•
Clinical Evaluation of the 350·kV Chest Radiography System 1
Diagnostic Radiology
George S. Hallenbeck, M.D. A chest radiography unit employing 350 kV was evaluated and found to be superior to conventional 10w-kV systems. Visualization of air/soft-tissue boundaries, mediastinal structures, the retrocardiac area, and lung apices was improved. Other benefits of the high-kV system include reproducibility, reliability, rapid installation, and economy of operation. INDEX TERMS:
Radiography, apparatus and equipment • Thorax, radiography
Radiology 117: 1-4, October 1975
position, so that the positioning of the patient was the only variable. The power requirement was 208/240 V A.C., single-phase, 50-60 cycles per second, 30 A. The ion chamber was employed at an average exposure time of 1/70 sec. (adult chest, PA projection). A 12:1, 85-line grid was interposed between the patient and the screen.
T HAS long been realized that increased kilovoltage can improve soft-tissue visualization on more than 50 % of the area of a chest film, particularly at soft-tissue boundaries in the retrocardiac area and beneath overlying bone shadows, which is of great importance in facilitating early detection and accurate diagnosis of chest pathology. With the development of the fieldemission x-ray tube, which requires less exposure time and offers improved resolution, it has been possible to construct supervoltage equipment compact enough for use in a clinical setting. Chest films taken from 150 to 2,300 kV were evaluated and 350 kV was selected as optimum, as it provided enhanced visibility of soft tissues (the main advantage of supervoltage equipment) while retaining adequate bone detail. Not only could conventional films, screens, and grids be used at 350 kV, but, surprisingly, the conventional grids effectively cleaned up scattered radiations which had previously been a serious problem with supervoltage equipment. This new field-emission tube has been incorporated in a free-standing capacitor discharge unit which is specially adapted for chest radiography. I now wish to outline my experience with this unit and to describe what I feel are the outstanding advantages of supervoltage chest radiography.
I
CASE REPORTS CASE I: A 66-year-old man presented with a history of coughing and fever. A 10w-kV chest film showed lobar pneumonia involving the right upper lobe. A second chest film taken on the 350-kV unit on the following day clearly demonstrated a tumor in the center of the pneumonic consolidation and also revealed a second mass completely occluding the right-upper-Iobe bronchus at its origin; this second mass was later verified by tomography. (NOTE: This case is illustrated in an accompanying paper, Ref. 5, Fig. 3.)
COMMENT: This case illustrates the capability of the 350-kV chest radiography unit to provide greater softtissue visibility simultaneously in more areas of the film. In addition to pneumonic consolidation, this patient had cancer as well as complete obstruction of the rightupper-lobe bronchus. Whereas diagnosis at a low kV required tomography in addition to the routine chest film, the 350-kV chest film provided the same information on a single radiograph.
EQUIPMENT AND TECHNIQUE
The Hewlett-Packard Model 43815 350-kV unit was installed in the radiology department of Oak Park Hospitalon June 10, 1973. All films were taken on a Du Pont chest-film changer using Cronex 4 film and the new Du Pont SP fluorescent screen at a fixed 350 kV with a current of 40 mA over an exposure time range of 6-65 msec. at a fixed distance of 1.8 m (6 ft.). The tube was centered on the screen of the changer and locked in 1
CASE II: A 53-year-old woman exhibited signs and symptoms of superior vena cava obstruction. A chest film taken at 350 kV (Fig. 1, A) showed a huge mass in the anterior mediastinum as well as other masses in both hili and numerous parenchymal nodules. A conventional 10w-kV film taken for comparison (Fig. 1, B) showed only a vague impression of the right hilar mass and demonstrated only two of the many parenchymal lesions seen in the high-kV film. CASE
III: A 51-year-old asymptomatic woman was being fol-
From the Department of Radiology, Oak Park Hospital, Oak Park, III. Accepted for publication in June 1975.
1
sjh
2
GEORGE
S.
HALLENBECK
October 1975
Fig. 1. A. 350-kV chest film clearly demonstrates the extent of the disease process. The silhouette sign can easily be applied, as the hilar vascular markings and descending aorta are clearly visible through the principal tumor mass. The extent of the hilar, paratracheal, and parenchymal involvement is also amply demonstrated. B. In comparison, the 10w-kV film shows very poor definition of the right hilar disease. The silhouette sign is difficult to apply, and only two of the several areas of parenchymal involvement are demonstrated.
Fig. 2. A. 350-kV film clearly shows fibrotic changes and nodular densities of old tuberculous disease in the left and right upper lobes despite the overlying ribs and clavicles. It would be difficult to see this on films taken in the 80-90-kV range. B. A later 350-kV film clearly demonstrates cavitary change in the nodular density immediately underlying the anterior aspect of the left upper lobe. Overlying bone does not hinder diagnosis with 350-kV films. C. Tomogram of the left upper lobe confirms the changes identified on the earlier 350-kV chest film.
Vol. 117
CLINICAL EVALUATION OF THE 350-KV CHEST RADIOGRAPHY SYSTEM
Fig. 3. The pneumothorax and underlying emphysematous blebs are clearly demonstrated, and there is excellent penetration of the mediastinal area and retrocardiac region. Such excellent visualization of all of these areas simultaneously would be difficult with lowkV techniques, especially in a patient with emphysema. lowed up yearly by routine chest films (Fig. 2, A) for evaluation of an old tuberculous process. These studies showed cavitary change in an old nodular density located beneath the anterior aspect of the second left rib, confirmed by tomography (Fig. 2, B). Bronchial brushing and scalene lymph-node biopsy were negative. Antituberculotic therapy produced progressive improvement in the appearance of the lesion.
COMMENT: This case illustrates that even with overlying bony structures, lung lesions can easily be identified on supervoltage films. CASE IV: A 43-year-old woman entered the hospital for evaluation of severe shortness of breath of two weeks duration. A 350-kV chest film (Fig. 3) demonstrated a large pneumothorax on the right with extensive collapse of the right lung and bullous emphysema involving both upper lobes.
COMMENT: Supervoltage techniques have been found to be particularly applicable in the visualization of emphysematous lungs, where the fine boundaries between air and the soft tissue of the blebs are accentuated. CASE V: A 22-year-old man complained of persistent backache of five days duration. Physical examination showed marked enlargement of the left testicle, and the history revealed that this condition had been present for six months. A 350-kV chest film (Fig. 4) demonstrated hilar and paratracheal masses as well as multiple peripherallung nodules. At orchiectomy, a malignant teratoma of the testic~wasfound. ' .
3
Diagnostic Radiology
Fig. 4. 350-kV chest film demonstrates several metastatic nodules in both lung fields as well as hilar and mediastinal metastases. Note the readily demonstrated compression of the left main bronchus.
DISCUSSION
At first there was a tendency to over-read the 350kV films, due largely to the greatly increased amount of information. The result was heightened suspicion of miliary infiltrates in patients who were actually normal, while the improved visualization of the lung apices led to a general suspicion of increased incidence of disease in these areas which was not verified by other examinations. After about four to six weeks of experience, however, the 350-kV radiographs could be evaluated with no more difficulty or time than was required for the lowkV films. Calcifications within small lesions have usually had to be verified by obtaining either a 10w-kV spot film or a tomogram of the area; through experience, however, calcifications can often be readily detected on the 350-kV chest films. Radiologists specializing in study of bone or the gastrointestinal tract required more experience to adjust to the apparent lack of contrast and the overall gray tone of the 350-kV chest films; however, this too was quickly resolved by constant practice. In addition to the cases illustrated above, the 350-kV unit permitted improved resolution of pulmonary vessels, facilitating earlier and more accurate diagnosis of congestive heart failure and other cardiac conditions. Diagnosis of small lesions was improved, particularly those within bone shadows. Clear-cut separation of vascular and nonvascular shadows in the hilar region,
4
GEORGE S. HALLENBECK
where lesions of considerable size can sometimes be difficult to discriminate, permitted rapid detection of hilar adenopathy and bronchogenic neoplasms. With the older radiography technique, chest films were made on upright Bucky units without the advantage of phototiming, resulting in approximately 10% retakes. Using the new system, the percentage of retakes has been cut to 2-3 %, and most of these are necessitated by the patient being too large for the chest to be fully encompassed by the vertical 35.6 X 43.2-cm (14 X 17-in.) film configuration employed with the Du Pont changer. Fluctuation in the phototimer settings is insignificant, resulting in excellent reproducibility of radiographic technique over the course of several examinations. This makes it much easier to compare radiographic findings than was true with the earlier system, in which there were wide ranges in radiographic technique despite a vigilant quality-control program. The 350-kV unit has given consistently good-quality and properly exposed radiographs in patients of all ages. In general, the 350-kV chest radiography unit can be installed more quickly than standard radiographic equip-
October 1975
ment. During the 23 months it has been in use in this department, there have been only 20 days of down time, which is an excellent reliability record considering the seven-day work week. With improvement in tube performance, the interval between tube changes has increased from 1,200 to 4,500 exposures. Changing the tube takes only about a half hour and does not necessitate recalibration of the equipment; it can be done on a routine basis in most institutions, depending on the case load. CONCLUSION
The 350-kV chest radiography system has proved to be of great clinical value. The quality of chest films has been improved, and earlier and more accurate diagno- . sis of chest pathology has been made possible, with corresponding savings in the cost of hospitalization and the length of the patient's stay. Department of Radiology Oak Park Hospital 520 S. Maple Ave. Oak Park, III. 60304
(See also pages 159 and 165)
Clinical Evaluation of the 350·kV Chest Radiography System 1
Diagnostic Radiology
George S. Hallenbeck, M.D. A chest radiography unit employing 350 kV was evaluated and found to be superior to conventional 10w-kV systems. Visualization of air/soft-tissue boundaries, mediastinal structures, the retrocardiac area, and lung apices was improved. Other benefits of the high-kV system include reproducibility, reliability, rapid installation, and economy of operation. INDEX TERMS:
Radiography, apparatus and equipment • Thorax, radiography
Radiology 117: 1-4, October 1975
position, so that the positioning of the patient was the only variable. The power requirement was 208/240 V A.C., single-phase, 50-60 cycles per second, 30 A. The ion chamber was employed at an average exposure time of 1/70 sec. (adult chest, PA projection). A 12:1, 85-line grid was interposed between the patient and the screen.
T HAS long been realized that increased kilovoltage can improve soft-tissue visualization on more than 50 % of the area of a chest film, particularly at soft-tissue boundaries in the retrocardiac area and beneath overlying bone shadows, which is of great importance in facilitating early detection and accurate diagnosis of chest pathology. With the development of the fieldemission x-ray tube, which requires less exposure time and offers improved resolution, it has been possible to construct supervoltage equipment compact enough for use in a clinical setting. Chest films taken from 150 to 2,300 kV were evaluated and 350 kV was selected as optimum, as it provided enhanced visibility of soft tissues (the main advantage of supervoltage equipment) while retaining adequate bone detail. Not only could conventional films, screens, and grids be used at 350 kV, but, surprisingly, the conventional grids effectively cleaned up scattered radiations which had previously been a serious problem with supervoltage equipment. This new field-emission tube has been incorporated in a free-standing capacitor discharge unit which is specially adapted for chest radiography. I now wish to outline my experience with this unit and to describe what I feel are the outstanding advantages of supervoltage chest radiography.
I
CASE REPORTS CASE I: A 66-year-old man presented with a history of coughing and fever. A 10w-kV chest film showed lobar pneumonia involving the right upper lobe. A second chest film taken on the 350-kV unit on the following day clearly demonstrated a tumor in the center of the pneumonic consolidation and also revealed a second mass completely occluding the right-upper-Iobe bronchus at its origin; this second mass was later verified by tomography. (NOTE: This case is illustrated in an accompanying paper, Ref. 5, Fig. 3.)
COMMENT: This case illustrates the capability of the 350-kV chest radiography unit to provide greater softtissue visibility simultaneously in more areas of the film. In addition to pneumonic consolidation, this patient had cancer as well as complete obstruction of the rightupper-lobe bronchus. Whereas diagnosis at a low kV required tomography in addition to the routine chest film, the 350-kV chest film provided the same information on a single radiograph.
EQUIPMENT AND TECHNIQUE
The Hewlett-Packard Model 43815 350-kV unit was installed in the radiology department of Oak Park Hospitalon June 10, 1973. All films were taken on a Du Pont chest-film changer using Cronex 4 film and the new Du Pont SP fluorescent screen at a fixed 350 kV with a current of 40 mA over an exposure time range of 6-65 msec. at a fixed distance of 1.8 m (6 ft.). The tube was centered on the screen of the changer and locked in 1
CASE II: A 53-year-old woman exhibited signs and symptoms of superior vena cava obstruction. A chest film taken at 350 kV (Fig. 1, A) showed a huge mass in the anterior mediastinum as well as other masses in both hili and numerous parenchymal nodules. A conventional 10w-kV film taken for comparison (Fig. 1, B) showed only a vague impression of the right hilar mass and demonstrated only two of the many parenchymal lesions seen in the high-kV film. CASE
III: A 51-year-old asymptomatic woman was being fol-
From the Department of Radiology, Oak Park Hospital, Oak Park, III. Accepted for publication in June 1975.
1
sjh
2
GEORGE
S.
HALLENBECK
October 1975
Fig. 1. A. 350-kV chest film clearly demonstrates the extent of the disease process. The silhouette sign can easily be applied, as the hilar vascular markings and descending aorta are clearly visible through the principal tumor mass. The extent of the hilar, paratracheal, and parenchymal involvement is also amply demonstrated. B. In comparison, the 10w-kV film shows very poor definition of the right hilar disease. The silhouette sign is difficult to apply, and only two of the several areas of parenchymal involvement are demonstrated.
Fig. 2. A. 350-kV film clearly shows fibrotic changes and nodular densities of old tuberculous disease in the left and right upper lobes despite the overlying ribs and clavicles. It would be difficult to see this on films taken in the 80-90-kV range. B. A later 350-kV film clearly demonstrates cavitary change in the nodular density immediately underlying the anterior aspect of the left upper lobe. Overlying bone does not hinder diagnosis with 350-kV films. C. Tomogram of the left upper lobe confirms the changes identified on the earlier 350-kV chest film.
Vol. 117
CLINICAL EVALUATION OF THE 350-KV CHEST RADIOGRAPHY SYSTEM
Fig. 3. The pneumothorax and underlying emphysematous blebs are clearly demonstrated, and there is excellent penetration of the mediastinal area and retrocardiac region. Such excellent visualization of all of these areas simultaneously would be difficult with lowkV techniques, especially in a patient with emphysema. lowed up yearly by routine chest films (Fig. 2, A) for evaluation of an old tuberculous process. These studies showed cavitary change in an old nodular density located beneath the anterior aspect of the second left rib, confirmed by tomography (Fig. 2, B). Bronchial brushing and scalene lymph-node biopsy were negative. Antituberculotic therapy produced progressive improvement in the appearance of the lesion.
COMMENT: This case illustrates that even with overlying bony structures, lung lesions can easily be identified on supervoltage films. CASE IV: A 43-year-old woman entered the hospital for evaluation of severe shortness of breath of two weeks duration. A 350-kV chest film (Fig. 3) demonstrated a large pneumothorax on the right with extensive collapse of the right lung and bullous emphysema involving both upper lobes.
COMMENT: Supervoltage techniques have been found to be particularly applicable in the visualization of emphysematous lungs, where the fine boundaries between air and the soft tissue of the blebs are accentuated. CASE V: A 22-year-old man complained of persistent backache of five days duration. Physical examination showed marked enlargement of the left testicle, and the history revealed that this condition had been present for six months. A 350-kV chest film (Fig. 4) demonstrated hilar and paratracheal masses as well as multiple peripherallung nodules. At orchiectomy, a malignant teratoma of the testic~wasfound. ' .
3
Diagnostic Radiology
Fig. 4. 350-kV chest film demonstrates several metastatic nodules in both lung fields as well as hilar and mediastinal metastases. Note the readily demonstrated compression of the left main bronchus.
DISCUSSION
At first there was a tendency to over-read the 350kV films, due largely to the greatly increased amount of information. The result was heightened suspicion of miliary infiltrates in patients who were actually normal, while the improved visualization of the lung apices led to a general suspicion of increased incidence of disease in these areas which was not verified by other examinations. After about four to six weeks of experience, however, the 350-kV radiographs could be evaluated with no more difficulty or time than was required for the lowkV films. Calcifications within small lesions have usually had to be verified by obtaining either a 10w-kV spot film or a tomogram of the area; through experience, however, calcifications can often be readily detected on the 350-kV chest films. Radiologists specializing in study of bone or the gastrointestinal tract required more experience to adjust to the apparent lack of contrast and the overall gray tone of the 350-kV chest films; however, this too was quickly resolved by constant practice. In addition to the cases illustrated above, the 350-kV unit permitted improved resolution of pulmonary vessels, facilitating earlier and more accurate diagnosis of congestive heart failure and other cardiac conditions. Diagnosis of small lesions was improved, particularly those within bone shadows. Clear-cut separation of vascular and nonvascular shadows in the hilar region,
4
GEORGE S. HALLENBECK
where lesions of considerable size can sometimes be difficult to discriminate, permitted rapid detection of hilar adenopathy and bronchogenic neoplasms. With the older radiography technique, chest films were made on upright Bucky units without the advantage of phototiming, resulting in approximately 10% retakes. Using the new system, the percentage of retakes has been cut to 2-3 %, and most of these are necessitated by the patient being too large for the chest to be fully encompassed by the vertical 35.6 X 43.2-cm (14 X 17-in.) film configuration employed with the Du Pont changer. Fluctuation in the phototimer settings is insignificant, resulting in excellent reproducibility of radiographic technique over the course of several examinations. This makes it much easier to compare radiographic findings than was true with the earlier system, in which there were wide ranges in radiographic technique despite a vigilant quality-control program. The 350-kV unit has given consistently good-quality and properly exposed radiographs in patients of all ages. In general, the 350-kV chest radiography unit can be installed more quickly than standard radiographic equip-
October 1975
ment. During the 23 months it has been in use in this department, there have been only 20 days of down time, which is an excellent reliability record considering the seven-day work week. With improvement in tube performance, the interval between tube changes has increased from 1,200 to 4,500 exposures. Changing the tube takes only about a half hour and does not necessitate recalibration of the equipment; it can be done on a routine basis in most institutions, depending on the case load. CONCLUSION
The 350-kV chest radiography system has proved to be of great clinical value. The quality of chest films has been improved, and earlier and more accurate diagno- . sis of chest pathology has been made possible, with corresponding savings in the cost of hospitalization and the length of the patient's stay. Department of Radiology Oak Park Hospital 520 S. Maple Ave. Oak Park, III. 60304
(See also pages 159 and 165)
