1977, British Journal of Radiology, 50, 824-826
Technical notes 1948), de Vries (1943) and Pirenne (1044), and was elaborated by Mallard and Corfield (1969) and Sharma and Fowler (1970). Let T and B be the total counts in the target and in an equal sized area of the background. The statistical significance of the difference between T and B is then given by the index, n, where T-B
the period when this work was performed. Grateful thanks are also given to members of the Department of Medical Physics, University of Aberdeen, for their help in performing the experiment. REFERENCES CORSO, J. F., 1967. The Experimental Psychology of SensoryBehaviour, 229-236 (Holt, Rinehart and Winston, Inc., New York). DE VRIES, H. L., 1943. The quantum character of light and its bearing upon threshold of vision, the differential threshold and visual acuity of the eye. Physica, X, 553— 564.
n— — T =
IINUMA, T. A., and FUKUHISA, K., 1972. Digital simulation
T~B i.e. detection contrast, B
of radioisotope imaging. (1) On the recognition of a defect in a plane source by a human observer. Nippon Acta Radiologica, 31 ,\ 270-1285. MALLARD, J. R., 1972. The radionuclide imaging process. Acta Radiologica Supplementum, 313,159-192.
VB
.
. (1)
where, for all but low values of T and B, n is a standard normal deviate. In statistical practice a value of n greater than 2 is usually taken as indicating that T is different from B. Mallard and Wilks found that n was approximately 5 from their results. However, substitution of the appropriate values from Fig. 5 into equation (1) gives a value of 12 for n. This is abnormally high if n is to be interpreted as a statistical index. Therefore, although the shape of the curve describing the relationship between detection contrast and the number of counts in the background (Fig. 2) is that predicted by statistical theories, equation (1), the corresponding value of the statistical index is much higher than expected. This suggests that the statistical theories are based on a rather over-simplified approach and that there is a need for a more accurate model if the interaction between display and observer is to be described in purely mathematical terms. ACKNOWLEDGMENTS
One of the authors (P.S.) would like to acknowledge the support of a grant from the Medical Research Council for
MALLARD, J. R., and CORFIELD, J. R., 1969. A statistical
model for the visualization of changes in the count density on radioisotope scanning displays. British Journal of Radiology, 42, 530-538. MALLARD, J. R., and WILKS, R. J., 1968. Characteristics of
display systems in scanning and a simple phantom procedure to evaluate overall scanner performance. Journal of Nuclear Medicine, 9, 96-109. PIRENNE, M. H., 1944. Discussion. Proceedings of the Physical Society, 56, 354. PIZER, S. M., 1966. Simulation of radioisotope scans by computer. Communications of the Association of computer Machinery, 9, 356. PLUTCHIK, R., 1968. Foundations of Experimental Research, 208-214, (Harper and Row, New York). ROSE, A., 1942. The relative sensitivities of television pickup tubes, photographic film and the human eye. Proceedings of the Institute of Radio Engineers, 30, 295. 1948. The sensitivity performance of the human eye on an absolute scale. Journal of the Optical Society of America, 38,196-208. SHARMA, R. R., and FOWLER, J. F., 1970. Threshold detec-
tion tests in radioisotope scanning. Physics in Medicine and Biology, 15, 289-300. SHARP, P. F., 1973. Ph.D. Thesis, University of Aberdeen. SHARP, P. F., and MALLARD, J. R., 1974. A proposed model
for the visual detection of signals in radioisotope display images. Physics in Medicine and Biology, 19, 348-361. 1976. The measurement of the performance of the display system of a radioisotope imaging device: the multi-element band display. British Journal of Radiology, 49, 270-277.
A simplified slide console for radiology teaching By R. LI. Davies, A.I.ST., and G. M. Roberts, M.R.C.P., F.R.C.R. Department of Diagnostic Radiology, Welsh National School of Medicine, Heath Park, Cardiff (Received March, 1977 and in revisedform July, 1977)
Medical teaching departments are increasingly using audio-visual aids for presenting material to undergraduate and postgraduate students. For radiological subjects there are difficulties in massproducing good quality slides of radiographs, and relatively few slide-tape lectures are available commercially in this country. Consequently some radiology departments produce their own teaching programmes from material that is readily available within these departments. 824
We describe a slide console that is easy to construct and to maintain, and which costs less than half the price of those manufactured commercially. It has no facility for taped lectures, but a teaching manual can be prepared for each programme of slides. The manual could contain legends to the slides, line diagrams, explanatory notes, tables, lists, and references to the literature. Programmes of this kind in radiology could cover subjects such as radiographic anatomy and radiological techniques.
NOVEMBER 1977
Technical notes TABLE I MATERIALS FOR CONSTRUCTING THE CONSOLE
£ in veneered chipboard 18 in X 14 ft 8 X 8 in front silvered mirror 12 X 12 in back-projection Perspex 2 brass hinges 14 ft veneered edging Woodworking adhesive, screws, stain, varnish Cost approximately Rollei Projector Total cost approximately
£15-00 £37-00 £52-00
Fig. 2. The dimensions of the cabinet.
y
i
i
Projector
Screen FIG. 1. Back-projection slide console.
Fig. 3. Plan of the console. The slide tray is introduced through the cut-out in the cabinet (arrowed).
Their design allows students to proceed at their own block. The mains lead and the control plug are speed, with the opportunity of repeating the placed into the projector in the usual way. The short programme at will. Furthermore, the programmes control lead allows the operator to control the slide can be revised, modified, and improved without the transfer mechanism and focus control within arm's need to produce new tape lectures. length of the sitting position in front of the viewing The design of the console is similar to that screen. described by Clarke (1973) without the facility for The hinged lid of the console is locked to prevent taped lectures. The materials necessary for its accidental damage to the mirror. The mirror is construction are listed in Table I. The projector is a supported at 45 deg to the beam and to the centre of Rollei 35A (Prinz Auto 35) and the cabinet is con- the viewing screen. A polished aluminium mirror structed of veneered chipboard which is stained and can be used instead of the front silvered mirror. varnished (Fig. 1). The overall dimensions of the Although a standard 85 mm projector lens is used cabinet are shown in Fig. 2. The projector is placed here to give an image on the viewing screen measurthrough a cut-out at the side and rear of the cabinet. ing 8 x 5 | in, a 60 mm lens could be used instead to This gives easy access for positioning the slide trays. give a larger image if desired. The positions of the projector, mirror and viewing It has not been found necessary to matt-black the screen are shown in Fig. 3. The projector is sup- interior of the cabinet. When viewing radiographs on ported by the cut-out in the cabinet and by a the screen, excessive "glare" can be reduced by wooden block fixed to the base of the console. The mounting "cleared" X-ray film on the inner surface projector is fixed in position by making a minor of the Perspex viewing screen. This does not reduce alteration to the tilt adjuster that rests on the wooden or interfere with the detail or clarity of the image. 825
VOL.
50, Mo. 5% Technical notes
The total cost of the console illustrated here was £52; a comparable slide console manufactured commercially costs ^120. The cabinet was constructed in two days and required no special skills or equipment other than those within the scope of the average do-it-yourself enthusiast. The timber used
is freely available in the dimensions quoted. The console has the additional advantage of being robust and easy to operate and maintain. REFERENCE CLARKE, M., 1973. A type-slide console for undergraduate teaching. Medical and Biological Illustration 23. 137-138.
Book reviews Quality Control in Diagnostic Radiology. Conference Report Series—26, pp 38, 1977, The Hospital Physicists' Association, £1 -00. This is the proceedings of a one-day conference on Quality Control organized by the Hospital Physicists' Association. Contributions were provided by radiologists, radiographers, hospital physicists and manufacturers of X-ray equipment. One session was devoted to X-ray generators and tubes, another to films, screens and processors, and the third to image intensifier systems. This booklet provides a useful summary of the meeting and is meeting and is recommended reading for anyone who is not aware of a need for better quality control in departments of diagnostic radiology.
hensive it is up-to-date and does straddle the whole field of computed tomography. Most radiologists dealing with any aspect of computed tomography will find something of interest, but the book is especially recommended to general radiologists involved in computed tomography of both the body and head. B. KENDALL.
Diagnostic Radiology. Edited by A. R. Margulis and C. A. Gooding, pp. xi +836,1977 (U.S.A.; C. V. Mosby. London; Henry Kimpton), £32-10. This book comprises 55 short papers by the contributors F. H. DOYLE. to the 20th Annual Postgraduate Course in Diagnostic Radiology presented by the University of California, San Francisco. It is divided into seven sections which include gastrointestinal, urological, paediatric, skeletal, chest and Computed Tomography. Edited by D. Norman, M. Korobkin, neurological radiology and an account of mammography. and T. H. Newton, pp. ix + 362, illust., 1977. (C. V. Mosby There is no index. Many of the contributions occupy between one and a half and three pages followed by Co., Missouri; Henry Kimpton, U.K.), £26-00. The book consists of edited papers originally presented at abundant illustrations and a list of recent references, a course on computed tomography held in the University of largely selected from the American literature, and in some California, San Francisco in 1977. The lectures are up-to- cases almost exclusively from those of the contributor. The date summaries of present knowledge on most aspects of the publishers have used a large, clear print which, together with the illustrations, are extravagent of space and there are subject given by leading experts in the field. The first half of the book is devoted to the physical and many blank pages. Thus the overall content of the book is technical aspects of computed tomography and to body substantially less than its size would imply. As is stated in the Preface, many of the concepts prescanning and the second half to scanning of the head and spine. There are useful chapters on ultrasound investi- sented are pragmatically orientated and have been specifigation of the liver and pancreas and on isotope scanning of cally selected for the benefit of the practising clinical the liver, with comparison of the results obtained from these radiologist. It is also claimed that in many instances the methods with those from computed tomography. There is material presented is unpublished data and represents the also a good basic description of cerebral tumours and frontier of radiology but these are more difficult to identify. pathophysiological changes induced by them. The book As is almost inevitable, with such collections from many finishes with a useful survey of the specifications of various authors, the standard varies widely throughout the book. Overall, this is an elegant volume containing many useful scanning units. All the full chapters are first class, but several of the con- accounts of subjects of topical interest. Most radiologists, tributions have been published elsewhere and only abridged however, will feel that it would constitute an expensive versions of some of these are included. However this is to luxury as a personal possession but it should be recommendsome extent compensated for by reference to the original ed for inclusion in the libraries of departments of radiology and teaching units where funds permit. material in the text. J. ROYLANCE. The book is well illustrated and though it is not compre-
826
Technical notes 1948), de Vries (1943) and Pirenne (1044), and was elaborated by Mallard and Corfield (1969) and Sharma and Fowler (1970). Let T and B be the total counts in the target and in an equal sized area of the background. The statistical significance of the difference between T and B is then given by the index, n, where T-B
the period when this work was performed. Grateful thanks are also given to members of the Department of Medical Physics, University of Aberdeen, for their help in performing the experiment. REFERENCES CORSO, J. F., 1967. The Experimental Psychology of SensoryBehaviour, 229-236 (Holt, Rinehart and Winston, Inc., New York). DE VRIES, H. L., 1943. The quantum character of light and its bearing upon threshold of vision, the differential threshold and visual acuity of the eye. Physica, X, 553— 564.
n— — T =
IINUMA, T. A., and FUKUHISA, K., 1972. Digital simulation
T~B i.e. detection contrast, B
of radioisotope imaging. (1) On the recognition of a defect in a plane source by a human observer. Nippon Acta Radiologica, 31 ,\ 270-1285. MALLARD, J. R., 1972. The radionuclide imaging process. Acta Radiologica Supplementum, 313,159-192.
VB
.
. (1)
where, for all but low values of T and B, n is a standard normal deviate. In statistical practice a value of n greater than 2 is usually taken as indicating that T is different from B. Mallard and Wilks found that n was approximately 5 from their results. However, substitution of the appropriate values from Fig. 5 into equation (1) gives a value of 12 for n. This is abnormally high if n is to be interpreted as a statistical index. Therefore, although the shape of the curve describing the relationship between detection contrast and the number of counts in the background (Fig. 2) is that predicted by statistical theories, equation (1), the corresponding value of the statistical index is much higher than expected. This suggests that the statistical theories are based on a rather over-simplified approach and that there is a need for a more accurate model if the interaction between display and observer is to be described in purely mathematical terms. ACKNOWLEDGMENTS
One of the authors (P.S.) would like to acknowledge the support of a grant from the Medical Research Council for
MALLARD, J. R., and CORFIELD, J. R., 1969. A statistical
model for the visualization of changes in the count density on radioisotope scanning displays. British Journal of Radiology, 42, 530-538. MALLARD, J. R., and WILKS, R. J., 1968. Characteristics of
display systems in scanning and a simple phantom procedure to evaluate overall scanner performance. Journal of Nuclear Medicine, 9, 96-109. PIRENNE, M. H., 1944. Discussion. Proceedings of the Physical Society, 56, 354. PIZER, S. M., 1966. Simulation of radioisotope scans by computer. Communications of the Association of computer Machinery, 9, 356. PLUTCHIK, R., 1968. Foundations of Experimental Research, 208-214, (Harper and Row, New York). ROSE, A., 1942. The relative sensitivities of television pickup tubes, photographic film and the human eye. Proceedings of the Institute of Radio Engineers, 30, 295. 1948. The sensitivity performance of the human eye on an absolute scale. Journal of the Optical Society of America, 38,196-208. SHARMA, R. R., and FOWLER, J. F., 1970. Threshold detec-
tion tests in radioisotope scanning. Physics in Medicine and Biology, 15, 289-300. SHARP, P. F., 1973. Ph.D. Thesis, University of Aberdeen. SHARP, P. F., and MALLARD, J. R., 1974. A proposed model
for the visual detection of signals in radioisotope display images. Physics in Medicine and Biology, 19, 348-361. 1976. The measurement of the performance of the display system of a radioisotope imaging device: the multi-element band display. British Journal of Radiology, 49, 270-277.
A simplified slide console for radiology teaching By R. LI. Davies, A.I.ST., and G. M. Roberts, M.R.C.P., F.R.C.R. Department of Diagnostic Radiology, Welsh National School of Medicine, Heath Park, Cardiff (Received March, 1977 and in revisedform July, 1977)
Medical teaching departments are increasingly using audio-visual aids for presenting material to undergraduate and postgraduate students. For radiological subjects there are difficulties in massproducing good quality slides of radiographs, and relatively few slide-tape lectures are available commercially in this country. Consequently some radiology departments produce their own teaching programmes from material that is readily available within these departments. 824
We describe a slide console that is easy to construct and to maintain, and which costs less than half the price of those manufactured commercially. It has no facility for taped lectures, but a teaching manual can be prepared for each programme of slides. The manual could contain legends to the slides, line diagrams, explanatory notes, tables, lists, and references to the literature. Programmes of this kind in radiology could cover subjects such as radiographic anatomy and radiological techniques.
NOVEMBER 1977
Technical notes TABLE I MATERIALS FOR CONSTRUCTING THE CONSOLE
£ in veneered chipboard 18 in X 14 ft 8 X 8 in front silvered mirror 12 X 12 in back-projection Perspex 2 brass hinges 14 ft veneered edging Woodworking adhesive, screws, stain, varnish Cost approximately Rollei Projector Total cost approximately
£15-00 £37-00 £52-00
Fig. 2. The dimensions of the cabinet.
y
i
i
Projector
Screen FIG. 1. Back-projection slide console.
Fig. 3. Plan of the console. The slide tray is introduced through the cut-out in the cabinet (arrowed).
Their design allows students to proceed at their own block. The mains lead and the control plug are speed, with the opportunity of repeating the placed into the projector in the usual way. The short programme at will. Furthermore, the programmes control lead allows the operator to control the slide can be revised, modified, and improved without the transfer mechanism and focus control within arm's need to produce new tape lectures. length of the sitting position in front of the viewing The design of the console is similar to that screen. described by Clarke (1973) without the facility for The hinged lid of the console is locked to prevent taped lectures. The materials necessary for its accidental damage to the mirror. The mirror is construction are listed in Table I. The projector is a supported at 45 deg to the beam and to the centre of Rollei 35A (Prinz Auto 35) and the cabinet is con- the viewing screen. A polished aluminium mirror structed of veneered chipboard which is stained and can be used instead of the front silvered mirror. varnished (Fig. 1). The overall dimensions of the Although a standard 85 mm projector lens is used cabinet are shown in Fig. 2. The projector is placed here to give an image on the viewing screen measurthrough a cut-out at the side and rear of the cabinet. ing 8 x 5 | in, a 60 mm lens could be used instead to This gives easy access for positioning the slide trays. give a larger image if desired. The positions of the projector, mirror and viewing It has not been found necessary to matt-black the screen are shown in Fig. 3. The projector is sup- interior of the cabinet. When viewing radiographs on ported by the cut-out in the cabinet and by a the screen, excessive "glare" can be reduced by wooden block fixed to the base of the console. The mounting "cleared" X-ray film on the inner surface projector is fixed in position by making a minor of the Perspex viewing screen. This does not reduce alteration to the tilt adjuster that rests on the wooden or interfere with the detail or clarity of the image. 825
VOL.
50, Mo. 5% Technical notes
The total cost of the console illustrated here was £52; a comparable slide console manufactured commercially costs ^120. The cabinet was constructed in two days and required no special skills or equipment other than those within the scope of the average do-it-yourself enthusiast. The timber used
is freely available in the dimensions quoted. The console has the additional advantage of being robust and easy to operate and maintain. REFERENCE CLARKE, M., 1973. A type-slide console for undergraduate teaching. Medical and Biological Illustration 23. 137-138.
Book reviews Quality Control in Diagnostic Radiology. Conference Report Series—26, pp 38, 1977, The Hospital Physicists' Association, £1 -00. This is the proceedings of a one-day conference on Quality Control organized by the Hospital Physicists' Association. Contributions were provided by radiologists, radiographers, hospital physicists and manufacturers of X-ray equipment. One session was devoted to X-ray generators and tubes, another to films, screens and processors, and the third to image intensifier systems. This booklet provides a useful summary of the meeting and is meeting and is recommended reading for anyone who is not aware of a need for better quality control in departments of diagnostic radiology.
hensive it is up-to-date and does straddle the whole field of computed tomography. Most radiologists dealing with any aspect of computed tomography will find something of interest, but the book is especially recommended to general radiologists involved in computed tomography of both the body and head. B. KENDALL.
Diagnostic Radiology. Edited by A. R. Margulis and C. A. Gooding, pp. xi +836,1977 (U.S.A.; C. V. Mosby. London; Henry Kimpton), £32-10. This book comprises 55 short papers by the contributors F. H. DOYLE. to the 20th Annual Postgraduate Course in Diagnostic Radiology presented by the University of California, San Francisco. It is divided into seven sections which include gastrointestinal, urological, paediatric, skeletal, chest and Computed Tomography. Edited by D. Norman, M. Korobkin, neurological radiology and an account of mammography. and T. H. Newton, pp. ix + 362, illust., 1977. (C. V. Mosby There is no index. Many of the contributions occupy between one and a half and three pages followed by Co., Missouri; Henry Kimpton, U.K.), £26-00. The book consists of edited papers originally presented at abundant illustrations and a list of recent references, a course on computed tomography held in the University of largely selected from the American literature, and in some California, San Francisco in 1977. The lectures are up-to- cases almost exclusively from those of the contributor. The date summaries of present knowledge on most aspects of the publishers have used a large, clear print which, together with the illustrations, are extravagent of space and there are subject given by leading experts in the field. The first half of the book is devoted to the physical and many blank pages. Thus the overall content of the book is technical aspects of computed tomography and to body substantially less than its size would imply. As is stated in the Preface, many of the concepts prescanning and the second half to scanning of the head and spine. There are useful chapters on ultrasound investi- sented are pragmatically orientated and have been specifigation of the liver and pancreas and on isotope scanning of cally selected for the benefit of the practising clinical the liver, with comparison of the results obtained from these radiologist. It is also claimed that in many instances the methods with those from computed tomography. There is material presented is unpublished data and represents the also a good basic description of cerebral tumours and frontier of radiology but these are more difficult to identify. pathophysiological changes induced by them. The book As is almost inevitable, with such collections from many finishes with a useful survey of the specifications of various authors, the standard varies widely throughout the book. Overall, this is an elegant volume containing many useful scanning units. All the full chapters are first class, but several of the con- accounts of subjects of topical interest. Most radiologists, tributions have been published elsewhere and only abridged however, will feel that it would constitute an expensive versions of some of these are included. However this is to luxury as a personal possession but it should be recommendsome extent compensated for by reference to the original ed for inclusion in the libraries of departments of radiology and teaching units where funds permit. material in the text. J. ROYLANCE. The book is well illustrated and though it is not compre-
826
