Can microcalcifications located within breast carcinomas be detected by ultrasound imaging?

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  • Ultrasound in Med. & Biol. Vol. 14, Sup. i, pp. 175-182, 1988 0301-5629/88 $3.00 + .00 Printed In the U.S.A. (c) 1988 Pergamon Press plc

    CAN MICROCALCIFICATIONS LOCATED WITHIN BREAST CARCINOMAS BE DETECTED BY ULTRASOUND IMAGING ?

    Fujio Kasumi, MD.

    Department of Surgery, Chief of Ultrasonic Laboratory Cancer Ins t i tu te Hospital, Tokyo, Japan

    ABSTRACT

    The author succeeded in detecting microcalc i f icat ions within breast carcinomas, by ultrasound(US) imaging, at the beginning of 1982, and published the results of his c l i n i ca l and experimental researches at the Third Internat ional Congress on the Ultrasonic Examination of the Breast held on June I0 - 12, 1983, in Tokyo, Japan~)

    After that , more deta i led c l i n i ca l evidence was acquired and new experiments, using breast phantoms, were carr ied out. This paper introduces an experiment using phantoms which shows that US can detect and iden t i f y even lO0-500M-sized t iny objects in an " idea l " low echoic area s imi lar to microca lc i f icat ions wi th in breast carcinomas. Actual c l i n i ca l evidence is also presented.

    Key Words : M ic roca lc i f i ca t ion , US detection, Breast Phantom, Bio-Gel.

    INTRODUCTION

    The author fabr icated breast cancer phantoms using d i f fe ren t densit ies of agar and d i f fe ren t sizes of minute glass beads o r i g i n a l l y designed to test the resolut ion of xerography. These phantoms were examined to determine whether US could detect minute glass beads less than Imm in diameter. I t was found that beads as small as I00~ were imaged by US as strong and impressives spots within the low echoic areas of the Phantom.

    However, i t was suggested that such phantoms were "too ideal" in terms of a c l i n i ca l picture. J. W. Hunt 2~ of the Ontario Cancer Ins t i t u te reported the use of "Bio-Gel" acrylamide, held wi th in an agar gel matrix, in which small scatters were used to mimic parenchyma, adipose t issue and cancer areas of the breast~) The author used such phantoms which were found to be very good with images closely resembling c l i n i ca l US images. Various sizes of glass beads were enveloped in the cancer area before the sol became a sol id gel. Phantoms were examined by US and xerography and then were compared with each other.

    MATERIALS AND METHODS

    Medical powder agar for a bacter ia l cul ture medium and acrylamide (which is usual ly used for electrophoresis and is avai lab le under the name of "Bio-Gel", manufactured by Bio-Rad laborator ies, catalog No. 150-1030) were used. In p last ic boxes, I% Bio-Gel in 2% boiled agar solut ion was mixed to simulate preglandular (sub-cutaneous) adipose t issue and, a f ter 15 minutes, 5% Bio-Gel in boi led 2% agar solut ion was added to form a second layer to simulate breast glandular t issue. After these layers become sol id , index- f inger - t ip -s ized holes were cut from behind and were f i l l e d with a 0.5% Bio-Gel solut ion containing a small number of glass beads of d i f fe ren t sizes. These beads were embedded in the solut ion in such a way that they did not overlap each other e i ther a x i a l l y or l a t e r a l l y . These beads were designed by XEROX for test ing the resolut ion of xerography. This arrangement was meant to simulate breast cancers with embedded microca lc i f ica t ions. To simulate the retroglandular adipose t issue, more I% Bio-Gel solut ion was added last to form a th i rd layer. Fi 9. 1 Removed from the i r p las t ic boxes, these phantoms were examined by US and xerography. Six phantoms which contained speci f ic sizes of glass beads were imaged by US and xerography.

    The US apparatus used was a Hitachi EUB2B mechanical l inear motion system. The transducer was a modified PVOF, 7.5 MHz single focus, one inch un i t . Fig. 2 The phantoms and probe were immersed in water and scanned. The xerography apparatus was a XEROX 125.

    175

  • 176 5th International Congress on the Ultrasonic Examination of the Breast

    B r e a s t C a n c e r P h a n t o m

    " " : : : . i 5%

    - 1 %

    Glass Beads Cancer 0.5%

    of Bio-Gel in 2% Agar

    Fig. 1

    Fig. 2-1

    Fig. 2-2

  • 5th International Congress on the Ultrasonic Examination of the Breast 177

    IDENTIFICATION OF GLASS BEADS IN AGAR

    BY ULTRASOUND AND XEROMAMMOGRAPHY

    MEAN ~AMETER OF BEADS ULTRASOUND XEROMAMMOGRAPHY

    I 1100p

    2 460

    3 300

    4 200

    5 160

    6 110

    Fig. 3

  • 178 5th Internatlonal Congress on the Ultrasonlc Examination of the Breast

    RESULTS

    Results are shown in ~Fig'3 s By xerography, 160~ was the lower l imi t for ident i f icat ion of the glass ; for a size-llO~ bead, detection was almost impossible. On the other hand, even llO~ beads were easily detected by US and adequately imaged separated ax ia l ly and latera l ly in low echoic cancer areas. Fig. 4,5 However, because of differences in resolution power, the size of glass beads was more accurately determined by xerography than by US.

    ,5 160p Fig. 4

    6 110k Fig. 5

    When the glass beads were enveloped di f fus ively within the 5% Bio-Gel area,however, even 460~-sized beads could not be detected by US because they exhibited the same ecogenicity as the 5% Bio-Ge]. Fig, 6 This i nab i l i t y to detect is similar to the fact that scattered microcalcifications found in f ibrocystic diseases or noninvasive ductal carcinoma without making remarkable mass can not be detected by US.

    Identification of Glass Beads in

    5% Bio-Gel,2% Agar

    420--500

    Fig.6-1 Fig:6-2

  • 5th International Congress on the Ultrasonic Examination of the Breast 179

    DISCUSSIONS

    The lOdB down resolution of the modified PVDF polymer transducer used in these studies is 800~ in the lateral direction and 400~ in the axial direction. Diameters of breast microcalcif ication are usually under Imm, with the majority between lO0 and 500~. The experiment described here shows that US can detect glass beads smaller than i ts theoretical resolution power, providing they exist in ideal low echoic areas. The images of the glass beads, shown as strong spots, were usually without acoustic shadows.

    Cl in ica l ly , when mammography (MMG) shows microcalcifications inside breast cancers, US detects f ine, strong echoes located within the low echoic cancer areas. Fig, 7-11 By c l in ical and pathological findings, these echogenic spots correspond to the microcalcif ications.

    Fig.7-1 Fig.7-2

    Fig.8-1 Fig.8-2

    Fig.9-1 Fig.9-2

    Fig.lO F ig . l l

    From the ultrasonographical point of view, this experiment connected US and xeromammography. US should detect minute calci f icat ions between l O0 and 500~ in diameter separated from each other, since breast cancers are imaged as low echoic areas, with the exception of scirrhous, shadow-type cancers.

  • 180 5th International Congress o n the Ultrasonic Examination of the Breast

    Fig. 12 shows the mutual re lat ionship between MMG and US in one hundred cases of breast cancer pat ients. By US, 25 + 56 cases were correct ly diagnosed, 13 were underdiagnosed, mainly because of the poorer resolut ion of US in comparison to MMG. The fact that MMG is a whole survey, while US is tomographic, must also be considered. Six of the cases were overdiagnosed by US. I t is true that US images strong echogenic spots some of which are not microca lc i f icat ions. For MMG, su f f i c ien t Ca3(P04)4 deposition

    may be necessary before the i den t i f i ca t i on of microca lc i f ica t ion can be made. I t is, however, probable that for US, s ign i~can t calcium deposit ion may not be necessary.

    MMG

    1 +

    2 +

    3

    4

    DE'I'I~CTICI~] OF MICROCALCIFICATIONS

    by MMG & US

    US

    + 25 correctly detected

    - 13 under diagnosed

    - 56 correctly denied

    + 6 over diagnosed

    * Detection of MicrocalcJfications by MMG 38%

    * Sensitivity of US 25/25+13 63

    * Specificity of US 56/56+6 90.3

    * Accuracy of US 25+56/100 81

    Fig.12

    Unti l the end of 1980, nothing had been published world-wi le about US detection of microcalc i f icat ions in breast cancers, and i t had been thought to be absolutely impossible to detact them by PZT 3-5MHz transducers. Under th is circumstance, in 1978 Kossoff, Je l l i ns and Reeve 4)reported a case of the v isua l i za t ion of macrocalci f icat ion as a br ight spot in a s tage- l l scirrhous carcinoma, but mentioned that the resolut ion of the System-I echoscope did not allow the display of the microca lc i f ica t ions.

    In 1980, Harper and Kelly-FryS) wrote that (1)US was not as capable as of c lear ly imaging microca lc i f icat ions of 0.2 - O.5mm in diameter, (2)the scanning device with the 3.7MHz single focus transducer was not designed to detect microca lc i f ica t ions, and (3)US could detect ca l c i f i ca t i ons larger than O.5mm; they reported a case of the v isua l iza t ion of macrocalci f icat ions in fibroadenomas.

    In 19806)and 1982~) Cole-Beuglet described a case of non-palpable cancer with microcalc i f icat ions v isual ized by System-I as a mass containing br ight echoes with poster ior shadowing.

    In 1982, Kopans, Meyer and SteinbockS)reported that two cases of clusters of microca lc i f icat ions seen on xeromammography were visual ized on the ultrasonograms by a real- t ime apparatus with a 3.2 MHz sector transducer as echogenic foci without evidence of shadowing.

    In 1979, the author adopted a PVDF 7.5MHz transducer as a subst i tute for the PZT 5oOMHz transducer in the EUB 2B mechanical l inear motion system;