MATERIALS AND METHODS

Thermographic Changes Following Preoperative Radiotherapy in Head and Neck Cancer 1

Robert L. White, M.D., Anas M. EI-Mahdl, M.D., Sc.D., Hugo L. Ramirez, M.D., Charles D. Teates, M.D., and William C. Constable, M.B., Ch.B., D.M.R.T. Thermography was used to assess vascular changes during and after head and neck irradiation in an attempt to predict the optimum time for surgery for patients receiving preoperative radiotherapy. Thermography is performed every one or two weeks throughout treatment and at longer periods after treatment. Eight of the 16 patients studied had an initial decrease in temperature during the first two weeks. The maximum increase was observed during the fifth week after receiving 5.000 rads . Return to pretreatment temperature levels was a gradual process. occurring between three and six weeks after completion of radiotherapy. TERMS: Head. ning • Thermography

INDEX

Work In Progress

WORK IN PROGRESS

Vol. 117

neoplasms. Neck.

neoplasms. Treatment

plan-

Radiology 117:469-471, November 1975

• Many institutions employ preoperative irradiation in the management of head and neck malignancy to reduce local recurrences with little or no increase in surgical morbidity. A waiting period of four to six weeks is often employed after the completion of radiation therapy before undertaking surgury. This period has been empirically determined from the persistence of radiation reactions and increased vascularity immediately following completion of radiotherapy. Operating at a later period is difficult because of increasing fibrosis, occluded vasculature and the obliteration of fascial planes with impaired healing. By using thermography as a quantitative means to assess the changes in vascularity due to irradiation, it is possible to determine the time required for the irradiated tissue to reach its pretreatment temperature level. It is assumed that return to this pretreatment temperature would indicate the return to normal of the blood supply and therefore the optimum time for surgery. The principle of thermography depends on StefanBoltzmann's law which relates the amount of energy an object radiates to the fourth power of its temperature. The thermograph, which consists of an optical scanning system and an infrared detector, converts infrared radiation into a video signal. The imaging of infrared radiation from the human body has been perfected to the point at which both resolution and reproducibility are useful and reliable (1,6).

Of the 24 patients studied, 16 have been followed through the irradiation course and postoperative recovery period . All 16 patients had preoperative irradiation to the entire neck to a tumor dose of 5,000 rads in 25 treatments over a five-week period with a cobalt-50 unit. Opposed lateral fields were employed with both fields being treated daily . The patients were allowed to equilibrate in a draft-free room maintained at 6870° F. The equilibration period lasted 10 minutes. The time of the examinations was not controlled but it was generally during the working day of the Department. Thermograms were taken prior to the beginning of radiation therapy and at one to two weekly intervals during treatment. Following treatment, thermography was performed less frequently. Anterior and oblique (both right and left) views were obtained. Film density was measured via photodensitometer in three standard areas over the neck on the negative oblique thermograms. The conversion from film density to temperature was made by constructing a graph of temperature versus density for each negative. A final temperature reading for each date is the overall average of the three readings on the two oblique views obtained for each patient. The conversion into skin temperature readings from thermograms was valuable for comparison in the study but may not represent true skin temperatures. RESULTS During the first two weeks of treatment the response was variable. Of the 16 patients, 8 showed a decrease in temperature; 2 of these had a brief increase in temperature which subsided and is believed to be caused by a transient erythematous reaction. There was an increase in temperature in the remaining 8 patients during this initial period but it was not as rapid as during the third to fifth weeks. During the third, fourth and fifth weeks, the temperature rise was uniform, reaching a maximum when irradiation was completed although the actual peak temperature varied from case to case. The increase in temperature was accompanied by the expected clinical erythema. After completion of treatment, temperatures gradually fell. Figure 1 shows a typical series of thermograms for one patient and Figure 2 demonstrates the patient's changes in temperature plotted against time. In this particular case, skin temperature returned to the pretreatment level 4-5 weeks after therapy.

c

B

Fig. 1. A. Pretreatment oblique thermogram (1124/74) . The film density scale on the patient's left represents the temperature range (OF). B. Increased skin temperature duringthe fourth week (2/27/74). C. Temperature returns to baselinelevel five weeks after completion of therapy (4/11/74).

469

470

2 PATIENTS WITH TRANSIENT ERYTHEMA

SKIN TEMPERATURE MEASUREMENTS

5OOOrods

103

+

LL

PRE-RADIATION 98 .5 tst,week 98.4

103

99.9

102

2nd.week 3rd. "",ek 4th. week

Sill . week

100.0 101.8 102.3

POST RADIATION 1st.week 2nd.week

102

.

November 1975

WORK IN PROGRESS

3rd.week 4th. week

101

5th. week 6th .week 7th. week

100 II::

UJ

...

5000 lADS

101

f

o

99.1 97.7

::l

.!:i

II::

UJ Q.

::IE

UJ

96

~

97 END OF TREATMENT

96

t 95 0 I 2 3 4 DURING TREATMENT

RETURN TO BASAL TEMP.

t

t

t

l---l_...J.._....L.._...l-_.l.-_'--......l_...J.._-'-_-,L---:':--J 1 2 3 • DURING TREATMENT

•o

3

q 4

10

11

12

S

6

7

AFTER TREATMENT

WEEKS

5 6 7 8 9 10 II 12 01234567 AFTER TREATMENT

WEEKS

Fig. 3. Two patients with a transient increased temperature during the first two weeks of treatment with temperature plotted against time .

Fig. 2. Skin temperature readings from thermograms of patient shown in Figure 1 plotted against time from start of treatment. Note fall in temperature at Week 1.

Two patients had an initial rise in temperature during the first week of treatment which was felt to represent transient erythema (2, 4) (Fig. 3) . Another patient's series of thermograms is shown in Figure 4.

A

RETURN TO BASALTEMP.

END OF TREATMENT

9. o

B

DISCUSSION Radiation induces sequential changes in the vascularity of the skin and subcutaneous tissues, manifested clinically as acute erythema. which is due to dermal vasodilatation and engorgement and the rise in temperature, a consequence of increased blood flow (2, 4) . Following the acute phase, endothelial hyperplasia progresses along with basement mem-

c

E Fig. 4. Series of thermograms from one of the patients plotted in Figure 3. A. Pretreatment oblique thermogram . The film density scale on the patient's left represents the temperature range (OF). B. Transient increased temperature during the second week of treatment. C. Cooling trend below the pretreatment temperature after two weeks of treatment. D. Increased skin temperature during the fourth week of treatment. E. Three weeks after completion of irradiation. F. Six weeks after completion of irradiation.

Work In Progress

47 1

WORK IN PROGRESS

Vol. 117

AVERAGE TEMPERATURE (16 PATIENTS)

AVERAGE TEMPERATURE OF 8 PATIENTS WITH EARLY COOLING PERIOD

103

103

102

T

102

5000 RAOS

... 0

W

:t-

101 100

TRANSIENT ERYTHEMA

::I

!;;:

c

til!

a:::

;:)

~

99

w

99

Q.

ffi

~

w

Q.

~

101

w a::: 100

98

I-

98

97 5000rads

97

96 96

END OF TREATMENT

t

END OF TREATMENT

+

1

95 0

2 3 4 DURING TREATMENT

OPERATIVE PERIOD

9

10

11'

12

4

5

6

7

AFTER TREATMENT

WEEKS

Fig. 5. The cooling trend in 8 of the 16 patients. temperature plotted against time. Brackets around the lines drawn through each point represent the range of temperature.

brane thickening. Telangiectatic vessels develop from the damaged superficial capillaries and compensate to some degree for the overall decrease in blood flow in the previously irradiated area. The chronic vascular changes are thought to contribute to subcutaneous fibrosis and should create a progressive decrease in skin temperature (3). Thermography is accepted as a means of demonstrating abnormal or increased vascularity in diseases such as cancer of the breast, Buerger's disease, thrombosis, etc. (1, 6). An initial increase in temperature noted in 2 patients during the first week is thought to represent transient erythema and may be due to the release of histamine-like substances. The minor cooling trend observed in the second week of treatment was not visible on the thermogram but was detected by the densitometer, and was observed during the first two weeks of treatment in 8 of the 16 patients. It may have been present in the others but not detected because of less frequent studies (Fig. 5). This is suggested by a very slow increase in temperature in all of the patients during the first two weeks of treatment (Fig. 6) which may have resulted from edema or vascular spasm. During the second week of treatment, hypoxia might possibly lessen the effect of irradiation on the tumor. The initial cooling trend was followed by a rapid rise in skin temperature, easily followed clinically as a progressive erythema. A maximum temperature increase in all patients coincided with completion of treatment at five weeks and 5,000 rads (Fig. 6). The initial recorded temperature and rate of increase in skin temperature varied in all 16 patients. Undoubtedly, individual variations depend on many factors, including differences in age, nutrition and general condition. The fall in temperature following completion of irradiation was at first thought to be uniform (5), the return to the pretreatment temperature occurring between three and six weeks. Further

I

2

3

DURING TREATMENT

4

5

o

6 I

7 8 9 234

10 5

II 6

12 7

AFTER TREATMENT

WEEKS Fig. 6. The average temperature of all 16 patients, temperature plotted aainst time, showing the initial slow rate of temperature change and the optimal time for operation.

studies, however, indicate that some patients recover more rapidly than others. The return to pretreatment levels of vascularity occurs between three and six weeks for most patients, in agreement with the recommended time for operation. The optimal time for surgery, it would appear, could be determined by obtaining a thermogram at the start, end, and three weeks after completion of treatment. By constructing a simple graph from these three points, one could predict pretreatment temperature return. Thermography has proved to be a satisfactory means of following vasculature changes during the course of irradiation and in the postradiation period. The three- to six-week waiting period following irradiation before and after surgery has apparently been confirmed.

REFERENCES 1. Introduction to Medical Thermography. Dallas, Texas, Texas Instruments, Inc., 1970 2. Moss WT, Brand WN, Battifora H: Radiatiofl Oncology. Rationale, Technique, Results. St. Louis, C.V. Moseby, 4th ed, 1973, pp 53-83,248-256 3. Reinhold HS: Radiations and microcirculation. [In] Frontiers of Radation Therapy and Oncology. Basel, Karger; also Baltimore, University Park Press, Vol 6, 1972, pp 44-56 4. Rubin P, Casarett GW: Clinical Radiation Pathology. Philadelphia, Saunders, Vol I, 1968, pp 62-119 5. Scruggs HJ, EI-Mahdi AM, Teates CD, et al: Use of thermography to evaluate the optimum time for surgery after preoperative radiation. Laryngoscope 85:.726-733, 1975 6. Van Voss H, Thomas P: Medical Thermography. Basel, Switzerland, S. Karger AG, 1969 1 From the Division of Radiation Oncology and Division of Nuclear Medicine, University of Virginia Hospital, Charlottesville, Va. Presented at the Sixtieth Scientific Assembly and Annual Meeting of the Radiological Society of North America, Chicago, III., Dec. 1-6, 1974. Reprints available from William C. Constable, M.D., Box 250, University of Virginia Hospital, Charlottesville, Va. 22901. shan

Thermographic changes following preoperative radiotherapy in head and neck cancer.

Thermography was used to assess vascular changes during and after head and neck irradiation in an attempt to predict the optimum time for surgery for ...
305KB Sizes 0 Downloads 0 Views