularly useful for this application and also has the potential of differentiating between various solid lesions. This paper presents the preliminary results obtained with grey scale echography in a series of forty patients in whom the nature of the lesions was subsequently confirmed following thyroidectomy. An isotope scan was also obtained in all of these patients to determine thyroid function.
* National Acoustic Laboratories, Sydney, Australian Department of Health. t Denartment of Nuclear Medicine at the Roval North Shore Hospital, Sydney. $ Professorial Unit in Surgery of the University of Sydney at the Royal North Shore Hospital, Sydney.
Thyroid
gland,
Thyroid
neoplasms,
TECHNIQUE
INTRODUCTION THE THYROID
diseases,
The patient is examined in a supine position with a water filled polythene coupling bag lowered on to the neck. The same echoscope is used for breast examinations and has been previously described (Jellins et al., 1971); Coupling jelly is used to exclude air bubbles between the plastic and skin interface. The transducer moves across the patient in a lateral plane whilst undergoing oscillations about its own axis. This combination of linear and sector scanning known as compound scanning gives a clear overall cross-sectional view of the thyroid and its relationship to other structures. Linear scans provide additional information as each tissue interface is viewed from one direction only and the display is not complicated by superposition of echoes from many differing lines of sight. In particular presence of air containing structures such as the trachea and the oesophagus are more readily recognized as on linear or sector scans these structures shade posterior detail. The frequency of operation of the transducer is 2 MHz and this gives a resolution of the order of 1 mm within the focal region. Echograms are taken at 2 mm intervals in areas of interest and altogether about 25 echograms
405
J. JI,LLINS. G
306
Kossobb.
J. WISEMAN, T. RFrvr
are used to visualize the whole gland. The graticule is photographed with each echogram and the separation between the major lines represents 1.3 cm in the patient.
REPRESENTATIVE
ECHOGRAMS
A thyroid gland together with a schematic drawing of the anatomy is illustrated in Fig. I. The thyroid lies below the skin with the two lobesjoincd by the isthmus. The left lobe in this patient is normal whilst the right one is enlarged. Diffusely refected echoes are obtained from within the contents. The distribution of echoes in the left lobe is uniform and characteristic of the normal thyroid tissue. The internal echo pattern distribution in the right lobe is uneven containing areas of low level echoes interspersed among the host thyroid tissue. The presence of the internal echoes indicates that this is a solid lesion with heterogeneous tissue distribution. All echograms unless otherwise notated are obtained with a gain setting of 30dB on the echoscope. The boundaries of the lobes are usually not clearly displayed over the whole surface. How-
Fig. I. tchogram 01‘thyroid gland and schematic of the anatomical cross-section.
and I. HALES
ever. the size of the lobe is apparent by the transition of the uniform echo pattern region of the lobe to either higher or lower level echoes from the surrounding structures. The trachea is visualized lying behind the isthmus. The anterior surface of the trachea is always displayed by a strong echo due to the large tissue air impedance mismatch. The side walls arc usually displayed by weaker echoes because of the unfavourable inclination to the ultrasonic beam. Due to shadowing caused by its air content. the posterior surface of the trachea is not visualized. On either side are seen the common carotid artery and the internal jugular vein. Structures such as the muscles and some of the larger nerves are also often \.isualized. The oesophagus on the other hand is not generally seen as it is shadowed by the trachea. The lesions most easily recognized are those whose contents are liquid. These appear as echo free regions surrounded by the solid host tissue. This is illustrated in Fig. 2 which shows a 2cm dia. cyst in the right lobe of the thyroid gland. The echo from the boundary of the cyst is not displayed but the size of the lesion is clearly demonstrated by the transition to the
drawing Fig. 2. Two cm dia. cyst and technetium
scan
Ultrasonic
grey scale visualization
of the thyroid
gland
Fig. 4. Adenoma
Fig. 3. Multilocular
cyst and photograph
of specimen
high level echoes from the surrounding soft tissue. The distribution of echoes within the compressed circumscribing soft tissue is not as uniform as the echo pattern in the isthmus and the left lobe. Surgical excision confirmed that this was a blood filled cyst surrounded by a layer of compressed thyroid tissue. Other structures such as the trachea. carotid arteries and jugular veins are visualized. The technetium scan shows a “cold” area in the right lobe corresponding to the echo free region in the echogram. A multilocular cyst is illustrated in Fig. 3. The presence of the cyst has enlarged the left lobe to 3 cm dia., whilst the normal lobe is less than 1 cm dia. The partitioning membranes in the cyst are seen as weak line echoes lobulating the echo free regions. The distribution of echoes within the layer of thyroid tissue surrounding the cyst is not uniform and appears to be more dense in the anterior section. The trachea is recognized by the strong echoes obtained from its anterior surface. Other echoes appearing within the trachea are due to multiple reflections between the tissueeair interface at the anterior surface of the trachea and the polythene-tissue interface at the skin line. The oesophagus is
407
and technetium
scan.
visualized in this echogram as the echo free area behind the trachea. The photograph of the sectioned specimen shows the thin dividing membranes which were visualized on the echogram. The presence of echoes within the lesion indicates that the contents are solid. The echogram in Fig. 4 shows a 3 cm dia. solid adenoma involving the right lobe. The distribution of echoes within this lesion is uniform and the amplitude of these echoes is lower than the echoes from the left lobe. These two features seem to be characteristic of adenomas with no degeneration. The boundaries of this lesion are well defined since the complete right lobe is involved. At the lateral edge of the lesion. the tissue appears to extend over the right common carotid artery. The internal jugular veins are seen as echo free regions behind and lateral to the carotid arteries. The level of the echogram is shown through the “cold” region of the technetium scan. Some lesions contain both solid and liquid matter. A degenerating follicular adenoma 5 cm dia., in the right lobe of the thyroid gland, is shown in Fig. 5. The number in the top right corner indicates the level in cm at which the echogram was obtained starting from the top of the larynx. The lesion is predominantly solid
408
J. JELLINS, G. KOSSOFF. J. WISEMAN. T. REEVE and I. HALES
big. 5. Echograms
with some interdispersed pockets of blood appearing at various levels. The echo pattern in the solid matter varies at the differing levels being more dense at the lower levels. The anterior boundary is visualized in all levels and the enlargement has displaced the trachea to the left. No characteristic pattern has yet emerged in diffuse goitres. A toxic thyroid with a particu-
Fig. 6. Thyrotoxicosls
of folhcular
adenoma
larly dense echo pattern evenly distributed through both lobes and the isthmus is shown in Fig. 6. This pattern was obtained at all levels indicating a homogeneous tissue distribution throughout the entire gland. The carotid arteries are outlined on the margin of each lobe and the trachea is particularly clearly visualized behind the isthmus. The even distribution of echoes is consistent with the even uptake of technetium
with technetium of specimen.
scan and photograph
Ultrasonic
Fig. 7. Echogram
of multinodular
grey scale visualization
goitre.
in the isotope scan, where the approximate position of the echogram is marked. The section of the specimen shows the homogeneous texture of the tissues. In other patients similar even distribution of echoes has been obtained, but with considerably diminished amplitude of echoes from the internal content. The echo patterns ‘originating from multinodular goitres are generally complex. The amplitude of the echoes together with the echo distribution may be different in each nodule. The echogram in Fig. 7 shows three separate nodules of differing characteristics. The echo pattern of the nodule in the left lobe contains mainly low level echoes with a uniform distribu-
Fig. 8. Advanced
of the thyroid
gland
409
tion. Centrally located is a region of very strong choes due to calcification. The second nodule, which is situated anteriorly to the trachea and between the two lobes of the gland, has a uniform echo distribution of high level echoes. The remaining nodule, occupying the right lobe of the gland, has an uneven distribution of echoes which diminishes in amplitude towards the medial surface. In other cases of multinodular goitres some of these patterns have been found to be present either singularly or collectively in each nodule. So far only one patient with carcinoma has been examined. The echograms are illustrated in Fig. 8, and show the normal echo pattern of the thyroid being completely replaced by the pathological tissue which on biopsy proved to be an advanced anaplastic carcinoma. The left lobe is considerably enlarged having a lateral projection and has pushed the trachea to the right. The bottom left echogram was obtained at a 6 dB greater gain in order to clearly display the solid contents of the tumour. The linear scan illustrated in the top right was taken with the transducer inclined to one side and clearly shows the existence of small echoes within the gland. It also shows the shadowing of detail posterior to the air filled trachea. This shadowing enables the trachea to be positively recognized in cases
anaplastic carcinoma specimen.
and photograph
of
410
J.
J~LLINS.
G.
Kossocr.
J. WISEMAN. T. REEVE:and I. HAL.I:S
where it is grossly displaced due to the pathology. The echograms are consistent with the lobular appearance of the excised specimen shown at the bottom right. RESULTS
The echograms illustrate some of the more common pathological conditions occurring in the thyroid gland. Of the 40 examined lesions all of the six cysts were correctly identified. There were six cases of adenomas which gave a characteristic pattern of uniformly distributed low level echoes throughout the lesion. In the eight cases of degenerating adenomas, the echo pattern was characterized by regions of medium strength echoes interdispersed with liquid filled areas representing the degenerating tissues. In the three cases of toxic thyroids. both lobes were symmetrically enlarged and uniformly distributed echoes were obtained throughout. The amplitude of the echoes was different in each case varying from low to relatively high levels, so that it is not likely that characterization by amplitude will be possible. More sophisticated echo pattern distinction such as number of echoes per unit area and echo scattering cross-section may be necessary for the characterization of this condition. The sixteen cases ofmultinodular goitres had varying echo pattern complexes differing in echo ampli-
No. of patients 6 8 6 3
16
I
Ultrasonic
appearance
Liqutd filled area surrounded by normal tissue Abnormal tissue containing Interspersed liquid filled areas Evenly distributed low level echoes Varying level echoes, c~cnly distrtbuted. Symmetrical enlargement of both lobes Complex echo patterns with uneven echo distributions Even dtstrtbution of very low level echoes
Pathology Cyst Degenerating Adenoma Adenoma Thyrotoxicosts
Multinodular Goitre Anaplastic Carctnoma
tude and echo distribution. In the only case of anaplastic carcinoma visualized, extremely low level echoes were uniformly distributed throughout both lobes. This extremely low level echo pattern has been recently reported by another investigation (Cracker ct ~1.. 1974) and in their study the pattern was consistent in each of the six carcinomas visualized. CONCLUSION
Ultrasonic examination of the thyroid provides an accurate method of differentiating between solid and cystic lesions. Abnormalities within the cyst such as small nodules in the wall or other debris can be clearly seen. By using grey scale echography the structural organization of tissues is displayed and the contents of solid lesions appear with characteristic echo patterns. Correlation of these echo patterns with the pathological results may allow ultrasonic classification of these lesions into pathological groups. A~,kno,c,/r~l~er~lrnr --This paper mission of the Director-General
IS published of Health.
with the per-
REFERENCES Blum, M.. Goldman, A. B., Herskovic, A. and Hernberg, J. (1971) Clinical applications of thyroid echography. Radiulonv 101, 651-656. Cracker, E:F., Booth, J. A., Uren, R. F., McLaughlin, A. F., Morris. J. G.. Jellins. J. and KossoH: G. ( 1974) Correlatton of the caesium scan with the ultrasonic investigation of the solitary ‘cold’ thyroid nodule. A.A.E.C. Puhliw~m~ Absiracrs of lhe 5th Annual Sc,ientific, Meeting qf the A.N.Z. So&y of‘Nu&ar Medicine. Sydney. Australia. Jellins, J., Kossotf, G., Buddee, F. W. and Reeve, T. S. (1971) Ultrasonic visualization of the breast. :Merl. J. .4ust. 1, 305-307. Miskin, M.. Rosen, I. B. and Wallfish. P. C. (1973) B-mode ultrasonography in assessment of thyroid gland lesions. Ann. Int&%. khd. 79, 5055510. Rasmussen, S. N.. Christiansen, N. J. B.. Jorgensen, J. S. and Helm, H. H. (1971) Differentiation between cystic and solid thyroid nodules by ultrasonrc examrnatton. Acta Chir. Sc,an. 137, 331-333. Thijs, L. G., Roes, P. and Wiener, J. D. (lY72). Use of ultrasound and digital sctntophoto analysis in the evaluation of solitary thyroid nodules. ./. &‘u~~/./Med. 13, 504509.
Med.
& Biol., Vol.
I, pp. 405410.
ULTRASONIC
J. JELLINS*,
Pergamon
Press, 1975. Printed
GREY SCALE THYROID G. KOSSOFF*,
m Great
Britam
VISUALIZATION GLAND
J. WISEMAN?,
T.
(Receiced 23 July 1974; and in$nalf&w
REEVEI
OF THE
and I. HALES?
11 October 1974)
Abstract-Ultrasonic examination of the thyroid provides an accurate method of differentiating between solid and cystic lesions. With grey scale echography contents of many solid lesions give rise to a characteristic echo pattern which may eventually allow the ultrasonic classification of these lesions. This preliminary study of 40 patients presents the echograms associated with some of the more common pathological conditions of the thyroid gland. Key words: Acoustic, Ultrasonics, Ultrasonic
Goitre, Graves’ disease, Thyroid scanning, Grey Scale technique.
gland situated just below the skin with no overlaying air or bony structure is a soft tissue organ amenable to ultrasonic examination (Rasmussen et al., 1971; Blum et (I[., 1971 ; Thijs et al., 1972; Miskin et al., 1973). The main emphasis has been on the differentiation between solid and cystic lesions as either of these may be present in a “cold” isotope scan and the distinction aids in the clinical management of the patient. Grey scale echography is particularly useful for this application and also has the potential of differentiating between various solid lesions. This paper presents the preliminary results obtained with grey scale echography in a series of forty patients in whom the nature of the lesions was subsequently confirmed following thyroidectomy. An isotope scan was also obtained in all of these patients to determine thyroid function.
* National Acoustic Laboratories, Sydney, Australian Department of Health. t Denartment of Nuclear Medicine at the Roval North Shore Hospital, Sydney. $ Professorial Unit in Surgery of the University of Sydney at the Royal North Shore Hospital, Sydney.
Thyroid
gland,
Thyroid
neoplasms,
TECHNIQUE
INTRODUCTION THE THYROID
diseases,
The patient is examined in a supine position with a water filled polythene coupling bag lowered on to the neck. The same echoscope is used for breast examinations and has been previously described (Jellins et al., 1971); Coupling jelly is used to exclude air bubbles between the plastic and skin interface. The transducer moves across the patient in a lateral plane whilst undergoing oscillations about its own axis. This combination of linear and sector scanning known as compound scanning gives a clear overall cross-sectional view of the thyroid and its relationship to other structures. Linear scans provide additional information as each tissue interface is viewed from one direction only and the display is not complicated by superposition of echoes from many differing lines of sight. In particular presence of air containing structures such as the trachea and the oesophagus are more readily recognized as on linear or sector scans these structures shade posterior detail. The frequency of operation of the transducer is 2 MHz and this gives a resolution of the order of 1 mm within the focal region. Echograms are taken at 2 mm intervals in areas of interest and altogether about 25 echograms
405
J. JI,LLINS. G
306
Kossobb.
J. WISEMAN, T. RFrvr
are used to visualize the whole gland. The graticule is photographed with each echogram and the separation between the major lines represents 1.3 cm in the patient.
REPRESENTATIVE
ECHOGRAMS
A thyroid gland together with a schematic drawing of the anatomy is illustrated in Fig. I. The thyroid lies below the skin with the two lobesjoincd by the isthmus. The left lobe in this patient is normal whilst the right one is enlarged. Diffusely refected echoes are obtained from within the contents. The distribution of echoes in the left lobe is uniform and characteristic of the normal thyroid tissue. The internal echo pattern distribution in the right lobe is uneven containing areas of low level echoes interspersed among the host thyroid tissue. The presence of the internal echoes indicates that this is a solid lesion with heterogeneous tissue distribution. All echograms unless otherwise notated are obtained with a gain setting of 30dB on the echoscope. The boundaries of the lobes are usually not clearly displayed over the whole surface. How-
Fig. I. tchogram 01‘thyroid gland and schematic of the anatomical cross-section.
and I. HALES
ever. the size of the lobe is apparent by the transition of the uniform echo pattern region of the lobe to either higher or lower level echoes from the surrounding structures. The trachea is visualized lying behind the isthmus. The anterior surface of the trachea is always displayed by a strong echo due to the large tissue air impedance mismatch. The side walls arc usually displayed by weaker echoes because of the unfavourable inclination to the ultrasonic beam. Due to shadowing caused by its air content. the posterior surface of the trachea is not visualized. On either side are seen the common carotid artery and the internal jugular vein. Structures such as the muscles and some of the larger nerves are also often \.isualized. The oesophagus on the other hand is not generally seen as it is shadowed by the trachea. The lesions most easily recognized are those whose contents are liquid. These appear as echo free regions surrounded by the solid host tissue. This is illustrated in Fig. 2 which shows a 2cm dia. cyst in the right lobe of the thyroid gland. The echo from the boundary of the cyst is not displayed but the size of the lesion is clearly demonstrated by the transition to the
drawing Fig. 2. Two cm dia. cyst and technetium
scan
Ultrasonic
grey scale visualization
of the thyroid
gland
Fig. 4. Adenoma
Fig. 3. Multilocular
cyst and photograph
of specimen
high level echoes from the surrounding soft tissue. The distribution of echoes within the compressed circumscribing soft tissue is not as uniform as the echo pattern in the isthmus and the left lobe. Surgical excision confirmed that this was a blood filled cyst surrounded by a layer of compressed thyroid tissue. Other structures such as the trachea. carotid arteries and jugular veins are visualized. The technetium scan shows a “cold” area in the right lobe corresponding to the echo free region in the echogram. A multilocular cyst is illustrated in Fig. 3. The presence of the cyst has enlarged the left lobe to 3 cm dia., whilst the normal lobe is less than 1 cm dia. The partitioning membranes in the cyst are seen as weak line echoes lobulating the echo free regions. The distribution of echoes within the layer of thyroid tissue surrounding the cyst is not uniform and appears to be more dense in the anterior section. The trachea is recognized by the strong echoes obtained from its anterior surface. Other echoes appearing within the trachea are due to multiple reflections between the tissueeair interface at the anterior surface of the trachea and the polythene-tissue interface at the skin line. The oesophagus is
407
and technetium
scan.
visualized in this echogram as the echo free area behind the trachea. The photograph of the sectioned specimen shows the thin dividing membranes which were visualized on the echogram. The presence of echoes within the lesion indicates that the contents are solid. The echogram in Fig. 4 shows a 3 cm dia. solid adenoma involving the right lobe. The distribution of echoes within this lesion is uniform and the amplitude of these echoes is lower than the echoes from the left lobe. These two features seem to be characteristic of adenomas with no degeneration. The boundaries of this lesion are well defined since the complete right lobe is involved. At the lateral edge of the lesion. the tissue appears to extend over the right common carotid artery. The internal jugular veins are seen as echo free regions behind and lateral to the carotid arteries. The level of the echogram is shown through the “cold” region of the technetium scan. Some lesions contain both solid and liquid matter. A degenerating follicular adenoma 5 cm dia., in the right lobe of the thyroid gland, is shown in Fig. 5. The number in the top right corner indicates the level in cm at which the echogram was obtained starting from the top of the larynx. The lesion is predominantly solid
408
J. JELLINS, G. KOSSOFF. J. WISEMAN. T. REEVE and I. HALES
big. 5. Echograms
with some interdispersed pockets of blood appearing at various levels. The echo pattern in the solid matter varies at the differing levels being more dense at the lower levels. The anterior boundary is visualized in all levels and the enlargement has displaced the trachea to the left. No characteristic pattern has yet emerged in diffuse goitres. A toxic thyroid with a particu-
Fig. 6. Thyrotoxicosls
of folhcular
adenoma
larly dense echo pattern evenly distributed through both lobes and the isthmus is shown in Fig. 6. This pattern was obtained at all levels indicating a homogeneous tissue distribution throughout the entire gland. The carotid arteries are outlined on the margin of each lobe and the trachea is particularly clearly visualized behind the isthmus. The even distribution of echoes is consistent with the even uptake of technetium
with technetium of specimen.
scan and photograph
Ultrasonic
Fig. 7. Echogram
of multinodular
grey scale visualization
goitre.
in the isotope scan, where the approximate position of the echogram is marked. The section of the specimen shows the homogeneous texture of the tissues. In other patients similar even distribution of echoes has been obtained, but with considerably diminished amplitude of echoes from the internal content. The echo patterns ‘originating from multinodular goitres are generally complex. The amplitude of the echoes together with the echo distribution may be different in each nodule. The echogram in Fig. 7 shows three separate nodules of differing characteristics. The echo pattern of the nodule in the left lobe contains mainly low level echoes with a uniform distribu-
Fig. 8. Advanced
of the thyroid
gland
409
tion. Centrally located is a region of very strong choes due to calcification. The second nodule, which is situated anteriorly to the trachea and between the two lobes of the gland, has a uniform echo distribution of high level echoes. The remaining nodule, occupying the right lobe of the gland, has an uneven distribution of echoes which diminishes in amplitude towards the medial surface. In other cases of multinodular goitres some of these patterns have been found to be present either singularly or collectively in each nodule. So far only one patient with carcinoma has been examined. The echograms are illustrated in Fig. 8, and show the normal echo pattern of the thyroid being completely replaced by the pathological tissue which on biopsy proved to be an advanced anaplastic carcinoma. The left lobe is considerably enlarged having a lateral projection and has pushed the trachea to the right. The bottom left echogram was obtained at a 6 dB greater gain in order to clearly display the solid contents of the tumour. The linear scan illustrated in the top right was taken with the transducer inclined to one side and clearly shows the existence of small echoes within the gland. It also shows the shadowing of detail posterior to the air filled trachea. This shadowing enables the trachea to be positively recognized in cases
anaplastic carcinoma specimen.
and photograph
of
410
J.
J~LLINS.
G.
Kossocr.
J. WISEMAN. T. REEVE:and I. HAL.I:S
where it is grossly displaced due to the pathology. The echograms are consistent with the lobular appearance of the excised specimen shown at the bottom right. RESULTS
The echograms illustrate some of the more common pathological conditions occurring in the thyroid gland. Of the 40 examined lesions all of the six cysts were correctly identified. There were six cases of adenomas which gave a characteristic pattern of uniformly distributed low level echoes throughout the lesion. In the eight cases of degenerating adenomas, the echo pattern was characterized by regions of medium strength echoes interdispersed with liquid filled areas representing the degenerating tissues. In the three cases of toxic thyroids. both lobes were symmetrically enlarged and uniformly distributed echoes were obtained throughout. The amplitude of the echoes was different in each case varying from low to relatively high levels, so that it is not likely that characterization by amplitude will be possible. More sophisticated echo pattern distinction such as number of echoes per unit area and echo scattering cross-section may be necessary for the characterization of this condition. The sixteen cases ofmultinodular goitres had varying echo pattern complexes differing in echo ampli-
No. of patients 6 8 6 3
16
I
Ultrasonic
appearance
Liqutd filled area surrounded by normal tissue Abnormal tissue containing Interspersed liquid filled areas Evenly distributed low level echoes Varying level echoes, c~cnly distrtbuted. Symmetrical enlargement of both lobes Complex echo patterns with uneven echo distributions Even dtstrtbution of very low level echoes
Pathology Cyst Degenerating Adenoma Adenoma Thyrotoxicosts
Multinodular Goitre Anaplastic Carctnoma
tude and echo distribution. In the only case of anaplastic carcinoma visualized, extremely low level echoes were uniformly distributed throughout both lobes. This extremely low level echo pattern has been recently reported by another investigation (Cracker ct ~1.. 1974) and in their study the pattern was consistent in each of the six carcinomas visualized. CONCLUSION
Ultrasonic examination of the thyroid provides an accurate method of differentiating between solid and cystic lesions. Abnormalities within the cyst such as small nodules in the wall or other debris can be clearly seen. By using grey scale echography the structural organization of tissues is displayed and the contents of solid lesions appear with characteristic echo patterns. Correlation of these echo patterns with the pathological results may allow ultrasonic classification of these lesions into pathological groups. A~,kno,c,/r~l~er~lrnr --This paper mission of the Director-General
IS published of Health.
with the per-
REFERENCES Blum, M.. Goldman, A. B., Herskovic, A. and Hernberg, J. (1971) Clinical applications of thyroid echography. Radiulonv 101, 651-656. Cracker, E:F., Booth, J. A., Uren, R. F., McLaughlin, A. F., Morris. J. G.. Jellins. J. and KossoH: G. ( 1974) Correlatton of the caesium scan with the ultrasonic investigation of the solitary ‘cold’ thyroid nodule. A.A.E.C. Puhliw~m~ Absiracrs of lhe 5th Annual Sc,ientific, Meeting qf the A.N.Z. So&y of‘Nu&ar Medicine. Sydney. Australia. Jellins, J., Kossotf, G., Buddee, F. W. and Reeve, T. S. (1971) Ultrasonic visualization of the breast. :Merl. J. .4ust. 1, 305-307. Miskin, M.. Rosen, I. B. and Wallfish. P. C. (1973) B-mode ultrasonography in assessment of thyroid gland lesions. Ann. Int&%. khd. 79, 5055510. Rasmussen, S. N.. Christiansen, N. J. B.. Jorgensen, J. S. and Helm, H. H. (1971) Differentiation between cystic and solid thyroid nodules by ultrasonrc examrnatton. Acta Chir. Sc,an. 137, 331-333. Thijs, L. G., Roes, P. and Wiener, J. D. (lY72). Use of ultrasound and digital sctntophoto analysis in the evaluation of solitary thyroid nodules. ./. &‘u~~/./Med. 13, 504509.