Oct.

User

Controlled

Overviews

of

an

Image

Library

A

Case

Study

of

the

Visible

Human

Chris

North

Ben

Shneiderman

and

Catherine

Plaisant

Human-Computer

Interaction

Laboratory

Department

of

Computer

Science

-LSB-

Institute

for

Systems

Research

University

of

Maryland

College

Park

MD

-LCB-

north

ben

plaisant

-RCB-

@cs

umd.edu

ABSTRACT

This

paper

proposes

a

user

interface

for

remote

access

of

the

National

Library

of

Medicine?s

Visible

Human

digital

image

library

Users

can

visualize

the

library

browse

contents

locate

data

of

interest

and

retrieve

desired

images

The

interface

presents

a

pair

of

tightly

coupled

views

into

the

library

data

The

overview

image

provides

a

global

view

of

the

overall

search

space

and

the

preview

image

provides

details

about

high

resolution

images

available

for

retrieval

To

explore

the

user

sweeps

the

views

through

the

search

space

and

receives

smooth

rapid

visual

feedback

of

contents

Desired

images

are

automatically

downloaded

over

the

internet

from

the

library

Library

contents

are

indexed

by

meta-data

consisting

of

automatically

generated

miniature

visuals

The

interface

software

is

completely

functional

and

freely

available

for

public

use

at

Proc

of

the

ACM

International

Conference

on

Digital

Libraries

-LRB-

Bethesda

MD

March

-RRB-

Video

abstract

appears

as

Browsing

anatomical

image

databases

A

case

study

of

the

Visible

Human

ACM

CHI

Conference

Companion

-LRB-

Vancouver

BC

Canada

April

-RRB-

Video

available

through

ACM

INTRODUCTION

The

Visible

Human

The

National

Library

of

Medicine

-LRB-

NLM

-RRB-

for

its

Visible

Human

Project

-LSB-

-RSB-

is

in

the

process

of

creating

a

large

digital

library

of

anatomical

images

of

the

human

body

It

contains

MRI

and

CT

scans

as

well

as

cryosection

images

-LRB-

digital

color

photographs

of

crosssections

Figure

-RRB-

Two

cadavers

one

male

and

one

female

were

carefully

chosen

as

the

subjects

The

male

dataset

MRI

and

CT

images

were

captured

using

the

respective

medical

imaging

scanners

The

MRI

images

were

captured

at

intervals

throughout

the

body

Each

is

pixels

in

resolution

with

gray

level

encoding

The

CT

images

were

captured

at

intervals

to

correspond

with

the

cryosections

Each

is

pixels

also

using

gray

level

To

capture

the

cryosection

images

the

cadaver

was

first

frozen

solid

inside

a

large

block

of

blue

gel

Then

thick

slices

were

successively

cut

away

from

an

axial

cross-section

-LRB-

planar

cut

perpendicular

to

the

longitudinal

axis

of

the

body

-RRB-

and

digital

color

images

were

taken

of

each

newly

exposed

cross-section

A

total

of

cryosection

images

were

taken

spanning

the

body

from

head

to

toe

Each

is

color

and

has

a

resolution

of

pixels

The

total

result

is

a

Gigabyte

image

dataset

of

the

male

body

The

female

dataset

will

be

captured

at

mm

slices

and

thus

is

expected

to

require

three

times

the

storage

space

of

the

male

dataset

In

addition

film

of

cryosections

may

be

scanned

at

higher

resolutions

for

details

of

various

anatomical

structures

The

NLM

provides

public

access

to

the

Visible

Human

digital

library

via

the

internet

The

entire

dataset

resides

on

a

high

capacity

storage

system

with

a

high

speed

internet

connection

A

simple

license

agreement

with

NLM

intended

for

tracking

data

usage

allows

any

user

with

an

internet

capable

computer

to

remotely

access

the

full

dataset

Each

image

is

stored

on

the

archive

as

a

separate

file

with

numerically

indexed

filenames

ordered

from

head

to

toe

Using

ftp

a

user

remotely

logs

onto

the

archive

machine

with

a

special

login

ID

and

password

provided

with

the

license

agreement

and

downloads

any

number

of

image

files

by

specifying

the

correct

numerical

filenames

The

images

can

then

be

displayed

locally

using

an

appropriate

image

browsing

software

package

Also

several

sample

images

are

available

to

those

without

a

license

agreement

on

the

Visible

Human

World

Wide

Web

page

at

Because

the

library

is

available

to

the

public

the

user

community

is

diverse

Users

are

of

varying

backgrounds

and

cover

a

wide

range

of

expertise

in

human

anatomy

and

computer

skills

The

most

prominent

user

groups

are

medical

professionals

and

students

interested

in

using

the

images

for

education

and

modeling

purposes

and

computer

science

researchers

and

software

developers

creating

medical

imaging

applications

Other

users

include

elementary

school

teachers

curious

internet

surfers

and

even

martial

arts

experts

Some

users

wish

to

simply

explore

the

dataset

in

an

open-ended

fashion

and

download

a

sampling

of

images

to

browse

Other

users

who

desire

a

specific

portion

of

the

dataset

use

a

more

directed

search

to

locate

and

download

images

Some

desire

only

a

single

image

or

small

set

of

images

perhaps

to

use

as

overheads

while

teaching

an

anatomy

class

Others

download

an

entire

continuous

block

of

images

representing

some

portion

of

the

body

In

this

case

the

images

are

often

used

for

modeling

of

anatomical

structures

For

example

a

medical

expert

might

download

all

the

cryosection

images

containing

the

heart

and

load

them

into

advanced

software

such

as

Mayo

Clinic?s

ANALYZE

to

visualize

ventricle

chambers

Very

few

attempt

to

download

the

entire

library

since

it

would

require

weeks

of

continuous

internet

activity

as

well

as

overwhelming

storage

capacity

Unfortunately

using

the

Visible

Human

digital

library

can

be

difficult

The

ftp

interface

merely

presents

users

with

a

Figure

A

Visible

Human

cryosection

image

of

the

male?s

head

Library

cryosection

images

are

full

color

and

have

pixel

resolution

larger

than

most

CRTs

long

list

of

sequential

image

filenames

Browsing

the

data

requires

a

trial-and-error

process

of

guessing

a

file

downloading

it

-LRB-

which

could

take

several

minutes

-RRB-

and

displaying

the

image

locally

A

Web

page

interface

that

displays

thumbnails

of

the

library

images

would

allow

the

user

to

visually

browse

the

contents

of

the

library

but

would

require

paging

through

hundreds

of

thumbnails

that

must

be

downloaded

for

each

access

Whether

a

user

wants

to

simply

browse

the

library

or

retrieve

images

for

some

other

use

it

is

important

to

avoid

unnecessary

downloads

Because

the

dataset

is

extremely

large

and

would

take

weeks

to

download

and

it

is

desired

that

users

with

smaller

computers

with

limited

storage

capacity

have

access

the

ability

to

remotely

explore

a

visual

representation

of

the

dataset

and

download

only

desired

images

is

a

requirement

Hence

there

is

a

great

need

for

an

effective

user

interface

to

assist

users

in

browsing

the

library

and

retrieving

images

Related

Work

As

digital

libraries

quickly

increase

in

number

researchers

are

continually

developing

improved

public

access

methods

for

the

many

different

types

of

library

information

The

primary

user

interface

approach

especially

for

libraries

containing

unstructured

collections

of

heterogeneous

documents

is

the

keyword

query

method

In

this

case

Information

Retrieval

systems

preprocess

documents

in

the

library

usually

using

automated

algorithms

to

generate

comprehensive

indices

-LRB-

meta-data

-RRB-

Then

when

a

user

enters

a

query

the

system

can

quickly

generate

a

list

of

matching

documents

Since

many

of

these

libraries

contain

textual

documents

only

such

as

computer

science

technical

reports

-LSB-

-RSB-

and

use

strictly

textual

queries

interfaces

are

often

text-based

for

simple

WWW

or

teletype

access

More

advanced

GUI

interfaces

afford

additional

capability

to

manipulate

and

visualize

the

textual

query

-LSB-

-RSB-

Image

libraries

may

also

provide

for

query

by

image

content

-LSB-

-RSB-

In

this

case

images

are

indexed

by

content

features

and

if

available

textual

annotations

These

interfaces

allow

users

to

specify

example

images

interactively

sketch

objects

or

use

an

image

content

description

language

to

create

a

query

KMeD

-LSB-

-RSB-

is

an

example

of

a

multimedia

library

in

the

medical

domain

which

combines

both

textual

and

medical

image

elements

Digital

video

libraries

expand

the

query

method

further

using

speech

recognition

on

the

audio

tracks

of

videos

for

textual

indexing

-LSB-

-RSB-

While

the

query

method

may

be

an

effective

means

for

retrieving

documents

based

on

keywords

or

image

features

it

does

not

provide

the

capability

to

explore

or

build

a

mental

model

of

the

contents

of

a

library

However

if

the

documents

within

a

library

are

organized

using

some

consistent

natural

comprehensible

orderly

structuring

method

then

interfaces

using

a

browsing

approach

are

also

applicable

Advanced

user

interface

techniques

for

information

exploration

can

be

used

to

explore

the

library

structure

usually

specified

by

metadata

and

its

contents

This

gives

users

a

way

to

learn

about

the

library

and

locate

interesting

documents

without

relying

on

keyword

search

Several

common

structuring

methods

exist

-LSB-

-RSB-

For

example

Hypertext

systems

such

as

the

WWW

organize

documents

in

a

hierarchy

or

other

graph

representation

With

an

interface

for

browsing

graph

structured

information

-LRB-

see

-LSB-

-RSB-

for

a

review

of

several

-RRB-

users

can

utilize

the

links

perhaps

representing

relationships

between

documents

to

discover

related

documents

that

might

be

found

using

a

query

Implementations

include

utilizing

the

Dewey

Classification

hierarchy

to

browse

a

library

catalogue

-LSB-

-RSB-

and

reference

citations

to

browse

articles

-LSB-

-RSB-

MeSHbrowse

-LSB-

-RSB-

is

an

interface

for

browsing

a

medical

terminology

hierarchy

containing

arbitrary

interrelationships

-LRB-

meta-data

-RRB-

as

an

index

to

a

medical

image

digital

library

Another

structuring

method

organizes

information

by

defined

textual

and

numerical

attributes

Doan

applies

dynamic

query

interface

techniques

to

arbitrary

distributed

information

of

this

form

allowing

users

to

quickly

learn

overall

contents

find

trends

and

locate

documents

of

interest

-LSB-

-RSB-

Browsing

computer

science

literature

has

been

handled

by

attribute

structure

as

well

using

author

names

publication

dates

and

sizes

etc.

-LSB-

-RSB-

Some

interfaces

use

the

map

motif

to

browse

spatial

information

in

which

case

attributes

represent

geographical

locations

-LSB-

-RSB-

All

of

these

systems

are

examples

of

how

advanced

information-exploration

user

interface

techniques

can

capitalize

on

the

structure

of

an

organized

library

to

add

a

new

dimension

namely

the

capability

to

browse

to

the

user?s

tool

set

for

the

task

of

information

retrieval

The

Visible

Human

digital

library

exemplifies

another

organizational

method

for

structuring

libraries

The

medical

imagery

although

un-annotated

is

concretely

structured

That

is

the

images

have

a

strict

sequential

ordering

defined

by

the

physical

objects

-LRB-

the

human

body

-RRB-

represented

Hence

because

of

the

previously

described

successes

we

expect

that

a

user

interface

which

utilizes

this

structure

to

provide

a

browsing

environment

would

be

an

effective

means

for

users

to

retrieve

desired

images

Guiding

principles

for

designing

a

user

interface

for

the

Visible

Human

library

come

from

related

research

of

browsing

techniques

Firstly

direct

manipulation

with

compelling

success

in

many

exploration

interfaces

provides

these

principles

-LSB-

-RSB-

Visual

representation

of

the

search

space

Rapid

incremental

reversible

exploratory

actions

Pointing

and

selecting

instead

of

typing

and

Immediate

continuous

visual

feedback

of

results

Research

in

digital

medical

atlases

has

developed

reconstruction

and

visualization

techniques

for

annotated

segmented

medical

image

data

-LSB-

-RSB-

Interface

elements

and

strategies

for

browsing

individual

images

are

thoroughly

identified

-LSB-

-RSB-

In

particular

a

coordinated

detail

view

and

overview

giving

contextual

feedback

as

well

as

extraneous

data

download

avoidance

are

essential

elements

for

remotely

browsing

very

large

images

-LSB-

-RSB-

Work

on

Query

Previews

-LSB-

-RSB-

shows

the

benefits

of

previewing

downloadable

data

as

a

filtering

process

by

issuing

dynamic

queries

on

meta-data

With

this

technique

users

drag

sliders

click

on

options

and

receive

rapid

visual

feedback

to

identify

desired

data

Figure

The

Visible

Human

Explorer

user

interface

showing

a

reconstructed

coronal

section

overview

and

an

axial

preview

image

of

the

upper

abdominal

region

Dragging

sliders

animates

the

cross-sections

through

the

body

available

for

retrieval

With

these

principles

as

our

motivation

we

designed

the

interface

described

in

the

following

section

THE

INTERFACE

We

have

developed

a

direct

manipulation

user

interface

called

the

Visible

Human

Explorer

-LRB-

VHE

-RRB-

for

remotely

exploring

the

Visible

Human

digital

library

and

retrieving

images

It

allows

users

to

rapidly

browse

on

their

own

machine

a

miniaturized

version

of

the

Visible

Human

dataset

and

based

on

that

exploration

download

desired

full

resolution

library

images

The

miniature

dataset

provides

an

overview

of

library

content

and

acts

as

a

preview

mechanism

for

retrieval

The

interface

along

with

the

miniature

dataset

is

downloaded

in

advance

and

then

used

as

an

accessor

to

the

archive

The

payoff

is

quick

since

downloading

the

VHE

is

equivalent

to

only

about

image

retrievals

With

this

paradigm

although

implemented

completely

outside

of

any

existing

web

browser

the

interface

can

be

thought

of

as

an

advanced

dynamic

web-page

application

for

browsing

a

medical

image

digital

library

The

VHE

direct

manipulation

interface

-LRB-

Figure

-RRB-

presents

the

user

with

a

coordinated

pair

of

orthogonal

crosssection

views

of

the

Visible

Human

body

The

left

viewwindow

or

overview

displays

a

miniature

coronal

section

a

front-view

longitudinal

cut

of

the

body

It

acts

as

an

overview

of

the

library

giving

the

user

a

general

understanding

of

the

contents

of

the

body

from

head

to

toe

The

images

for

this

view

were

reconstructed

directly

from

the

cross-section

images

taking

advantage

of

the

structural

organization

of

the

library

by

sampling

a

single

row

of

pixels

from

successive

images

to

simulate

a

perpendicular

cut

The

resolution

is

decreased

to

approximately

The

right

view-window

or

preview

displays

a

miniature

axial

section

the

type

of

cut

typically

seen

in

medical

atlas

textbooks

The

images

for

this

view

are

reduced

resolution

thumbnail

images

-LRB-

-RRB-

of

the

original

library

cross-sections

and

act

as

a

preview

of

those

higher

resolution

images

The

magnification

of

this

view

is

twice

that

of

the

overview

giving

the

user

more

detail

of

the

library

A

horizontal

indicator

on

the

overview

indicates

the

vertical

position

on

the

body

of

the

axial

section

shown

in

the

preview

The

indicator

is

attached

to

a

vertical

slider

widget

spanning

the

height

of

the

overview

and

can

be

dragged

vertically

across

the

body

to

sweep

the

cut

shown

in

the

preview

through

the

body

As

the

user

drags

the

indicator

the

preview

provides

smooth

rapid

feedback

-LRB-

-RRB-

reflecting

the

axial

cross-section

at

the

sliding

cut

plane

resulting

in

a

dynamic

animated

effect

of

motion

through

the

body

This

gives

the

user

the

ability

to

easily

explore

the

contents

of

the

entire

body

Likewise

a

sliding

indicator

in

the

preview

controls

the

view

shown

in

the

overview

For

example

the

user

can

slide

the

overview

to

show

a

coronal

section

nearer

to

the

front

or

back

of

the

body

-LRB-

See

video

report

-LSB-

-RSB-

for

a

demonstration

of

the

dynamic

interaction

-RRB-

While

exploring

when

the

user

locates

an

axial

section

in

the

preview

for

which

high

resolution

data

is

desired

pressing

the

Full-Size

Image

button

opens

the

Retrieval

dialog

box

-LRB-

Figure

-RRB-

This

dialog

handles

the

details

of

accessing

the

Visible

Human

library

archive

After

users

type

their

Visible

Human

login

ID

and

password

into

the

corresponding

textboxes

and

press

the

Retrieve

button

the

system

begins

to

download

the

requested

full

resolution

cryosection

image

from

the

NLM

digital

library

over

the

internet

to

the

user?s

computer

Since

retrieval

may

take

several

minutes

depending

on

internet

traffic

a

status

meter

provides

feedback

on

the

progress

of

the

retrieval

Users

have

the

option

to

cancel

the

downloading

at

any

time

Once

the

meter

reaches

the

download

is

complete

and

the

image

is

then

displayed

in

a

large

detail

view

Figure

The

VHE

Retrieval

dialog

box

meters

downloading

from

the

Visible

Human

digital

library

Since

downloading

over

the

internet

can

be

a

time

consuming

process

the

system

does

have

provisions

for

users

with

computers

containing

ample

storage

space

It

can

accumulate

retrieved

high

resolution

images

on

the

user?s

computer

thereby

allowing

the

user

to

browse

not

only

the

remote

library

but

also

a

local

cache

as

well

A

vertical

bar

aligned

next

to

the

overview

image

shows

tic

marks

indicating

which

axial

cryosections

are

contained

in

the

local

cache

When

one

of

these

cross-sections

is

previewed

by

placing

the

cut

plane

slider

over

a

tic

mark

a

flag

in

the

preview

window

highlights

to

indicate

that

the

corresponding

full-size

image

is

in

the

cache

Clicking

on

the

Display

button

will

then

display

the

image

from

the

cache

saving

the

download

time

Below

the

overview

a

text

box

shows

the

name

of

the

user

selectable

directory

containing

the

local

image

cache

This

feature

is

particularly

useful

for

users

who

acquire

their

own

copy

of

the

Visible

Human

digital

library

since

they

can

use

the

VHE

to

browse

it

as

well

The

VHE

also

provides

the

capability

to

download

any

user

specified

range

of

cross-section

images

into

this

cache

at

once

The

user

simply

places

range

indicators

next

to

the

overview

slider

and

selects

a

button

to

begin

retrieval

using

the

Retrieval

dialog

box

Two

smaller

axial

crosssection

views

display

images

of

the

top

and

bottom

slices

of

the

user

specified

range

Feedback

on

the

number

of

images

within

the

range

and

the

total

size

in

megabytes

of

those

library

images

is

also

provided

This

feature

is

useful

for

retrieving

commonly

examined

portions

of

the

body

a

priori

or

for

obtaining

a

continuous

block

of

images

for

use

in

modeling

applications

Figure

VHE

menus

for

selecting

amongst

datasets

Also

using

the

icon

buttons

adjacent

to

the

overview

the

user

can

select

amongst

different

overview

image

types

including

the

coronal

section

sagital

section

-LRB-

side

view

longitudinal

section

-RRB-

and

a

simple

front

view

of

the

body

-LRB-

no

cut

-RRB-

This

gives

the

user

a

variety

of

views

of

the

overall

search

space

Menu

options

-LRB-

Figure

-RRB-

enable

selecting

between

the

male

or

female

subjects

and

between

the

MRI

CT

and

cryosection

medical

image

types

Currently

only

the

male

cryosection

meta-data

is

loadable

Implementation

and

Performance

The

VHE

is

implemented

in

the

UNIX

X/Motif

environment

on

a

Sun

Sparcstation

The

key

to

implementation

is

the

use

of

meta-data

consisting

of

the

miniature

Visible

Human

thumbnail

images

which

acts

as

the

library

index

The

benefit

is

two-fold

Firstly

the

meta-data

provides

a

manageable

dataset

for

interactively

browsing

the

library

Secondly

each

axial

section

thumbnail

provides

a

preview

of

and

an

index

to

the

corresponding

full

size

library

image

for

automated

retrieval

purposes

For

optimal

browsing

performance

the

meta-data

is

stored

locally

on

the

user?s

machine

and

is

preformatted

in

bit

XImage

-LSB-

-RSB-

format

Hence

as

a

slider

is

dragged

new

thumbnail

images

can

be

moved

directly

from

disk

to

screen

using

X

Windows

shared

memory

On

an

older

Sparcstation

images

are

updated

at

approximately

per

second

As

a

result

we

expect

that

an

implementation

on

a

PC

or

Mac

with

reasonable

I/O

capabilities

could

also

yield

acceptable

interactive

performance

The

meta-data

is

pre-generated

and

comes

packaged

with

the

VHE

software

To

create

the

meta-data

we

developed

several

tools

to

automatically

generate

it

from

the

library

images

The

thumbnail

meta-data

preformatted

for

the

axial

preview

window

is

cropped

spatially

sampled

and

color

quantized

directly

from

library

images

and

requires

under

Megabytes

of

storage

space

The

overview

metadata

formatted

as

coronal

images

is

spatially

sampled

and

reconstructed

from

the

axial

meta-data

and

requires

under

Megabytes

of

space

The

total

cryosection

meta-data

is

of

the

total

size

of

the

full

resolution

cryosection

library

data

Benefits

The

VHE

interface

design

was

chosen

to

be

in

harmony

with

user

tasks

The

tightly

coupled

views

of

the

dataset

combined

with

rapid

dynamic

user

control

of

movement

through

the

third

dimension

provides

a

highly

interactive

interface

yet

avoids

unnecessary

complexities

The

result

is

an

elegant

interface

affording

convenient

user

exploration

of

the

image

data

for

both

novice

and

expert

users

The

need

for

learning

time

is

essentially

eliminated

Feedback

is

fast

enough

to

engage

the

user

Users

can

quickly

learn

about

the

entire

library

by

sweeping

the

views

through

the

body

absorbing

MB

of

data

in

just

a

few

seconds

Then

slower

smaller

movements

to

carefully

examine

interesting

portions

of

the

library

help

locate

optimal

images

for

downloading

Also

when

dragging

a

slider

visualizing

the

resulting

motion

of

the

structural

patterns

in

the

cross-section

thumbnails

provides

additional

insight

over

for

example

simply

viewing

thumbnails

side

by

side

or

in

a

click-and-wait

incremental

fashion

As

has

been

discovered

in

exploration

interfaces

for

many

other

types

of

data

a

visual

overview

of

the

data

space

is

extremely

helpful

-LSB-

-RSB-

When

users

search

for

specific

data

the

VHE

overview

quickly

guides

them

to

the

desired

location

It

provides

context

for

the

axial

preview

thumbnails

some

of

which

would

otherwise

be

difficult

to

interpret

exactly

It

also

promotes

user

exploration

of

the

library

by

eliminating

the

penalty

of

the

possibility

of

getting

lost

or

not

being

able

to

return

to

a

desired

location

in

a

timely

fashion

The

preview

allows

users

to

select

images

filtering

out

unwanted

information

and

download

and

zoom

only

on

desired

detailed

data

on

demand

DISCUSSION

Orthoviewer

While

developing

the

VHE

interface

we

also

implemented

another

prototype

dubbed

the

Orthoviewer

-LRB-

Figure

-RRB-

that

generalizes

the

VHE

motif

It

presents

the

user

with

all

three

orthogonal

views

-LRB-

sagital

coronal

and

axial

-RRB-

of

the

Visible

Human

body

simultaneously

Each

view

contains

both

a

vertical

and

horizontal

indicator

line

which

reflects

the

position

with

respect

to

the

view

of

the

cut

planes

of

the

other

two

views

Each

of

these

six

indicators

can

be

dragged

as

in

the

VHE

to

slide

one

of

the

views

through

the

body

Pairs

of

corresponding

indicators

are

tightly

coupled

For

example

dragging

the

vertical

indicator

in

the

sagital

section

animates

the

coronal

view

and

also

slides

the

horizontal

indicator

in

the

axial

section

which

reflects

the

position

of

the

same

cutting

plane

Interestingly

we

discovered

that

the

Orthoviewer

interface

confuses

many

users

The

addition

of

a

third

view

and

four

indicators

makes

it

difficult

to

decipher

which

indicator

manipulates

which

view

Users

typically

resort

to

a

trial-and-error

process

to

find

the

appropriate

indicator

to

operate

Also

since

each

indicator

is

tightly

coupled

to

other

components

when

dragging

an

indicator

the

user

is

distracted

by

the

additional

motion

The

interface

simply

provides

too

much

dynamic

information

for

many

users

to

process

Users

cognition

is

consumed

by

the

Orthoviewer

interface

instead

of

the

data

itself

As

a

result

we

designed

the

VHE

interface

with

a

distinct

overview-preview

pair

as

used

in

many

successful

browsing

interfaces

in

other

domains

-LSB-

-RSB-

User

Feedback

In

July

we

publicly

released

the

VHE

system

on

our

Web

site

enabling

users

to

download

and

use

it

to

access

the

Visible

Human

library

Our

access

logs

indicate

that

over

users

from

all

over

the

world

have

downloaded

the

software

after

just

months

As

a

result

we

received

some

informal

feedback

about

the

interface

and

its

usage

from

actual

users

We

received

responses

Of

those

who

indicated

their

occupation

or

field

of

study

users

were

evenly

distributed

between

medicine

and

computer

science

and

between

professional

and

student

Others

were

simply

curious

internet

users

The

medical

users

identified

their

use

of

the

library

information

being

primarily

for

learning

and

teaching

gross

anatomy

and

as

a

reference

for

radiology

The

computer

scientists

identified

their

primary

usage

as

test

data

for

image

processing

and

computer

graphics

algorithms

research

All

of

whom

gave

in-depth

comments

reported

that

the

VHE

interface

was

very

helpful

for

visualizing

the

Visible

Human

library

One

user

stated

Now

I

have

a

far

better

understanding

of

how

the

whole

data-set

looks

Users

who

need

to

download

specific

individual

images

were

very

pleased

that

with

the

VHE

interface

they

were

finally

able

to

quickly

locate

and

retrieve

the

proper

library

image

Before

using

the

VHE

it

was

always

a

bit

of

a

problem

to

get

the

right

images

Short

responses

indicated

the

users

excitement

with

the

interface?s

highly

interactive

nature

fast

feedback

and

quick

learnability

trademarks

of

a

direct

manipulation

interface

Also

some

suggestions

for

improvement

were

offered

Multiple

users

suggested

increasing

the

size

of

the

preview

image

by

a

factor

of

or

enabling

visualization

of

most

major

organs

One

user

felt

that

simply

displaying

the

existing

preview

images

larger

without

an

increase

in

actual

data

resolution

would

be

sufficient

Several

users

were

wary

of

the

size

of

the

meta-data

Another

suggestion

was

to

display

MRI

CT

and

cryosection

previews

simultaneously

enabling

the

user

to

browse

all

three

portions

of

the

library

at

once

Generalizations

and

Limitations

The

VHE

interface

demonstrates

a

browsing

approach

that

could

be

generalized

to

other

image

sets

in

which

images

are

sequenced

in

some

meaningful

progression

The

Visible

Human

library

contains

spatially

sequenced

images

or

volumetric

data

While

medical

imaging

is

the

most

common

form

the

interface

could

be

used

to

browse

other

cross-sectional

or

volumetric

datasets

such

as

geological

or

atmospheric

samplings

allowing

users

to

visualize

pattern

changes

in

sedimentation

layers

or

storm

turbulence

Images

could

also

be

sequenced

by

time

of

capture

as

in

digital

video

In

this

case

axial

cross-sections

would

correspond

to

individual

frames

of

the

video

sequence

and

longitudinal

sections

would

show

motion

patterns

of

video

action

across

frames

-LSB-

-RSB-

In

fact

we

originally

encoded

the

VHE

meta-data

as

an

MPEG

video

but

opted

for

another

representation

for

performance

reasons

Also

the

images

themselves

could

be

visual

representations

of

more

abstract

scientific

measurements

For

example

Figure

The

Orthoviewer

prototype

interface

shows

three

orthogonal

views

of

the

body

Dragging

any

of

the

six

indicators

animates

corresponding

views

astronomers

could

browse

a

library

of

spectrograms

collected

over

a

period

of

time

to

view

changes

in

wave

patterns

Applying

the

VHE

interface

to

these

different

datasets

would

simply

require

creation

of

the

miniature

meta-data

-LRB-

we

developed

tools

to

automate

this

process

for

the

Visible

Human

project

-RRB-

and

alteration

of

interface

dimensions

to

accommodate

the

appropriate

image

sizes

Currently

the

VHE

interface

approach

is

limited

to

libraries

containing

such

sequenced

images

For

libraries

containing

heterogeneous

collections

of

arbitrary

unrelated

images

or

textual

documents

the

overview

window

would

need

to

be

redesigned

to

show

a

meaningful

representation

of

the

library

For

example

chronological

timelines

or

simple

page

numbers

would

provide

additional

understanding

of

library

contents

In

this

case

the

ability

to

quickly

flip

through

many

images

or

pages

like

flipping

through

a

book

would

be

very

helpful

when

exploring

large

libraries

Future

Work

With

respect

to

the

VHE

interface

improvements

could

be

made

including

those

suggested

in

the

User

Feedback

Also

a

helpful

new

capability

might

allow

the

user

to

browse

higher

resolution

detailed

data

-LRB-

retrieved

from

the

Visible

Human

library

-RRB-

of

a

smaller

portion

of

the

body

in

the

same

fashion

used

to

browse

the

initial

miniature

body

For

example

if

the

user

wishes

to

see

the

heart

in

higher

detail

retrieving

portions

of

all

the

library

axial

crosssections

containing

the

heart

might

be

preferred

over

a

single

large

axial

image

A

schema

could

allow

the

user

to

specify

a

small

sub-region

of

the

body

to

zoom

on

then

after

retrieval

the

entire

interface

would

be

reused

for

exploring

that

sub-region

in

higher

resolution

The

overview

and

preview

windows

would

display

views

of

the

zoomed

sub-region

for

example

a

coronal

and

axial

section

-LRB-

respectively

-RRB-

of

the

heart

Naturally

the

user

could

return

back

to

explore

the

initial

miniature

Visible

Human

body

at

any

time

With

this

zooming

method

users

could

browse

high

detailed

data

using

the

same

interface

techniques

as

described

in

this

paper

instead

of

simply

viewing

high

resolution

data

only

as

single

large

axial

images

In

addition

investigation

of

other

visual

overview

representation

and

browsing

techniques

for

this

type

of

digital

library

structure

is

needed

As

computer

hardware

progresses

representation

techniques

are

becoming

more

tractable

and

attractive

Human

factors

research

is

required

to

determine

usability

measures

of

differences

between

representations

of

which

the

VHE

is

an

example

and

potential

representations

In

the

broader

picture

as

the

Visible

Human

digital

library

grows

to

include

textual

annotations

segmented

images

attribute

indexes

relationship

graphs

video

animations

and

many

other

forms

of

information

additional

user

interface

browsing

techniques

will

apply

The

graphical

interface

approach

presented

in

this

paper

could

be

combined

with

Korn?s

textual

browser

intended

for

navigating

a

medical

terminology

hierarchy

containing

links

to

the

Visible

Human

images

-LSB-

-RSB-

If

the

two

interfaces

were

tightly

coupled

manipulating

either

the

graphical

or

textual

interface

elements

would

immediately

show

effects

in

the

other

domain

Users

could

browse

using

a

combined

strategy

utilizing

their

knowledge

of

both

medical

terminology

and

visual

appearance

of

human

anatomy

We

believe

that

integrating

different

interface

approaches

for

various

information

types

would

provide

a

rich

comprehensive

browsing

environment

for

an

expanding

Visible

Human

digital

library

ACKNOWLEDGMENTS

Chris

North

received

a

National

Library

of

Medicine

fellowship

administered

by

the

Oak

Ridge

Institute

for

Science

and

Education

Additional

funding

was

provided

by

a

National

Library

of

Medicine

grant

and

National

Science

Foundation

grant

EEC

SOFTWARE

The

VHE

interface

software

is

fully

functional

and

freely

available

for

public

use

For

information

on

obtaining

it

see

vhe.html

or

anonymous

ftp

to

ftp.cs.umd.edu

in

pub/hcil/Demos

VHP

REFERENCES

-LSB-

-RSB-

R.

Allen

Navigating

and

Searching

in

Hierarchical

Digital

Library

Catalogs

Proc

Digital

Libraries

Conf

pg

-LSB-

-RSB-

W.

Chu

A.

Cardenas

and

R.

Taira

KMeD

A

Knowledge-Based

Multimedia

Medical

Distributed

Database

System

Information

Systems

vol

pg

-LSB-

-RSB-

D.

Carr

C.

Plaisant

and

H.

Hasegawa

The

Design

of

a

Telepathology

Workstation

Exploring

Remote

Images

University

of

Maryland

Dept.

of

Computer

Science

Technical

Report

-LSB-

-RSB-

K.

Doan

C.

Plaisant

and

B.

Shneiderman

Query

Previews

in

Networked

Information

Systems

University

of

Maryland

Dept.

of

Computer

Science

Technical

Report

-LSB-

-RSB-

E.

Elliott

and

G.

Davenport

Video

Streamer

Conf

Companion

Human

Factors

in

Computing

Systems

Conf

pg

-LSB-

-RSB-

C.

Faloutsos

R.

Barber

M.

Flickner

J.

Hafner

W.

Niblack

D.

Petrovic

and

W.

Equitz

Efficient

and

Effective

Querying

by

Image

Content

Journal

of

Intelligent

Information

Systems

vol

pg

-LSB-

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Evans

J.

Gauch

G.

Minden

D.

Niehaus

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The

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Proc

Digital

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Conf

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L.

Heath

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L.

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Wake

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Korn

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Pedersen

M.

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J.

Mackinlay

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vol

pg

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browsing
digital library
information exploration
information retrieval
internet
medical image
remote access
user interface
visualization