1979, British Journal of Radiology, 52, 421
MAY
1979
Correspondence (The Editors do not hold themselves responsible for opinions expressed by correspondents) Interface dosimetry
Cu-Dair
THE EDITOR—SIR,
In a recent letter Lowe (1978) claimed that the measurements of Dutreix et al. (1962) on the variation in ionization across a copper-carbon interface are misrepresented in later publications by Dutreix and Bernard (1966) and Spiers (1969). The original measurements were of the ionization in an air-filled cavity at positions on either side of the interface and the results were initially presented graphically with the ratio of the observed ionization to that obtained for a carbon chamber of equilibrium wall thickness U(Cu/C) plotted as the ordinate. It is indeed true that in the subsequent publications this axis was relabelled in terms of a dose ratio. The ratio is not however simply that of the absorbed dose to the medium at the position in question relative to the equilibrium dose in the lower atomic number medium, as Lowe seems to assume. Dutreix and Bernard (1966) clearly state that "the dotted curve in the copper corresponds to the dose in an infinitely small mass of water located in the copper", while Spiers (1969) similarly notes that "the curves inside the Cu zone give the doses in a very small air (or tissue) volume within the copper". If ^C,H 2 O is the absorbed dose in the low atomic number component (carbon or water) at a point remote from the interface, where electronic equilibrium has been reestablished, the corresponding dose in the copper Dcu will, assuming negligible attenuation across the interface, be given by:
where ^cu and jtic,H2o are the mass energy absorption coefficients of the media involved. The doses to a small volume of medium Z contained within a cavity located in such regions will, however, be: mSz
^
for a cavity in the low atomic number component and mSz mSz mScn mScu for a cavity in the copper, mSz, mScu and mSc being the mass stopping powers for medium Z, copper and carbon respectively. Taking mass energy absorption coefficients for 60Co from Evans (1968) and mass stopping power values for electrons of ~10 keV from Berger and Seltzer (1964), the various equilibrium dose ratios are then as follows: 1. Air-filled cavity in copper relative to air-filled cavity in carbon (analagous to the original measurement conditions, Dutreix etal, 1962): Cu-Dair cDa.iT
mSair
Dc
mScxi
/AC
2. Water-filled cavity in the copper relative to the equilibrium dose in water (Dutreix and Bernard, 1966): = 1.45. -DH2O
3. Air or muscle-filled cavities within the copper relative to the equilibrium dose in carbon (Spiers, 1969) :
Cu-Pmuscle
Dc
MCu_1 , , — I .JO.
WJmuscle fJ-Cu .. - n
S
The ratios derived in 1 and 2 above are, as far as can be ascertained, identical to those presented by Dutreix et al. (1962), and Dutreix and Bernard (1966), while the value shown by Spiers (1969) corresponds to the mean of the air and muscle values. The original figures are thus substantiated and the only "error" would appear to lie in Lowe's somewhat idiosyncratic interpretation. Yours, etc., P. J. DARLEY.
Central Electricity Generating Board, Research Division, Berkeley Nuclear Laboratories, Berkeley, Gloucestershire, GL13 9PB (Received Novenber, 1978) REFERENCES BERGER, M. J., and SELTZER, S. M., 1964. Tables of energy
losses and ranges of electrons and positrons. report NASA SP 3012.
NASA
DUTREIX, J., DUTREIX, A., and BERNARD, M., 1962. Etude de
la dose au voisinage de l'interface entre deux mileux de composition atomique differente exposes aux rayonnement du 60Co. Physics in Medicine and Biology, 7, 69-82. DUTREIX, J., and BERNARD, M., 1966. Dosimetry at inter-
faces for high energy X and gamma rays. British Journal of Radiology, 39, 205-210. EVANS, R. D., 1968. X-ray and y-ray interactions. In Radiation Dosimetry Ed. F. H. Attix and W. C. Roesch, Vol. I, pp. 93-155 (Academic Press, New York). LOWE, D., 1978. Interface dosimetry. Letter to the Editor, British Journal of Radiology, 51, 60. SPIERS, F. W., 1969. Transition zone dosimetry. In Radiation Dosimetry, Ed. F. H. Attix, W. C. Roesch and E. Tochilin, Vol. Ill, pp. 809-867 (Academic Press, New York).
Metrizamide in hysterosalpingography THE EDITOR—SIR,
We have recently had the opportunity of using metrizamide (Amipaque) during routine hysterosalpingography. It was used alternatively with Dimer-X in 44 patients. The metrizamide was dissolved using 4.7 ml of solvent with 3.75 g of metrizamide, giving an iodine concentration of 280 mg per ml—the same as Dimer-X. Assessment of the ease of injection, radiographic density and the quality of pictures in the two groups showed no significant difference. Patients were asked 30 min after the examination, whether they had any discomfort in the abdomen, and this was graded by the patient as in Table I. Metrizamide requires a short time to prepare before the examination, which is particularly disadvantageous if more contrast is needed during an examination, above that originally prepared. The other disadvantage of metrizamide is its expense, but it may be that in the future cost per dose will be reduced. Apart from these disadvantages, we feel that both these contrast media are suitable for hysterosalpingography, and
421
VOL.52, No.
617
Correspondence that there is no difference between them with regard to quality of radiographs, ease of injection or peritoneal irritation. We are grateful to Nyegaard & Co. A.S., for providing us with the metrizamide for this study. Yours, etc.,
TABLE I ABDOMINAL DISCOMFORT, AS GRADED BY PATIENT, 30 MIN AFTER THE EXAMINATION
Severe Moderate Slight Nil
Dimer-X
Metrizamide
0 2 6 14
0 2 7
J. G. B. RUSSELL, B. G. MAGUIRE.
Saint Mary's Hospital, Whitworth Park, Manchester M13 OJH.
13
{Received December, 1978)
Book reviews Radiological Atlas of Biliary and Pancreatic Disease. By H.
Baddeley, D. J. Nolan, and P. R. Salmon, pp. 218 illus., 1978 (HM & M Publishers Ltd., Aylesbury) £18-00. ISBN 0-85602-054-0. The last few decades have witnessed great advances in gastroenterology. Improved imaging techniques have played a large part in this and their impact has been especially great on diseases of the liver and pancreas. Many of the techniques, such as endoscopic retrograde cholangiopancreatography, ultrasonography and computerized tomography, are new and not yet covered in textbooks. This atlas aims to fill the need for a book on the appearances of the biliary system and pancreas obtained both by the established and the newer techniques. The structure of the atlas is well conceived : it is divided into two sections, on the biliary system and on the pancreas. Each section has brief descriptions of the clinical presentation of the diseases followed by accounts of the radiological techniques available for their investigation. Chapters on normal appearances and congenital abnormalities are followed by systematic accounts of the major groups of diseases. What then are the requirements of a radiological atlas and how well does this book fulfill them ? First, descriptions of the available imaging techniques and of both the normal anatomy and common congenital variants are obviously needed. These are well covered. However, the inclusion of descriptions of scintiscanning, ultrasonography and computerized tomography appears strange when these techniques are not illustrated in the atlas (apart from four pancreatic CT scans). Second, each chapter starts with brief descriptions of the diseases illustrated. These are terse and to the point although the short references to treatment are probably unnecessary in a radiological atlas. However, the authors have defined the indications for each technique and the appropriate order of investigation. The authors' bias sometimes shows through here! Many would disagree that ERCP is the investigation of first choice in a patient with bile duct cancer (p. 126). Third, an atlas must be comprehensive. The authors have certainly achieved this, collecting together both common diseases and a fascinating array of rarities. Finally, the quality of reproduction of the pictures should be good—it is. This book ably measures up to the requirements and only minor criticisms can be made. It fills the gap as a well-written atlas of the biliary system and pancreas and should be a popular reference book for both the gastroenterologist and the radiologist.
Pathology in Computed Tomography of the Brain. By Scott
D. Henderson, pp. xi +197, illus.. 1978 (Charles C. Thomas, Springfield, Illinois), $17.50. This atlas of pathological lesions of the brain demonstrable by CT is intended to be a reference guide for all persons concerned with cranial computer assisted tomography. The author is the senior computer tomography technician at the Rush-Presbyterian-St. Luke's Medical Center in Chicago. The book consists of 19 short chapters containing 800 illustrations of the CT appearances of the commoner lesions of the brain and orbits. Each chapter has a paragraph or two of introduction and the illustrations, six to a page, are accompanied by brief legends on most of the pages. The quality of the illustrations are, on the whole, fairly good but those intended to show a variety of orbital lesions are of rather poor quality. Disconcertingly, the first chapter on cerebral atrophy contains a series of illustrations with no legends and it is difficult for those unfamiliar with CT images of the brain to tell whether they show a series of scans of the same patient or selected levels from different patients. There are no illustrations of a normal CT examination for comparison with the abnormal scans. This would help the atlas to fulfil its intended purpose, an introduction for beginners to this relatively new diagnostic method. Many of the legends for the figures are cryptic and a lot of space which could have been devoted to describing the images is wasted in over-elaborate acknowledgments to the sources of some of the material. The pages are numbered only at the beginning of each chapter which makes quick reference to a particular section rather difficult. The publishers state that this atlas will "greatly facilitate learning and will continue to serve the tomography technician, resident and practising radiologist as a reference of unparalleled comprehensiveness and clarity". Even when allowance is made for publishers hyperbole this has not been achieved nor, I am sure, was it the aim of the author to do so. Mr. Henderson is to be congratulated on his initiative in writing this atlas and for a good first try. Should a second edition be contemplated fewer illustrations of better quality, inclusion of a normal CT examination, a more lengthy introduction to each chapter and more lucid legends for the illustrations would greatly enhance its value as an introduction for both radiographers and trainee radiologists to cranial computer assisted tomography.
J. A . SUMMERFIELD.
422
T. D. HAWKINS.
MAY
1979
Correspondence (The Editors do not hold themselves responsible for opinions expressed by correspondents) Interface dosimetry
Cu-Dair
THE EDITOR—SIR,
In a recent letter Lowe (1978) claimed that the measurements of Dutreix et al. (1962) on the variation in ionization across a copper-carbon interface are misrepresented in later publications by Dutreix and Bernard (1966) and Spiers (1969). The original measurements were of the ionization in an air-filled cavity at positions on either side of the interface and the results were initially presented graphically with the ratio of the observed ionization to that obtained for a carbon chamber of equilibrium wall thickness U(Cu/C) plotted as the ordinate. It is indeed true that in the subsequent publications this axis was relabelled in terms of a dose ratio. The ratio is not however simply that of the absorbed dose to the medium at the position in question relative to the equilibrium dose in the lower atomic number medium, as Lowe seems to assume. Dutreix and Bernard (1966) clearly state that "the dotted curve in the copper corresponds to the dose in an infinitely small mass of water located in the copper", while Spiers (1969) similarly notes that "the curves inside the Cu zone give the doses in a very small air (or tissue) volume within the copper". If ^C,H 2 O is the absorbed dose in the low atomic number component (carbon or water) at a point remote from the interface, where electronic equilibrium has been reestablished, the corresponding dose in the copper Dcu will, assuming negligible attenuation across the interface, be given by:
where ^cu and jtic,H2o are the mass energy absorption coefficients of the media involved. The doses to a small volume of medium Z contained within a cavity located in such regions will, however, be: mSz
^
for a cavity in the low atomic number component and mSz mSz mScn mScu for a cavity in the copper, mSz, mScu and mSc being the mass stopping powers for medium Z, copper and carbon respectively. Taking mass energy absorption coefficients for 60Co from Evans (1968) and mass stopping power values for electrons of ~10 keV from Berger and Seltzer (1964), the various equilibrium dose ratios are then as follows: 1. Air-filled cavity in copper relative to air-filled cavity in carbon (analagous to the original measurement conditions, Dutreix etal, 1962): Cu-Dair cDa.iT
mSair
Dc
mScxi
/AC
2. Water-filled cavity in the copper relative to the equilibrium dose in water (Dutreix and Bernard, 1966): = 1.45. -DH2O
3. Air or muscle-filled cavities within the copper relative to the equilibrium dose in carbon (Spiers, 1969) :
Cu-Pmuscle
Dc
MCu_1 , , — I .JO.
WJmuscle fJ-Cu .. - n
S
The ratios derived in 1 and 2 above are, as far as can be ascertained, identical to those presented by Dutreix et al. (1962), and Dutreix and Bernard (1966), while the value shown by Spiers (1969) corresponds to the mean of the air and muscle values. The original figures are thus substantiated and the only "error" would appear to lie in Lowe's somewhat idiosyncratic interpretation. Yours, etc., P. J. DARLEY.
Central Electricity Generating Board, Research Division, Berkeley Nuclear Laboratories, Berkeley, Gloucestershire, GL13 9PB (Received Novenber, 1978) REFERENCES BERGER, M. J., and SELTZER, S. M., 1964. Tables of energy
losses and ranges of electrons and positrons. report NASA SP 3012.
NASA
DUTREIX, J., DUTREIX, A., and BERNARD, M., 1962. Etude de
la dose au voisinage de l'interface entre deux mileux de composition atomique differente exposes aux rayonnement du 60Co. Physics in Medicine and Biology, 7, 69-82. DUTREIX, J., and BERNARD, M., 1966. Dosimetry at inter-
faces for high energy X and gamma rays. British Journal of Radiology, 39, 205-210. EVANS, R. D., 1968. X-ray and y-ray interactions. In Radiation Dosimetry Ed. F. H. Attix and W. C. Roesch, Vol. I, pp. 93-155 (Academic Press, New York). LOWE, D., 1978. Interface dosimetry. Letter to the Editor, British Journal of Radiology, 51, 60. SPIERS, F. W., 1969. Transition zone dosimetry. In Radiation Dosimetry, Ed. F. H. Attix, W. C. Roesch and E. Tochilin, Vol. Ill, pp. 809-867 (Academic Press, New York).
Metrizamide in hysterosalpingography THE EDITOR—SIR,
We have recently had the opportunity of using metrizamide (Amipaque) during routine hysterosalpingography. It was used alternatively with Dimer-X in 44 patients. The metrizamide was dissolved using 4.7 ml of solvent with 3.75 g of metrizamide, giving an iodine concentration of 280 mg per ml—the same as Dimer-X. Assessment of the ease of injection, radiographic density and the quality of pictures in the two groups showed no significant difference. Patients were asked 30 min after the examination, whether they had any discomfort in the abdomen, and this was graded by the patient as in Table I. Metrizamide requires a short time to prepare before the examination, which is particularly disadvantageous if more contrast is needed during an examination, above that originally prepared. The other disadvantage of metrizamide is its expense, but it may be that in the future cost per dose will be reduced. Apart from these disadvantages, we feel that both these contrast media are suitable for hysterosalpingography, and
421
VOL.52, No.
617
Correspondence that there is no difference between them with regard to quality of radiographs, ease of injection or peritoneal irritation. We are grateful to Nyegaard & Co. A.S., for providing us with the metrizamide for this study. Yours, etc.,
TABLE I ABDOMINAL DISCOMFORT, AS GRADED BY PATIENT, 30 MIN AFTER THE EXAMINATION
Severe Moderate Slight Nil
Dimer-X
Metrizamide
0 2 6 14
0 2 7
J. G. B. RUSSELL, B. G. MAGUIRE.
Saint Mary's Hospital, Whitworth Park, Manchester M13 OJH.
13
{Received December, 1978)
Book reviews Radiological Atlas of Biliary and Pancreatic Disease. By H.
Baddeley, D. J. Nolan, and P. R. Salmon, pp. 218 illus., 1978 (HM & M Publishers Ltd., Aylesbury) £18-00. ISBN 0-85602-054-0. The last few decades have witnessed great advances in gastroenterology. Improved imaging techniques have played a large part in this and their impact has been especially great on diseases of the liver and pancreas. Many of the techniques, such as endoscopic retrograde cholangiopancreatography, ultrasonography and computerized tomography, are new and not yet covered in textbooks. This atlas aims to fill the need for a book on the appearances of the biliary system and pancreas obtained both by the established and the newer techniques. The structure of the atlas is well conceived : it is divided into two sections, on the biliary system and on the pancreas. Each section has brief descriptions of the clinical presentation of the diseases followed by accounts of the radiological techniques available for their investigation. Chapters on normal appearances and congenital abnormalities are followed by systematic accounts of the major groups of diseases. What then are the requirements of a radiological atlas and how well does this book fulfill them ? First, descriptions of the available imaging techniques and of both the normal anatomy and common congenital variants are obviously needed. These are well covered. However, the inclusion of descriptions of scintiscanning, ultrasonography and computerized tomography appears strange when these techniques are not illustrated in the atlas (apart from four pancreatic CT scans). Second, each chapter starts with brief descriptions of the diseases illustrated. These are terse and to the point although the short references to treatment are probably unnecessary in a radiological atlas. However, the authors have defined the indications for each technique and the appropriate order of investigation. The authors' bias sometimes shows through here! Many would disagree that ERCP is the investigation of first choice in a patient with bile duct cancer (p. 126). Third, an atlas must be comprehensive. The authors have certainly achieved this, collecting together both common diseases and a fascinating array of rarities. Finally, the quality of reproduction of the pictures should be good—it is. This book ably measures up to the requirements and only minor criticisms can be made. It fills the gap as a well-written atlas of the biliary system and pancreas and should be a popular reference book for both the gastroenterologist and the radiologist.
Pathology in Computed Tomography of the Brain. By Scott
D. Henderson, pp. xi +197, illus.. 1978 (Charles C. Thomas, Springfield, Illinois), $17.50. This atlas of pathological lesions of the brain demonstrable by CT is intended to be a reference guide for all persons concerned with cranial computer assisted tomography. The author is the senior computer tomography technician at the Rush-Presbyterian-St. Luke's Medical Center in Chicago. The book consists of 19 short chapters containing 800 illustrations of the CT appearances of the commoner lesions of the brain and orbits. Each chapter has a paragraph or two of introduction and the illustrations, six to a page, are accompanied by brief legends on most of the pages. The quality of the illustrations are, on the whole, fairly good but those intended to show a variety of orbital lesions are of rather poor quality. Disconcertingly, the first chapter on cerebral atrophy contains a series of illustrations with no legends and it is difficult for those unfamiliar with CT images of the brain to tell whether they show a series of scans of the same patient or selected levels from different patients. There are no illustrations of a normal CT examination for comparison with the abnormal scans. This would help the atlas to fulfil its intended purpose, an introduction for beginners to this relatively new diagnostic method. Many of the legends for the figures are cryptic and a lot of space which could have been devoted to describing the images is wasted in over-elaborate acknowledgments to the sources of some of the material. The pages are numbered only at the beginning of each chapter which makes quick reference to a particular section rather difficult. The publishers state that this atlas will "greatly facilitate learning and will continue to serve the tomography technician, resident and practising radiologist as a reference of unparalleled comprehensiveness and clarity". Even when allowance is made for publishers hyperbole this has not been achieved nor, I am sure, was it the aim of the author to do so. Mr. Henderson is to be congratulated on his initiative in writing this atlas and for a good first try. Should a second edition be contemplated fewer illustrations of better quality, inclusion of a normal CT examination, a more lengthy introduction to each chapter and more lucid legends for the illustrations would greatly enhance its value as an introduction for both radiographers and trainee radiologists to cranial computer assisted tomography.
J. A . SUMMERFIELD.
422
T. D. HAWKINS.
