Dual-Isotope SPECT of Skull-Base Invasion of Head and Neck Tumors Mitsutaka Fukumoto, Shoji Yoshida, Daisuke Yoshida and Seiji Kishimoto Departments ofRadio1o@' and Otola,yngology, Kochi Medical Schoo4 Koch4 Japan however, detection by CT or MRI is often inconclusive. Skull-base invasions of head and neck tumors were examined

Cr imagesare sometimesobscured by artifacts, arising

by simultaneous

from complexbony structures of the skull base, whereas

bone

and tumor dual-isotope

SPECT

(S

SPECT)with°°@rc-hydroxy-methy1ene-diphosphonate (°@rc MRI has the inherent drawback of weak signal detection

HMDP)and20@fl-chIodde. Theeffecth,eness andreliabilfty of (signal void) from the bone cortex.

tumor diagnosis by this method was the primary interest in this study. Methods: Before S-SPECT imaging, a phantom expen ment using dned skull-bonespecimenswas pertormedto estab lishanatomicaldetailsofthe skullbasewiththe SPECT camera.

Several studies have shown that planar bone scintigra

phy is a useful technique for demonstrating skull bone invasion

of head

and neck

tumors

(1—5), but the specific

Radionudide crosstalk, window widths andcontrol patients were localization of these lesions was often difficult to ascertain also examined prior to S-SPECT imaging.Twenty patientswith because of the complexity of the skull base. Brown et a!. suspected tumor invasion of the skull base underwent (6) reported that the normal and abnormal transaxial anat S-SPECT. Results: Preliminary expenments revealed that omy of the face and skull could be clearly definedby crosstalk effects could be disregarded with adequate window SPECT. Despite their significant results, at the time, width and routine administrative doses of the radionudkies. SPEC!'hadpoorspatialresolution.Thisproblemhasbeen S-SPECTdetectedbonedestruc@on and the extentof tumor greatly reduced with the introduction of three-detector invas@n for all 12 palients in whom skull-base invohiement was SPECT' cameras equipped with fanbeam collimators. This diagnosed by CT or MRI. For the three patients in whom CT or instrumentation provides significantly better spatial resolu MRIrevealed notumorinvasion, theS-SPECT images didnot tion and imageclarity than previous SPEC!' models.

show any abnormal accumulabon in similar regions. In the re maining

five patients

without CT and MRI confirmation

of skull

base invasion,the S-SPECT findings showed skull-baseabnor maiities in three. Tumor invasionwas confirmed surgicallyor by clinical follow-up. The remaining two patients had negative S-SPECT images.Conclusion: S-SPECT is an effectiveand reliable diagnostic technique for detecting tumor invasion in the complex bony regions of the skull base. Key Words: single-photon emission computed tomography; technetium-99m-HMDP; thallium-201-chlonde; skull base inva sion; head and neck tumors

Bone SPEC!' with @Tc-HMDPhas become an impor tant diagnostic tool. Yui et a!. (7) showed how bone SPEC!' can be successfully used in skull-base regions and has high sensitivity for bone lesions detection. Moreover,

the sensitivityof this methodcan provideearlier diagnosis of bone abnormalities.These findingsare often more con clusive than those obtained by CT', MRI or planar bone

scintigraphy. Inaddition,201T1-Cl, a radionuclidethatdisplaysprefer ential accumulationin a variety of tumor types, is com monly used in SPECT tumor imaging. Several reports have demonstrated its efficacy in evaluating and localizing ma lignant tissue, especially in the lungs (8, 11 ), brain (9,10) and skull base (12,13).

J NucI Med 1995; 36:1740-1746

This studywas undertakento providea reliablediagnos alignant head and neck tumors are commonly known to invade the skull base. Although not all invasive patterns

are direct,

occasionally

there

is protrusion

through

the neurovascularforamina. In many cases, resorption or destruction

of the surrounding

bony regions is observed.

Todate,thediagnosisoflesionsintheskullbasehavebeen limited to the use of CT and MRI. When the lesion is localized near the cortical regions of the skull-base bone,

tic method for the early detection of skull-base invasion of

head and neck tumors. To achieve our goal, we used si multaneousbone and tumor dual SPEC!' (S-SPECT)im a@igfor co-localizationof bone and tumor-specificradio nuclidesin patients with suspected skull-baseinvasion. MATERIALS AND METhODS

Preliminary Study Prior to clinical application, a preliminaryexamination of a ReceivedSept.13,1994;revisionacceptedJan.26,1995. dried skull was conducted to establish anatomical details of the Forcorrespondence orreprintscont@ Mitsutaka Fukum@o, MD,Depait@,ent ofRadkilogy, KochiMedialSchool,Kohasu,Okoh.cho,NankOkU-City, Kochi783, skull base. A dried skull was first labeled by immersion for 1 hr in Japan.

1740

4000 ml

@“Tc-HMDP diluted with physiological saline and sub

TheJournalof NudearMediane• Vol.36 • No.10• October1995

sequently dried with warm air to produce a phantom specimen. Bone SPECT was performed on the phantom skull and a control image of the skull base was obtained. The phantom image was compared with a bone SPECT image of the skull of a normal patient who had no symptoms of head and neck disease. Addi tionally, the neurovascularforaminaof the @‘Tc-HMDP labeled

dry skull were filledwith smallcotton balls soaked with 20111Cl (containing

approximately

10—25MBq each),

and S-SPECT

was

performed to determine the anatomical locations of the foramina by superimposingthem on the bone SPEC!' image. Crosstalkevaluation of the radionuclideswas examined in the rangeof 68—80 keV to determine @“@Tc scattereffects on the 201'fl photopeak.

The count per unit volume

of 201@flmeasured

B. The crosstalk

(CR) effect that

Bone

SPECTDiagnosisPositivePositiveTumor SPECTTumor base.PositiveNegativeSkull

contactingthe skull baseboneabnormality withnotumorinvasion. Possibilityof no20111 uptake (falsenegative)or bony tumor.NegativePositivePattern inflammationaround Protrusionof is rare.

tumorthroughthe neurovascuiarforaminawith

from a

homogeneous 2o―fl aqueous solution (37.5 MBq/1 ml) was desig nated as variable A. In addition, a mixed aqueous solution con tamingequalvolumes of 2o―fl (37.5 MBq/1ml mixed solution)and @Tc (37.5 MBq/1ml mixed solution)was examined. In this case, the count per unit volume of @°‘T1 of the above mixture was variable

TABLE I S-SPECT Results of Skull-Base Invasion

invasion.NegativeNegativeSkull

no

baseis notinvolved.No tumorcontactwiththe skull base.

@“Tc had on the 2o―fl

window was approximated by the following formula: CR=(B-A)/Ax

100(%).

The energy window width for S-SPECT was changed to 10%, 15%, 20% and 30% and the respective crosstalks were calculated.

Because administered doses of radionuclides are different in clinical practice, @“Tc crosstalk in the energy window of 201'fl(at 10% window width) was also studied with a variety of mixed solutions.

The radionuclides

were combined

in aqueous

solutions

with the proportionsof @‘@Tc to 201'flrangingfrom4:1 to 4:4 and subsequently examined for crosstalk. We chose these mixture ratios based on the results from single-isotope SPECT analysis of normal physiological distribution ratios of @“@Tc-HMDP (555 MBq, 4.5 hr) and 201iia (111MBq, 2.0 hr)obtained from the skull bases of normal individuals. Normal physiological distribution ratios in the range of 4:2 to 4:3 were observed in the preliminary clinical trials and were used for reference in the clinical studies. ClInIcal Study Following the preliminary studies, 20 patients (16 men, 4 women, aged 22 to 78 yr) with suspected skull-base tumor inva sion had S-SPECT. The imaging protocol was: 1. Intravenous injection of @“Tc-HMDP (555 MBq) with a 2.5 hr waiting time. 2. Whole-body planar bone scintigraphy was performed. 3. After bone scintigraphy,

intravenous injection of 20111-Cl

(111 MBq). 4. At 2 hr postinjection of 201'fl@ (4.5 hr postinjection of @‘@Tc-HMDP), S-SPED' of the skull base was performed.

5. Bone and tumor S-SPED' imageswere evaluated. A three-detectorSPECT cameraequippedwith a fanbeamcol limator with 7.3 mm spatial resolution

(FWHM,

at the rotation

center) was used for the preliminary and clinical studies. Each detector was rotated at 4°step angles (30-sec step inter vals). Fanbeamprojectiondata from 90 steps were acquiredover

15mmandcollectedon a 256x 256matrix.Thefanbeamprojec tion datawere then converted to the parallel-beamprojectiondata on a 128 x 128 matrix, and SPECT images with 1.7 mm slice thickness were constructed by Butterworth and ramp filters for preprocessing and backprojection, respectively. Axial, coronal

and sagittal images of bone and tumor SPECT were obtained simultaneously.Diagnosis of the skull-baseinvasionwas madeby

Bone and Tumor SPECT at Skull Base • Fukumotoet al.

analysis ofboth kinds of images. Examples of positive or negative findings and a brief description of their significance are given for each radionuclidein Table 1. RESULTS Preliminary Study Comparison of bone SPEC!' images obtained from the dried skull phantom and the normal control patient re

vealed no majordifferencesin skull-baseanatomicaldetails (Fig. 1). Applicationof S-SPECT to the dry bone phantom (labeled with @Tc-HMDP)containing 201'flQ labeled cotton balls in the neurovascular foramina made it possible to determine the locations of the foramina in S-SPECT images (Fig. 2). Results of the crosstalk study, in equal

doses of

@‘@Tc and @°@‘fl, revealed slightly increased

crosstalk in the 1O%—20%window width, whereas in the

30% window width, greater than 30% crosstalk was ob served (Table 2). When the mixture ratios of 9@―Tc to @°‘Tl

were changed, the crosstalk was slightly increased, except when the mixture ratio of @‘@Tc to @°‘Tl was 4:1 (Table 2).

ClinicalStudy The results of S-SPECT evaluation of skull-base tumor invasion and other modalities (CT, MRI and surgical find ings) are given in Table 3. For the patients with conclusive

Cr and MRI results of skull-basedestruction and tumor invasion, S-SPECT also visualized abnormal tracer accu mulations in both the bone and tumor SPECT images.

In the three patients in whom Cl.' and MRI showed noncontacting tumor at the skull base, S-SPED.' analysis revealed no alterations in the bony anatomy of the skull base and a complete separation of tumor from the bone.

The remainingfive patients displayed problematicsigns of skull-base destruction. S-SPEC!' detected tumor invasion in three of five patients with inconclusive findings; surgery

later confirmed tumor invasion. In two patients with sus pected skull-base invasions, S-SPED.' was negative and surgery

confirmed

the S-SPECT

results.

Four typical

cases

of S-SPECT application are illustrated (Figs. 3—6).Al

1741

@

B

;

A

iii, 6

P

7

9

8

@,t

2:@RAM&i WALE 3:@R*M@4 @UM

,@

.

.%

15 10

11

12

CANE

s@mm@o@u@

-@ 14 @

17

15

FIGURE2. SPECTimagesof the

..,4 m

.@

@

$

411T,AUDflORY

‘ p

p

@‘Tc-HMDP-iabaled dried

skull containingsmallcottonswabsin the majorneurovascularto ramina Cottonballslabeledwith @°ii alsowere placedaroundthe CnStagab. TABLE 2 CrosstalkStudyResults

p

Comparisonof WindowW@thto Crosstalk(@°11 window) WindowwklthCrosstalk ratio30%

@

•.• .1@

31

12

15

.4@

wkfth37% 2.5%20% ± 2.1%15%width11%±2.2%1O%wklth7%±1.5% width18% ±

,a@

CrosstalkEvaluationof Four MixtureRatios (@°i1 window)

34

MixtureratioCrosstalk ratio(@rc:@°111)(10% fixed)4:135%±5.2%4:220%±4.1%4:317%±3.1%4:411% width

•4@ •e@

FiGURE 1. Bone SPECT imagesof skull-baseregionsfrom a

@rc-HMDP-labeled driedskull(A)andcontrolpatient(B).Corn parison of anatomical structures revealed no major differences. No

mandibleis presentonthedriedskullspecimen. TABLE 3 Assessment of Skull Base Invasion Patient no. SPECTEvaluation1 DiagnosisCT/MRIS-SPECT

in SkullBaseInvasion SPECTTumor biopsy)Bone

(ope,

SCCPositivePositivePositiveInvasion(+)2 Maxillary ca

SCCPositivePositivePositiveInvasion(+)3 Madllatyca AdenoPositivePositivePositiveInvasion(+)4 Parotidca neuroblastomaObscurePositivePositiveInvasion(+)5 Nasal SCCPositivePositivePositiveInvasion(+)6 Nasalca

SCCPositivePositivePositiveInvasion(+)7 Epiphatyngeal ca SCCPositivePositivePositiveInvasion(+)8 Epipharyngeal ca

SCCPoabvePositivePositiveInvasion(+)9 Maxillary ca SCCPositivePositivePositrveInvasion(+)10 Epipharyngeal Ca SCCObscurePositivePositiveInvasion(+)11 Epipharyngeal ca opPositivePositivePositiveInvasion(+)12 Chondrosarcoma. pre

Invasion(—)13 Maxillary caSCCNegativeNegativeNegativeNo

lymphomaObscurePositiveNegativeInvasion(+)14 Maxillary Invasion(—)15 Maxillaryca SCCNegativeNegativeNegativeNo Residual(—)16 Chondrosarcoma. postopObscurePositiveNegativeNo

papillomaPositivePositiveNegativeInvasion(+)17 Palateinverted ca*PositivePositiveNegathfeInvasion(+)18 Undifferentiated Invasion(-)19 Mmdllaiy caSCCNegativeNegativeNegativeNo SCCPositivePositivePositiveInvasion(+)20 E@pharyngeal ca

Invasion(—)tumor Maxillary caSCCObscurePositiveNegativeNo

ongin).ca (parapharyngeal = carcinoma;adeno= adenocarcinoma;SCC =squamous-call carcinoma.

I 742

TheJournalof NuclearMedicine• Vol.36 • No.10• October1995

A

@

I

:

V

FIGURE4. (A)CTscans(bone-window CTabove,contrast-en manwithmaxillary cancerlocal FIGURE 3. (A) CT (above) and MRI (below) of a 67-yr-old hancedCTbelow)froma 66-yr-old womanwith epipharyngealsquamous-callcarcinomareveala con uzedinthe postero-lateralwallofthe maxillarysinusare negativefor spicuous lesion on the rightside indicativeofskull-base invasion. (B) skull-baseinvasion.(B)BoneSPECTrevealedhighaccumulationin S-SPECT shows abnormal high @Fc-HMDP accumulations (small theskullbase(smallarrows);tumorSPECTwasnegativein this arrows) correspondingto tumor-positivesites (largearrows) in a regionjust bek)wthe rightforemenlacerum.

area (largearrow).

DISCUSSION though the sample number was small, we performed sta tistical analysis. S-SPECT sensitivity for detecting skull base tumor invasion was 93.3% (Table 4). S-SPEC!' bone image, on the other hand, had a sensitivity, specificity and accuracy of 100%, 60% and 90%, respectively (Table 4).

Skull-base invasion of head and neck tumors signifi cantly affect a patient's prognosis. Therefore, it is cx tremely important to detect the location and determine the

extent of tumor involvement in this region of the skull. Otherclinicians (1—5) have reportedthatbone scintigraphy The sensitivity, specificity and accuracy of tumor was sufficientfor detecting head and neck tumorinvasions S-SPECF were 80%, 100% and 85%, respectively (Table at the skull bone. Unfortunately, the complex structureof 4). We found no accumulation of 201'fl in patients with the skull base and lack of distinction between the numer

malignant lymphoma, verted papilloma.

undifferentiated

carcinoma

or in

A postoperative case of chondrosarcoma at the skull base was of interest. Although the tumor was completely

removed, Cl' scans showed abnormalsoft-tissue density in the skull base as a result of bone reinforcementtechniques and postoperative changes (Fig. 6A). In this patient, CT determination

of residual abnormality

or recurrent lesion

was not possible. S-SPECT, however, showed that bone damage was a result of surgery, and tumor SPECT re vealed the absence of malignanttissue (Fig. 6B).

Bone and Tumor SPECT at Skull Base • Fukumotoat al.

ous structure in this region are major limitations of bone scintigraphy. Brown et al. (6) distinguished between nor ma! and abnormal bony regions fairly distinctly by using

bone SPED.', but their findingswere limited by the spatial resolution of the SPECT camera. Technological improve ments have revolutionized

SPECT

imaging, making it

more accurateand reliablefor detecting tracerlocalization.

In many patients, extensive tumordevelopmentand skull-base destruction can be diagnosed accurately with CT or MRI. Yui et al. (7,13) reported that bone SPECT

could detect skull base abnormalities, even though CT or

1743

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1' @:i:-.@--@ :@

@

i@@&@p.: :

0

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Axial

13

‘1$

18

19

TI SPECT

Bone SPECT

Coronal

21

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0

4@

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j

‘I

ft

20

iS,

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P@e[@@ .4

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‘S

scans from a 22-yr-oldwoman with nasalneuroblastomawere incondusivefor skull-baseinvasion.(B) S-SPECTrevealedpositivebonereactivityin the posteriornasal regionwith sometumor invasion(largearrows).A smallaccumula tion of tracer was Visualized I,, the right temporal bone in the bone

SPECTimage(smallarrow).

!1s

BoneSPECT %

19

18

TI SPECT 19

Post Ope.

MRI showed normal anatomy, when a tumor existed just

below or near the skull base. Their studies, however, used single SPECT analysis of the radionuclide, and the rela tionships of bone with the tumor were inconclusive.

FIGURE 6. (A) PreoperativeCT scanfrom a 37-yr-oldmanwith chondrosarcoma of the skull base dearly revealed skull-base in

In our study, a directcomparisonof tumorand bone

volvement. (B) Preoperative S-SPECT images were positive. The

could be obtained by simultaneous visualization of both

skullbasewasextensivelyinvaded(largearrows)withdestructionof

radionuclides. Technetium-99m-HMDP sensitive

radiopharmaceuticals

is one of the most

for detecting

bone

disease,

and although false-positives are sometimes observed, con firmation can be achieved by examining the accumulation

of 201Tl-Clrelative to the false-positive site. In this study, delayed 20111-Climages were suitable for detecting malignant tumors because of delayed washout observed in malignancies (8,15—17). Some studies using

bonyregions.Postoperative 5-SPECTrevealeda positivebone SPECT as a result of reconstructivemeasuresin the skull base (smallarrow)and completeabsenceof @°ii accumulationin the tumor SPECT, indicatingcomplete removal of malignant tissue.

invasion and changes in bone structureor an inflammatory

the tumor SPECT image and that a delayed image was not

response. False-positive results can be avoided by analyz ing the delayed images. Thallium-201 Cl accumulations in inflammatory disease or benign lesions have been shown to decrease gradually with time, whereas delayed washout

acquired (12, 18—21 ). This protocol is possible if positive

was observed in malignanttumors (8,22). Examination of

determination of the tumor as malignant can be made by

the delayed image is an accurate method because it allows better differentiation between inflammatory and benign le sions from malignant lesions. In our study, we waited 2 hr before imaging, which appeared to be a suitable amount of time to permit contrast of the tumor from the surrounding tissues.

@-°‘Tl-Cl foundthatonlytheearlyimagewas usedto obtain

biopsy or other methods. When reactive inflammation has an effect on the skull

base regions, 201Tl-Clmay show high accumulations in the inflamed areas in early images. In this situation, it is often difficult to determine whether these results reflect actual

1744

The Journal of Nuclear Medicine• Vol. 36 • No. 10 • October 1995

TABLE 4 Sensitivity, Specificity and Accuracy of Bone and Tumor SPECT

CONCLUSION

S-SPECT is a useful technique that provides a complete anatomicaland physiological picture, detailingnormal and abnormal tissues. Even when skull-base destruction was

SensitivitySpecificityAccuracyBone

evident

SPECT100%60%90%Tumor SPECT80%100%85%S-SPECT

on CT or MRI,

S-SPECT

clearly

visualized

the

lesion as well as changes in the bone that were undetect able morphologicallyby CT or Mill. S-SPECT also proved an extremely useful diagnostic tool for the detection of silent or subclinical lesions and possible recurrent malig nancies in instances when the CT or MRI results were inconclusive.

detectabilityof skullbaseinvasion= 93.3%.

A drawback of tumor SPEC!' using @°‘Tl-Cl is no signif icant accumulation

of 201Tl-Cl in certain tumors in some

patients. Yui et al. (23) also reportedan absence of labeling in the first two types of manifestations. On the other hand, Sehweil et al. (24) reported that detectability of mediastinal lymphoma using @°‘Tl was 84.6%. They reported negative scans for patients with Hodgkin's and non-Hodgkin's lym

phoma. Nonaccumulation of 201'flis not a rare phenome

non in some types of malignanttumor.Furtherexamina tion with regardsto cellular kinetics of each tumor type is required. Tumors of squamous-cell variety, however, were de

tected in this study with high specificity and sensitivity, indicatingthe usefulness of 201Tl-Clfor reliabledetection of these types of tumors. Most malignant head and neck tu

mors are classified as squamous-cell carcinoma, which is the basis for using S-SPECT in head and neck tumors. When we evaluate negative 201'fluptake SPECT images of tumors, we must determine whether there was 201'flaccu mulation in the tumor to avoid false-negative results. Thal

hum is believed to act as a potassium analog that can stimulate the activity of the Na@-K@ATP-asedependent pump of cell membranes, resulting in active transport of 20111 into the cytoplasm.

Although

thallium

uptake

is not

identical to potassium (i.e.. 201'fl appears to bind to two sites on the enzyme), this process is also sensitive to

ouabain and sodium fluoride, which block the Na@-K@ pump (25). Delayed washout (or possibly prolonged up

take) in metastatic tissue may be reflective of the Na@-K@ ATP-ase activities of the tissue's constituent cells, a differ

ACKNOWLEDGMENTS The authors thank Mr. Naoki Akagi, Kochi Medical School, for assistance

with the SPECT camera and Mr. Patrick Nahirney

for reviewing and preparingthe manuscript.

REFERENCES 1. AlexanderJM. Radionuclide bonescanning inthediagnosis oflesions ofthe maxillofacial region. I Oral Swg 1976;34:249—256. 2. Higashi 1, Sugimoto K, ShimuraA, Ctal. Technetium-99m bone imaging in the evaluation of cancer of the maxillofacial region. I Oral Sui@ 1979;37:

254—259. 3. Bergstedt HF, Linf MG. Facial bone scintigraphy. Act Rod Diag 1981;22: 609—618. 4. Baker HL, Woodbury DH, Krause Ci, Ctal. Evaluation of bone scan by

scintigraphytodetectsubclinicalinvasionofthe mandibleby squamouscell carcinomaoftheoral cavity. Otolwy@golHeadNeckSuig 1983;90:327-336. 5. Gates GF, Goris ML Maxillaiy-facial abnormalities assessed by bone im

aging.RathoIo@'j1976;121:677—682. 6. Brown ML, Keyes JW, Leonard PF, et al. Facial bone scanning by emis sion tomography. I NuciMed 1978;18:1184—1188. 7. Yui N, Togawa T, Kinoshita F, et al. Assessment ofskullbase involvement of nasopharyngeal carcinoma by bone SPEC!' using three detector system.

Kaku Igaku 1992;29:37-47. 8. Tonami N, Shuke N, Yokoyama K, et al. Thallium-201single-photon emis sion computed tomography in the evaluation of suspected lung cancer. J Nuci Med 1989;30:997-1004. 9. Black KL, Hawkins PA, Kim KT, Becker DP, Lerner C, Marciano D. Use of thallium-201SPECT to quantitate malignancy grade of glioma. JNeuro siag1989;71:342—346. 10. Kim KT, Black KL, Marciano D, et al. Thallium-201 SPED' imaging of brain tumors: methods and results. I Nuci Med 1990;31:%5—969. 11. Matsuno S, Tanabe M, Kawasaki Y, et at. Effectivenessofplanar image and single-photon emission computed tomography of thallium-201 compared with gallium-67 in patients with primaty lung cancer. Eur I Nuci Med 1992;19:86—95. 12. Togawa T, Yui N, Kinoshita F, Shimada F, Omura K, Takemiya S. Visu alization ofnasopharyngealcarcinomawithTl-201 chloride and a three-head rotating gamma camera SPECT system. Ann NuciMed 1993;7:105—113.

ence that may explain the variation in thallium accumulation in differenttumors (17,26). 13.Yui N, SekiyaN, AkiyamaY, et al. Single-photon emissioncomputed The results of S-SPECT for detecting skull-base invasion

were 93.3%. It must be emphasized that the combinationof bone and tumor SPED' imaging enabled considerably higher detectability rates than either modality alone. Fur thermore,

if tumor

detection

by CF or MRI

is possible,

it

can augment S-SPECT to evaluate the extent of bone in

volvement and localized reactive inflammation.For exam

ple, S-SPECTimagingmay indicatean abnormalityin a wider region of the skull base than CT or MRI. On the

other hand, S-SPECT imagingproved useful in localizing skull-base invasions undetectable by both CT and MRI; tumor invasion was later confirmed by surgery and ap peared to be silent or subclinical in nature.

Bone and Tumor SPECT at Skull Base • Fukumotoat al.

tomography in the diagnosis of skull base invasion of nasophaiyngeal car cinoma. Kaku Igalat 1986;23:367-373. 14. Yui N, Kinoshita F, Akiyama Y, et al. ainiCal evaluation oftransaxial bone imaging with technetium-99m-phosphate compounds. Radio&sotopes1982; 31:515—528. 15. Jinnouchi S, Hoshi H, Ohnishi T, et at. Thallium-201SPED' for predicting

histologicaltypes of meningiomas.I NuciMed 1993;34:2091-2094. 16. Mahmoud El-Desouki. Thallium-201 thyroid imaging in differentiatingbe

nignfrom malignantthyroidnodules.ClinNuciMed 1991;16:425-430. 17.OchiH, SawaH, Fukuda1, et a].Thallium-201-chloride thyroidscintigra phy to evaluate benign and/or malignant nodules: usefulness of the delayed scan. Cancer 1982;50:236-240. 18. Kaplan WD, Takvorian T, Morris JH, RumbaughCL, Connoly BT, Atkins HL. Thallium-201braintumor imaging;a comparative studywith pathologic

correlation.I NuciMed 1987;28:47—52. 19. Schwartz RB, Caivaiho PA, Alexander E, Loeffler iS, Folkerth R, Holman BL. Radiation necrosis versus high-grade recurrent glioma: differentiation

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23. Yui N, Kinoshita F, Shimada F. aink@1 evaluation ofhead and neck tumor

scintigramwith @°‘Tl-chloride. Kaku Igaku 1979;16:221—227. 24. Sehweil AM, Mckillop JH, Milroy R, et al. Thallium-201scintigraphy in the

21.VanderwallHans,MurrayIPC,Huckstep RL, PhilipsRL.Theroleof

staging of lung cance@r, breast cancer and lymphoma.

Nuci Med Commun

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scintigraphyin excludingmalignancyin bone. CliiiNuciMed 1993;18:551- 25. Britten iS, Blank M. Thallium activation of the (Na@-K@)activated AlP 557.

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Scatter (Continuedfrom page 3A)

radiation safety officers nod approvingly to committees assembled to develop policy for this practice. I have met oncologists who will not schedule patients for an office visit on the day ofa bone scan because they are anxious about their own exposure to the radiation from the patient.

Although I do not argue with prudentradiationsafety procedures, regulatory agencies and radiation safety personnel have fostered the

erroneous notion that all detectable radiation is dangerous, that regulatory limits indicate dangerous levels ofexposures and that risks exist at all levels ofexposure. This evolves into the notion that all detectable radiation is dangerous and represents meaningful risk and that some cancers are caused by any exposure above background. No mention is made that background levels may vary in magnitude in various locales and that the incremental

background exposure in certain areas is many times the exposure received from certain occcupational activities. Despite intense scrutiny ofthese high background areas for many years, no adverse effect on the population has been observed. I wonder what the Martians think of all this?

Stanley J. Goldsmith, Editor-in-Chief

1746

MD

The Journal ofNuclear Medicine October 1995

TheJournalof NuclearMedicine• Vol.36 • No. 10• October1995